Benefits of Variable Injection Timing - Houston Advanced Research ...

Funding Opportunity RFGA-03 

Area of Interest: Development and Testing of Engine Upgrade/Retrofit 

Kit for Existing Engines 

Applicant: Motive Engineering Co. 

19 Old Town Square 

Suite 238 

Fort Collins, CO 80524 

Point of contact: Michael B. Riley, President 

Telephone: (970) 221-9600 / (970) 218-0141 

Fax: (970) 221-3863 

Email: miker@mec.com 

Project Title: A Novel Method of Mechanical Variable Injection 

Timing to Reduce NOx Emissions 

Date: January 11, 2007 

Phase 1: Benefits of Variable Injection Timing 

Phase 1 Report Grant N-12 Page 1/15

Benefits of Variable Injection Timing 

When emissions standards for heavy-duty diesel engine manufacturers tightened in 1991 

the industry made the transition from mechanical, fixed injection timing, meaning fixed 

start of injection (SOI), to more expensive electronically varied SOI. This report seeks to 

summarize research work conducted both before and after that time to quantify the 

benefits of variable injection timing (VIT.) 

There are numerous studies that report the effects of variable SOI [1, 2, 3, 4, 5.] The 

studies cited from 1981 to 2002, and generally measure the effect of SOI change on fuel 

consumption and NOx emissions. 

Locomotive Application 

In [1] the authors studied the emissions and fuel economy effects on locomotive engines. 

Of particular interest is the GE 7FDL locomotive engine whose unit pump injection 

system is a good candidate for MEC’s eccentric sleeve phasing (ESPi) system for 

variable SOI. These engines are normally tested over an eight-point duty cycle, but to 

reduce total testing time their timing sweeps for determining the effects on fuel economy 

and emissions were conducted at three points. The points chosen were at idle, notch 5 

and notch 8. Results quoted are weighted with 50% at the idle condition, and 25% each 

to the other two points. Extrapolating from the data in the paper they indicate that a 

reduction of 25% in NOx would require the SOI to be retarded by just over 6° crank, with 

corresponding drop in fuel economy of just over 3%. 

Midrange 

The engine tested in [2] was a 9.5 L truck engine certified to Euro 2 emissions. The aim 

of the study was to determine the emissions from different diesel fuel formulations, 

however by testing at the stock, fixed timing, and one other setting with constant NOx 

output, useful extrapolations could be made on their reference fuel. Testing was 

conducted over a 13-mode European cycle, again averaging the results. One of the fuels 

used represented a low-sulfur European fuel, and results using this fuel are referenced. 

The engine used a fixed SOI of 10° BTDC for the baseline tests. SOI was then altered to 

produce a fixed NOx level of 6.3 g/kW-hr, or a reduction of 7%. While extrapolating 

these results to a 25% reduction in NOx may not be linear it points to fuel consumption 

worsening by approximately 4%, with retarding the SOI by some 5° crank. 

Initially it appears that it is possible to reduce NOx by 25%, simply by retarding SOI by 

an average of 5° to 6° crank, but the penalty is paid in fuel economy. In most references 

[1, 2, 4, 5] data reported are averaged over some sort of representative cycle, disguising 

the effects of SOI change at different speeds and loads. In [3] however, specific 

examples are given of these effects, as shown in Figure 1 below. 


Figure 1: Test results reported in [3] for BSFC vs. SOI at different speeds and loads 

Heavy Duty 

Testing was performed on a single-cylinder test engine, representing a heavy duty truck 

application. Data for 25%, 50% and 100% load were taken at 1130 and 1420 rpm. Like 

all other studies reported they show that advancing SOI at all speeds and loads results in 

increasing NOx output as shown in Figure 2 below. The effect on fuel economy is more 

varied. In this case it is obvious from Figure 1 that the location of optimal timing for fuel 

consumption shifts significantly with load, and somewhat with speed. Further, at some 

load conditions the effect on fuel consumption appears flat over a wide range of timing, 

allowing timing selection to be made to minimize NOx emissions. 

Figure 2: Test results reported in [3] for BSNOx vs. SOI at different speeds and loads 

Assuming that static SOI would occur at 16° BTDC it is possible to estimate the changes 

in BSFC, BSNOx and, to a certain extent, particulates. (The scale chosen for the 

particulate plots made it difficult to determine changes in emissions with any degree of 

accuracy.) 


For the case of full load at 1130 rpm, the NOx level was 12 g/kW-hr. Reducing the NOx 

level to 9 g/kW-hr required a 7.5° timing retard, and fuel consumption worsened by 

1.5%. However at 25% load the initial NOx level was 31 g/kW-hr. When this was 

reduced by 25% to 23 g/kW-hr the timing retard was 4°, and fuel consumption improved 

by 1.6%. In this case it was more beneficial to retard the timing further, by 10°, which 

gave an improvement in fuel consumption of almost 4%. 

With different SOI values feasible at different speeds and loads it may be possible to 

reduce overall NOx emissions by the 25% target required while having little impact, if 

any, on fuel consumption. As an example the 1420 rpm data could be considered at full 

load. In Figure 1 it is apparent that the fuel consumption varies very little between 14° 

BTDC and 11° BTDC. (There is no data at the 16° BTDC point.) However the NOx 

level falls off by 12%. Depending on the duty cycle of the engine concerned this may be 

a suitable trade-off between NOx emissions and fuel economy over the entire cycle while 

the overall target of 25% is achieved. From all the data found so far in the literature it 

appears that preserving fuel economy is not feasible with a fixed SOI retard. 

Mechanical Injector Design Considerations 

Dual and Single Helix Pumps 

The data in Figure 2 show that NOx increases significantly as load decreases with fixed 

SOI timing. This is due to the excess air in unthrottled diesel engines at part load. To 

counteract this tendency, as NOx emissions regulation began, many non-electronic (or 

mechanical-only) fuel systems changed to modified designs known as “dual helix” 

plungers to retard SOI timing as fueling decreases. Mechanical-only systems control SOI 

and how much fuel is injected by machined cuts in the outer cylindrical surface of the 

injection plunger. As the injection plunger begins to move upward, fuel flows through 

the cut plunger passages into a “spill port” in the pump barrel until the lower edge of the 

cut is reached, which closes the port, and traps fuel in the pumping volume. This trapped 

volume is then pressurized by the plunger upward motion for injection. End of injection 

(EOI) occurs when another cut in the plunger connected to the pressurized injection 

volume reaches the spill port and releases the fuel pressure. A “single helix” plunger has 

a horizontal edge cut for (fixed timing) SOI, and regulates the amount of fuel injected by 

rotating the plunger so that a helical cut ends injection, with the amount injected a 

function of the distance between the SOI horizontal cut and the EOI helical cut at the spill 

port position. A “dual helix” plunger has a second helical edge cut (instead of horizontal) 

for SOI so that as the plunger is rotated to regulate fuel quantity, the SOI timing is also 

modified. 

SOI Lag Due to Line Length 

Although dual helix plunger systems have much less variation in NOx versus engine 

load, the SOI timing is still a direct function of the amount of fuel injected and does not 

change with engine speed. With pump/line/nozzle (PLN) systems, using either a single 

multicylinder inline pump assembly, or several separated single cylinder unit pumps, 

there is still a significant delay between the beginning of an injection pulse at the pump 


and the resulting pulse reaching the injector tip, due to the speed of sound in the fuel and 

the distance along the length of the injection line and through the injector. These delays 

in each line and nozzle are nearly constant in absolute time (seconds), meaning that the 

delay in engine crank angle (degrees) varies with engine speed. Thus SOI timing retards 

as speed is increased. For example, for a 720 mm line length, the delay can increase from 

2.6 deg at 800 RPM to 7.2 deg at 2200 RPM, causing a 5.6 deg retard in SOI at 2200 vs. 

800. This runs opposite to the desired trend in SOI versus speed, where for constant 

BSNOx, SOI timing is usually advanced as engine speed increases. 

Resulting Compromises in SOI Timing 

Thus even with a dual helix system, the phasing of the injection pump and resulting SOI 

timings are usually limited by one or only a few speed/load regions at which the highest 

NOx is produced, usually at the lower speed and high load ranges. With a single helix 

system, the phasing is often limited by the very high NOx lower speed and lower load 

ranges. All other points then are not optimized in SOI timing for the best BSNOx vs. 

BSFC tradeoff. This results in higher overall fuel consumption throughout the full 

speed/load range, which is magnified if the application duty cycle requires significant 

amounts of time in the higher speed range. With VIT, the SOI timings can be 

independently tailored so that in the highest NOx regions, SOI timing is retarded, and in 

the lower NOx regions, SOI timing is advanced. Thus overall NOx can be reduced 

without a significant penalty in fuel consumption, and even sometimes an improvement, 

depending on application duty cycle. 

Summary statement 

Fixed retard of SOI for NOx reduction of 25% results in a fuel economy penalty of 3 – 

4%. VIT can achieve the same level of NOx reduction with a fuel economy penalty that 

is much lower, and may sometimes even be an improvement, depending on the duty 

cycle. 

EFI Conversion Cost Estimates 

Finding suitable cost information for comparison purposes has been difficult. Some 

information has been found on the difference in cost between mechanical injection 

systems, and their subsequent model electronic versions, and will be summarized here. 

Some of this information has been provided through personal contacts, and should be 

regarded as approximate. Other numbers are for retail systems that may be purchased 

through distributors. However there are no readily available cost numbers that allow 

direct costing of converting existing mechanical injection systems to electronically 

controlled, fully variable SOI timing systems. 

The initial cost information is for replacing a mechanical in-line pump for 6-cylinder 

heavy-duty diesel engines with an electronically controlled pump. This comparison is 

made difficult by the difference in architecture between this style of pump, and the MEC 

ESPi system which is intended for applications using unit pumps. 


The mechanical in-line pump units are estimated to cost $1,000 to $1,200 to the engine 

manufacturer. A replacement electronically controlled pump (for varying SOI) is 

estimated to cost $2,200. (Note that this cost comparison assumes that a direct 

replacement pump is available for the particular engine under consideration. If a generic 

electronic pump replaces an existing tailored unit the costs are certain to be considerably 

higher.) The estimated OEM cost of the appropriate engine control module (ECM) is 

$400 to $450. If the markup for retail sale is in the range of 50 – 100%, then the 

additional cost of variable SOI to the end customer is in the range of $2,100 to $3,300 for 

the components alone for a six-cylinder, in-line diesel engine. The cost of labor for 

removal of the old system and installation of the new system must be added to these 

numbers, and the cost of replacement nozzles should be added as well. 

In comparison, the cost of hardware for the MEC ESPi system for this engine type to 

vary SOI timing only is estimated to be $3,400 (including modified unit pumps) from the 

information given in the proposal application. As above, labor is additional, but should 

be comparable. Timing maps for different speed/load conditions for a 25% NOx 

reduction will have to be generated during the verification stage of the MEC ESPi 

system. These costs have not been included here. They are difficult to estimate due to 

uncertainty in the numbers of possible candidate engines. However they should be 

comparable to conversion costs to electronic systems if they were not tailored to the 

candidate engine. 

Current retail prices for heavy duty unit injectors (with wiring) for electronically (spill 

valve) controlled systems are in the range of $400 per injector or $2,400 for a 6-cylinder 

engine. The ECM for these systems is estimated to cost $1,500. Sensors ($300) and a 

gear pump for pressurizing the fuel ($300) would bring the hardware cost estimate for 

this type of system up to $4,500. It is not clear whether EFI conversions require different 

cam profiles, necessitating either replacing or modifying the existing camshaft. If so this 

cost would be additional, and is not included here. 

If suitable solenoid controlled injectors are not available for older, candidate engines then 

the conversion cost to the MEC ESPi system should be considerably lower than 

electronically controlled SOI injection systems. In the case where such injectors are 

available, the hardware cost estimates for replacement hardware to convert existing 

mechanical injection systems to electronically controlled SOI timing appear to be in the 

same range, or slightly more expensive, than the proposed MEC system. 

NOx Reduction Approaches 

NOx is formed in-cylinder as a consequence of the combustion process. There are two 

general areas to reducing NOx, and techniques in these areas may be used in tandem. 

The first is in-cylinder, where the conditions that lead to the formation of NOx are 

modified so that there is less NOx produced. VIT is one of the techniques that can 

achieve this, but there are others, as described below. 


The second approach is to accept the levels of NOx produced in-cylinder and then 

chemically reduce it in the exhaust. Such aftertreatment approaches may be used in 

conjunction with in-cylinder techniques to lower the overall NOx output. Their 

combined use is more a matter of economics than practicality. 

Available Technologies – In-Cylinder 

The previous section described the effects of variable SOI on NOx emissions, fuel 

economy and particulates. The use of higher injection pressures can assist in reducing 

NOx if later SOI is used with the resulting smaller fuel particles [6]. The following plot 

[7] contains a concise summary of the different technologies for dealing with NOx and 

particulates. For in-cylinder technologies the plot demonstrates the effect of SOI on 

NOx and particulates (more advanced timing leads to higher NOx and lower 

particulates), and the effects of EGR (more EGR leads to higher particulates and lower 

NOx.) Meanwhile a combination of aftertreatment approaches helps engine 

manufacturers in achieving the 2007 emissions standards (shown in the lower left hand 

corner of the plot.) 

Figure 3: Summary of in-cylinder and aftertreatment technologies 

from [7] in reducing emissions 

Besides new combustion system approaches like HCCI (homogeneous charge 

compression ignition) and PCC (partial HCCI) the primary technique used to reduce NOx 

in-cylinder is exhaust gas recirculation (EGR), which, to be most effective, requires 

cooling. This approach requires external valving and piping, and a cooler for the exhaust 

gas. (HCCI and PCCI will not be addressed here. For older engines where retrofit 


technologies are being considered it is highly likely that these new combustion systems 

would require greater changes to the engine than would be economic.) 

EGR works by displacing oxygen in the intake charge with relatively inert gases. With 

less oxygen available the combustion process will be somewhat slower, leading to lower 

temperatures. In addition the added CO2 and water vapor in the exhaust stream affects 

the rate of temperature rise due to their high thermal capacitance relative to other gases. 

It is also the lower oxygen levels of the intake charge that reduces the oxidation of soot 

particles, leading to higher PM emissions. 

The following diagram [8] show the effect of cooled vs. uncooled EGR on NOx, 

particulates and intake manifold temperature. While the effect of cooling the EGR has 

little effect on NOx, the effect is substantial on particulates. 

Figure 4: Effect of EGR temperature on NOx, PM and 

intake manifold temperature from [8] 

EGR approaches usually increase the load on the engine cooling system, and impose a 

fuel economy and particulates penalty [9, 10], although the latter may be mitigated if 

combined with a diesel particulate filter (DPF.) A further constraint that will apply to 

retrofit applications is whether the engine is turbocharged or not, and whether a highpressure 

or low-pressure loop is selected for returning the EGR to the cylinder, as shown 

in the following diagram. 


Figure 5: High pressure EGR loop (left) and low pressure EGR (right) from [8] 

EGR has certain drawbacks though. With higher particulates the gas stream diverted 

back to the engine will increase wear. (If used with a DPF this is not as much of an issue, 

although the low pressure loop must be used, incurring a fuel economy penalty to 

recompress the EGR, and adversely affecting transient response. Also the combination 

would be expensive for retrofitting older engines.) During transients the volume of EGR 

in the piping and heat exchanger will cause additional particulates due to the rate of 

fueling exceeding the available air even more than a non-EGR engine. Piping, heat 

exchanger and valving for EGR can be cumbersome and expensive. 

Available Technologies – Aftertreatment 

There are a number of aftertreatment technologies available for reduction of both NOx 

and particulates. These technologies are: 

• SCR – selective catalyst reduction 

• LNT – lean NOx trap 

• DPF – diesel particulate filter 

• DOC – diesel oxidation catalyst 

Technologies that reduce particulates are included in this study because both VIT and 

EGR impact particulates. If particulate levels are worse due to reduced NOx (and 

possibly improved fuel economy) there will be a trade-off at some point to maintain air 

quality. 

SCR Technology 

This approach introduces a reducing agent into the exhaust stream, either by the addition 

of urea or ammonia directly, or the addition of extra fuel to provide the reducing reagent 

[9, 11, 12, 13.] The resulting chemical reaction reduces NOx to oxygen and nitrogen. 

This approach has been used in stationary power plants for some time. Efficiencies are 

very high for engines that operate under constant conditions, but are lower for operation 

under transient conditions. (Model-based algorithms are under development to allow 

more accurate prediction of the amount of ammonia required when the anticipated 

quantity of NOx changes with load and speed.) 


Of potential concern is ammonia slip, where some of the reducing agent escapes the 

exhaust system into the atmosphere. The major logistical problems are that an additional 

storage tank is required on each vehicle, and a refilling infrastructure is required. 

The promise of significant reductions in NOx means that SOI can be advanced again for 

improved efficiency, resulting in better fuel economy than other approaches. Particulates 

are also improved with this approach. However, in certain applications the temperature 

of the exhaust stream may be too low for effective operation of the catalytic reaction. In 

those cases an additional heat source may be required, either a burner or an electric 

heating element. Either of these options will result in a reduction of fuel economy of the 

engine. 

There is potentially a 6% improvement in fuel economy, although this is offset by the 

cost of urea. One study [13] found that urea must cost less that $1.50 per gallon for there 

to be an equivalent fuel economy benefit using an SCR. 

A schematic of a system developed by Bosch is shown below. 

Figure 6: A commercial SCR system with a DOC as shown in [14] 

LNTs 

LNTs adsorb NOx and oxygen during lean operation modes, then during occasional rich 

operation the NOx is catalyzed to nitrogen. Sulfur in the exhaust causes performance 

degradation over time [12] so that periodic desulfation is required. There are some 

operational issues with these NOx adsorbers for the regeneration phase. Either a dual-leg 

layout is needed where one of the two legs may be regenerated while the other continues 

to adsorb NOx, or a single-leg layout requires periodic injection of diesel fuel into the 

exhaust to facilitate the reduction process. Using fuel as a reductant has a substantial fuel 

economy penalty. Schematics of the two approaches are shown below. 


Figure 7: Single and double leg LNT systems from [10] 

DPF Technology 

This consists of a closed filter that physically traps particulates then oxidizes them. The 

oxidation process requires a particular temperature range, which is often controlled by a 

burner, impacting fuel economy. Some filters are catalytic, reducing the fuel economy 

impact. They also trap ash from combustion of engine oil, which cannot be oxidized. 

Consequently they require periodic cleaning. 

DOC Technology 

This approach is similar to the use of catalyst in automotive applications, except that it 

does not reduce NOx emissions due to the oxygen-rich environment. These oxidize 

unburned hydrocarbons and carbon monoxide as well as some particulates (although not 

as effectively as DPFs for the latter.) They are passive devices with no maintenance 

required. 

The following table shows a summary of the effectiveness of both in-cylinder and 

aftertreatment approaches on emissions, including a range of costs for retrofit situations, 

based on the references given at the end of this report. 


Table 1: NOx reduction alternatives at a glance 

Technology NOx 

Reduction 

PM 

Reduction 

VIT Up to 50% Could 

increase 

50% 

EGR (cooled) 40 – 60% Could 

increase 

300% 

HC 

Reduction 

CO 

Reduction 

Phase 1 Report Grant N-12 Page 12/15 

Effect on Fuel Economy Estimated Cost 1 

- - Less than fixed retard, may 

even be neutral 

$7,400 

Increased Increased 1 – 4% worse $13,000 – 15,000 

SCR 60 – 90% 20 – 30% 99% 76% Possibly up to 6% improved, 

but have reductant 

costs/consumption 

$10,500 - $50,000 

LNT >80% - - - 3 – 7% worse $5,000 - $10,000 

DOC - 10 – 50% 50% 40% - $500 - $2,000 

DPF - 

1 Estimates based on 10 – 15 L heavy duty diesel engine 

2 Requires ULS diesel 

80 – 90% 85% 85% Depending on heat source for 

activation 

$5,000 - $10,000 2

The following diagram from [7] gives a good comparison of EGR, SCR and NOx 

adsorber approaches on other performance issues. As noted above, the advantage that 

SCRs have with fuel economy is somewhat negated by the need to recharge the reductant 

tank periodically. The alternative approach of on-board reforming to provide the 

reductant reduces this advantage somewhat. 

Figure 8: Performance effects of different NOx reducing technologies from [7] 

Another potential NOx reducing technology is that of the lean NOx catalyst. 

Unfortunately to date there have been no successful, durable lean NOx catalysts that can 

reduce NOx under the typical oxygen-rich environment of a diesel engine exhaust. Even 

if one is found, there is expected to be a fuel economy penalty of 3% or more due to the 

addition of a suitable reductant [10, 12]. 


Summary of Retrofits 

Each of the technologies listed above has a number of advantages and disadvantages. 

The table below is intended to offer a summary of the pros and cons of applying these 

systems as retrofits to older diesel engines for the purposes of NOx reduction. 

Table 2: Pros and cons of different NOx reduction alternatives 

Technology Advantages Disadvantages 

Mechanical 

VIT 

Transparent to user 

Constant over engine life 

Little impact on fuel economy 

Cooled EGR Effective NOx reduction 

No user intervention required 

SCR NOx reduction high 

Potentially best fuel economy 

May be invasive in engine 

May require higher injection pressures 

PM, HC, CO worse 

Additional engine wear 

Higher PM during transients 

Hardware packaging 

Additional cooling system demands 

Requires reductant 

User intervention required 


Expensive 

LNT Potentially high NOx reduction High fuel economy penalty 


DOC Low cost control of HC, CO, 

PM 

Does nothing for NOx 

DPF Reduces PM with timing retard Does nothing for NOx 

Requires heat source 


Summary 

A low-cost VIT solution may be a very attractive approach for older diesel engines to 

achieve a 25% reduction in NOx emissions. While there are other approaches that reduce 

NOx further they appear to be substantially more expensive, and in some cases require 

user intervention. 

Further VIT appears to offer very good fuel economy results for the cost, an issue that is 

sure to be of concern to users of older engines who will see no economic benefit to lower 

NOx emissions. 


References 

1) V. O. Markworth, S. G. Fritz, G. R. Cataldi, “The Effect of Injection Timing 

Enhanced Aftercooling, and Low-Sulfur, Low-Aromatic Diesel Fuel on 

Locomotive Exhaust Emissions,” Transactions of the ASME, pp. 488 – 495, 

Vol. 114, July 1992 

2) R. Stradling, P. Gadd, M. Signer, C. Operti, “The Influence of Fuel Properties 

and Injection Timing on the Exhaust Emissions and Fuel Consumption of an 

Iveco Heavy-Duty Diesel Engine,” SAE Paper 971635, 1997. 

3) D. A. Kouremenos, D. T. Hountalas, K. B. Binder, A. Raab, M. H. Schnabel, 

“Using Advanced Injection Timing and EGR to Improve DI Diesel Engine 

Efficiency at Acceptable NO and Soot Levels,” SAE Paper 2001-01-0199, 

1999. 

4) P. Lauvin, A. Loffler, A. Schmitt, W. Zimmermann, W. Fuchs, 

“Electronically Controlled High Pressure Unit Injector System for Diesel 

Engines,” SAE Paper 911819, 1991. 

5) R. C. Yu, S. M. Shahed, “Effects of Injection Timing and Exhaust Gas 

Recirculation on Emissions from a D.I. Diesel Engine,” SAE Paper 811234, 

1981. 

6) J. M. Desantes, J. V. Pastor, J. Arregle, S. A. Molina, “Analysis of the 

Combustion Process in a EURO III Heavy-Duty Direct Injection Diesel 

Engine,” ASME J. Eng. Gas Turbines Power, 124, pp. 636-644 

7) M. Schittler, “State-of-the-Art and Emerging Technologies,” 9 th Diesel Engine 

Emissions Reductions Conference, August 2003 

8) “Exhaust Gas Recirculation,” DieselNet Technology Guide, Engine Design 

for Low Emissions, 2005 

9) “Overview of Clean Diesel Requirements and Retrofit Technology Options,” 

F. J. Acevedo, Michigan Clean Fleet Conference, March 2006 

10) G. Weller, “EPA Engine Implementation Workshop – 6/7 August 2003, 2007 

Technology Primer,” Presentation by Ricardo 

11) “Diesel Powered Machines and Equipment: Essential Uses, Economic 

Importance and Environmental Importance,” Diesel Technology Forum, June 

2003 

12) H. Hu, J. Reuter, J. Yan, J. McCarthy Jr., “Advanced NOx Aftertreatment 

System and Controls for On-Highway Heavy Duty Diesels,” SAE Paper 2006- 

01-3553, 2006 

13) R. Krishnan, T. J. Tarabulski, “Economics of Emission Reduction for Heavy- 

Duty Trucks,” DieselNet Technical Report, January 2005 

14) W. Addy Majewski, “SCR Systems for Mobile Engines,” DieselNet Technical 

Report, 2006 


Table of Contents 

1. Executive Summary .............................................................................................................................. 6 

2. Introduction ........................................................................................................................................... 8 

3. Project Objectives/Technical Approach .............................................................................................. 10 

3.1. Inclusion of Variable Valve Timing with Variable Injection Timing ......................................... 11 

4. Tasks ................................................................................................................................................... 12 

4.1. Phase 1 ........................................................................................................................................ 12 

4.1.1. Phase 1 Task 1 NOx Aftertreatment Alternatives ............................................................... 12 

4.1.2. Task 2 VIT Compared to Aftertreatment in Reducing NOx ............................................... 13 

4.1.3. Task 3 Engine Simulation Predictions ................................................................................ 13 

4.2. Phase 2 ........................................................................................................................................ 28 

4.2.1. Task 1 Selection of Candidate Engine ................................................................................ 28 

4.2.2. Phase 2 Task 2 Design of a VIT/VVT System to Retrofit onto the Candidate Engine ....... 29 

4.2.3. Phase 2 Task 3 Analysis of critical components ................................................................. 32 

4.2.4. Phase 2 Task 4 Fabrication of VIT and VVT hardware ...................................................... 38 

4.2.5. Phase 2 Task 5 Proof-of-Concept System Fabrication........................................................ 40 

4.2.6. Phase 2 Task 6 Engine Testing ........................................................................................... 43 

5. Finance and Schedule ......................................................................................................................... 47 

6. Discussion/Observations ..................................................................................................................... 50 

6.1. Objectives vs. Results ................................................................................................................. 50 

6.2. Critical Issues .............................................................................................................................. 50 

6.3. Technical and Commercial Viability of the Proposed Approach ............................................... 50 

6.4. Scope for Future Work ................................................................................................................ 50 

7. Intellectual Properties/Publications/Presentations .............................................................................. 51 

8. Summary/Conclusions ........................................................................................................................ 52 

9. Acknowledgements ............................................................................................................................. 52 

10. References ....................................................................................................................................... 53 

11. Appendices ...................................................................................................................................... 54 

11.1. Appendix 1: Comparison of NOx reduction technologies ..................................................... 54 

11.2. Appendix 2: Modeling Results of VIT/VVT on Roots-Blown EMD 645 Engine ................... 1 

11.3. Appendix 3: SwRI Testing Report of Mechanical VIT/VVT System ..................................... 7 

Final Report NTRD Program N-12 Page 2

Table of Figures 

Figure 1: Test locomotive for VIT/VVT retrofit.......................................................................................... 7 

Figure 2: Technologies used by US heavy duty engine manufacturers in the 1980’s to 1990’s ................. 8 

Figure 3: Tradeoff between NOx and particulates with different injection timing ...................................... 9 

Figure 4: Effect of NOx reduction on fuel economy ................................................................................... 9 

Figure 5: GT Power map of Roots-blown EMD 16-645 engine ................................................................. 14 

Figure 6: Phasing of valve event with VVT ............................................................................................... 15 

Figure 7: Valve lift and duration change .................................................................................................... 15 

Figure 8: Explanation of modeling results for variation in SOI and valve lift, duration and phase ........... 16 

Figure 9: BSFC and BSNOx at notch 2 with 88% of stock engine valve duration .................................... 17 

Figure 10: BSFC and BSNOx at notch 2 with 92% of stock engine valve duration .................................. 17 


Figure 12: BSFC and BSNOx at notch 2 with 100% of stock engine valve duration ................................ 18 














Figure 26: Effect of exhaust valve timing and duration on location of minimum BSFC ........................... 26 

Figure 27: Valve rocker arm positions for advanced, centered and retarded timing .................................. 30 

Figure 28: Model of EMD 645 head with VIT/VVT hardware incorporated. Cap that controls movement 

path of rocker arms shown as translucent. .................................................................................................. 31 

Figure 29: VIT/VVT hardware installed on EMD 645 engine ................................................................... 31 

Figure 30: Pressure angle for roller-cam interface of valve rocker arm in centered position ..................... 33 

Figure 31: Pressure angle for roller-cam interface of valve rocker arm in 8° retarded position ................. 34 

Figure 32: Pressure angle for roller-cam interface of valve rocker arm in 8° advanced position ............... 34 

Figure 33: Forces on rocker arm tip in centered position at rated speed .................................................... 35 

Figure 34: Valve rocker arm geometries used for FEA. Stocker rocker arm on left, thinned rocker arm on 

right ............................................................................................................................................................. 35 

Figure 35: Von Mises stresses in the stock rocker arm ............................................................................... 36 

Figure 36: Von Mises stresses in the modified rocker arm ......................................................................... 37 

Figure 37: Modified injector rocker arm with shortened pivot shaft section and control yoke. Oil delivery 

groove visible in center section of yoke. ..................................................................................................... 39 


Figure 38: Underside of control cap. Legs to cap not included here. ........................................................ 39 

Figure 39: Witness mark on rocker arm after contact with cap .................................................................. 40 

Figure 40: Contact point between yoke and rocker arm ............................................................................. 41 

Figure 41: Cap area clearanced to ensure proper range of motion of injector rocker arm .......................... 41 

Figure 42: VIT/VVT hardware fits under the valve covers on the engine .................................................. 42 

Figure 43: Isolated exhaust system section on four of sixteen cylinders of EMD 645 ............................... 43 

Figure 44: Exhaust emissions equipment on four cylinders of sixteen cylinder EMD 645 ........................ 44 

Figure 45: Schematic of fuel delivery system to test cylinders with separate circuit ................................. 45 

Figure 46: Fuel rails showing separation of test cylinders from rest of engine .......................................... 45 

Figure 47: Monthly project costs for N-12 ................................................................................................. 47 

Figure 48: Cumulative project costs for N-16 ............................................................................................ 48 


Table of Tables 

Table 2: SOI required to achieve 25% NOx reduction and the effect on BSFC at stock valve timing ...... 27 

Table 4: SOI and valve timing changes required to achieve 25% NOx reduction and to minimize the 

effect on BSFC ............................................................................................................................................ 28 

Table 6: Difference between SOI only versus SOI plus variable valve timing to achieve 25% NOx 

reduction and the effect on BSFC ............................................................................................................... 28 

Table 7: Summary of FEA on valve rocker arm ......................................................................................... 37 


1. Executive Summary 

NOx emissions have been linked directly with the formation of ground-level ozone. Efficiency 

levels of diesel engines are good, with one consequence being high NOx emissions levels. 

Numerous approaches have been investigated to reduce these NOx levels while maintaining the 

efficiency levels of diesel engines. Two major classifications of emissions reduction technology 

are in-cylinder NOx reduction, and aftertreatment. 

Efforts to reduce NOx emissions in-cylinder include the following: retarded injection timing, 

cooled exhaust gas recirculation (EGR), and charge air cooling. Of these three retarding 

injection timing is the simplest and easiest to implement, although it has the drawbacks of 

increased particulate emissions and worsened fuel economy, especially if the amount of injection 

timing retard is fixed. Modern electronic fuel injection systems avoid some of these issues by 

varying the start of injection (SOI) to meet emissions levels while minimizing the impact of the 

other two. Retarding SOI a fixed amount by adjusting the injector on mechanical systems may 

also lead to difficulties at higher load settings where the cam may fall off the end of the injector 

lobe before the schedule end of injection point. 

Aftertreatment systems have one advantage over in-cylinder methods in that the base engine may 

remain unaffected, although this is not always true. SCR systems are gaining popularity due to 

the potentially high NOx conversion efficiencies – up to 80% for mobile applications – but the 

cost and complexity of these systems is still of concern. 

In TERC’s RFGA-03 the State of Texas was seeking technologies that would be applicable for 

retrofit to older diesel engines for NOx reduction. Motive Engineering Co. had developed a 

mechanical variable valve timing technology that was originally intended for use on gasoline 

engines for improving fuel economy, emissions and performance. MEC proposed using this 

technology to allow a form of mechanical variable injection timing as a low-cost way of 

retrofitting older diesel engines that may not have a viable electronic fuel injection (EFI) system 

available. In the process of identifying a suitable older diesel engine for retrofit it became 

obvious that engines for mobile applications up to over-the-road trucks were unsuitable targets 

for retrofit. However locomotive engines appeared to be ideal. Although small in number the 

average locomotive engine produced much higher levels of NOx emissions annually than these 

smaller engines, due to both size and duty cycle. Of the locomotive engines available, the EMD 

645 presented the best opportunity from both an economic perspective and a NOx tonnage saved 

potential. This change in application also brought about a change in the intended technology. 

The original eccentric sleeve phasing system (ESPi) suited to four-stroke, pushrod engines was 

no longer suitable. A new, novel variable timing system was developed and implemented in this 

project. 

An engine simulation program as carried out on the supercharged EMD engine (rather than the 

turbocharged version) to determine the extent of injection timing change required to deliver the 

minimum 25% NOx reduction required by TERC. Simultaneously a matrix of valve timing 

values was investigated to determine if variable valve timing would deliver any advantages to the 

process. It was found that variable injection timing had the predominant effect on NOx 

emissions, while variable valve timing delivered improvements in fuel economy at some 


operating conditions. SOI retard of approximately 5.5° yielded the 25% NOx reduction, 

although variations of 2° from this average were required at different speeds an loads. Valve 

timing variations of 3° advanced to 14° retarded were required to optimize fuel economy. The 

best fuel economy prediction occurred at notch 2 (where switcher locomotives spend much of 

their operation), with a 3% improvement over stock, with a 25% NOx reduction. (The modeling 

did not predict particulate matter (PM) emissions. Testing of the engine was required to measure 

PM. With EMD two-stroke engines the majority of PM emissions are due to oil consumption, so 

the effect of SOI retard on PM was unclear prior to testing.) 

The design developed for the EMD engine lent itself to both mechanical variable injection timing 

(VIT) and mechanical variable valve timing (VVT.) The modeling work suggested the likely 

ranges of injection and valve timing variation that would optimize both emissions and fuel 

economy. Hardware was designed and fabricated that incorporated the adjustment ranges 

recommended by modeling. 

At this stage the program was still proof-of-concept, so to minimize the hardware cost only four 

of sixteen cylinders of an EMD 16-645 engine were retrofitted. The choice of the supercharged 

engine meant that the four cylinders chosen could be isolated from the rest of the engine and 

performance, fuel economy and emissions data could be compared to the stock engine. 

Testing of a modified EMD 645 engine was carried out at Southwest Research Institute’s (SwRI) 

Locomotive Technology Center in San Antonio, TX. The locomotive, shown in Figure 1, was 

tested in both stock (baseline) configuration, and as modified, over a wide range of valve and 

injection timing, and from idle to notch 6. 

Figure 1: Test locomotive for VIT/VVT retrofit 


Resuults 

fro om testting 

weere 

…………… 

….. 

2. Introduction 

NOx emiissions 

are directly d linkeed 

to ground-level 

ozonee, 

one of the principal coomponents 

inn 

smog [1] . The high efficiencies e of diesel enggines 

make tthem 

one of the major soources 

of NOOx 

emissionns. 

Over the past twenty years a nummber 

of new technologiess 

have been introduced tto 

meet eveer-tightening 

emissions sstandards, 

ass 

shown in Fiigure 

2 [2]. 

Figurre 

2: Techn nologies usedd 

by US heaavy 

duty engine 

manuffacturers 

in the 1980’s tto 

1990’s 

The geneeral 

trend of the technoloogies 

listed iin 

Figure 2 iis 

to reduce engine-out eemissions. 

OOver 

the past ddecade 

or so o more and mmore 

technologies 

have ffocused 

on trreating 

thosee 

emissions aafter 

they leavve 

the cylind der, such as NNOx 

traps, SSCR 

(selectivve 

catalyst reeduction), 

LNNT 

(lean NOOx 

traps), DPPF 

(diesel particulate 

fillters), 

and DOC 

(diesel ooxidation 

cattalysts.) 

One methhod 

used to reduce r NOxx 

has been too 

retard injecction 

timing. Retarding iinjection 

redduces 

the tempeeratures 

of peak p combusstion 

where NNOx 

forms. If this apprroach 

is to bee 

used, theree 

are 

certain drrawbacks 

that 

must be wworked 

arounnd. 

When innjection 

timiing 

is retardeed 

by a fixedd 

amount the 

output of f particulatess 

will rise, ass 

shown in FFigure 

3 beloow 

[3]. 

Final Repoort 

NTRD Prog gram N-12 

PPage 

8

Figure 3: Tradeoff between NOx and particulates with different injection timing 

Simultaneously if the only change is retarded injection timing the fuel consumption will worsen. 

This is logical given that the most efficient operation of a diesel engine will generate the highest 

temperatures (and pressures), and retarded timing reduces those temperatures. Figure 4 below 

[4] shows the effects of NOx reduction on fuel economy. The higher NOx emissions levels can 

be reduced more easily with less impact on fuel economy. 

Figure 4: Effect of NOx reduction on fuel economy 


Over the past fifteen years many diesel engines have incorporated some form of electronic 

variable injection timing (VIT.) By being able to vary the start-of-injection (SOI) manufacturers 

have been able to trade off fuel economy, NOx and particulates [3]. Mechanical VIT has been 

implemented experimentally on a few large, expensive engines by using a movable follower 

between the cam and the unit injector [5]. Such systems are not suitable for most cam-driven 

injector geometries due to lack of space. 

Consequently an essential requirement to make mechanical VIT viable is to be able to package 

the necessary components in the space available in a wide range of engines, while meeting the 

requirements of structural integrity and durability. 

VIT has been accomplished with common rail injection systems, as well as variable timing 

distributor pumps and solenoid-controlled unit injectors, but at a substantial cost. The fact that 

industry has moved in the direction of electronic control of injection is anecdotally supportive of 

the need for variable injection timing on SOI. Until now there has not been a simple, low-cost 

mechanical solution for older engines. Even so, it is difficult to find published data from 

manufacturers that justify this approach. 

The vehicle and equipment descriptions in the State of Texas grant solicitation (RGFA-03) 

indicate many of the engines concerned in affected counties are probably too old to be fitted with 

many newer technologies. The state government of Texas is soliciting a range of different 

technologies that can provide a worthwhile reduction in the NOx emissions of these older diesel 

engines. Older diesel engines emit many times the NOx emissions for a given power output than 

the newer engines. 

3. Project Objectives/Technical Approach 

The principal objective of this program was to demonstrate a feasible low-cost, retrofittable 

technology for enabling VIT in older diesel engines. This entailed showing that VIT will reduce 

NOx emissions with the best balance of cost, packaging and least impact on fuel consumption of 

the currently available choices. The proposed program included two phases whose objectives are 

listed below. A third phase was listed as being dependent on the successful completion of phase 

two, at which time an application for continuation funding would be lodged. 

MEC had developed an innovative system for variable valve actuation that provides independent 

timing for intake and exhaust valves for spark-ignited, cam-in-block engines [6]. The phasing 

needs of a diesel injection system are much narrower than those of variable valve timing in a 

spark-ignited engine, typically 6 - 10° crank compared to 30 – 50° crank. At the same time the 

contact stresses between the cam and roller lifter may be higher in diesel engines. This system 

allows the timing of the rollers on the injector-only cams to be varied while the valve timing is 

unaffected. The project as proposed initially would adapt this technology to fuel injection 

(versus valve) timing on four-stroke, cam-in-block diesel engines, focusing on selection of the 


engine with the highest overall opportunity of NOx reduction, based on numbers of engines in 

the field, duty cycle, power output, age. 

During the early stages of the project it became apparent that there were not sufficient numbers 

of suitable older diesel engines whose architecture was suited to this type of mechanical variable 

injection mechanism. The target engine became a two-stroke, supercharged, uniflow diesel 

engine as found in many older locomotives. Despite the change in engine architecture most of 

the remaining objectives of the project were applicable, except for the addition of the 

development of a new concept to provide mechanical VIT to this engine. 

With the target engine chosen the next objective was to provide design and analysis data of VIT 

components to fit this engine. In the original proposal it was suggested that at least two 

alternative packaging designs be proposed, based on previous experiences with fitting the (now 

inapplicable) design to four-stroke, spark-ignited engines. The new engine geometry provided 

the opportunity to design a VIT system that would be a simple drop-on to replace the stock 

valvetrain. Given the program was delayed in determining the target engine a single design was 

created for the retrofit to save further delay in the schedule. 

The new concept provided an additional potential benefit: mechanical variable valve timing 

(VVT) was simple to add to VIT. To make the most of this possibility the optional task of an 

engine simulation model became more critical to determine the range of authority required by 

both VIT and VVT. 

Initially the primary hardware objective was to deliver two completed ESPi VIT-equipped 

engines for testing. This objective was based on the selection of a typical six-cylinder trucksized 

engine. With the switch to a locomotive engine the objective was modified to encompass a 

section of one of these large engines to prove the concept. Four of sixteen cylinders of a 

locomotive engine were fitted with proof-of-concept hardware. This hardware was run to 

demonstrate its operation, and report on testing showing NOx emissions reductions of at least 

25% with engine testing, while documenting the effects on fuel economy and other emissions. 

3.1. Inclusion of Variable Valve Timing with Variable Injection Timing 

The primary aim of this project was to demonstrate a mechanically variable injection scheme to 

reduce engine-out NOx by a minimum of 25%. The development of the system reported here 

also offered the opportunity to vary valve timing as an enabler to VIT (via altering effective 

compression ratio) but also as a possible influence on in-cylinder work and pumping work, to 

affect fuel economy. 

The same mechanism for VIT allows for VVT, although the phase change range for VVT is 

higher than for VIT. The design issues required to make VIT work are identical for VVT, so 

incorporating both in the one design meant the addition of one actuator and the redesign of 

several (minor) components. 


4. Tasks 

The following list of phases and tasks was produced at the start of the project. 

• Phase 1: NOx aftertreatment alternatives, fuel economy consequences of heating exhaust 

gases, and potential SCR poisoning 

Task 1: NOx aftertreatment alternatives 

Task 2: Fuel economy effects of thermal regulation approaches 

Task 3: Engine simulation model of candidate engine to determine 

required range of authority for mechanical VIT system. Originally 

intended as optional task, but required after selection of locomotive 

engine. Amended to investigate VVT as well. 

• Phase 2: Construct proof-of-concept engine(s) and perform preliminary testing 

Task 1: Selection of candidate engine 

Task 2: Design of VIT (and VVT) system 

Task 3: Analysis of critical components 

Task 4: Fabrication of VIT and VVT hardware 

Task 5: Proof-of-concept system fit and function 

Task 6: Engine testing 

The modeling task (Phase1, Task 3) was not decided upon until Phase 2 was commenced. 

4.1. Phase 1 

4.1.1. Phase 1 Task 1 NOx Aftertreatment Alternatives 

4.1.1.1. Phase 1 Task 1 Objective 

The goal of this task was to outline the different alternatives available to engine manufacturers to 

reduce NOx levels from diesel engines. 

4.1.1.2. Phase 1 Task 1 Technical Details 

The report included in-cylinder and aftertreatment approaches used by many researchers 

investigating methods to reduce NOx levels. Emphasis was given to the in-cylinder effects of 

variable injection timing, as that was one of the main thrusts of project N-12. 

SCR systems appear to offer the best option of NOx reduction, with the possibility of improved 

fuel consumption due to being able to advance timing then cope with the higher NOx with the 

aftertreatment system. 


4.1.1.3. Phase 1 Task 1 Major Issues/Critical Paths 

This task was a literature study. There were no major issues or critical paths. 

4.1.1.4. Phase 1 Task 1 Deliverables 

The deliverable from this task is the report given in Appendix 1. 

4.1.2. Task 2 VIT Compared to Aftertreatment in Reducing NOx 


The goal of this task was to investigate and catalog the comparable effects on fuel economy of 

exhaust aftertreatment systems for NOx reduction, such as SCR and LNT. 


Most approaches to reducing NOx have a negative impact on fuel economy. This task focused 

on results in the literature that correlated NOx reduction to fuel economy penalties. 

None. 



The deliverable from this task is the report given in Appendix 1. 

4.1.3. Task 3 Engine Simulation Predictions 


The goal of this task was to construct an engine simulation model to investigate the effects of 

variable injection timing relative to a fixed timing change. This task was originally optional with 

the possible implementation of the eccentric sleeve phasing system proposed for a four-stroke 


engine. However with the change in engine selection to a two-stroke, Roots-blown locomotive 

engine it was felt that this step was essential. In addition to the estimation of NOx reduction 

with injection timing retard, the model allowed investigation into the effects on fuel economy of 

variable valve timing as well. 


A simulation model of the Roots-blown EMD 645 engine was constructed in collaboration with 

engineers at SwRI. The model was calibrated at three notch settings, notches 2, 5 and 8, the 

extent of the test data available for such calibration. These engines normally run from idle 

through notch eight. Having an engine simulation model allowed the opportunity of 

investigating the effects of variable valve timing, an area of little research for diesel engines, 

especially for two-strokes. The engine simulation varied injection timing and valve timing 

through a broad range to determine optimum timing settings for achieving a NOx reduction of 

25%, and minimizing the penalty on fuel economy. 

The GT Power model of the 16-cylinder EMD 645 engine is shown in Figure 5. 

Figure 5: GT Power map of Roots-blown EMD 16-645 engine 

NOx reduction was estimated with the model by retarding SOI up to 7° at each notch setting. 

Fuel economy effects were estimated by varying the valve timing up to 18° each side of the stock 


valve timing, and altering the duration from 12% less than stock to 4% more. Schematic 

representations of the changes in valve timing and lift/duration are shown in plots of crank angle 

versus valve lift in Figure 6 and Figure 7. 

Figure 6: Phasing of valve event with VVT 

Figure 7: Valve lift and duration change 

Fuel economy improvements were the most dramatic at notch 2 of the three sets of test points 

investigated. Figure 8 gives an explanation for the various components of the modeling results 

for changing SOI and valve lift, phase and duration. 


Figure 8: Explanation of modeling results for variation in SOI and valve lift, duration and 

phase 

As SOI is retarded the NOx levels drop at a given valve timing, as shown in Figure 8. The effect 

on fuel economy is does not always move monotonically however. Figure 9, Figure 10, Figure 

11, Figure 12 and Figure 13 show plots for five different valve durations (and their 

corresponding maximum lifts) at notch 2. The location of minimum BSFC and BSNOx is shown 

on each plot. 


Figure 9: BSFC and BSNOx at notch 2 with 88% of stock engine valve duration 







At notch 5 the fuel consumption and NOx changes were subtle with valve duration and timing. The 

following plots show how these parameters changed over a smaller range of valve duration. 












The following plots at notch 8 show how dramatic the change in location of the BSFC minimum 

can be with duration, while showing a more subtle shift in the BSNOx levels with valve timing. 









One outcome of this study was the observation that optimal fuel consumption occurred with later 

valve timing at lower notch settings. This is shown in Figure 26. 

EV Centerline (deg ATDC) 

184 

180 

176 

172 

168 

164 

Exhaust Valve Duration & Centerline at Minimum BSFC 

Notch 2 

Notch 5 

Notch 8 

160 

88% 92% 96% 100% 104% 

Exhaust Valve Duration (% of stock) 

Figure 26: Effect of exhaust valve timing and duration on location of minimum BSFC 



This task became key after the decision was made to pursue VIT and VVT on a locomotive 

engine. Prior to designing and fabricating hardware for test purposes an estimate of the extent of 

injection and valve timing changes required was desirable. Without this information a viable 

system may have been designed, built and tested only to find out that the range of timing 

variability, and the center of that timing range, was poorly selected for the aims of the project. 

The modeling effort became critical to allow proper selection of timing variation for the 

mechanical system of injection and valve timing change. 


The deliverables from this task include recommendations for the following: 

• Amount of injection timing retard required to reduce NOx emissions by 25% from the 

stock engine at notch settings for which validation data are available for the stock engine 

• The change in valve timing, lift and duration for these notch settings and for a 25% NOx 

reduction at which the fuel consumption was minimized. 

One critical issue with a drop-on replacement mechanical VIT/VVT system is whether the 

camshafts must be replaced or modified. For the proof-of-concept evaluation of this technology 

a decision was made to retain the stock camshafts and their lobes. Accordingly the following 

tables show the recommended changes in SOI timing and valve timing to achieve a 25% 

reduction in NOx emissions, with the optimal fuel economy and the stock valve duration. 

For reference, Table 1 shows the amount of SOI retard predicted by the model to produce a 25% 

NOx reduction at each of the three notch settings. Valve timing was kept stock for this study. 

Table 1: SOI required to achieve 25% NOx reduction and the effect on BSFC at stock valve 

timing 

Notch Change in SOI 

(from stock) 

Exhaust Centerline 

Variation from Stock 

BSFC Improvement 

2 -7.7° 0° -1.61% 

5 -6.5° 0° -1.22% 

8 -5.5° 0° -1.01% 

Table 2 shows the effect of allowing valve timing to change with injection timing to find the 

25% NOx reduction settings, and the effect on fuel consumption. 


Table 2: SOI and valve timing changes required to achieve 25% NOx reduction and to 

minimize the effect on BSFC 

Notch Change in SOI Exhaust Centerline BSFC Improvement 

(from stock) Variation from Stock 

2 -5.0° 15° retard +2.76% 

5 -6.5° 0° -0.98% 

8 -5.5° 3° advance -0.92% 

Table 3 shows the anticipated improvement in fuel consumption of adding VVT to a strategy of 

VIT only to reduce NOx by 25% on the Roots-blown EMD 645 engine. 

Table 3: Difference between SOI only versus SOI plus variable valve timing to achieve 25% 

NOx reduction and the effect on BSFC 

4.2. Phase 2 

Notch BSFC 

Improvement 

with VVT 

2 4.30% 

5 0.23% 

8 0.08% 

4.2.1. Task 1 Selection of Candidate Engine 


The goal of this task was to select an appropriate candidate engine with the highest overall 

opportunity for NOx reduction based on the numbers of engines in the field, their duty cycle, 

power output and age. 


Initial engine choices focused on older diesel engines found in a variety of equipment. Engine 

geometries favoring the ESPi system were sought out. Many of these engines were no longer in 

service, and the commercial opportunities were limited. The search was broadened to include 

other engine geometries, including locomotive engines. 

Engines from Deere and Deutz were investigated for four-stroke, truck-sized engines. While the 

basic engine geometry was suitable, the numbers of engines in the field was discouraging, so 


these choices were eliminated. The GE 7FDL locomotive engine was looked at, but the low 

numbers in the field made this choice unattractive. 

Two-stroke engines from Detroit Diesel and EMD were investigated. There are numerous older 

Detroit Diesel engines that might be eligible for retrofit, but the economics of a cost-effective 

system were questionable. Finally, the EMD two-stroke locomotive engine seemed the most 

attractive choice for a host of reasons. In particular the Roots-blown EMD 645 engine was a 

good choice: there are over 3,000 of them in service in the United States; many of these engines 

are over thirty years old; they are used for switching duty, which means most, if not all, of their 

time is spent in a particular geographic region. In addition this choice was the most costeffective 

engine for the purposes of validating the concepts of VIT and VVT in a preliminary test 

program. 


One issue was the cost of developing a proof-of-concept engine on a large, 16-cylinder 

locomotive engine. There were risks in retrofitting an engine with prototype hardware, so the 

decision was made to limit engine testing to four of 16 cylinders. With the Roots-blown engine 

these four cylinders could be isolated from the remainder of the engine so that emissions and fuel 

economy could be compared to the stock engine. (The turbocharged engine would not allow this 

isolation because of the need for the exhaust gases to pass through the turbocharger.) 


The deliverable for this task was a recommendation for the candidate engine on which to retrofit 

a mechanical VIT and VVT system. That engine is the Roots-blown EMD 645 locomotive 

engine. This engine was first delivered into service in 1965, and was replaced by the newer 710 

model in 1984. 

4.2.2. Phase 2 Task 2 Design of a VIT/VVT System to Retrofit onto the Candidate 

Engine 


The goal of this task was to design a suitable VIT and VVT system to apply to the candidate 

engine. A proof-of-concept system was the goal at this stage. 


4.2.2.2. 

The EMDD 

645 engine e has an oveerhead 

camshhaft 

layout wwith 

center ppivot 

rocker aarms. 

Varyiing 

the timinng 

of the inje ectors mechaanically 

mighht 

be accompplished 

in seeveral 

differeent 

ways, 

includingg: 

• Phase 

the entire 

camshaftt 

in a manner 

similar to pphasing 

systtems 

used in automotive 

appplications 

• Phase 

each in njector lobe oonly 

• Phase 

the foll lower of eacch 

rocker armm 

on the camm 

The first approach mentioned, m phhasing 

the enntire 

camshaaft, 

was undeesirable 

as thhis 

would givve 

the same timing chan nge for the exhaust 

valvees 

as the injeectors. 

There 

are few opperating 

poinnts 

where thee 

valve and injection timming 

require identical phhasing. 

The secoond 

approach h would requuire 

a lobe phhasing 

mechhanism 

on eaach 

injector llobe 

(for 

injection only) and se eparate movving 

lobes for 

the exhausst 

valves. Thhe 

close proxximity 

of all 

three lobes 

on each cylinder c wouuld 

make thiss 

task challennging, 

and thhe 

length of f the camshafft 

sections wwould 

add to o the packagging 

difficultty. 

The thirdd 

approach was w adopted, and each roocker 

arm waas 

to be movved 

through aan 

angle 

corresponnding 

to the amount of pphasing 

channge 

required. 

(Recommeendations 

froom 

modelingg 

work would 

be used to determinee 

the range rrequired 

for iinjection 

andd 

valve timinng.) 

Phasing oof 

each rock ker arm requiired 

determining 

the movement 

pathh 

of the pivott 

shaft centeer 

as 

the rockeer 

arm was moved m from a limit of maaximum 

advvanced 

timinng 

to maximuum 

retarded 

timing. OOnce 

determ mined the suppport 

structuure 

for allowing 

this movvement 

couldd 

be designeed. 

Figure 277 

shows view ws of one rocker 

arm in the advanced, 

centered aand 

retardedd 

timing 

positionss. 

Figuure 

27: Valv ve rocker arrm 

positions 

for advanced, 

centereed 

and retarrded 

timingg 

A schematic 

of the ov verall VIT/VVVT 

mechannism 

on the hhead 

is showwn 

in Figure 28. 

Final Repoort 


Phase 2 Taask 

2 Techniical 

Details 

Paage 

30

Figure 28: Model of EMD 645 head with VIT/VVT hardware incorporated. Cap that 

controls movement path of rocker arms shown as translucent. 

For comparison Figure 29 shows the hardware installed on the test engine. 

Figure 29: VIT/VVT hardware installed on EMD 645 engine 


The support cap to control the movement path of the rocker arms was designed to fit beneath the 

existing rocker covers of the engine. A manual adjustment mechanism was chosen for this 

proof-of-concept design. 


A number of technical issues had to be overcome in the design process. Movement of the rocker 

arms independently required the rocker shaft length be reduced to fit each rocker arm only. Thus 

there were three independent rocker arm segments. 

These technical issues included: 

• Delivery of oil to the rocker shaft sections, and then to the rocker arms 

• Delivery of oil to the valve bridges 

• Force transfer between the rocker arm tips and the valve bridges 

• Force transfer between the pivot shaft sections to the supporting cap 

• Restraint of the valve bridge to maintain orientation both rotationally about an axis 

parallel with the engine cylinder and in a path parallel to the two valve stems actuated by 

each bridge 

• Simple adjustment of timing changes. 


The deliverable for this task was a set of detailed drawings that would allow fabrication of 

hardware for the retrofit of the VIT/VVT system onto an EMD 645 engine. 

Drawings of all the components used in the project are available upon request. 

4.2.3. Phase 2 Task 3 Analysis of critical components 

4.2.3.1. Phase 2 Task 3 Objectives 

The goals of this task were to: 

• Ensure the limits of phasing of the rocker arms did not cause the pressure angles on the 

rocker arm followers to become problematic 

• Determine the peak forces applied to the rocker arms 

• Use these forces to investigate the change in stresses of the modified rocker arms 



Phasing of the exhaust valves was selected as ±8° from the stock setting. GT Power was used to 

check that the phasing of the rocker arm did not cause too large a change in the pressure angle. 

The pressure angle over valve operation is shown in Figure 30. The pressure angle maximum is 

approximately 17°. 

Figure 30: Pressure angle for roller-cam interface of valve rocker arm in centered position 

Plots for pressure angles at the phasing extremes are shown in Figure 31 and Figure 32. In each 

of these cases the extreme of pressure angle are 26°, which is acceptable. 


Figure 31: Pressure angle for roller-cam interface of valve rocker arm in 8° retarded 

position 

Figure 32: Pressure angle for roller-cam interface of valve rocker arm in 8° advanced 

position 

The maximum load on the rocker arm tip is shown in Figure 33 


Force (lb) 

3500 

3000 

2500 

2000 

1500 

100 

120 

Figure 33 3: Forces onn 

rocker armm 

tip in centtered 

positioon 

at rated speed 

Valvetraiin 

forces we ere estimatedd 

to create mmodels 

for finnite 

element analysis of tthe 

valve roccker 

arm. Thee 

stock rocke er arm was mmodified 

to aallow 

the coonstraining 

yyokes 

(holdinng 

the shorteened 

pivot shaaft 

section) to o fit over thee 

pivot shaftt 

section. Thhe 

stock and thinned geoometries 

are 

shown inn 

Figure 34. 

Figure 334: 

Valve ro ocker arm geeometries 

uused 

for FEAA. 

Stocker rocker armm 

on left, thinnned 

rockerr 

arm on rigght 

Final Repoort 


Roocker 

AArm 

Tip Forcess 

140 

160 

Cam anggle 

180 2000 

2200240 

Paage 

35

Peak loadds 

on the val lve rocker arrm 

were estiimated 

from a valvetrainn 

analysis chheck 

in GT 

Power. TThe 

same loa ad was appliied 

to the stoock 

and moddified 

rockerr 

arms. 

The equivalent 

(Von Mises) stressses 

for the sstock 

rockerr 

arm are shoown 

in Figurre 

35. 

The equivalent 

(Von Mises) stressses 

for the mmodified 

roccker 

arm are shown in Fiigure 

36. 

Final Repoort 


Figure F 35: VVon 

Mises stresses 

in thhe 

stock roccker 

arm 

Paage 

36

The diffeerences 

in pe erformance oof 

the two geeometries 

is summarizedd 

in Table 4. 

Table 4: Summary of FEA on vvalve 

rockerr 

arm 

Maximuum 

equivalen nt stress 559,139 

psi 

Maximuum 

deformation 

00.0104” 

Given thee 

variations in casting beetween 

rockker 

arm sampples, 

the variiations 

in streesses 

and 

deformattions 

were vi iewed as beiing 

acceptabble 

for normaal 

engine opeeration. 

None. 

4.2.3.3. 

4.2.3.4. 

Final Repoort 


Fig gure 36: Voon 

Mises strresses 

in the modified roocker 

arm 

SStock 

rockeer 

arm MModified 

rocker 

arm CChange 

Phase 2 Taask 

3 Major Issues/Critiical 

Paths 

Phase 2 Taask 

3 Deliverables 

611,752 

psi 

0. 0111” 

44.4% 

66.7% 

Paage 

37

The deliverables for this task are the results of the analyses carried out, as reported above. The 

modes of operation of the phase change hardware are within acceptable operating limits of the 

engine. 

4.2.4. Phase 2 Task 4 Fabrication of VIT and VVT hardware 


The goal of this task was to fabricate all the required hardware to retrofit four cylinders of a 

Roots-blown EMD 645 engine with VIT and VVT hardware. 


Detailed drawings were given to several machine shops to fabricate components from specified 

materials. Some of these components underwent heat treatment where required for a hard 

surface finish. 

A number of stock components were modified to perform their function. These included: 

• Valve and injector rocker arms 

• Valve bridges 

• Pivot shafts 

A modified injector rocker arms is shown in Figure 37, along with the shortened pivot shaft 

section and the yoke that both transfers forces to the cap, and controls the movement of the 

rocker arm. 


Figure 37: Modified injector rocker arm with shortened pivot shaft section and control 

yoke. Oil delivery groove visible in center section of yoke. 

The control caps were fabricated from 8620, and case hardened. Legs for these caps were made 

separately to allow machining of certain surfaces. Oil passages were included to deliver oil to 

the separate pivot shaft sections. The underside of the control cap is shown in Figure 38. The oil 

delivery holes are evident in the curved control surfaces. 

Figure 38: Underside of control cap. Legs to cap not included here. 


Design information was not available from the engine manufacturer. Consequently parts 

measurements were used to estimate the locations and sizes of components. With cast parts, 

such as the rocker arms, it was difficult to know the envelope allowances that should be made. 



The deliverables for this task were the modified an fabricated components that would be used to 

convert four cylinders of an EMD 645 engine to mechanical VIT and VVT operation, with 

manual control of timing change. 

4.2.5. Phase 2 Task 5 ProofofConcept System Fabrication 


The goal of this task was to assemble four cylinders of a sixteen-cylinder EMD 645 engine with 

the VIT/VVT mechanism and ensure correct operation, range of authority and adjustability. 


Initial work involved fitting a single cylinder with the VIT/VVT hardware. This process allowed 

checking of clearances, necessary as design information from the manufacturer was not 

available. 

Several instances of interference between the rocker arms and the supporting cap were 

encountered. Witness marks were used to identify the contact areas, with some examples shown 

in Figure 39 and Figure 40. 

Figure 39: Witness mark on rocker arm after contact with cap 


Figure 40: Contact point between yoke and rocker arm 

The control caps holding the rocker arms and adjustment mechanism showed signs of the rocker 

arms contacting in several spots. Figure 41 shows where the injector rocker arm was making 

contact with the cap. 

Figure 41: Cap area clearanced to ensure proper range of motion of injector rocker arm 

Several iterations of minor modifications were required to provide the appropriate clearance for 

the VIT/VVT mechanism as it operated through its full range. During this process the 

assemblies were installed on engine for checking of fit and function. Figure 42 shows the four 

assemblies installed on-engine, and one of the two rocker cover lids is closed. All hardware fits 

under the rocker covers. 


Figure 42: VIT/VVT hardware fits under the valve covers on the engine 


The lack of detailed drawings from the engine manufacturer meant that additional time was spent 

in measuring components to create accurate drawings. Several of the components were castings, 

and the draft on these components was not always estimated with enough of a tolerance 

envelope. As a consequence there was inadequate clearance on a number of components. None 

of this prevented the program from being successful, but it certainly added weeks or months to 

the overall timetable. 

A second issue was the lack of availability of the test cell at SwRI. Another TERC program was 

being run on the test engine, and this program ran over schedule. Testing began several months 

later than initially anticipated. 


The deliverables for this task were four complete cylinder sets of VIT/VVT hardware, with 

manual adjustment capability, delivered to SwRI for installation on a Roots-blown EMD 645 

engine. 


4.2.6. Phase 2 Task 6 Engine Testing 


The primary goal for the testing phase was to run the Roots-blown EMD 645 engine through its 

operating range with a broad matrix of SOI timing and valve timing, and to measure NOx (and 

other) emissions and fuel economy. 

A secondary goal was to gather time and experience with the VIT/VVT hardware during engine 

operation. 


4.2.6.2.1. Test Engine Setup at SwRI 

Four of the sixteen cylinders on a Roots-blown EMD 645 engine were used for test measurements. 

Measurements of emissions and fuel economy were made on the same four cylinders, with separate fuel 

systems and emissions measurement on those four cylinders. Figure 43 shows the exhaust system with 

the two separate sections. Cylinders 3 – 8 and 11 – 16 are connected to the exhaust section to the left, and 

cylinders 1, 2, 9 and 10 to the separate system on the right, leading to the emissions measurement 

equipment. 

Figure 43: Isolated exhaust system section on four of sixteen cylinders of EMD 645 

The emissions equipment for these four cylinders is shown from the other side of the engine in 

Figure 44. 


Figure 44: Exhaust emissions equipment on four cylinders of sixteen cylinder EMD 645 

The fuel system was isolated between the four test cylinders and the remaining sixteen. This is 

shown schematically in Figure 45. 


Figure 445: 

Schemat tic of fuel deelivery 

systeem 

to test cyylinders 

witth 

separate ccircuit 

Several diifferent 

Micro oMotion corioolis 

meters wwere 

used to mmeasure 

the fuuel 

mass flow rate into the 

separate ffuel 

system. Fuel F flow is ccontrolled 

by a float systemm, 

and the fueel 

demand of tthe 

isolated foour 

cylinders is measured by b the MicroMMotion(s) 

intoo 

the settling tank, part of the MicroMootion 

Fuel Sysstem. 

The methood 

of splitting g the fuel deliivery 

and retuurn 

lines is shhown 

in Figurre 

46. 

FFigure 

46: Fuel F rails shhowing 

separation 

of test 

cylinderss 

from rest oof 

engine 

Final Repoort 


Paage 

45

4.2.6.2.2. Test Procedure to Evaluate Performance of VIT/VVT Hardware 

Cost limitations for converting the valvetrain of the EMD 645 engine constrained the project to 

testing only four of sixteen cylinders. Further, achieving a 5.5° cam retard on the test cylinders 

resulted in having three different SOI and valve timing settings across the engine. Cylinders 1 – 

4 and 9 - 12 had this 5.5° retard, but half of those cylinders (1, 2, 9 and 10) had the capability of 

adjusting both injection and valve timing (with the exhaust system modified to capture the 

emissions from them and the fuel system modified to measure fuel flow to them.) Meantime 

cylinders 5 – 8 and 13 – 16 had stock injection and valve timing. 

As a consequence of the varied timing across the engine the testing had to be approached 

differently from usual full-engine tests. Normally emissions and fuel economy would be 

normalized on a brake specific basis. However in this case the power output of the cylinders 

would vary between the three different groups of cylinders. To avoid complications with 

normalizing by brake power, indicated power was used as the basis for comparison. High-speed 

pressure transducers in cylinders 9 and 10 were used to calculate indicated power. 

The engine was operated several times over the range of notch settings (from idle to notch 8) in 

the stock configuration to produce a baseline for the modified cylinders. 

The modified engine was tested across a matrix of test points, from idle to notch 6, and the 

emissions and fuel consumption were compared to the stock engine. (Notches 7 and 8 were not 

tested as they constitute only 1% of the switcher duty cycle.) 

The following ??? shows the matrix of injection and valve timing that was used to evaluate the 

VIT/VVT system across engine operation. 

TABLE OF SOI AND VALVE TIMING TO BE INSERTED HERE 

XXX 

XXX 

XXX 

4.2.6.2.3. Results of Baseline Testing 

4.2.6.2.4. Results of VIT/VVT Testing 

4.2.6.2.5. Comparisons Between Stock and Modified Engine Operation 


5. Finance and Schedule 

The monthly expenditures for project N-16 are shown in Figure 47. 

$120,000 

$100,000 

$80,000 

$60,000 

$40,000 

$20,000 

$0 

The cumulative costs are shown in Figure 48. 

N‐12 Monthly Project Costs 

Monthly project cost Monthly NTRD Monthly cost share 

Figure 47: Monthly project costs for N-12 


$800,000 

$700,000 

$600,000 

$500,000 

$400,000 

$300,000 

$200,000 

$100,000 

$0 

Figure 48: Cumulative project costs for N-16 

The initial contract period for project N-12 was from 11/28/2006 to 8/31/2007. Several 

extensions were granted. They were: 

• Grant Amendment #1: Extension: to 12/31/2007 






There were several revisions to the budget. These included: 

• January 2009 

o Budget increase for Contractual costs 

• March 2009 

o Budgeted items under Travel and Supplies moved to Personnel Costs. No change 

to budget total. 

• May 2009 

o Remaining budgeted balances transferred to Personnel Costs 

Explanatory notes for budget changes: 

N‐12 Cumulative Project Costs 

Monthly project cost Monthly NTRD Monthly cost share 

• January 2009: change from anticipated truck-size six-cylinder engine to locomotive 

sixteen-cylinder engine 

• March – May 2009: activity increase due to testing at SwRI 


• May 2009 – NTRD budgeted amount depleted, and costs were absorbed by cost share 


6. Discussion/Observations 

6.1. Objectives vs. Results 

The objective of this project was to demonstrate a feasible, cost-effective mechanical system to 

vary injection and valve timing to achieve a reduction in NOx emissions exceeding 25%. 

Results from testing have shown that the overall NOx reductions over the switcher duty cycle 

amounted to XXX%. In addition the impact on fuel economy was XXX. 

The test engine operated for XXX hours with the VIT/VVT hardware installed. Aside from one 

minor component failure the system proved to be quite durable. It is known that several 

components should be redesigned to improve the robustness of the system, and to reduce its cost. 

6.2. Critical Issues 

Improve the durability and lower the cost of the hardware. 

Implement a fully automated adjustment mechanism. 

6.3. Technical and Commercial Viability of the Proposed Approach 

It is obvious from the test results that the combination of variable injection timing and variable 

valve timing produces desirable results in both NOx emissions and fuel economy. 

Durability of the system still requires units operating in the field, but if the cost is reasonable this 

system should be very attractive to locomotive owners to reduce emissions. This approach 

should have a positive payback schedule, quite different from aftertreatment systems that 

usually do not have a reduction in operating costs. 

6.4. Scope for Future Work 

An application for continuation funding has been submitted to HARC. There is strong interest 

from railroad companies in the technology, and any further work will be watched with great 

interest. 


7. Intellectual Properties/Publications/Presentations 

There are no intellectual property developments as a result of this project. 

MEC is planning to prepare a paper for publication at the ASME Internal Combustion Engine 

conference in Lucerne, Switzerland, in September 2009. 

MEC made a presentation at a HARC workshop in Houston in February of 2008. 


8. Summary/Conclusions 

The following conclusions may be drawn from the data presented: 

XXX 

1. XXX 

2. XXX 

9. Acknowledgements 

The preparation of this report is based on work funded in part by the State of Texas through a 

grant from the Texas Environmental Research Consortium with funding provided by the Texas 

Commission on Environmental Quality. 

The advice, efforts and experience of the personnel at SwRI under Steve Fritz were greatly 

appreciated. John Hedrick at SwRI worked tirelessly to complete the test process, and ensure 

consistent and complete results from testing at SwRI. The experience and efforts of Ford 

Phillips of SwRI were essential in creating and validating the engine model used for the 

simulation work. 


10. References 

1. http://www.ci.austin.tx.us/airquality/ozone.htm, All About Ozone 

2. Engine Design for Low Emissions, DieselNet, 2003 

3. Bosch, 2004, Diesel-Engine Management, Third Edition, Robert Bosch GmbH 

4. Khair, K. M., “Progress in Diesel Engine Emissions Control,” ASME paper 92- 

ICE-14 

5. Bosch, 1994. "Diesel Fuel Injection", Robert Bosch GmbH 

6. M. B. Riley, P.Troxler, W. Hull, B. Willson, “Application of a Simple Mechanical 

Phasing Mechanism for Independent Adjustment of Valves in a Pushrod Engine,” 

SAE Paper 2003-01-0037, 2003 


11. Appendices 

11.1. Appendix 1: Comparison of NOx reduction technologies 



Area of Interest: Development and Testing of Engine Upgrade/Retrofit Kit for 

Existing Engines 



Suite 238 



Telephone: (970) 221-9600 / (970) 218-0141 

Fax: (970) 221-3863 


Project Title: A Novel Method of Mechanical Variable Injection Timing to Reduce 

NOx Emissions 

Date: January 11, 2007 

Phase 1: Benefits of Variable Injection Timing 

N-12 Modeling Report on NOx Reduction of EMD 645 engine 1

Benefits of Variable Injection Timing 

When emissions standards for heavy-duty diesel engine manufacturers tightened in 1991 the 

industry made the transition from mechanical, fixed injection timing, meaning fixed start of 

injection (SOI), to more expensive electronically varied SOI. This report seeks to summarize 

research work conducted both before and after that time to quantify the benefits of variable 

injection timing (VIT.) 

There are numerous studies that report the effects of variable SOI [1, 2, 3, 4, 5]. The studies 

cited from 1981 to 2002, and generally measure the effect of SOI change on fuel consumption 

and NOx emissions. 

Locomotive Application 

In [1] the authors studied the emissions and fuel economy effects on locomotive engines. Of 

particular interest is the GE 7FDL locomotive engine whose unit pump injection system is a 

good candidate for MEC’s eccentric sleeve phasing (ESPi) system for variable SOI. These 

engines are normally tested over an eight-point duty cycle, but to reduce total testing time their 

timing sweeps for determining the effects on fuel economy and emissions were conducted at 

three points. The points chosen were at idle, notch 5 and notch 8. Results quoted are weighted 

with 50% at the idle condition, and 25% each to the other two points. Extrapolating from the 

data in the paper they indicate that a reduction of 25% in NOx would require the SOI to be 

retarded by just over 6° crank, with corresponding drop in fuel economy of just over 3%. 

Midrange 

The engine tested in [2] was a 9.5 L truck engine certified to Euro 2 emissions. The aim of the 

study was to determine the emissions from different diesel fuel formulations, however by testing 

at the stock, fixed timing, and one other setting with constant NOx output, useful extrapolations 

could be made on their reference fuel. Testing was conducted over 13-mode European cycle, 

again averaging the results. One of the fuels used represented a low-sulfur European fuel, and 

results using this fuel are referenced. 

The engine used a fixed SOI of 10° BTDC for the baseline tests. SOI was then altered to 

produce a fixed NOx level of 6.3 g/kW-hr, or a reduction of 7%. While extrapolating these 

results to a 25% reduction in NOx may not be linear it points to fuel consumption worsening by 

approximately 4%, with retarding the SOI by some 5° crank. 

Initially it appears that it is possible to reduce NOx by 25%, simply by retarding SOI by an 

average of 5° to 6° crank, but the penalty is paid in fuel economy. In most references [1, 2, 4, 5] 

data reported are averaged over some sort of representative cycle, disguising the effects of SOI 

change at different speeds and loads. In [3] however, specific examples are given of these 

effects, as shown in Figure 1 below. 


Figure 1: Test results reported in [3] for BSFC vs. SOI at different speeds and loads 

Heavy Duty 


application. Data for 25%, 50% and 100% load were taken at 1130 and 1420 rpm. Like all other 

studies reported they show that advancing SOI at all speeds and loads results in increasing NOx 

output as shown in Figure 2 below. The effect on fuel economy is more varied. In this case it is 

obvious from Figure 1 that the location of optimal timing for fuel consumption shifts 

significantly with load, and somewhat with speed. Further, at some load conditions the effect on 

fuel consumption appears flat over a wide range of timing, allowing timing selection to be made 

to minimize NOx emissions. 

Figure 2: Test results reported in [3] for BSNOx vs. SOI at different speeds and loads 

Assuming that static SOI would occur at 16° BTDC it is possible to estimate the changes in 

BSFC, BSNOx and, to a certain extent, particulates. (The scale chosen for the particulate plots 

made it difficult to determine changes in emissions with any degree of accuracy.) 


For the case of full load at 1130 rpm, the NOx level was 12 g/kW-hr. Reducing the NOx level to 

9 g/kW-hr required a 7.5° timing retard, and fuel consumption worsened by 1.5%. However at 

25% load the initial NOx level was 31 g/kW-hr. When this was reduced by 25% to 23 g/kW-hr 

the timing retard was 4°, and fuel consumption improved by 1.6%. In this case it was more 

beneficial to retard the timing further, by 10°, which gave an improvement in fuel consumption 

of almost 4%. 

With different SOI values feasible at different speeds and loads it may be possible to reduce 

overall NOx emissions by the 25% target required while having little impact, if any, on fuel 

consumption. As an example the 1420 rpm data could be considered at full load. In Figure 1 it 

is apparent that the fuel consumption varies very little between 14° BTDC and 11° BTDC. 

(There is no data at the 16° BTDC point.) However the NOx level falls off by 12%. Depending 

on the duty cycle of the engine concerned this may be a suitable trade-off between NOx 

emissions and fuel economy over the entire cycle while the overall target of 25% is achieved. 

From all the data found so far in the literature it appears that preserving fuel economy is not 

feasible with a fixed SOI retard. 

Mechanical Injector Design Considerations 

Dual and Single Helix Pumps 

The data in Figure 2 show that NOx increases significantly as load decreases with fixed SOI 

timing. This is due to the excess air in unthrottled diesel engines at part load. To counteract this 

tendency, as NOx emissions regulation began, many non-electronic (or mechanical-only) fuel 

systems changed to modified designs known as “dual helix” plungers to retard SOI timing as 

fueling decreases. Mechanical-only systems control SOI and how much fuel is injected by 

machined cuts in the outer cylindrical surface of the injection plunger. As the injection plunger 

begins to move upward, fuel flows through te cut plunger passages into a “spill port” in the pump 

barrel until the lower edge of the cut is reached, which closes the port, and traps fuel in the 

pumping volume. This trapped volume is then pressurized by the plunger upward motion for 

injection. End of injection (EOI) occurs when another cut in the plunger connected to the 

prssuirzed injection volume reaches the spill port and releases the fuel pressure. A “single helix” 

plunger has a horizontal edge cut for (fixed timing) SOI, and regulates the amount of fuel 

injected by rotating the plunger so that a helical cut ends injection, with theamount injected a 

function of the distance between the SOI horizontal cut and the EOI helical cut at the spill port 

position. A “dual helix” plunger hasa second helical edge cut (instead of horizontal) for SOI so 

that as the plunger is rotated to regulate fuel quantity, the SOI timing is also modified. 

SOI Lag Due to Line Length 

Although dual helix plunger systems have much less variation in NOx versus engine load, the 

SOI timing is still a direct function of the amount of fuel injected an does not change with engine 

speed. With pump/line/nozzle (PLN) systems, using either a single multicylinder inline pump 

assembly, or several separated single cylinder unit pumps, there is still a significant delay 

between the beginning of an injection pulse at the pump and the resulting pulse reaching the 

injector tip, due to the speed of sound in the fuel and the distance along the length of the 

injection line and through the injector. These delays in each line and nozzle are nearly constant 

in absolute time (seconds), meaning that the delay in engine crank angle (degrees) varies with 


engine speed. Thus SOI timing retards as speed is increased. For example, for a 720 mm line 

length, the delay can increase from 2.6 deg at 800 RPM to 7.2 deg at 2200 RPM, causing a 5.6 

deg retard in SOI at 2200 vs. 800. This runs opposite to the desired trend in SOI versus speed, 

where for constant BSNOx, SOI timing is usually advanced as engine speed increases. 

Resulting Compromises in SOI Timing 

Thus even with a dual helix system, the phasing of the injection pump and resulting SOI timings 

are usually limited by one or only a few speed/load regions at which the highest NOx is 

produced, usually at the lower speed and high load ranges. With a single helix system, the 

phasing is often limited by the very high NOx lower speed and the lower load ranges. All other 

points then are not optimized in SOI timing for the best BSNOx vs. BSFC tradeoff. This results 

in higher overall fuel consumption throughout the full speed/load range, which is magnified if 

the application duty cycle requires significant amounts of time in the higher speed range. With 

VIT, the SOI timings can be independently tailored so that in the highest NOx regions, SOI 

timing is retarded, and in the lower NOx regions, SOI timing is advanced. Thus overall NOx can 

be reduced without a significant penalty in fuel consumption, and even sometimes an 

improvement, depending on the application duty cycle. 

Summary statement 

Fixed retard of SOI for NOx reduction of 25% results in a fuel economy penalty of 3 – 4%. VIT 

can achieve the same level of NOx reduction with a fuel economy penalty that is much lower, 

and may sometimes even be an improvement, depending on the duty cycle. 

EFI Conversion Cost Estimates 

Finding suitable cost information for comparison purposes has been difficult. Some information 

has been found on the difference in cost between mechanical injection systems and their 

subsequent model electronic versions, and will be summarized here. Some of this information 

has been provided through personal contacts, and should be regarded as approximate. Other 

numbers are for retail systems that may be purchased through distributors. However there are no 

readily available cost numbers that allow direct costing of converting existing mechanical 

injection systems to electronically controlled, fully variable SOI timing systems. 

The initial cost information is for replacing a mechanical in-line pump for 6-cylinder heavy-duty 

diesel engines with an electronically controlled pump. This comparison is made difficult by the 

difference in architecture between this style of pump, and the MEC ESPi system which is 

intended for applications using unit pumps. 

The mechanical in-line pump units are estimated to cost $1,000 to $1,200 to the engine 

manufacturer. A replacement electronically controlled pump (for varying the SOI) is estimated 

to cost $2,200. (Note that this cost comparison assumes that a direct replacement pump is 

available for the particular engine under consideration. If a generic electronic pump replaces and 

existing tailored unit the costs are certain to be considerably higher.) The estimated OEM cost of 

the appropriate engine control module (ECM) is $400 to $450. If the markup for retail sale is in 

the range of 50 – 100%, then the additional cost of variable SOI to the end customer is in the 

range of $2,100 to $3,300 for the components alone for a six-cylinder, in-line diesel engine. The 


cost of labor for removal of the old system and installation of the new system must be added to 

these numbers, and the cost of replacement nozzles should be added as well. 

In comparison, the cost of hardware for the MEC ESPi system for this engine type to vary SOI 

timing only is estimated to be $3,400 (including modified unit pumps) from the information 

given in the proposal application. As above, labor is additional, but should be comparable. 

Timing maps for different speed/load conditions for a 25% NOx reduction will have to be 

generated during the verification stage of the MEC ESPi system. These costs have not been 

included here. They are difficult to estimate due to uncertainty in the numbers of possible 

candidate engines. However they should be comparable to conversion costs to electronic 

systems if they were not tailored to the candidate engine. 

Current retail prices for heavy duty unit injectors (with wiring) for electronically (spill valve) 

controlled systems are in the range of $400 per injector or $2,400 for a 6-cylinder engine. The 

ECM for these systems is estimated to cost $1,500. Sensors ($300) and a gear pump for 

pressurizing the fuel ($300) would bring the hardware cost estimate for this type of system up to 

$4,500. It is not clear whether EFI conversions require different cam profiles, necessitating 

either replacing or modifying the existing camshaft. If so this cost would be additional, and is 

not included here. 

If suitable solenoid controlled injectors are not available for older, candidate engines then the 

conversion cost to the MEC ESPi system should be considerable lower than electronically 

controlled SOI injection systems. In the case where such injectors are available, the hardware 

cost estimates for replacement hardware to convert existing mechanical injection systems to 

electronically controlled SOI timing appear to be in the same range, or slightly more expensive 

than the proposed MEC system. 

NOx Reduction Approaches 

NOx is formed in-cylinder as a consequence of the combustion process. There are two general 

areas to reducing NOx, and techniques in these areas may be used in tandem. The first is incylinder, 

where the conditions that lead to the formation of NOx are modified so that there is less 

NOx produced. VIT is one of the techniques that can achieve this, but there are others, as 

described below. 

The second approach is to accept the levels of NOx produced in-cylinder and then chemically 

reduce it in the exhaust. Such aftertreatment approaches may be used in conjunction with incylinder 

techniques to lower the overall NOx output. Their combined use is more a matter of 

economics than practicality. 

Available Technologies – In-Cylinder 

The previous section described the effects of variable SOI on NOx emissions, fuel economy and 

particulates. The use of higher injection pressures can assist in reducing NOx if later SOI is used 

with the resulting smaller fuel particles [6]. The following plot [7] contains a concise summary 

of the different technologies for dealing with NOx and particulates. For in-cylinder 


technologies the plot demonstrates the effect of SOI on NOx and particulates (more advanced 

timing leads to higher NOx and lower particulates), and the effects of EGR (more EGR leads to 

higher particulates and lower NOx.) Meanwhile a combination of aftertreatment approaches 

helps engine manufacturers in achieving the 2007 emissions standards (shown in the lower left 

hand corner of the plot.) 

Figure 3: Summary of in-cylinder and aftertreatment technologies 

from [7] in reducing emissions 

Besides new combustion system approaches like HCCI (homogeneous charge compression 

ignition) and PCC (partial HCCI) the primary technique used to reduce NOx in-cylinder is 

exhaust gas recirculation (EGR), which, to be most effective, requires cooling. This approach 

requires external valving and piping, and a cooler for the exhaust gas. (HCCI and PCCI will not 

be addressed here. For older engines where retrofit technologies are being considered it is highly 

likely that these new combustion systems would require greater changes to the engine than 

would be economic.) 

EGR works by displacing oxygen in the intake charge with relatively inert gases. With less 

oxygen available the combustion process will be somewhat slower, leading to lower 

temperatures. In addition the added CO2 and water vapor in the exhaust stream affects the rate of 

temperature rise due to their high thermal capacitance relative to other gases. It is also the lower 

oxygen levels of the intake charge that reduces the oxidation of soot particles, leading to higher 

PM emissions. 


The following diagram [8] show the effect of cooled vs. uncooled EGR on NOx, particulates and 

intake manifold temperature. While the effect of cooling the EGR has little effect on NOx, the 

effect is substantial on particulates. 

Figure 4: Effect of EGR temperature on NOx, PM and 

intake manifold temperature from [8] 

EGR approaches usually increase the load on the engine cooling system, and impose a fuel 

economy and particulates penalty [9, 10], although the latter may be mitigated if combined with 

a diesel particulate filter (DPF.) A further constraint that will apply to retrofit applications is 

whether the engine is turbocharged or not, and whether a high-pressure or low-pressure loop is 

selected for returning the EGR to the cylinder, as shown in the following diagram. 

Figure 5: High pressure EGR loop (left) and low pressure EGR (right) from [8] 

EGR has certain drawbacks though. With higher particulates the gas stream diverted back to the 

engine will increase wear. (If used with a DPF this is not as much of an issue, although the low 

pressure loop must be used, incurring a fuel economy penalty to recompress the EGR, and 

adversely affecting transient response. Also the combination would be expensive for retrofitting 

older engines.) During transients the volume of EGR in the piping and heat exchanger will cause 


additional particulates due to the rate of fueling exceeding the available air even more than a 

non-EGR engine. Piping, heat exchanger and valving for EGR can be cumbersome and 

expensive. 

Available Technologies – Aftertreatment 

There are a number of aftertreatment technologies available for reduction of both NOx and 

particulates. These technologies are: 

• SCR – selective catalyst reduction 

• LNT – lean NOx trap 

• DPF – diesel particulate filter 

• DOC – diesel oxidation catalyst 

Technologies that reduce particulates are included in this study because both VIT and EGR 

impact particulates. If particulate levels are worse due to reduced NOx (and possibly improved 

fuel economy) there will be a trade-off at some point to maintain air quality. 

SCR Technology 

This approach introduces a reducing agent into the exhaust stream, either by the addition of urea 

or ammonia directly, or the addition of extra fuel to provide the reducing reagent [9, 11, 12, 13]. 

The resulting chemical reaction reduces NOx to oxygen and nitrogen. This approach has been 

used in stationary power plants for some time. Efficiencies are very high for engines that operate 

under constant conditions, but are lower for operation under transient conditions. (Model-based 

algorithms are under development to allow more accurate prediction of the amount of ammonia 

required when the anticipated quantity of NOx changes with load and speed.) 

Of potential concern is ammonia slip, where some of the reducing agent escapes the exhaust 

system into the atmosphere. The major logistical problems are that an additional storage tank is 

required on each vehicle, and a refilling infrastructure is required. 

The promise of significant reductions in NOx means that SOI can be advanced again for 

improved efficiency, resulting in better fuel economy than other approaches. Particulates are 

also improved with this approach. However, in certain applications the temperature of the 

exhaust stream may be too low for effective operation of the catalytic reaction. In those cases an 

additional heat source may be required, either a burner or an electric heating element. Either of 

these options will result in a reduction of fuel economy of the engine. 

There is potentially a 6% improvement in fuel economy, although this is offset by the cost of 

urea. One study [13] found that urea must cost less that $1.50 per gallon for there to be an 

equivalent fuel economy benefit using an SCR. 

A schematic of a system developed by Bosch is shown below. 


Figure 6: A commercial SCR system with a DOC as shown in [14] 

LNTs adsorb NOx and oxygen during lean operation modes, then during occasional rich 

operation the NOx is catalyzed to nitrogen. Sulfur in the exhaust causes performance 

degradation over time [12] so that periodic desulfation is required. There are some operational 

issues with these NOx adsorbers for the regeneration phase. Either a dual-leg layout is needed 

where one of the two legs may be regenerated while the other continues to adsorb NOx, or a 

single-leg layout requires periodic injection of diesel fuel into the exhaust to facilitate the 

reduction process. Using fuel as a reductant has a substantial fuel economy penalty. Schematics 

of the two approaches are shown below. 

Figure 7: Single and double leg LNT systems from [10] 

DPF Technology 

This consists of a closed filter that physically traps particulates then oxidizes them. The 

oxidation process requires a particular temperature range, which is often controlled by a burner, 

impacting fuel economy. Some filters are catalytic, reducing the fuel economy impact. They 

also trap ash from combustion of engine oil, which cannot be oxidized. Consequently they 

require periodic cleaning. 

DOC Technology 

This approach is similar to the use of catalyst in automotive applications, except that it does not 

reduce NOx emissions due to the oxygen-rich environment. These oxidize unburned 


hydrocarbons and carbon monoxide as well as some particulates (although not as effectively as 

DPFs for the latter.) They are passive devices with no maintenance required. 

The following table shows a summary of the effectiveness of both in-cylinder and aftertreatment 

approaches on emissions, including a range of costs for retrofit situations, based on the 

references given at the end of this report. 


Table 1: NOx reduction alternatives at a glance 

Technology NOx 

Reduction 

PM 

Reduction 

VIT Up to 50% Could 

increase 

50% 

EGR (cooled) 40 – 60% Could 

increase 

300% 

HC 

Reduction 

CO 

Reduction 

Effect on Fuel Economy E 

- - Less than fixed retard, may 

even be neutral 

Increased Increased 1 – 4% worse $1 

SCR 60 – 90% 20 – 30% 99% 76% Possibly up to 6% improved, 

but have reductant 

source/consumption 

$1 

LNT >80% - 

- 

- 

3 – 7% worse $5 

DOC - 

- 

DPF - 

- 

10 – 50% 

1 Estimates based on 10 – 15 L heavy duty diesel engine 

2 Requires ULS diesel 

50% 40% - 

80 – 90% 85% 85% Depending on heat source for 

activation 

Phase 1 Report Grant N-12 Page 12/15 

$7 

$5 

$5

The following diagram from [7] gives a good comparison of EGR, SCR and NOx adsorber 

approaches on other performance issues. As noted above, the advantage that SCRs have with 

fuel economy is somewhat negated by the need to recharge the reductant tank periodically. The 

alternative approach of on-board reforming to provide the reductant reduces this advantage 

somewhat. 

Figure 8: Performance effects of different NOx reducing technologies from [7] 

Another potential NOx reducing technology is that of the lean NOx catalyst. Unfortunately to 

date there have been no successful, durable lean NOx catalysts that can reduce NOx under the 

typical oxygen-rich environment of a diesel engine exhaust. Even if one is found, there is 

expected to be a fuel economy penalty of 3% or more due to the addition of a suitable reductant 

[10, 12]. 


Summary of Retrofits 

Each of the technologies listed above has a number of advantages and disadvantages. The table 

below is intended to offer a summary of the pros and cons of applying these systems as retrofits 

to older diesel engines for the purposes of NOx reduction. 

Table 2: Pros and cons of different NOx reduction alternatives 

Technology Advantages Disadvantages 

Mechanical 

VIT 

Cooled 

EGR 

Transparent to user 

Constant over engine life 

Little impact on fuel economy 

Effective NOx reduction 

No user intervention required 

SCR NOx reduction high 

Potentially best fuel economy 

May be invasive in engine 

May require higher injection pressures 

PM, HC, CO worse 

Additional engine wear 

Higher PM during transients 


Additional cooling system demands 

Requires reductant 

User intervention required 


Expensive 

LNT Potentially high NOx reduction High fuel economy penalty 


DOC Low cost control of HC, CO, PM Does nothing for NOx 

DPF Reduces PM with timing retard Does nothing for NOx 

Requires heat source 


Summary 

A low-cost VIT solution may be a very attractive approach for older diesel engines to achieve a 

25% reduction in NOx emissions. While there are other approaches that reduce NOx further 

they appear to be substantially more expensive, and in some cases require user intervention. 

Further VIT appears to offer very good fuel economy results for the cost, an issue that is sure to 

be of concern to users of older engines who will see no economic benefit to lower NOx 

emissions. 


References 

1) V. O. Markworth, S. G. Fritz, G. R. Cataldi, “The Effect of Injection Timing Enhanced 

Aftercooling, and Low-Sulfur, Low-Aromatic Diesel Fuel on Locomotive Exhaust Emissions,” 

Transactions of the ASME, pp. 488 – 495, Vol. 114, July 1992 

2) R. Stradling, P. Gadd, M. Signer, C. Operti, “The Influence of Fuel Properties and Injection 

Timing on the Exhaust Emissions and Fuel Consumption of an Iveco Heavy-Duty Diesel 

Engine,” SAE Paper 971635, 1997. 

3) D. A. Kouremenos, D. T. Hountalas, K. B. Binder, A. Raab, M. H. Schnabel, “Using Advanced 

Injection Timing and EGR to Improve DI Diesel Engine Efficiency at Acceptable NO and Soot 

Levels,” SAE Paper 2001-01-0199, 1999. 

4) P. Lauvin, A. Loffler, A. Schmitt, W. Zimmermann, W. Fuchs, “Electronically Controlled High 

Pressure Unit Injector System for Diesel Engines,” SAE Paper 911819, 1991. 

5) R. C. Yu, S. M. Shahed, “Effects of Injection Timing and Exhaust Gas Recirculation on 

Emissions from a D.I. Diesel Engine,” SAE Paper 811234, 1981. 

6) J. M. Desantes, J. V. Pastor, J. Arregle, S. A. Molina, “Analysis of the Combustion Process in a 

EURO III Heavy-Duty Direct Injection Diesel Engine,” ASME J. Eng. Gas Turbines Power, 124, 

pp. 636-644 

7) M. Schittler, “State-of-the-Art and Emerging Technologies,” 9 th Diesel Engine Emissions 

Reductions Conference, August 2003 

8) “Exhaust Gas Recirculation,” DieselNet Technology Guide, Engine Design for Low Emissions, 

2005 

9) “Overview of Clean Diesel Requirements and Retrofit Technology Options,” F. J. Acevedo, 

Michigan Clean Fleet Conference, March 2006 

10) G. Weller, “EPA Engine Implementation Workshop – 6/7 August 2003, 2007 Technology 

Primer,” Presentation by Ricardo 

11) “Diesel Powered Machines and Equipment: Essential Uses, Economic Importance and 

Environmental Importance,” Diesel Technology Forum, June 2003 

12) H. Hu, J. Reuter, J. Yan, J. McCarthy Jr., “Advanced NOx Aftertreatment System and Controls 

for On-Highway Heavy Duty Diesels,” SAE Paper 2006-01-3553, 2006 

13) R. Krishnan, T. J. Tarabulski, “Economics of Emission Reduction for Heavy-Duty Trucks,” 

DieselNet Technical Report, January 2005 

14) W. Addy Majewski, “SCR Systems for Mobile Engines,” DieselNet Technical Report, 2006 


11.2. Appendix 2: Modeling Results of VIT/VVT on RootsBlown EMD 

645 Engine 



Area of Interest: Development and Testing of Engine Upgrade/Retrofit 

Kit for Existing Engines 



Suite 238 



Telephone: (970) 221-9600 / (970) 218-0141 

Fax: (970) 221-3863 


Project Title: A Novel Method of Mechanical Variable Injection 

Date: April 21, 2008 

Timing to Reduce NOx Emissions 

Phase 2: Results of Modeling of Variable Injection 

Timing, Variable Valve Timing and Duration on a Roots- 

blown EMD 645 Locomotive Engine 

The preparation of this report is based on work funded by the State of Texas through a 

grant from the Texas Environmental Research Consortium with funding provided by the 

Texas Commission on Environmental Quality. 


Introduction 

Initial engine selection for conversion to a mechanical variable injection timing system 

centered on truck applications. After reviewing the candidate engines in the field and 

estimating the opportunity for NOx reduction a decision was made to apply this 

technology to a Roots-blown EMD 645 locomotive engine. These engines predate the 

use of electronic fuel injection, and there are still large numbers of them in service in 

Texas. 

It is well known that retarding injection timing will reduce engine-out NOx emissions, 

but there is concern over the effects on fuel economy. Data reported in [1] on a GE 

7FDL locomotive engine indicate that a 25% reduction in NOx is achievable by retarding 

injection timing by 6°, but fuel economy worsened by 3%. Locomotive engines consume 

large quantities of fuel annually, so it is vital that any fuel penalty be minimized. The 

state of Texas is seeking solutions that will reduce NOx by a minimum of 25% over an 

engine’s duty cycle. 

Variation in exhaust valve timing and duration is one control strategy that has not been 

investigated extensively for diesel engines. It was thought that some of the fuel economy 

losses experienced with retarded injection timing might be offset, but the extent of the 

improvements possible was unknown. This study seeks to investigate the possible 

benefits of variable valve timing, particularly in conjunction with retarded injection 

timing for NOx reduction. 

Objective of Modeling Study 

While the extent of injection timing change is reasonably well understood, the effects of 

exhaust valve timing and duration are not. An engine model of the Roots-blown EMD 

645 engine was created to explore the effects of both changing start-of-injection (SOI) 

and exhaust valve phase and duration. From the modeling effort it was hoped that 

recommended ranges for exhaust valve phasing and duration could be made. It would be 

unwise to attempt to create hardware to vary exhaust valve timing and duration without a 

firm idea of the range required. 

The modeling effort concentrated on varying the following: 

• Start-of-injection varying from stock timing to 7° retarded 

• Valve timing centerline change from 14° advanced to 17° retarded 

• Valve duration from 88% of stock to 104% of stock. 

Exercising of the engine model was done at three notch settings for which suitable 

calibration data were available. Table 1 below shows the values of speed and load for the 

three notch settings evaluated. 


Table 1: Roots-blown EMD 645 speed and load settings at three notch settings evaluated 

Notch Speed Load 

(rpm) (BMEP – bar) 

2 388 2.3 

5 648 5.0 

8 900 6.2 

Model Creation 

Southwest Research Institute was engaged to create and calibrate the model. The 

modeling package used was Gamma Technology’s GT Power. 

A full sixteen-cylinder model was created. Initial concerns were that the model would 

take an excessive amount of time to run with all sixteen cylinders. This proved not to be 

the case so the complete model was run. Variations in airflow from cylinder-to-cylinder 

were evaluated to ensure that imbalance was not a significant issue. 

Experimental data from three notch settings were used to calibrate the model. Burn rates 

and rates of NOx production were matched carefully to ensure the model was accurate. 

NOx and BSFC may be predicted reasonably accurately, so even if the model calibration 

varied slightly from test results the comparative nature of the runs performed would be 

useful in predicting these trends. However particulates are not predicted at all, so effects 

of SOI on particulates will be estimated from other references within the literature. An 

engine map from the GT Power model is shown in Figure 1. 

Figure 1: GT Power map of Roots-blown EMD 645 sixteen-cylinder, two-stroke 

locomotive engine. 


Modeling Results 

Initial modeling investigations used coarse variations in injection timing and valve timing 

and duration. These sweeps were executed to understand the trends in NOx and BSFC 

across the three notch settings. 

The following plot (Figure A4 from Appendix A) shows NOx on the left vertical axis and 

BSFC on the right vertical axis. The solid lines represent different start-of-injection 

timing settings (SOI), while the exhaust valve centerline timings are shown on the 

horizontal axis. The dotted lines represent BSFC, the same color being used as for the 

solid lines to denote the same SOI. The stock exhaust event duration is denoted as 100%. 

The tan or light purple lines (solid and dotted) represent the stock settings for SOI. 

Exhaust valve duration of less than 100% means that the valve event is shrunk about the 

centerline. The corresponding valve lift will be the square root of the duration change. 

For example, if the duration is shrunk to 96% of the stock valve duration, then the lift 

will be 98% of the stock valve lift. Besides shrinking (or expanding) the valve event, the 

location of the centerline was investigated as well to determine optimum valve timing 

along with the change in duration. 

For a suitable reference the light blue filled circle represents the stock timing – injection 

and valve – for NOx, and the green diamond is the stock value for fuel economy. 

The thick black line across the lower portion of each plot represents the 25% NOx 

reduction level. It is apparent that the SOI must be retarded between 5° and 6° to achieve 

this level of reduction. 

Results are presented in Appendices A through F. Appendices A through C show results 

for NOx predictions and corresponding BSFC predictions for broad sweeps in valve lift 

and duration, as well as SOI swings. Appendices D through F show results for more 

narrow sweeps of valve and injection timing. 


BSNOx (g/kWh) 

17 

16 

15 

14 

Notch 8 - Effect of SOI and Valve Phasing on NOx, BSFC 

Exhaust Valve Duration 100% 

13 

12 

NOx 100% EV -18 SOI 







Stock NOx 

75% stock NOx 

BSFC 100% EV -18 SOI 

230 

11 







10 

Stock BSFC 

225 

150 155 160 165 170 175 180 185 

Exhaust max lift timing (deg ATDC) 

Figure A4: Notch 8 NOx and BSFC vs EV centerline at 100% stock EV duration and 

SOI 

Coarse Plots, Notch 8 – See Appendix A 

Figures A1 through A5 show the results for coarse timing sweeps for notch 8. Each plot 

shows successively longer exhaust valve event durations, from 88% of stock to 104%. 

Within each plot it is apparent that the overall minimum for BSFC at each SOI timing 

occurs with valve duration between 96% and 100% of stock. As the valve duration is 

increased the location of BSFC minimum drifts slowly to more retarded valve timing. 

NOx appears to be far more sensitive to SOI timing than valve timing. There is a weak 

minimum with advanced valve timing, which shows on the shorter valve duration plots 

(Figures A1 and A2.) Initial impressions are that stock valve and injection timing at 

notch 8 are good compromises to minimize both BSFC and NOx. The minima in both 

BSFC and NOx are within approximately 4º crank for valve timing. 

Coarse Plots, Notch 5 - See Appendix B 

The same general shapes appear at notch 5 as for notch 8. However the occurrence of the 

BSFC minimum occurs at later valve timing. In this case the difference between the 

locations of the minima in BSFC and NOx appears to be approximately 7º to 8º with 

valve timing. The overall minimum in BSFC appears to occur with the exhaust valve 

duration around 96% of stock, but is somewhat insensitive within a few degrees. 

N-12 Modeling Report on NOx Reduction of EMD 645 engine 5 

245 

240 

235 

BSFC (g/kWh)

The NOx minimum is more sensitive to retarded injection timing, as in the notch 8 

results. 

Coarse Plots, Notch 2 - See Appendix C 

The trend for locations for minima for BSFC and NOx occur at valve timing values that 

are considerably later than for notch 5 and 8. In fact in the model results, the location of 

the minimum for NOx was not found. It appears that with later valve timing than 

modeled the NOx levels should continue to decline. 

The minimum location for BSFC appears to occur with a valve event duration near 

100%. 

Fine Plots, Notch 8 - See Appendix D 

Figures D1 to D7 show a refinement of the sweeps in Figures A1 to A5 for notch 8. The 

exhaust valve centerline adjustment has been reduced from 12° to 6°, and the SOI curves 

start at a 5° retard, and step through to 7° retard in 0.5° increments. Reducing NOx by 

25% requires SOI retard in this range. 

As noted in the coarse sweeps above the sensitivity of the engine to valve timing changes 

is low. 

Fine Plots, Notch 5 - See Appendix E 

Figures E1 to E7 show a refinement of the sweeps in Figures B1 to B5 for notch 5. 

Because of the separation between the NOx minimum and the BSFC minimum with 

valve timing the optimal combination of SOI and timing to achieve a 25% NOx reduction 

is somewhat insensitive. 

Fine Plots, Notch 2 - See Appendix F 

Figures F1 to F7 show a refinement of the sweeps in Figures C1 to C5 for notch 2. It 

appears that a greater valve duration and later centerline timing would reduce NOx and 

BSFC even further. (At some stage the practical limitation of the valve phasing device 

selected will interfere with this trend.) 

Both NOx and BSFC are reduced easily below the levels of the stock engine. 

Analysis – Effect of Valve Timing and Duration on Location of Minimum BSFC 

At different notch settings the centerline of valve timing for minimum BSFC changes. 

As notch settings increase valve timing should occur earlier, as shown in Figure 2. 


EV Centerline (deg ATDC) 

184 

180 

176 

172 

168 

164 

Exhaust Valve Duration & Centerline at Minimum BSFC 

Notch 8 

160 

88% 92% 96% 100% 104% 

Exhaust Valve Duration (% of stock) 


Notch 2 

Notch 5 

Figure 2: Effect of exhaust valve centerline and duration on location of minimum BSFC 

Minimum BSFC does not occur at the same location as minimum NOx. However the 

plot serves to show that optimum timing occurs later with lower notch settings, regardless 

of the exhaust valve duration. From notch 8 to notch 5 exhaust valve timing should be 

retarded 5°, and from notch 5 to notch 2 by 11°. It is likely that idle should have later 

timing still. 

The recommended exhaust valve timing change should be at least 18° to cover the full 

range of engine operation. 

Analysis – SOI Retard to Achieve 25% NOx Reduction and the Effect on BSFC 

With stock valve timing the level of SOI retard required to achieve a 25% reduction in 

NOx is shown in Table 2. 

Table 2: SOI required to achieve 25% NOx reduction and the effect on BSFC at stock 

valve timing 

Notch SOI (from stock) 

(ATDC) 


(ATDC) 

2 -7.7° 168° -1.61% 

5 -6.5° 168° -1.22% 

8 -5.5° 168° -1.01% 

In all cases the fuel efficiency of the engine will decrease. 

BSFC 

Improvement

Analysis – SOI Retard to Achieve 25% NOx Reduction Combined with Variable 

Valve Timing and Duration and the Effect on BSFC 

In Table 3 below valve timing and duration have been varied as well as SOI to deliver a 

25% reduction in NOx, and optimize BSFC. 

Table 3: SOI and valve timing changes required to achieve 25% NOx reduction and to 

minimize the effect on BSFC 

Notch Change in SOI 

(from stock) 

(ATDC) 


Change 

Exhaust 

Duration 


BSFC 

Improvement 

2 -5.0° 15° retard 104% +2.88% 

5 -6.5° 0° 100% -0.98% 

8 -5.5° 3° advance 100% -0.92% 

The only notch setting with valve event duration different from stock is notch 2. Table 4 

below shows the effect on fuel economy of maintaining stock valve event duration at 

notch 2. 

Table 4: Effect on BSFC improvement at notch 2 with 100% and 104% of valve event 

duration at the required SOI retard to achieve 25% NOx reduction 

Notch BSFC Improvement BSFC Improvement 

with 100% Valve with 104% 

Duration 

Valve Duration 

2 +2.76% +2.88% 

The difference in fuel economy is small with the valve event duration change listed 

above. Providing phasing alone would be simpler than phasing plus duration change, so 

the results below will be quoted for phase change in valve timing only. 

Analysis – Effect of Variable Valve Timing only Over and Above SOI Retard only 

on BSFC 

In Table 5 below the difference between SOI retard only and SOI retard with variable 

valve timing (but not duration) is shown on BSFC. 

Table 5: Difference between SOI only versus SOI plus variable valve timing to achieve 

25% NOx reduction and the effect on BSFC 

Notch BSFC 

Improvement 

with VVT 

2 4.30% 

5 0.23% 

8 0.08%

Comparison Between Modeled Results and Literature 

The following material, with some modifications, was presented in an earlier report [2] 

after a literature survey on the effects of injection timing and valve timing changes for 

project N-12. 

There are numerous studies that report the effects of variable injection timing [1, 3, 4, 5, 

6]. The studies cited from 1981 to 2002 generally measure the effect of injection timing 

change on fuel consumption and NOx emissions. 

In [1] the authors studied the emissions and fuel economy effects on locomotive engines. 

The GE 7FDL locomotive engine is normally tested over an eight-point duty cycle, but to 

reduce total testing time their timing sweeps for determining the effects on fuel economy 

and emissions were conducted at three points. The points chosen were at idle, notch 5 

and notch 8. Results quoted are weighted with 50% at the idle condition, and 25% to the 

other two points. Extrapolating from the data in the paper they indicate that a reduction 

of 25% in NOx would require the timing to be retarded by just over 6° crank, with 

corresponding drop in fuel economy of just over 3%. 

The engine tested in [3] was a 9.5 L truck engine certified to Euro 2 emissions. The aim 

of the study was to determine the emissions from different diesel fuel formulations, 

however by testing at the stock, fixed timing, and one other setting with constant NOx 

output, useful extrapolations could be made on their reference fuel. Testing was 

conducted over a 13-mode European cycle, again averaging the results. One of the fuels 

used represented a low-sulfur European fuel, and results using this fuel are referenced. 

The engine used a fixed injection timing of 10° BTDC for the baseline tests. Injection 

timing was then altered to produce a fixed NOx level of 6.3 g/kW-hr, or a reduction of 

7%. While extrapolating these results to a 25% reduction in NOx may not be linear it 

points to fuel consumption worsening by approximately 4%, with retarding the start of 

injection by some 5° crank. 

Initially it appears that it is possible to reduce NOx by 25%, simply by retarding injection 

timing by an average of 5° to 6° crank, but the penalty is paid in fuel economy. In most 

references [1, 3, 5, 6] data reported are averaged over some sort of representative cycle, 

disguising the effects of injection timing change at different speeds and loads. In [4] 

however, specific examples are given of these effects, as shown in Figure 3 below. 


Figure 3: Test results reported in [4] for BSFC vs. injection timing at different speeds 

and loads 


application. Data for 25%, 50% and 100% load were taken at 1130 and 1420 rpm. Like 

all other studies reported they show that advancing injection timing at all speeds and 

loads results in increasing NOx output as shown in Figure 4 below. The effect on fuel 

economy is more varied. In this case it is obvious from Figure 3 that the location of 

optimal timing for fuel consumption shifts significantly with load, and somewhat with 

speed. Further, at some load conditions the effect on fuel consumption appears flat over 

a wide range of timing, allowing timing selection to be made to minimize NOx 

emissions. 

Figure 4: Test results reported in [4] for BSNOx vs. injection timing at different speeds 

and loads 

Assuming that static injection timing would occur at 16° BTDC it is possible to estimate 

the changes in BSFC, BSNOx and, to a certain extent, particulates. (The scale chosen for 


the particulate plots made it difficult to determine changes in emissions with any degree 

of accuracy.) 

For the case of full load at 1130 rpm, the NOx level was 12 g/kW-hr. Reducing the NOx 

level to 9 g/kW-hr required a 7.5° timing retard, and fuel consumption worsened by 

1.5%. This appears to be reasonably close to the 1.04% increase in BSFC for notch 8 

from the modeling. 

However at 25% load the initial NOx level was 31 g/kW-hr. When this was reduced by 

25% to 23 g/kW-hr the timing retard was 4°, and fuel consumption improved by 1.6%. 

In this case it was more beneficial to retard the timing further, by 10°, which gave an 

improvement in fuel consumption of almost 4%. 

With different injection timing values feasible at different speeds and loads it may be 

possible to reduce overall NOx emissions by the 25% target required while having little 

impact, if any, on fuel consumption. As an example the 1420 rpm data could be 

considered at full load. In Figure 3 it is apparent that the fuel consumption varies very 

little between 14° BTDC and 11° BTDC. (There is no data at the 16° BTDC point.) 

However the NOx level falls off by 12%. Depending on the duty cycle of the engine 

concerned this may be a suitable trade-off between NOx emissions and fuel economy 

over the entire cycle while the overall target of 25% is achieved. Both from all the data 

found so far in the literature and the modeling results it appears that preserving fuel 

economy is not feasible with a fixed injection timing retard. 


Summary 

From the modeling it appears that the use of SOI retard only will deliver a NOx reduction 

of 25%, but at a penalty in fuel economy. The extent of that penalty will depend on the 

duty cycle of the engine. With only three of eight notch settings modeled for the EMD 

645 engine, and a lack of useful duty cycles, it is difficult to predict the overall impact on 

fuel economy. However, based on the three notch settings evaluated the fuel economy 

penalty will be in the 1.0 – 1.5% range. 

Combining retarded (and variable) SOI with variable valve timing and duration should 

deliver an improvement in fuel economy over SOI retard only. Depending on duty cycle 

it may be possible to deliver the 25% NOx reduction with little or no reduction in fuel 

economy. Either further modeling is required at the other notch settings, or experimental 

data are required to validate this. Either way a suitable duty cycle is required. 

Modeling results have suggested that phase change only for valve timing is sufficient to 

reduce the fuel economy penalty significantly, if not eliminate it. Varying valve phasing 

appears unnecessary at this stage. 

Most of the fuel economy benefits are to be found at the lower notch settings. Engines 

with low power duty cycles will benefit the most. 

The range of SOI variation from stock to achieve the 25% NOx reduction is between 5.0 

and 6.5° retard from stock. The range of exhaust valve phasing necessary for improved 

fuel economy is between 3° advanced and 15° retarded. 


References 

1) V. O. Markworth, S. G. Fritz, G. R. Cataldi, “The Effect of Injection Timing 

Enhanced Aftercooling, and Low-Sulfur, Low-Aromatic Diesel Fuel on 

Locomotive Exhaust Emissions,” Transactions of the ASME, pp. 488 – 495, 

Vol. 114, July 1992 

2) M. B. Riley, “Phase 1: Benefits of Variable Injection Timing,” HARC report 

for project N-12, December 2006 

3) R. Stradling, P. Gadd, M. Signer, C. Operti, “The Influence of Fuel Properties 

and Injection Timing on the Exhaust Emissions and Fuel Consumption of an 

Iveco Heavy-Duty Diesel Engine,” SAE Paper 971635, 1997. 

4) D. A. Kouremenos, D. T. Hountalas, K. B. Binder, A. Raab, M. H. Schnabel, 

“Using Advanced Injection Timing and EGR to Improve DI Diesel Engine 

Efficiency at Acceptable NO and Soot Levels,” SAE Paper 2001-01-0199, 

1999. 

5) P. Lauvin, A. Loffler, A. Schmitt, W. Zimmermann, W. Fuchs, 

“Electronically Controlled High Pressure Unit Injector System for Diesel 

Engines,” SAE Paper 911819, 1991. 

6) R. C. Yu, S. M. Shahed, “Effects of Injection Timing and Exhaust Gas 

Recirculation on Emissions from a D.I. Diesel Engine,” SAE Paper 811234, 

1981. 


Appendix A: Coarse Timing Sweeps at Notch 8 

BSNOx (g/kWh) 

17 

16 

15 

14 

NOTCH 8 - Effect of SOI and Valve Phasing on NOx, BSFC 


13 

12 








Stock NOx 

75% stock NOx 


230 

11 







10 

Stock BSFC 

225 

150 155 160 165 170 175 180 185 



245 

240 

235 

Figure A1: NOx and BSFC vs EV centerline at 88% stock EV duration and SOI Figure A2: NOx and BSFC vs EV centerline at 92% stock EV duration and SOI 

BSNOx (g/kWh) 

17 

16 

15 

14 



13 

12 








Stock NOx 

75% stock NOx 


230 

11 







10 

Stock BSFC 

225 

150 155 160 165 170 175 180 185 


245 

240 

235 

Figure A3: NOx and BSFC vs EV centerline at 96% stock EV duration and SOI Figure A4: NOx and BSFC vs EV centerline at 100% stock EV duration and SOI 

BSNOx (g/kWh) 

17 

16 

15 

14 



13 

12 








Stock NOx 

75% stock NOx 


230 

11 







10 

Stock BSFC 

225 

150 155 160 165 170 175 180 185 


Figure A5: NOx and BSFC vs EV centerline at 104% stock EV duration and SOI 

245 

240 

235 

BSFC (g/kWh) 

BSFC (g/kWh) 

BSFC (g/kWh) 

BSNOx (g/kWh) 

BSNOx (g/kWh) 

17 

16 

15 

14 



13 

12 








Stock NOx 

75% stock NOx 


230 

11 







10 

Stock BSFC 

225 

150 155 160 165 170 175 180 185 


17 

16 

15 

14 



13 

12 








Stock NOx 

75% stock NOx 


230 

11 







10 

Stock BSFC 

225 

150 155 160 165 170 175 180 185 


245 

240 

235 

245 

240 

235 

BSFC (g/kWh) 

BSFC (g/kWh)

Appendix B: Coarse Timing Sweeps at Notch 5 

BSNOx (g/kWh) 

17 

16 

15 

14 



13 





215 

12 




Stock NOx 

75% stock NOx 

11 








210 

10 

Stock BSFC 

205 

150 155 160 165 170 175 180 185 



235 

230 

225 

220 

Figure B1: NOx and BSFC vs EV centerline at 88% stock EV duration and SOI Figure B2: NOx and BSFC vs EV centerline at 92% stock EV duration and SOI 

BSNOx (g/kWh) 

17 

16 

15 

14 



13 





215 

12 




Stock NOx 

75% stock NOx 

11 



BSFC 96% EV -10SOI 





210 

10 

Stock BSFC 

205 

150 155 160 165 170 175 180 185 


235 

230 

225 

220 

Figure B3: NOx and BSFC vs EV centerline at 96% stock EV duration and SOI Figure B4: NOx and BSFC vs EV centerline at 100% stock EV duration and SOI 

BSNOx (g/kWh) 

17 

16 

15 

14 



13 





215 

12 




Stock NOx 

75% stock NOx 

11 








210 

Stock BSFC 

10 

205 

150 155 160 165 170 175 180 185 


Figure B5: NOx and BSFC vs EV centerline at 104% stock EV duration and SOI 

235 

230 

225 

220 

BSFC (g/kWh) 

BSFC (g/kWh) 

BSFC (g/kWh) 

BSNOx (g/kWh) 

BSNOx (g/kWh) 

17 

16 

15 

14 



13 





215 

12 




Stock NOx 

75% stock NOx 

11 








210 

10 

Stock BSFC 

205 

150 155 160 165 170 175 180 185 


17 

16 

15 

14 



13 





215 

12 




Stock NOx 

75% stock NOx 

11 








210 

Stock BSFC 

10 

205 

150 155 160 165 170 175 180 185 


235 

230 

225 

220 

235 

230 

225 

220 

BSFC (g/kWh) 

BSFC (g/kWh)

Appendix C: Coarse Timing Sweeps at Notch 2 

BSNOx (g/kWh) 

16 

15 

14 

13 



12 

11 








Stock NOx 

75% stock NOx 


230 

10 







9 

Stock BSFC 

225 

150 155 160 165 170 175 180 185 



245 

240 

235 

Figure C1: NOx and BSFC vs EV centerline at 88% stock EV duration and SOI Figure C2: NOx and BSFC vs EV centerline at 92% stock EV duration and SOI 

BSNOx (g/kWh) 

16 

15 

14 

13 



12 

11 








Stock NOx 

75% stock NOx 



230 

10 






Stock BSFC 

9 

225 

150 155 160 165 170 175 180 185 

Exhaust centerline timing (deg ATDC) 

245 

240 

235 

Figure C3: NOx and BSFC vs EV centerline at 96% stock EV duration and SOI Figure C4: NOx and BSFC vs EV centerline at 100% stock EV duration and SOI 

BSNOx (g/kWh) 

16 

15 

14 

13 



12 

11 








Stock NOx 

75% stock NOx 


230 

10 







9 

Stock BSFC 

225 

150 155 160 165 170 175 180 185 

Exhaust max lift timing (deg ATDC)) 

Figure C5: NOx and BSFC vs EV centerline at 104% stock EV duration and SOI 

245 

240 

235 

BSFC (g/kWh) 

BSFC (g/kWh) 

BSFC (g/kWh) 

BSNOx (g/kWh) 

BSNOx (g/kWh) 

16 

15 

14 

13 



12 

11 








Stock NOx 

75% stock NOx 


230 

10 







9 

Stock BSFC 

225 

150 155 160 165 170 175 180 185 


16 

15 

14 

13 



12 

11 








Stock NOx 

75% stock NOx 


230 

10 







9 

Stock BSFC 

225 

150 155 160 165 170 175 180 185 


245 

240 

235 

245 

240 

235 

BSFC (g/kWh) 

BSFC (g/kWh)

Appendix D: Fine Timing Sweeps at Notch 8 

BSNOx (g/kWh) 

17 

16 

15 

14 



13 

12 



NOx 96% EV -12.5 SOI 

NOx 96% EV -12.0 SOI 

NOx 96% EV -11.5 SOI 

NOx 96% EV -11.0 SOI 

Stock NOx 

75% stock NOx 


230 

11 


BSFC 96% EV -12.5 SOI 




10 

Stock BSFC 

225 

160 165 170 175 



245 

240 

235 

BSFC (g/kWh) 

Figure D1: NOx and BSFC vs EV centerline at 96% stock EV duration and SOI Figure D2: NOx and BSFC vs EV centerline at 97% stock EV duration and SOI 

BSNOx (g/kWh) 

17 

16 

15 

14 



13 

12 



NOx 98% EV -12.5 SOI 

NOx 98% EV -12.0 SOI 

NOx 98% EV -11.5 SOI 

NOx 98% EV -11.0 SOI 

Stock NOx 

75% stock NOx 


230 

11 






10 

Stock BSFC 

225 

160 165 170 175 


245 

240 

235 

BSFC (g/kWh) 


BSNOx (g/kWh) 

17 

16 

15 

14 



13 

12 



NOx 100% EV -12.5 SOI 

NOx 100% EV -12.0 SOI 

NOx 100% EV -11.5 SOI 

NOx 100% EV -11.0 SOI 

Stock NOx 

75% stock NOx 


230 

11 


BSFC 100% EV -12.5 SOI 

BSFC 100% EV -12.0 SOI 

BSFC 100% EV -11.5 SOI 

BSFC 100% EV -11.0 SOI 

10 

Stock BSFC 

225 

160 165 170 175 


245 

240 

235 

BSFC (g/kWh) 


BSNOx (g/kWh) 

17 

16 

15 

14 



13 

12 



NOx 102% EV -12.5 SOI 

NOx 102% EV -12.0 SOI 

NOx 102% EV -11.5 SOI 

NOx 102% EV -11.0 SOI 

Stock NOx 

75% stock NOx 


230 

11 


BSFC 102% EV -12.5 SOI 

BSFC 102% EV -12.0 SOI 

BSFC 102% EV -11.5 SOI 

BSFC 102% EV -11.0 SOI 

10 

Stock BSFC 

225 

160 165 170 175 


Figure D7: NOx and BSFC vs EV centerline at 102% stock EV duration and SOI 

245 

240 

235 

BSFC (g/kWh) 

BSNOx (g/kWh) 

BSNOx (g/kWh) 

BSNOx (g/kWh) 

17 

16 

15 

14 



13 

12 



NOx 97% EV -12.5 SOI 

NOx 97% EV -12.0 SOI 

NOx 97% EV -11.5 SOI 

NOx 97% EV -11.0 SOI 

Stock NOx 

75% stock NOx 


230 

11 






10 

Stock BSFC 

225 

160 165 170 175 


17 

16 

15 

14 



13 

12 



NOx 99% EV -12.5 SOI 

NOx 99% EV -12.0 SOI 

NOx 99% EV -11.5 SOI 

NOx 99% EV -11.0 SOI 

Stock NOx 

75% stock NOx 


230 

11 






10 

Stock BSFC 

225 

160 165 170 175 


17 

16 

15 

14 



13 

12 



NOx 101% EV -12.5 SOI 

NOx 101% EV -12.0 SOI 

NOx 101% EV -11.5 SOI 

NOx 101% EV -11.0 SOI 

Stock NOx 

75% stock NOx 


230 

11 


BSFC 101% EV -12.5 SOI 

BSFC 101% EV -12.0 SOI 

BSFC 101% EV -11.5 SOI 

BSFC 101% EV -11.0 SOI 

10 

Stock BSFC 

225 

160 165 170 175 


245 

240 

235 

245 

240 

235 

245 

240 

235 

BSFC (g/kWh) 

BSFC (g/kWh) 

BSFC (g/kWh)

Appendix E: Fine Timing Sweeps at Notch 5 

BSNOx (g/kWh) 

16 

15 

14 

13 




NOx 96% EV -7.0 SOI 

214 

12 





Stock NOx 

11 

75% stock NOx 







212 

Stock BSFC 

10 

210 

155 160 165 170 175 180 



220 

218 

216 

BSFC (g/kWh) 

Figure E1: NOx and BSFC vs EV centerline at 96% stock EV duration and SOI Figure E2: NOx and BSFC vs EV centerline at 97% stock EV duration and SOI 

BSNOx (g/kWh) 

16 

15 

14 

13 





214 

12 





Stock NOx 

11 

75% stock NOx 







212 

Stock BSFC 

10 

210 

155 160 165 170 175 180 


220 

218 

216 

BSFC (g/kWh) 


BSNOx (g/kWh) 

16 

15 

14 

13 




NOx 100% EV -7.0 SOI 

NOx 100% EV -6.5 SOI 

214 

12 

NOx 100% EV -6.0 SOI 

NOx 100% EV -5.5 SOI 

NOx 100% EV -5.0 SOI 

Stock NOx 

11 

75% stock NOx 







212 

10 

Stock BSFC 

210 

155 160 165 170 175 180 


220 

218 

216 

BSFC (g/kWh) 


BSNOx (g/kWh) 

16 

15 

14 

13 




NOx 102% EV -7.0 SOI 

214 

12 

NOx 102% EV -6.5 SOI 

NOx 102% EV -6.0 SOI 

NOx 102% EV -5.5 SOI 

NOx 102% EV -5.0 SOI 

Stock NOx 

11 

75% stock NOx 







212 

Stock BSFC 

10 

210 

155 160 165 170 175 180 


Figure E7: NOx and BSFC vs EV centerline at 102% stock EV duration and SOI 

220 

218 

216 

BSFC (g/kWh) 

BSNOx (g/kWh) 

BSNOx (g/kWh) 

BSNOx (g/kWh) 

16 

15 

14 

13 





214 

12 





Stock NOx 

11 

75% stock NOx 







212 

Stock BSFC 

10 

210 

155 160 165 170 175 180 


16 

15 

14 

13 





214 

12 





Stock NOx 

11 

75% stock NOx 







212 

Stock BSFC 

10 

210 

155 160 165 170 175 180 


16 

15 

14 

13 




NOx 101% EV -7.0 SOI 

214 

12 

NOx 101% EV -6.5 SOI 

NOx 101% EV -6.0 SOI 

NOx 101% EV -5.5 SOI 

NOx 101% EV -5.0 SOI 

Stock NOx 

11 

75% stock NOx 







212 

Stock BSFC 

10 

210 

155 160 165 170 175 180 


220 

218 

216 

220 

218 

216 

220 

218 

216 

BSFC (g/kWh) 

BSFC (g/kWh) 

BSFC (g/kWh)

Appendix F: Fine Timing Sweeps at Notch 2 

BSNOx (g/kWh) 

15 

14 

13 

12 



11 






NOx 96% EV 0.0 SOI 

NOx 96% EV +0.5 SOI 

Stock NOx 

75% stock NOx 


225 

10 





BSFC 96% EV 0.0 SOI 

BSFC 96% EV +0.5 SOI 

Stock BSFC 

9 

220 

160 165 170 175 180 185 



240 

235 

230 

BSFC (g/kWh) 

Figure F1: NOx and BSFC vs EV centerline at 96% stock EV duration and SOI Figure F2: NOx and BSFC vs EV centerline at 97% stock EV duration and SOI 

BSNOx (g/kWh) 

15 

14 

13 

12 



11 








Stock NOx 

75% stock NOx 


225 

10 







Stock BSFC 

9 

220 

160 165 170 175 180 185 


240 

235 

230 

BSFC (g/kWh) 


BSNOx (g/kWh) 

15 

14 

13 

12 



11 








Stock NOx 

75% stock NOx 


225 

10 







Stock BSFC 

9 

220 

160 165 170 175 180 185 


240 

235 

230 

BSFC (g/kWh) 


BSNOx (g/kWh) 

15 

14 

13 

12 



11 



NOx 102% EV -1.5 SOI 

NOx 102% EV -1.0 SOI 

NOx 102% EV -0.5 SOI 


NOx 102% EV +0.5 SOI 

Stock NOx 

75% stock NOx 


225 

10 







Stock BSFC 

9 

220 

160 165 170 175 180 185 


Figure F7: NOx and BSFC vs EV centerline at 102% stock EV duration and SOI 

240 

235 

230 

BSFC (g/kWh) 

BSNOx (g/kWh) 

BSNOx (g/kWh) 

BSNOx (g/kWh) 

15 

14 

13 

12 



11 








Stock NOx 

75% stock NOx 


225 

10 







Stock BSFC 

9 

220 

160 165 170 175 180 185 


15 

14 

13 

12 



11 








Stock NOx 

75% stock NOx 


225 

10 







Stock BSFC 

9 

220 

160 165 170 175 180 185 


15 

14 

13 

12 



11 



NOx 101% EV -1.5 SOI 

NOx 101% EV -1.0 SOI 

NOx 101% EV -0.5 SOI 


NOx 101% EV +0.5 SOI 

Stock NOx 

75% stock NOx 


225 

10 







Stock BSFC 

9 

220 

160 165 170 175 180 185 


240 

235 

230 

240 

235 

230 

240 

235 

230 

BSFC (g/kWh) 

BSFC (g/kWh) 

BSFC (g/kWh)

11.3. Appendix 3: SwRI Testing Report of Mechanical VIT/VVT System

Benefits of Variable Injection Timing - Houston Advanced Research ...

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