Abstract
New transmission and powertrain technologies as well as hybrid systems offer development engineers many opportunities to tune the entire system. Vehicle comfort, NVH behaviour and drivability have to be considered as part of system integration as well as fuel consumption and exhaust emissions. The great challenge of powertrain calibration is to achieve the optimal results in a short period of time, to harmonise opposing development objectives, such as performance, fuel consumption and drivability. An important part of automotive development is securing that the vehicle is in compliance with regulations. Standardized but regional individual driving cycles are defined to assess the emission levels and fuel economy in passenger cars. With these the manufacturer tests and certifies the vehicle for the different markets. A high dynamic engine test bed is used to calibrate exhaust emissions in early development stages of the engine. Exhaust emission certification as well as calibration is executed on a chassis dynamometer. These system tests are executed late in the development caused by the mandatory availability of all components and modules to be integrated into a vehicle. The objective of this paper is to identify whether exhaust emission calibration could be performed on a Powertrain-in-the-Loop test bed using only a powertrain setup without having the entire vehicle. The intention is to simulate a front-loading situation where the powertrain is developed to a certain stage without the availability of the corresponding vehicle. A correlation to an emission chassis dynamometer is mandatory to identify the capability Powertrain-in-the-Loop test bed. Therefore five different test bed phases were defined: Running emission test cycles on a chassis dynamometer as reference value. Running emission test cycles on a Powertrain-in-the-Loop test bed using the complete vehicle setup. Running emission test cycles on a Powertrain-in-the-Loop test bed with the engine compartment around the powertrain to make sure that the powertrain behaviour was comparable to the vehicle setup. Running emission test cycles on a Powertrain-in-the-Loop test bed with a powertrain setup where only the bumper and grill component is mounted to identify the influence of hood, fenders, etc. Finally running emission test cycles on a Powertrain-in-the-Loop test bed with a powertrain setup where no chassis components are attached to the powertrain at all, engine and transmission are only connected to the main parts of the chassis. ECU actuator behaviour, coolant, oil and exhaust gas temperature development and emission formation was analysed for the five different set ups to identify the influence of different test environments and different test configurations on the measurement results. A test series was executed to correlate engine out emissions as well as tailpipe emissions. The differences and trends between the different configurations (vehicle powertrain) will be shown and explained.
KEYWORDS – Emission Calibration, Powertrain in the Loop, System Integration, Chassis Dynamometer, Emission Correlation