WinPEP User Guide - Dynojet Research

WinPEP User Guide 

For the Snowmobile Dynamometer 

Software under Windows 95/98 

Dynojet ® Research Inc. 

Revision B 6/23/99 

Document #98168101

© 1993, 1994, 1995, 1996, 1997,1998 and 1999 Dynojet 

Research Inc. All Rights Reserved. 

Dynojet WinPEP User Guide for use with Microsoft Windows 

95. 

This manual, as well as the software described in it, is furnished 

under license and may only be used or copied in accordance 

with the terms of such license. The information in this 

manual is furnished for informational use only, is subject to 

change without notice, and should not be construed as a commitment 

by Dynojet Research Inc. Dynojet Research Inc. 

assumes no responsibility or liability for any errors or inaccuracies 

that may appear in this book. 

The Dynojet Logo is a trademark of Dynojet Research Inc. 

Printed in the USA. 

Document #9168101

Contents 

Chapter 1 ..............................................1 - 1 

Introduction 

About the Guide......................................................................1 - 1 

System Requirements............................................................1 - 2 

WinPEP Package Contents....................................................1 - 2 

Technical Support...................................................................1 - 3 

Chapter 2 ..............................................2 - 1 

Installing WinPEP 

Important Points of Interest ..................................................2 - 1 

Install WinPEP ........................................................................2 - 2 

Chapter 3..............................................3 - 1 

Basic Concepts 

Windows Environment...........................................................3 - 1 

WinPEP Interface....................................................................3 - 1 

Workspace Menu....................................................................3 - 3 

Workspace Toolbar.................................................................3 - 5 

Work Group Toolbar................................................................3 - 6 

Graph View Toolbar.................................................................3 - 7 


Document #98168101 

1i

Chapter 4...............................................4 - 1 

Making a Run with a Sled 

Rear Idler Assembly Layout..................................................4 - 1 

Connecting the Dyno to a Sled.............................................4 - 2 

Connecting the RPM Pickup............................................... 4 - 11 

Make a Pre-run Inspection...................................................4 - 13 

Running WinPEP...................................................................4 - 14 

Selecting a Name..................................................................4 - 15 

Editing the Notes and Parameters..................................... 4 - 17 

Making a Dyno Run..............................................................4 - 21 

Disconnecting Sled from Dyno...........................................4 - 23 

Chapter 5...............................................5 - 1 

Viewing Graphs 

Viewing a Fourth Gear Roll-on............................................. 5 - 1 

Graph Features.......................................................................5 - 3 

Smoothing............................................................................5 -4 

Correction Factor..................................................................5 -4 

Zooming In...........................................................................5 -5 

Unzooming...........................................................................5 -5 

Copy graph to clipboard.......................................................5 -5 

Graph Options......................................................................5 -6 

Axis Selection...................................................................... 5-7 

Multiple Graph Selection.......................................................5 -9 

Full Screen Zoom................................................................ 5 -13 

Right Mouse Button Menu................................................... 5 -14 

Graph Options.................................................................... 5 -14 

Cursor................................................................................ 5 -15 

Cursor Line........................................................................ 5 -15 

Scaling............................................................................... 5 -17 

Font Size............................................................................ 5 -17 

Grid Lines.......................................................................... 5 -18 

Grid in Front....................................................................... 5 -18 

Graph Lines........................................................................ 5 -18 

Export Dialog......................................................................5 -19 

Printing a Graph.................................................................... 5- 20 

Print Preview...................................................................... 5 -21 

Changing Graphic Header...................................................5 -23 

Print Options......................................................................5 -27 

1ii Document #98168101

Chapter 6 ..............................................6 - 1 

Racing Vehicles 

Chapter 7 ..............................................7 - 1 

Notes / Search Features 

Viewing /Editing Notes ..........................................................7 - 1 

Search ......................................................................................7 - 3 

Chapter 8 ..............................................8 - 1 

Tools 

WinPEP Tools ..........................................................................8 - 1 

Group Tools ............................................................................8 - 4 

System Information ................................................................8 - 5 

Other Tools ..............................................................................8 - 6 

Options ....................................................................................8 - 8 

Chapter 9 ..............................................9 - 1 

Theory of Operation 

WinPEP Tools ..........................................................................9 - 1 

Power........................................................................................9 - 1 

Torque ......................................................................................9 - 2 

Correction Factors..................................................................9 - 3 

Hardware and Software..........................................................9 - 5 

Conclusion ..............................................................................9 - 6 

Document #98168101 

1iii

Chapter 10...........................................10 - 1 

Interpreting Graphs 

Ratcheting..............................................................................10 - 1 

Jetting Change......................................................................10 - 2 

Helix Change.........................................................................10 - 3 

Starting Speed......................................................................10 - 3 

Notes: 

1iv Document #98168101

Chapter 1 

Introduction 

Welcome to WinPEP-- Dynojet’s Windows ® 95/98 

based performance evaluation program. Dynojet’s 

software and dynamometers will give you the power to 

get the maximum performance out of vehicles you 

evaluate. Whether you are new to the benefits of a 

chassis dynamometer or an experienced performance 

leader, the repeatability and diagnostic tools of 

WinPEP software and a Dynojet Dynamometer will 

give you the professional results for which you are 

looking. 

About the Guide 

Before you begin using WinPEP, be sure to read 

this guide for software installation instructions, 

program features, and other important 

information. The Dynojet WinPEP User’s Guide 

provides detailed information about WinPEP 

features and commands, dynamometer use, a 

theoretical background, and a hands-on tutorial. 

This guide is designed to be a reference tool in 

your everyday work. 

Revision C 2/9/00 

Document #98198100 1 - 1

System Requirements 

To use WinPEP, your system must meet the 

following minimum requirements: 

• Pentium P5-100 processor 

• Microsoft ® Windows ® 9x 

• 800 Megabyte Hard Drive 

• 16MBofRam 

• 800x600 (SVGA) 16k Color Video 

• 8x CD-ROM Drive 

Dynojet Research, Inc., however, recommends 

the following hardware and software: 

• Pentium P5-133 or greater processor 

• 1.2 Gigabyte Hard Drive or better 

• 16 MB of Ram (32 MB for Windows 98) 

• 1024x768 (SVGA) 16k Color Video or better 

• 8x CD-ROM Drive 

• 28.8 K Modem or better 

Disk space requirements: 

8 MB of free hard disk space is required to install 

WinPEP. 

WinPEP Package Contents 

The WinPEP software package includes the 

following items: 

• WinPEP Software CD 

• WinPEP User Guide (on the above CD) 

1 - 2 Document #98198100

Note: Your WinPEP software is dyno/drum 

specific. That means that the precise 

drum mass for your individual dyno has 

been calibrated and tied directly to the 

WinPEP software that came with your 

dyno. The software will not give accurate 

results if it is used with some other 

dynamometer. 

Technical Support 

If you have any questions or need technical 

support, we can be reached at: 

Dynojet Research, Inc. 

2191 Mendenhall Drive 

North Las Vegas, NV 89031 

Phone: (800) 992-4993 

(702)399-1423 

Fax: (702) 339-1431 

Web: www.dynojet.com 

Our presence on the World Wide Web offers you 

the Performance Industry advantage. We provide 

state of the art technical support, on-line 

shopping, 3D visualizations, and press releases 

about our latest product line. 

Also, as a Dyno Owner or Dealer, you have 

access to jet kit fact sheets, newsletters, and 

dealer pricing in @PREFFERED.Dynojet.com 

with just a click of a mouse. 

Document #98198100 1 - 3

Notes. 

1 - 4 Document #98198100

Chapter 2 

Installing WinPEP 

From CD 

Getting Started 

Note: 

It is strongly recommended that you exit 

all other Windows programs before 

running this setup program. 

(1) When you load the Dynojet Install CD, the 

interface screen should appear and offer you 

various options. 

(2) Click the “Install WinPEP” button and follow 

the instructions provided in the manual. 


98198100 2-1

Install WinPEP 

Use the following steps as a guide to install WinPEP 

for Windows ® 95 / 98. 

(1) Read the WinPEP Copyright notice and click 

“NEXT”. 

(2) Carefully read the WinPEP license agreement 

and click “Yes” if you agree to the terms. 

2-2 98198100

(3) Select the Dynamometer that your are 

installing the software for, and then click 

“Next”. 

98198100 2-3

(4) You will need to select the type of hardware 

that you have. Refer to the picture below, 

make your selection, and then click “Next”. 

If you have a “Hardware 

Stack” as shown to the left, 

select the “Dynoware 

EX+” option. 

Dynoware EX+ 

If you do not have a 

“Hardware Stack”, choose 

the “Internal PC Card” 

option. 

2-4 98198100

(5) Select a drive and directory where you 

would like WinPEP to be installed. 

Click the “Next” button after you have made 

your selection. 

(6) On a typical installation, the boxes in the 

picture on the next page will be checked. 

Note: 

If you are reading this manual on your 

computer screen, you already have Adobe 

Acrobat Reader installed. If you are reading a 

hard copy, you may want to check the “Install 

Acrobat Reader” box. 

98198100 2-5

! Leaving the “Copy Manuals” 

box checked will install the 

selected manuals on your 

hard drive. If you choose to 

uncheck the box, you’ll still 

be able to access the manuals. 

from the CD. 

! Clicking on the “Copy 

Manuals” text will allow you 

to pick and choose the 

manuals you would like to 

install. 

Click the “Next” button after you have made 

your selections. 

(7) Choose the language you prefer the units to 

be displayed in, and then click the “Next” 

button. 

2-6 98198100

(8) Review the selections in the “Current 

Settings” window. If the selections look 

OK, click the “Next” button. 

(9) You should notice the screen below while 

installation occurs, no action is necessary. 

98198100 2-7

(10) If you had a previously installed version of 

WinPEP or PEP, the Setup Program will 

find your configuration file and create a 

backup. If this is your initial installation, 

the screen shown below will not appear. 

Click OK and continue. 

(11) The next screen prompts you to turn on 

your Dynojet Hardware if it is installed. 

If you have the Dynoware EX+ Hardware, 

the power switch is on the front of the CPU 

Module. 

(12) If you left the “Copy Manuals” box 

checked in Step 6, the selected manuals will 

be copied into the WinPEP directory. 

!The “Install Adobe Acrobat” box in Step 6 

was checked by default, and Acrobat 

Reader will automatically install itself. 

!Acrobat Reader is a software package that 

will allow you to view the Dynojet 

Installation and User Manuals. 

2-8 98198100

(13) Setup will add program icons to the 

“Program Folder” shown in the picture 

below. You may type a new folder name, or 

select one from the “Existing Folders” list. 

Click “Next” to continue. 

(14) Click “Yes” if you would like a “WinPEP” 

icon placed on the Start Menu. 

98198100 2-9

(15) Setup is now complete, leave the “Yes I 

want to view the help file now” box 

checked. This will allow a screen to pop up 

with useful information that may help you 

find answers to common questions. 

Click the “Finish” button. 

2-10 98198100

Notes: 

98198100 2-11

Chapter 3 

Basic Concepts 

Windows Environment 

WinPEP Interface 

The following chapter will introduce you to effective 

and efficient use of WinPEP. 

For a complete understanding of Windows ® 95 

interface and environment, please refer to the 

“Introducing Microsoft ® Windows ® 95” booklet 

that came with Windows ® 95 Software. 

WinPEP is designed to be user-friendly and 

intuitive. Once you understand the basic layout, 

it will be easy to obtain information efficiently. 

Workspace 

Work Group 

Run Browser Tree 

Selection List 

Run Browser Tabs 

Graph View 


Document #98198100 3 - 1

Workspace 

The Workspace is WinPEP’s working desktop. 

Work Group 

The Work Group is the dialog that contains the 

current runs being made or viewed. A work 

group can contain from 1 to 12 runs. 

The work group is broken into 4 quadrants (Tree, 

Tabs, Selection List and Data View). 

Run Browser Tree 

Using the tree structure for viewing dyno runs 

allows you to access your runs from a standard 

Windows ® tree format. 

Run Browser Tabs 

The Run Browser Tabs mirror the way the Run 

Browser Tree moves, but resembles the same 

functionality of the DOS Pep. This feature may 

be easier to use than the Run Browser Tree for 

former DOS users. 

Selection List 

The Selection List displays the currently selected 

runs. The list will store up to 12 runs. 

Data View 

The Data View portion of the screen displays the 

run data in graph format. While in the 

“Preview Graphs” mode, the graph will only 

preview the currently selected run that is active in 

the Tree or the Tab. However, when you click the 

“Graph View” icon, the graph will display all the 

data from the graphs in the Selection List. {Refer 

to Work Group Toolbar} 

3 - 2 Document #98198100

Workspace Menu 

File Menu 

• New (Ctrl - N): Start a new Work Group for 

making dyno runs. 

• Open (Ctrl - O): Open a Work Group. 

• Save (Ctrl - S): Save current Work Group with 

1 to 12 dyno runs. 

• Save As (Ctrl - S): Save current Work Group 

to a different name. 

• Close (Ctrl - W): Close current Work Group. 

• Close All: Close all open Work Groups. 

• Print: Print current dyno Graph or Notes. 

• Print Setup: Edit properties of the printer. 

• Exit (Ctrl - Q): Exit WinPEP. 

Dyno Menu 

• Dyno Parameters: Edit the parameters of 

your dynamometer and the environment. 

• Graph / Race Colors: Edit the images in 

WinPEP for the different functions using 12 

distinct colors. 

• Make Run Option: Configure the options for 

making a dyno run and viewing the sampling 

screen. 

• Make Run Graph Options: This options page 

allows the user to configure the graph 

parameters for the graph that is generated after 

making a run. 

• Make Run: Prior to making a dyno run, enter 

a name for the new run, a title for the run, and 

other applicable parameters. 

Tools Menu 

• Group Tools: Group tools to copy or delete 

the currently selected Work Group. 

Document #98198100 3 - 3

• System Information: View the current system 

resources. Shown Below. 

• Other Tools 

New Root Directory: Set the drive and 

directory as the root when looking for runs. 

Printer Parameters: Control the output of the 

dyno graphs. 

Clear Clipboard: Clear any data that may be 

on the clipboard in order to gain memory. 

Sort Runs: The user can change the order in 

which the runs are displayed in the Browser 

sections tree and tab. 

• Window Menu 

Cascade (Shift - F5): Cascade a number of 

Work Groups so that you can easily see the 

different Groups on the Workspace. 

Tile (Vertical): Tile Vertical aligns your Work 

Groups vertically on the Workspace. 

Tile (Horizontal): Tile Horizontal aligns 

Work Groups horizontally on the Workspace. 

Arrange Icons: Arrange the Work Groups into 

an organized manner at the base of the 

Workspace when minimized. 

Minimize All: Shrinks the Work Groups to 

make more space when beginning another 

Work Group. 

Work Space 1: View the current Work Groups 

available on the Workspace. The current 

Work Group will be check marked. 

3 - 4 Document #98198100

Note: You may flip between Work Space 1,2,3, 

etc. by hitting the (Ctrl + Tab) keys. 

Workspace Toolbar 

Help Menu 

• Contents: Electronic help file for WinPEP 

• About WinPEP: Displays credits, version and 

release date. 

A B C D E F 

• (A) Make Dyno Run: Prepares WinPEP to 

acquire data from the dynamometer. 

• (B) Work Group: The New Work Group icon 

does the same thing as the File>New menu, 

changing the Work Group into a view and edit 

mode for dyno runs. 

• (C) Open Group: The Open Group icon does 

the same function as the File>Open menu, 

opening a saved Work Group. 

• (D) Graph / Race Colors: Edit the images 

used in WinPEP for the different functions; 

including race routine, graph, and the image 

used for printing. Here you can also select the 

color of the images with 12 distinct colors. 

• (E) Exit Program: Exit WinPEP software. 

• (F) Help: The Help icon gives concise 

electronic help that can be used to find answers 

relating to WinPEP. If more involved 

information is necessary, refer to this User 

Guide. 

Document #98198100 3 - 5

Work Group Toolbar 

A B C D E F G H 

• (A) Graph View: Place the Work Group dialog 

into the graph edit and view mode. This is the 

mode in which you will be able to view all the 

selected dyno runs (ranging from 1 to 12) as a 

group comparison. You can zoom in on any 

portion of the graph data, set the conversion 

modes and view multiple graphs of the same 

data in different modes. 

• (B) Preview Graph: Place the Work Group 

dialog into the preview mode. This mode 

allows a quick way to view runs without adding 

them to the selection list. 

• (C) Notes/Parameters: Place the Work Group 

dialog into the notes view and edit mode. Here 

you can view each of the runs and edit them as 

you review the data from the run. 

• (D) Search: Search for a run using a keyword 

in the run title or notes. 

• (E) Print: Print a graph of the runs selected 

and the respective notes if desired. 

• (F) Delete: Delete the currently selected run or 

directory in the Selected Runs List. The 

deleted dyno run or directory will be sent to the 

Recycle Bin on the Windows ® desktop. 

• (G) New Root Directory: If the dyno runs are 

in a different folder or hard drive, change the 

directory that WinPEP uses to view runs and 

make new runs. 

• (H) Clear Selected: The Clear List Icon can 

clear all selected runs from the selection list. 

3 - 6 Document #98198100

Graph View Toolbar 

A B C D E 

• (A) Graph Options (Shown below): 

(1) Change what values are to be displayed on 

the left and right Y axis, and what is to be 

displayed on the bottom X axis. 

(2) Change from single to multiple graphs. 

(3) Select options : Display Negative Value, 

Mazimize Graph Automatically and Force 

Scaling. 

(4) Choose to: Display Maximum Values, 

Display Conditions, Display Titles or None. 

• (B) Copy Graph to Clipboard: Copy the 

currently displayed graph to the clipboard in 

order to move the data between applications. 

• (C) Maximize Graph: The Maximize Graph 

icon will display the current graph in full 

screen mode. 

• (D) Correction Factor: The Correction Factor 

menu changes the view of the graph using 

either SAE, DIN, EEC or STD (Standard) 

correction factors. 

• (E) Smoothing: The Smoothing menu shows 

five different levels of detail in a graph. 

Smoothing level one shows the most detail 

where smoothing level five shows the least 

detail (Note. Level three is the default setting). 

Document #98198100 3 - 7

Notes: 

3 - 8 Document #98198100

Chapter 4 

Making a Run with a Sled 

Rear Idler Assembly Layout 

This chapter is a step by step tutorial on the 

attachment of the dynamometer to a sled in 

preparation for making a run and making a 

run using Dynojet’s WinPEP software. 

The following 2 pictures shows how the rear idler 

assembly looks mounted on the rails and layout 

of the order they go in. 

Middle Spacer 

Inside Driver 

Inside Driver Spacer 

Track Tensioning 

Guide 

Outside Driver 

Driver Spline Shaft 


Document #98168101 4 - 1

Connecting the Dyno to a Sled 

Use the following steps to Connect a Sled to the 

dyno: 

Step 1 

Check the inside to inside and the outside to outside 

distances between the rails. Record this information in 

the Tech Sheet (see appendix A). 

Step 2 

The dyno comes with two drive spline shafts ( red 

and green). Use the red short shaft for rail 

spacing around 8 3 / 4 " and the green long shaft for 

rail spacing around 9 3 / 4 ". 

Rail spacing can be different from model to 

model you may have to insert shims before you 

can install the inside driver spacers. Provided 

with the dynamometer are 6 large shims of 

varying thickness: 

2 - 1/32" shims 

2 - 1/16" shims 

2 - 1/8" shims 

4 - 2 Document #98168101

Take the actual measurement of the inside of the 

rails minus ( 8 3 / 4 "or9 3 / 4 ") and divide by two. 

This is the thickness of shims you must use on 

each side. You will be able to achieve spacing 

that is close enough with a combination of shims 

from the large shim pack. Place the desired 

shim(s) onto the color Coordinated spacers. 

Step 3 

Now, insert the inside driver spacers into the 

bearing of the inside driver hubs. 

Step 4 

Remove the rear idler assembly as per 

manufacturer instructions. 

Document #98168101 4 - 3

Step 5 

If you are testing a Yamaha put the threaded rods 

into the inside driver spacers (marked blue) to 

tension the track. 

• Place inside drivers with inside driver spacers 

into the track between the rails. 

• Place the middle spacer between the drivers. 

• Pay close attention to the alignment of the 

driver wheels. Each wheel has a lineup hole. If 

testing a Yamaha, make sure the tensioning 

rods are in the tensioning mounts. 

4 - 4 Document #98168101

Step 6 

Insert the correct color spline shaft through the 

rail, drivers and spacers so it is centered. Make 

sure the drivers still line up properly after the 

shaft is installed. 

Step 7 

Place the track tensioning guide piece so the 

housing fits into and fully seats in the tensioning 

slot of the rail. 

Note: 

Each dyno comes with three sets of 

spacers. Use the spacer that provides the 

least clearance. 

Document #98168101 4 - 5

You may have to back the tensioning bolt 

completely off to get clearance. You may 

temporary replace the stock tension blocks with 

the ones that come with the dyno if the stock 

tension blocks are in the way. 

Step 8 

Place the allen head bolt with lock washer in the 

outside driver hub. 

• Before the outside hub is placed on the shaft, a 

small shim (equal in width to the shim on the 

inside spacer) must be placed inside the hub. 

Refer to the picture on the next page. 

4 - 6 Document #98168101

Step 9 

Place the outside drivers so the nose fits into the 

bearing of the track tensioning guide. With the 

reference holes lined up, start the bolt. Do not 

tighten the bolt at this time. 

Step 10 

Tension the track to the manufacturers specification. 

Now properly tighten the track tensioning guide bolt 

to 18 ft-lb. of torque. Check the track tension again 

and ensure the track can move freely. 

Document #98168101 4 - 7

Step 11 

Position the sled and dyno so the arms of the dyno 

are on either side of the track. 

• Use the jack to position the arms at the correct 

height so the splined holes in the end of the 

arms line up with the splined holes in the 

outside driver. 

Note: 

If the sled and dyno are not level to one 

another the spline shafts may be difficult 

to install. 

4 - 8 Document #98168101

Step 12 

Install the short spline shafts, one side at a time. 

Note: 

Be sure to tap the shafts in as far as 

possible and add the necessary shims. 

(Refer to the Video). 

• Once the shafts are in place, install the 

retainer clips. If you are using the red driver 

shaft, place the retaining clip so that the red dot 

is showing. Place the retaining clip so that the 

green dot is showing when using the green 

driver shaft. 

• Torque the bolts to 18 ft-lb. 

Document #98168101 4 - 9

Step 13 

Using the dyno jack, raise the rear of the sled 

off the ground so the track’s lowest point is 

approximately 2" above the ground. 

• With the sled at the correct height, hand 

tighten the jack lock. 

• Install the dyno guard and tighten the bolts. 

• You will need to supply the nipple to thread 

into the regulator assembly. Be sure to wrap it 

with thread tape to ensure a tight seal. 

• Attach the air source to the nipple. The 

regulator should be set for 40 psi. 

4 - 10 Document #98168101

Connecting the RPM Pickup 

Use the following to connect the RPM Pickup. 

Connect the Tachometer Pickup (Primary Wire). 

• Attach the Primary wire inductive pickup to the 

primary wire of the coil. Place the pickup in a 

position that is isolated from electronic noise 

produced by the Sled. 

Warning!! 

The inductive pickups contain a fragile 

Ferrite Core that is sensitive to engine 

heat and vibration. Do not drop the 

inductive pickup or snap it closed. Use 

extreme care in the handling and 

placement of the pickups ! 

Document #98168101 4 - 11

Optional Secondary Inductive 

• The secondary inductive pickup may require two 

adjacent spark plug wires to work correctly. If you 

are using a single cylinder sled or a single fire 

ignition system then connect only one inductive 

pickup. 

Note: 

When using one secondary pickup, 

disconnect the other pickup from the 

amplifier box. 

Warning!! 

The inductive pickups contain a fragile 

Ferrite Core that is sensitive to engine 

heat and vibration.Do not drop the 

inductive pickup or snap it closed. Use 

extreme care in the handling and 

placement of the pickups. 

4 - 12 Document #98168101

Make a Pre-run Inspection 

Perform a vehicle inspection before making a 

run. Check the following: 

• Radiator coolant level. 

• Oil level. 

• Fuel source. 

• Rotate the track and check for debris caught in 

the tread that could fly out. 

• Visually inspect the sled. Make sure it is in 

safe running order. 

• Make sure safety glasses and ear protection is 

used when the dyno is being operated. 

• Keep all rotating components clear at all times. 

• Only the operator should be near the dyno or 

sled during the test. 

• Never make adjustments to the sled or dyno 

while the sled engine is running. 

• Never allow any person(s) to stand behind the 

dyno or sled when it is being operated. 

• Never operate the dyno with any of the guards 

or covers removed. 

• Ensure the sled and dyno are on a stable 

surface. The dyno and sled should not move 

during testing. 

• Perform any other safety inspections 

appropriate to running the sled on the dyno. 

Document #98168101 4 - 13

Running WinPEP 

Use the following steps to run WinPEP: 

Step 1 

Turn your computer on and allow it to boot. 

Step 2 

Click the WinPEP icon on the desktop. 

Step 3 

Click on the “Make Run” icon in the workspace 

toolbar. 

If the following Error Message is displayed the 

user will need to select a different Com port 

(DynoWare EX+) or a different Address (PC 

Card). 

The Dyno Parameters page will automatically 

load to facilitate this. 

After correcting the problem click on the make 

4 - 14 Document #98168101

Click the “Make Run” Icon again to enter the 

make run screen if you received an error message 

the first time. 

Selecting a Name for Run Title 

Use the following steps to make a run. This example 

will use an Arctic Snowpro owned by Bill Jones. 

Step 1 

Select the Make. 

• Using the mouse click on Arctic in the tree 

structure to the right. 

Document #98168101 4 - 15

Step 2 

Select the Model. 

! Press the key to insert a new model. 

! Type the name of your vehicle in from the 

keyboard. The name can be 1 to 8 characters 

long with no spaces. You can use small or 

capital letters. 

Example: 

SnowPro 

! Click 

! Type the customer name or work order 

number in from the keyboard. 

4 - 16 Document #98168101

Example: Jones 

! Click 

The screen should look like the following: 

Editing the Notes and Parameters 

Now you need to fill in the data necessary for 

making a dyno run. 

Next Run Name 

Enter the name of the run from the keyboard. It 

must be 1 to 8 characters without spaces. This 

name will appear on the graph when it prints. 

Example: 

Bill 

Run Title 

Enter the description of the run in the Run Title. 

Example: 60/54 yellow/org/whte/310/320 

Document #98168101 4 - 17

Plug fire 

Enter the number of plug degrees the crankshaft 

turns between plug firings. 

Examples: 

! Every Other Revolution = 720 degrees. 

! Every Revolution = 360 degrees. 

! Twice Every Revolution = 180 degrees. 

! This engine is a two stroke. It fires once per 

revolution. Degrees between plug fires = 360. 

If you don’t know the number of degrees to enter, 

just leave it at it’s default. 

Redline 

Enter the Tachometer Redline from your sled. 

Example: 9,000 RPM = 9 

This places a redline on the tachometer on the 

computer screen during a run. If you exceed this 

redline during your run, the tachometer needle on 

the computer screen will change colors. 

4 - 18 Document #98168101

Max. Track Speed: 110 MPH 

Caution!! 

Do not exceed this speed. The computer 

will stop the run and damage could 

result from exceeding maximum speed. 

The last three items, Absolute Pressure, Room Air 

Temperature, and Relative Humidity are 

determined from sensors and cannot be changed. 

Run Type 

Select the abbreviation for the type of run. 

! RO = Roll-On 

Example: RO 

Notes 

Enter up to 5 lines of information about your 

run. 

Example: 

1998 SNOPRO ALL STOCK 

Document #98168101 4 - 19

Optional make run settings. 

Auto Download: 

! Automatically saves a delimited text file in a 

numbers data format after each run. The name 

of the file will be the same as the run with a 

DAT extension and will be stored in the same 

directory as the run. 

Hold Baseline: 

! When this option is checked the first run in the 

selection list or the first run made is held in the 

number one slot on the graph for comparison. 

! To change the base run, change the run in the 

number one slot in the selection list on the work 

group form. 

Graph Data Following Run: 

! This option allows the user to toggle on and off 

the graph after making a run. 

Display Neg Values: 

! The user can elect to view negative values on 

the graph after making a run. 

Press the “MAKE RUN” button or key 

to start the run. 

4 - 20 Document #98168101

Your computer screen should look like the 

following: 

Making a Dyno Run 

The standard roll on test may be initiated from an 

initial speed of 5 to 10 MPH. When you find a test 

procedure you are comfortable using, use it 

consistently. It is very important, regardless of the 

procedure, to perform each test the same way. 

Warning!! 

Never begin a test from rest (0 MPH). 

Damage to the outside shafts will result. 

Step 1 

Setup the software for specific sled. 

The pendent has two buttons on it. The green 

button on the pendent controls the sampling of the 

dyno. When the green light is on, the computer 

is gathering data. The red button on the pendent 

controls the brake. When the red light is on the 

brakeison. 

Document #98168101 4 - 21

Pendant 

Green “Sample” Button 

Red Brake Button 

Step 2 

Attach the secondary inductive pick up to the 

spark plug wire. 

Note: 

See Page 4-13 for Pre-Run Inspection. 

4 - 22 Document #98168101

Step 3 

Start the sled and ensure the tach is working and 

the parameters are set correctly. 

In order for the test to be repeatable, the engine 

and drive train must be warmed up before a run 

can be made. For a two stroke engine, consistent 

head and pipe temperatures are very important for 

tuning and testing. The temperature at the 

beginning of each run should be noted so each run 

starts with the temperatures close to each other. 

Step 4 

When everything is up to temperature hold the 

sled at a constant speed of around 10 MPH. 

Press the green button. It will light up and the top 

of the make run screen will now read “sampling”. 

Now press the accelerator fully. When the 

desired speed has been attained release the 

throttle completely and press the green button 

again. Press the red button to activate the brake to 

aid in slowing the dyno and track down. 

Warning!! 

Repeat these steps two more times. These are 

baselines for comparison. If the temperature of 

DO NOT use the brake on the sled. Use 

of the sleds brakes will result in damage 

to the sled, the dyno, or both. 

The use of the sleds brakes can be used in 

“Emergency Stop Situations only! 

the engine and pipe have come up to operating 

temperature these runs should repeat. 

Document #98168101 4 - 23

Disconnecting Sled from Dyno 

The removal of the sled from the dynamometer and 

replacing the stock idler assembly is the reverse of the 

install section of this manual. The only addition is the 

use of a extractor tool to remove the short spline shafts. 

• Lower the dyno arms so the track is back on the 

ground. Be sure the arms are neither holding the 

sled off the ground or pushing the sled down.) 

Remove the 3/8" bolts and the retainer clips. 

• Place the puller housing over the shaft and 

thread the extractor bolt into the short spline 

shaft. 

• Turn the handle to pull out the spline shaft. 

Continue with the rest of the removal. 

Extractor Tool 

4 - 24 Document #98168101

Notes: 

Document #98168101 4 - 25

Chapter 5 

Viewing Graphs 

Viewing a Fourth Gear Roll-on 

WinPEP corrects for altitude and atmospheric 

conditions and automatically adjusts power curves for 

different weather conditions producing consistent 

power graphs. This unique feature is just another 

example of our common sense approach to precision 

and diagnostics. 

The run used in this chapter may not be in the demo 

runs that came with your dyno, so just select a make, 

model and run that interests you) 

Step 1 Selecting the Make 

Using the mouse, click once on the top of the 

tree or on the “MAKE” tab to collapse the tree. 

Select a make from the tree or tab window. For 

this example we chose an Acura. 

Step 2 Selecting the Model 

Using the mouse, we click once on “Integra” in 

the tree structure to the left. 

Step 3 Selecting the Name 

We click once on “Jones” in the tree structure to 

the left. 

The screen should look similar to the following: 


Document #98198100 5 - 1

Step 4 

We click on Jones.001 and it is graphed in the 

preview runs Graph to the right of the tab 

window. 

Step 5 Adding Run to the Selection List 

By double clicking on JONES.001 in the tree 

structure to the left the run is added to the 

selection list. Refer to the image on the next 

page. 

5 - 2 Document #98198100

Step 6 Graphing the Selected Run 

Click on the “Graph View” icon in the workspace 

toolbar or click the mouse over the graph to graph 

the selected run(s). 

Graph Features 

Smoothing 

The “Smoothing” slider controls the level of 

detail of the graph. Smoothing level one shows 

the most detail where smoothing level five shows 

the least detail (Level three is default). 

Document #98198100 5 - 3

Correction Factor 

Graphs can be viewed using either SAE, DIN, 

EEC or STD (Standard) correction factors. To 

change the correction factor click on the “Correction 

Factor” pulldown and select the desired 

option. 

Zooming In 

Step 1 

Left mouse click on the graph area, hold the 

mouse button down, and move the mouse down 

and to the right. 

The screen should look similar to the image 

shown below. 

5 - 4 Document #98198100

Step 2 

Release the mouse button and the graph will 

magnify the selected area. 

Unzooming 

With the mouse cursor over the graph, click the 

right mouse button. 

Select Undo Zoom. 

Copy graph to clipboard 

With the mouse, click once on the “Copy Graph 

to Clipboard” icon. Once copied to the clipboard, 

the graph can be imported (pasted) into other 

applications. 

To clear the graph from the Clipboard, go to the 

Tools / Other Tools menu and click once on the 

“Clear Clipboard” menu option. 

Document #98198100 5 - 5

Graph Options 

Click on the “Graph Options” icon in the Graph 

View Toolbar or right click on the graph to bring 

up the Right Click Menu and select “Graph 

Options”. 

Display Neg Values: 

Graph Negative values. 

Maximize Graph: 

Maximize the screen after graphing. 

Force Scaling: 

Force right and left Y axes scaling. 

Max Values / Run Conditions / Run Titles 

This area of the graph axis selection dialog allows 

you to display either Maximum Values, 

Conditions or Run Titles on the graph. 

5 - 6 Document #98198100

Axis Selection 

Step 1 

Using the mouse click once on “Axis Selection.” 

Step 2 

Click on Power in the displayed option box. 

Note: 

Available selection may differ depending 

on dyno model and configuration. 

Document #98198100 5 - 7

Step 3 

Click on Torque in the displayed option box. 

Step 4 

Click on Engine RPM in the option box. 

Step 5 

Click on the gear ratio you want displayed in the 

option box. 

5 - 8 Document #98198100

The following graph will be generated. 

Multiple Graph Selection 

Step 1 

Using the mouse, click once on “Multiple 

Graph”. 

Step 2 

Move the mouse cursor over the highlighted 

division bar at the top of the graph template. 

While holding the left mouse button down, 

position split bar where you want the top graph to 

end. Refer to the images on the next page. 

Document #98198100 5 - 9

Step 4 

Click . 

Step 5 

Click on POWER in the displayed option box. 

Step 6 

Click on TORQUE in the displayed option box. 

5 - 10 Document #98198100

Step 7 

Click on TIME in the displayed option box. 

Click . 

You will now have a multi -graph. 

Remove a Graph from Multi-graph 

The following steps will demonstrate how to 

remove a graph from a multi-graph situation. 

Document #98198100 5 - 11

Step 1 

Go back to the Graph Options Dialogue. 

Step 2 

Click on “Multiple Graph” and position the 

cursor over the line that you want removed. 

Step 3 

Double click the right mouse button to remove 

the line. 

5 - 12 Document #98198100

Step 4 

Click on “OK”. 

Step 5 

Select the properties of the Axes that you desire 

and click on “Ok” to Regraph. 

Full Screen Zoom 

By clicking on the Full Screen Icon the graph will 

fill the monitor screen. The same icon will reduce 

it again. (A double click of the mouse over the 

graph screen will do the same thing.) 

Document #98198100 5 - 13

Right Mouse Button Menu 

By placing the mouse cursor over the graph and 

clicking the right mouse button, the menu shown 

below will be generated. 

Graph Options 

The Graph Options dialogue box (shown below) 

can be accessed through this option. 

5 - 14 Document #98198100

Right Mouse Button Menu continued... 

Cursor 

This option toggles the graph cursor on and off. 

(Refer to the next page for more information on 

the graph cursor.) 

Cursor Line 

This option allows the user to change the 

thickness of the cursor to improve visibility. 

Document #98198100 5 - 15


If the user clicks on the graph when the cursor is 

toggled on then a vertical line will be drawn on 

the graph at that spot and values will be displayed 

on the graph where the line intersects the graphed 

run(s). 

X axis cursor value 

HP = 481.3 

The up and down arrow keys move the cursor in 

large even steps. The left and right arrow keys 

move the cursor in small even steps. Hold down 

the CTRL key for even smaller stems while using 

the arrow keys. 

5 - 16 Document #98198100


Scaling 

If “Scaling” is selected a scaling dialogue will be 

generated. 

The user can choose to manually set the maximum 

right and left Y axes values. 

Note: 

When used with the Graph Option “Force 

Scaling”, only the larger of the two values 

are used. 

Font Size 

By choosing the font size on the displayed graph 

can be set to improve visibility. 

Document #98198100 5 - 17


Grid Lines 

By choosing the grid lines on the displayed graph 

can be set to improve visibility. 

Grid in Front 

Choose “Grid In Front.” Using this feature, the 

grid lines on the displayed graph can be set to the 

front, over the displayed data sets. 

Graph Lines 

The “Graph Lines” option allows the user to set 

the size of the graphed run(s) to improve 

visibility. 

5 - 18 Document #98198100


Export Dialog 

With the right mouse button, click on the 

displayed graph. By choosing the export dialog 

feature, the data points can be exported. 

The export dialog allows the user to export to a 

Windows Metafile or a Windows Bitmap 

After selecting either Metafile or Bitmap and 

clicking on the “OK” button the appropriate 

dialogue will load with the proper extension and 

allow you to select a name for the file and the 

directory where you want the file to be saved. 

Document #98198100 5 - 19

Printing a Graph 

Step 1 

Click on the “Print” icon in the workspace toolbar 

or use the Right Click Graph Menu and Select 

“Print” 

Step 2 

Using the mouse click once on “Print.” 

Step 3 

Using the mouse, click once on “Ok” . 

This will send the current graph to the default 

printer. To cancel the print, click once with the 

mouse on “Cancel.” Either operation will return 

you to the WinPEP program. 

Note: 

For quick black and white prints, click on 

the graph and press the “S” key. The 

graph should change from color to black 

and white. Press the “P” key to send it to 

your printer. 

5 - 20 Document #98198100

Print Preview 

Step 1 

Click on the “Print” icon in the workspace toolbar 

or use the Right Click Graph Menu and Select 

“Print” 

Notes: 

The Print Dialogue has several unique 

options. 

(1) The user can print/preview the graph 

alone. (Default) 

(2) The user can print/preview the graph 

and notes on the same page. (Limited to 3 

runs) 

(3) The user can force the notes to separate 

pages. 

(4) The user can toggle on and off the 

graphic placed at the top of the graph 

page. 

Document #98198100 5 - 21

Step 2 

Using the mouse, click once on “Print With 

Notes” 

The Notes Printing section will be enabled with 

“Print With Notes on Same Page (Limit 3)” 

selected as default. 

Step 3 

Leave the Notes Printing as default and click on 

the Preview button. The following screen will be 

displayed. 

You can send the page to the printer by clicking 

on the Print button, Zoom in and out of the page, 

5 - 22 Document #98198100

pan the image when zoomed or cancel the 

preview by clicking on Close button or the X 

button in the top right corner. When the user 

finishes with the preview screen they will be 

returned to the print options dialogue. 

Changing Graphic Header 

Step 1 

Using the mouse, click once on “Page Graphic.” 

Step 2 

Using the mouse, click once on “Load Bitmap.” 

Document #98198100 5 - 23

Step 3 

After selection of bitmap file, click once on the 

Open button. 

Step 4 

Adjust the printed image size. 

Step 5 

After sizing the bitmap file, click on the Update 

Bitmap button. 

5 - 24 Document #98198100

Step 6 

After updating the bitmap, click once on “Place 

Graphic.” 

Note: 

Step 7 

With the left mouse button held down, position 

the graphic on the page where it will appear on 

printed page. 

This may take a few tries to get the map to 

appear right in the preview screen. It may 

be necessary to place the graphic a bit off 

to the left of the page to get it to center in 

the preview screen. 

Document #98198100 5 - 25

Step 8 

With the mouse, click once on “Print Graph” and 

then the Preview button to check it’s placement. 

All previews and graphs sent to the printer will 

now have the new graphic. 

5 - 26 Document #98198100

Print Options 

Font Selection 

With the mouse, click once on “Font.” 

The following selection dialog will be displayed. 

This dialog allows you to change the default font 

properties of the run titles above the graph. Font 

sizes over 16 are not recommended. 

Document #98198100 5 - 27

Setting Margins for graph output 

This area of the print dialog allows you to change 

the default margin of the entire graph. 

Page Orientation 


the page orientation for the entire graph. 

The illustration below demonstrates Portrait and 

Landscape graph output. 

No Graphic on Output 

This area of the print dialog enables/disables 

graphic above the graph. 

5 - 28 Document #98198100

Text printed at top of graph 


the text that is displayed at the top of the printed 

graph. 

Document #98198100 5 - 29

Notes: 

5 - 30 Document #98198100

Chapter 6 

Racing Vehicles 

The Race Routine is a unique feature in WinPEP that 

places the Work Group area into race mode. The 

mode races the currently selected runs against each 

other for performance comparisons. 

This chapter will be sent out with the software 

update that enables the Race Routine in WinPEP. 


Document #98198100 6 - 1

Notes. 

6 - 2 Document #98198100

Chapter 7 

Notes / Search Features 

Viewing / Editing Notes 

This chapter will introduce you to the different features 

of the Notes capabilities and search function. 

Step 1 

Click on the “Notes/Parameters” icon in the Work 

Group toolbar. 

Step 2 

Click once on the dyno run file that contains the 

notes you wish to view. 


Document #98198100 7 - 1

Step 3 

Using the mouse, click once on the title field. 

This will allow the current run title to be edited. 

Once the cursor is blinking on the title field, you 

may type in any corrections, additions, or 

changes. 

Step 4 

Use the mouse to bring down the run type field. 

This will allow you to choose a different run type. 

7 - 2 Document #98198100

Step 5 

Using the mouse, click once on the notes field to 

alter any note corrections and additions. 

Step 6 

Finally, click once on “Save Changes.” This 

writes your changes to the run file. 

Search 

Step 1 

Click on the “Search” icon in the Work Group 

toolbar. 

Step 2 

Select the desired drive and directory to search. 

Document #98198100 7 - 3

Step 3 

Using the mouse, click once on the box labeled 

“Search For” and enter the keyword for the 

search. 

Step 4 

Finally, click once on “Search.” This will initiate 

the search procedure. 

7 - 4 Document #98198100

Step 5 

Simply double click on the runs of interest to automatically 

add the run to the selection list. 

Document #98198100 7 - 5

Notes: 

7 - 6 Document #98198100

Chapter 8 

Tools 

WinPEP’s tools enable the dynamometer to produce 

fast, repeatable, and reliable results for increasing 

performance and providing diagnostic changes. 

WinPEP Tools 

A work group is the heart of WinPEP. The work group 

is where selected runs can be compared , notes read 

and edited and runs can be renamed and reorganized. 

When WinPEP loads it automatically creates a blank 

(New) work group. The user can use this blank one or 

close it and open a previously saved one. Work groups 

are meant to be saved in the root directory where 

WinPEP is located. 

There are some distinct advantages to working with 

saved work groups. 

(1) A saved work group maintains the directory 

structure that the user was last using before saving 

the group. 

(2) The selected runs (after a save) will remain 

selected when the group is opened at a later date. 

(3) The user can use a saved group to copy the selected 

runs and their primary directory structure to another 

directory or drive (Even a floppy disk). This makes 

copying runs for dyno customers easy. There is a 

very distinct difference between saving a work group 

and copying one. 


Document #98198100 8 - 1

Several of WinPEP’s Tools involve saved work groups 

so we will begin this chapter by reviewing saving and 

opening work groups. 

Save Group 

Step 1 

With the mouse, click on the “File” menu then 

position the cursor over “Save”, click once. 

The following dialog will then prompt for a 

descriptive file name to save the group as and 

where you want to save it. Dynojet recommends 

that you save your work groups in the same 

directory where your version of WinPEP is 

currently running. This directory will come up 

automatically when you save a group. 

8 - 2 Document #98198100

Step 2 

Type in a file name. Don’t change or delete the 

“.DGP” file extension after the name. 

Step 3 

Click on the Save button. 

Open Group 

Once a dyno operator has saved one or more work 

groups they can be loaded easily. 

Step 1 

Click on the “Open Group” icon in the workspace 

toolbar or from the File Menu. 

Step 2 

Using the mouse click once on the group file 

name to be opened. 

Step 3 

Click “OK”. 

Your saved group will now be opened into a new 

Work Group. 

Document #98198100 8 - 3

Group Tools 

Copy Group 

Step 1 

Click “Copy Group” from the “Group Tools” 

menu. 

Step 2 

The following dialog will allow selection of the 

destination for the current selection list and files. 

Delete Group 

Step 1 

Click “Delete Group” from the “Group Tools” 

menu. 

8 - 4 Document #98198100

Step 2 

The following dialog will confirm the deletion of 

the group file to the “Recycle Bin.” 

Note: 

the run files associated with the group file 

will not be removed. 

System Information 

Step 1 

Click “System Information” from the “Tools” 

menu. 

The following dialog displays the current 

working drive, the current Windows ® version, 

processor information, and the free system 

resources available to WinPEP. 

Document #98198100 8 - 5

Other Tools 

New Root Directory 

WinPEP uses a fixed directory structure to store 

runs. To change the root directory of the WinPEP 

software do the following. 

Step 1 

Click on the “Select New Root” icon in the Work 

Group toolbar. 

The following pull down menu example demonstrates 

an alternate method of executing the 

command. 

Step 2 

The following dialog will allow changing the 

default root directory for run viewing. 

8 - 6 Document #98198100

Printer Parameters 

Step 1 

With the mouse, click on the “Other Tools” menu 

then position the cursor over “Printer Parameters.” 

Click once. 

Note: 

This option is disabled until the user has 

selected and graphed a minimum of one 

run. 

The following dialog will then appear. For 

detailed information on printing, see the chapter 

on Viewing Graphs. 

Document #98198100 8 - 7

Clear Clipboard 

This option is quite self explanatory. 

(empties) the clipboard. 

It clears 

Sort Runs 

The user can have the runs in the tree view and 

tab window sorted by Name, Date, Run Title and 

Run Type. 

Options 

Use the Options menu item brings up the Dyno 

Parameter Tab page. 

8 - 8 Document #98198100

Dyno Parameters 

The altitude number placed in this box will be 

saved in the run file for display and dyno operator 

knowledge. 

The Barometric Pressure Calibration settings are 

used to adjust the absolute pressure sensor on the 

Motorcycle Model 150 Dynamometer (for all 

other Dynojet Dynamometers, set both options to 

1.0000). 

WinPEP will halt the sampling of data once 

maximum tire speed has been reached. 

When comparing dyno runs from different 

sessions, the room air temperature must be fairly 

consistent. If the temperature difference is 

greater than the predicted preset degree, a 

warning notice will appear on the screen. 

Document #98198100 8 - 9

This area of the Dyno Parameters dialog allows 

you to change the default Laptop Adapter port, 

PC Card Address or Hardware Serial port to your 

current hardware configuration. 

This information is display only and can not be 

edited. 

Graph / Race Colors 

The left area of the Graph / Race Colors dialog 

allows you to change the default color order for 

displayed graphs. 

The right area of the Graph / Race Colors dialog 

allows you to change the default background / 

foreground colors for displayed graphs. 

8 - 10 Document #98198100

Make Run Options 

This area of the Make Run Options dialog allows 

you to change the Gauge Screen (or Sample 

Screen) colors as well as the run abbreviation for 

various run types. For example, the default abbreviations 

are RO for a Roll On, AG for All 

Gear, FA for Fast Acceleration, and NG Negative 

Horsepower. The user can edit them as well as 

add two new ones. 

Make Run Graph Options 

The graph after making a run can be customized. 

Document #98198100 8 - 11

The Display section allows the user to choose 

from a variety of options to display on the graph 

after making a run. 

The Axes Selection allows for a custom multi 

axes graph. 

Checking this box will allow you to make axis 

selections from the main graph. If the selections 

that you made are not available in any of the 

selected runs, then the “Make Run” graph will be 

set to the default axis selection (HP vs. Speed). 

The axis selection will be restored when you 

remove the runs that lack the information to 

execute your selections. 

Fonts and Lines on the graph can be individually 

changed 

8 - 12 Document #98198100

The correction factor, smoothing and the 

maximum number of runs to graph at a time after 

making a run can be preset. 

If the user checks the check box marked “Control 

these settings from the Main Graph”, the maximum 

number of runs that will be graphed at a 

time after making a run will be 12 and the 

smoothing and correction factor will be taken 

from the settings on the Main Graph. 

Document #98198100 8 - 13

Chapter 9 

Theory of Operation 

Power 

Dynojet’s inertia dynamometer is a measuring device 

for recording and displaying power and torque of an 

engine. Its method of measurement is a direct 

implementation of the definitions of power and torque. 

Correction factors assist in the comparison of these 

measurements under various test conditions, making 

computer hardware and software necessary to obtain, 

interpret, and display the data. 

Power in mechanical terms is the ability to 

accomplish a specified amount of work in a given 

amount of time. By definition, one horsepower is 

equal to applying a 550 pound force through a 

distance of 1 foot in one second. In real terms, it 

would take 1 HP to raise a 550 pound weight up 

1 foot in 1 second. So to measure horsepower, we 

need to know force (in pounds) and velocity (in 

feet per second). 

Dynojet’s inertia dynamometer measures power 

according to the terms just described. It measures 

velocity by measuring the time it takes to rotate a 

heavy steel drum one turn. The dyno measures 

force at the surface of the drum by indirectly 

measuring its acceleration. Acceleration is 

simply the difference in velocity at the surface of 


Document #98198100 9 - 1

the drum from one revolution to the next. The 

force applied to the drum is calculated from 

acceleration using Newton’s 2nd law, (F)orce = 

(M)ass x (A)cceleration. 

Power is coupled to the drum by friction 

developed between the driving tire of the vehicle 

and the knurled steel surface on the drum of the 

dynamometer. 

Torque 

When an object rotates around a point, its speed 

of rotation depends on both an applied force and 

the moment arm. The moment arm is the distance 

from the point of rotation to where the force is 

being applied. Torque is the product of the force 

and the moment arm. For example, if a rope, 

wrapped around a drum of 1 foot radius, is pulled 

with 550 pounds of force, the resulting force is 

550 foot-pounds. 

The Torque on the dyno’s drum can be calculated 

by multiplying the force applied by the drum’s 

radius. However, engine torque is not equal to 

drum torque because the gearing through the 

drive train changes the moment arm. The change 

in the moment arm is proportional to the ratio of 

engine speed to drum speed. Therefore, 

tachometer readings are necessary to calculate 

and display engine torque. 

9-2

Correction Factors 

The calculation of horsepower or the accuracy of 

our dynamometer is not dependent on the 

location or conditions during the measurement. 

The performance of the internal combustion 

engine is, however, sensitive to atmospheric 

conditions, especially air density and air 

temperature. To compare power measurements 

taken at different times or places, it is necessary 

to compensate for differing atmospheric 

conditions. 

Correction Factors are used to compensate engine 

horsepower measurements for differences in 

operating conditions during engine testing. The 

typical correction factor (CF) is calculated based 

on the absolute barometric pressure, air 

temperature and water content of the air used for 

combustion by the engine under test. It attempts 

to predict the horsepower that would be 

developed if the engine were tested at sea level 

under standard pressure and temperature 

conditions. 

Absolute barometric pressure is a measure of how 

hard the air molecules are being pushed closer to 

one another. The unit of measurement is typically 

inches of mercury (inches Hg). The more 

pressure, the more molecules there are in a liter of 

air and the more air the engine gobbles up during 

the intake stroke. Absolute barometric pressure is 

equal to Relative barometric pressure only at sea 

level. Relative barometric pressure is reported at 

airports and by weather barometers. A good 

9-3

approximation for converting relative barometric 

pressure to absolute barometric pressure is: 

AbsHg = RelHg - (Elev/1000) 

Where: 

AbsHg = Absolute barometric 

pressure 

RelHg = Relative barometric 

pressure 

Elev = test location elevation in 

feet above sea level 

Water content is calculated from the ambient wet 

and dry bulb temperatures. Dry bulb temperature 

is normal room temperature. Wet bulb 

temperature is always less than or equal to dry 

bulb temperature. As air is blown over the wet 

bulb thermometer the water evaporates and cools 

the thermometer. The dryer the air, the cooler the 

wet thermometer indicates. If the ambient air is 

saturated (humidity = 100%), very little water 

evaporates and the wet bulb temperature is equal 

to the dry bulb temperature. These measurements 

are then converted to partial pressure in inches of 

mercury and used in the correction formula. 

Water vapor displaces oxygen and reduces the 

amount of combustion air ingested during the 

intake stroke. 

Air temperature is the temperature of the air 

entering the intake system of the engine under 

test. In some cases this is ambient air 

temperature, but in other cases the intake air is 

significantly heated by the engine and is different 

than ambient air. Heat tends to spread air 

9-4

molecules apart. So as temperature increases, 

there are less molecules in a liter of air and less 

air is swallowed during the intake stroke. 

Dynojet’s WinPEP (Performance Evaluation 

Program for Windows 95) software uses the 

SAE’s latest correction formula (June 1990). 

This formula assumes a mechanical efficiency of 

85% and is much more accurate than earlier 

formulas at extreme conditions. The formula 

used is: 

CF= 1.18 x (29.22/Bdo) x To+460 / 537) - 0.18 

Where: 

To = Intake air temperature in 

degrees F 

Hardware and Software 

Bdo = Dry ambient absolute 

barometric pressure 

The dynamometer electronics acquire data 

necessary for power, torque, and correction factor 

calculations. This includes air temperature, 

absolute barometric pressure, drum timing, and 

engine rpm. 

During a run, the data is stored in the dyno 

electronics memory. 

After a dyno run is finished, data from the dyno 

electronics, calibration data and user notes are 

saved to a file on the computer’s hard disk. Each 

run file is saved in a directory structure composed 

of “Make”, “Model” and “Name” which 

organizes the data for quick and easy retrieval. 

9-5

When the user selects a run, the data is loaded 

from the hard disk into computer memory. Data 

from up to twelve runs can be placed in memory 

at once. This information can be used for either 

viewing horsepower graphs or racing vehicles. 

The drum data is used to calculate and display 

power while viewing graphs. Data can either be 

viewed as measured (“uncorrected”) or as 

corrected according to standard atmospheric 

conditions. 

The drum data can also be used for determining 

speed and distance traveled in a simulated race. 

When not correcting to standard atmospheric 

conditions, the vehicle speed is equal to the drum 

speed and distance traveled equivalent to the 

number of drum revolutions times drum 

circumference. The relations are no longer equal 

when correcting to standard conditions. Both 

speed and distance are then predicted from the 

corrected acceleration of the drum. 

Conclusion 

By accelerating a massive drum, measurement of 

power and torque is straight forward and 

accurate. The use of correction factors allows 

comparison of those measurements under various 

test conditions. The use of modern computers 

provides an economical yet logical method of 

obtaining and viewing the information. Dynojet’s 

inertia dynamometer is fast becoming the 

industry standard because of its accuracy, 

repeatability and design simplicity. 

9-6

Notes: 

9-7

Chapter 10 

Graph Interpretation 

Ratcheting 

The graph above and on the next page are 

indications of “ratcheting”. Track ratcheting can 

vary. When the track is too loose the drivers 

cannot fully engage the track. The key is that the 

track is slipping on the driver, causing a spike in 

the graph. If the track continuously slips, the 

graph will show a harsh frequency and there will 

be an low vibration noise during the run. To fix 

this problem, check the track tension, and driver 

spacing and tighten as necessary. 


Document #98168101 10 - 1

Warning: 

If a ratcheting condition occurs while 

making a dyno run, terminate the run 

immediately. Make the necessary 

adjustments to the track tension or driver 

spacing to correct this problem before 

continuing dyno testing. Damage can be 

done to the sled, the dyno or both if 

ratcheting is allowed to continue. 

Jetting Change 

Here is a change in jetting, note the 

characteristics of the graph remain the same 

because we are seeing an increase in engine 

performance through the same clutching. 

10 - 2 Document #98168101

Helix Change 

The above graphs show the result of changing the 

helix angle. The clutch will shift faster or slower 

depending on the helix angle 

Starting Speed 

If you are doing a rolling start it is very important 

to start at the same speed for every run. The 

above graph shows what happens when the 

operator is not consistent with the starting speed. 

The first part of the graph (steepest part) is when 

the engine is revving up and the clutch is shifting. 

The second part of the graph (flatter part) is when 

the engine is at maximum RPM and the clutches 

are shifting. 

Document #98168101 10 - 3

Notes 

10 - 4 Document #98168101

WinPEP User Guide - Dynojet Research

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