ABSTRACT - Hexagon Studio

ABSTRACT
In USA, there are various regulations, related to safety, fuel economy and emissions. In this study, all
NYC federal and US governmental regulations and requirements are surveyed and taken into consideration while
building a sustainable driveline. The performance requirements are set according to driving conditions and duty
cycle. Firstly, power pack (engine & transmission) specifications are defined to obtain desired acceleration
performance and maximum velocity requirements. Moreover, an automatic transmission is selected according to
customer needs.
Almost ten engine and transmission combinations with different final drive ratios are simulated.
Different engine sizes from 1.6 liters to 3.0 liters are combined with different transmissions from 4-speed to 6-
speed. Software simulations are done by concerning fuel economy, fuel consumption, exhaust emissions (CO,
CO 2 , NO x , Soot, HC), acceleration performance, shift smoothness and gradeability.
After done with software simulations and optimizations, it is seen that engine must be down-sized and
propulsion system should be changed regarding the environment and emission & fuel economy regulations. In
US and especially in NYC, Federal Fuel Economy is regulated by NHTSA under the CAFE. Federal emission
requirements are set by EPA under Tier 2. Also, New York City accepts the California state emission
requirements which are under the CARB LEV II and GHG emission requirements. These regulations generally
depend on the physical footprint of the vehicle or vehicle class like passenger car, light duty truck etc.
Therefore, two options for the alternative propulsion system technologies are considered on the light duty truck
platform. One is natural gas and the other is plug-in gasoline-electric vehicle.
It is seen that desired acceleration performance and top speed can be achieved by using 1.6 liters monofuel
natural gas engine and required CNG tank capacity for the desired autonomy should be about 100 liters
regarding the fuel economy in specified duty cycle. Fuel economy simulations are done in FTP75, US06, SC03
and highway duty cycles to represent city cycle, aggressive driving, A/C usage and extra-urban duty cycles
respectively to find the combined fuel consumption value. According to simulations, almost no change in the
fuel consumption rate (gasoline gallon equivalent) when compared to same gasoline engine however about 25-
30% reduction in most exhaust emissions and Green House Gases.
6-speed automatic transmission is engaged with 1.6 liters mono-fuel natural gas engine. 6 th gear is overdrive
gear and it is given to reduce highway fuel consumption and gear train wear. Also, transmission gearing
ratios and final drive ratios are optimized by using simulation softwares according to acceleration performance
and desired top speed concerning fuel economy and gear train wear. Outstanding acceleration performance is
obtained by means of the optimization of the gearing ratios while promising fuel economy is achieved.
Moreover, to support sustainable driveline strategy extended range electric vehicle (E-REV) concept is
considered. In this strategy, 1.2 liter, 3 cylinders gasoline engine is used only to power the 60kW generator. The
energy produced by the generator is stored in the Li-ion battery via inverters and converters managed by the
control unit. The battery can also be charged by a standard 120V/15A household outlet, and by a 240VAC outlet
for fast charging. Li-ion battery is chosen for its high power density. The vehicle is always driven by the 55 kW
electric motor. This strategy allows the vehicle to move pure electric mode up to 50 km depending on the battery
size. Also, it will give a chance to make a full electric vehicle by reducing the engine size while increasing the
battery size. According to optimizations done by simulation software, it is seen that same performance
characteristics can be achieved by E-REV, while fuel economy is doubled and emissions are strictly decreased.
In conclusion, effects of governmental rules and regulations on the drive train are scrutinized in detail for the
light duty commercial vehicle, in this study. Fuel economy, exhaust emissions and performance targets have
great effects on the selection of the engine and transmission. Various drive train components and strategies are
simulated and optimized by using appropriate simulation software. Engine is tried to be downsized to give better
fuel economy and reduced exhaust emissions while giving promising performance characteristics by optimizing
the gearing ratios. As a result, it is seen that minimized engine size and best environmental friendly vehicle can
be achieved by using alternative propulsion systems like natural gas and E-REV.

Title
“A case study in the development of sustainable vehicle driveline strategies – NYC ToT*”
Four Subtitles
Regarding the environment and emission & fuel economy regulations
Downsizing the engine for the light commercial vehicle applications and duty cycle requirements
Optimizing the gear train ratios to obtain outstanding acceleration performance while giving promising
fuel economy
Setting an alternative driveline concepts for the NYC ToT (natural gas-E-REV**)
* New York City Taxi of Tomorrow
** Extended Range Electric Vehicle
Related Topics
Transmission and Drive train requirements
Environment-friendly drives: Downsizing and alternative drives for cars, commercial vehicles and all
wheel-drive vehicles