### CHASSIS TESTING VERSUS POWERTRAIN TESTING FOR HEAVY

- DUTY VEHICLE GREENHOUSE GAS EMISSION 

### MEASUREMENTS Joseph Anthony, Jayant Sarlashkar,
Southwest Research Institute

Houshun Zhang, James Sanchez, Matthew Spears, Angela Cullen, US EPASAE INTERNATIONAL 2 

# Introduction

• Heavy

- duty, on

- highway market vehicles are powered by engines that have been emissions

- certified as an individual component

.

• EPA/NHTSA Greenhouse Gas Emission and Fuel Efficiency regulations require evaluation of the entire vehicle

.

• EPA/NHTSA are researching methods to validate fuel efficiency results from vehicle simulation models

.

• This presentation is a comparison of two methods used for model validation

. g/hp

- hr g/ton

- mileSAE INTERNATIONAL 3 

# Chassis Dynamometer Facility Compared To 

# Powertrain Test Facility

Cons

• Large facility required for full vehicle

• Climate control for entire test cell

• Road speed fan Pros

• Convenient vehicle evaluation

• Does not require OEM support to operate a powertrain in a vehicle

• Correct packaging and heat transferSAE INTERNATIONAL 4 

# Powertrain Test Facility Compared To Chassis 

# Dynamometer Facility

Cons

• Questions about representative packaging and heat transfer

• Requires engine and transmission control integration

• Difficult test systems that deliver/ absorb power through the wheels, i.e. hybrid with wheel hub motors. Pros

• Uses existing engine test cell equipment

• Easier to simulate different vehicle configurations

• Easier to controlSAE INTERNATIONAL 5 

# Key Differences Between Chassis Testing and



# Powertrain Testing

Engine Trans Driveline Wheels Torque

Speed

T
1 Physical

Inertia, friction Dyno

- Set simulated inertia, road load T
2

Cut

Engine Trans Driveline Wheels Torque

Speed

T
1 Physical

Inertia, friction Simulated inertia, road load T
2

Cut Chassis dynamometer includes,

Powertrain testing does not

• Both simulate the same static inertia and road load forces

• Chassis dynamometer testing requires the “Dyno

- Set” coefficients to be determined to account of the portion of the vehicle road load that is present by having the vehicle on the chassis dynamometer.SAE INTERNATIONAL 6 

# Powertrain Test Cell Operation

Pedal Position (Torque Command)

Vehicle
Transmission
Energy Storage (electric, hydraulic, flywheel) Software Models

Dyno Motor Speed Control

Driveshaft Torque/Speed Feedback Driveshaft

Speed Command

Drive Cycle

(Vehicle Speed vs. Time) DriverSAE INTERNATIONAL 7 

# Powertrain Test Cell Implementation

Pedal Position (Torque Command)

Dyno Motor Speed Control

Driveshaft Torque/Speed Feedback Driveshaft

Speed Command

dSPACE MABX I Pedal, Driveshaft Speed Target Cycle Speed via

CANSAE INTERNATIONAL 8 

# Powertrain Test Cell Facility Used for this WorkSAE INTERNATIONAL 9 

# Close

- up View Friction Brake Required to Hold 

# Zero Speed

DRAFTSAE INTERNATIONAL

Uncertainty interval of plus

- minus two standard errors

10 

# Average fuel economy over each drive cycle for 

# the powertrain cell tests compared to the chassis dynamometer tests

1.5% 2.2% 3.8% 2.4% 6.0%
3.0%

0 0 0 0 0 0 0

4 6 8 10 12 14 16 18

55 MPH 65 MPH ARB Transient WHVC CILCC Parcel Fuel Economy, MPG Chassis

Powertrain

% Diff Steady

- state driveshaft power match The primary source of difference is described in the following slides

DRAFTSAE INTERNATIONAL 11 

# Different Driving Behaviors Produce Different 

# Fuel Economy Results

DRAFTSAE INTERNATIONAL 12 

# Different Driving Behaviors Produce Different 

# Fuel Economy Results

- Cont’d

DRAFTSAE INTERNATIONAL 13 

# Different Driving Behaviors Produce Different 

# Fuel Economy Results

- Cont’d

DRAFTSAE INTERNATIONAL Replaced torque

- based controller with a speed

- based controller

Replaced human driver with software model used in powertrain test cell

14 

# Recent Chassis Development For Improved 

# CorrelationSAE INTERNATIONAL 

### The results from our studies at SwRI:

• The chassis and powertrain fuel economy results are statistically different, but the standard error is quite small.



### • Powertrain testing can appropriately represent the overall operation of the vehicle.

• Test result variation is approximately the same for each method.

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# Summary (1)SAE INTERNATIONAL 

### The following contribute to the difference in fuel economy results between the chassis and powertrain testing:

• Driver Behavior affects transmission shifting , resulting in significant fuel economy differences

• Aftertreatment thermal management differences between chassis and powertrain testing



### • Dyno

- to

- dyno control and response differences

• Heat exchanger behavior

• Modeling of driveline characteristics

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# Summary (2)