Influences of Real-World Conditions on In-Use Emission from Heavy-Duty Diesel Engines

The 1998 Consent Decrees between the settling heavy-duty diesel engine manufacturers and the United States Government require the engine manufacturer to perform in-use emissions testing to evaluate their engine designs and emissions when the vehicle is placed into service. This additional requirement will oblige the manufacturer to account for real-world conditions when designing engines and engine control algorithms and include driving conditions, ambient conditions, and fuel properties in addition to the engine certification test procedures. Engine operation and ambient conditions can be designed into the engine control algorithm. However, there will most likely be no on-board determination of fuel properties or composition in the near future. Therefore, the engine manufacturer will need to account for varying fuel properties when developing the engine control algorithm for when in-use testing is performed.

A comparison of the emissions from a heavy-duty engine has shown that commercially available fuel can dramatically affect the emissions along with the test cycle used to evaluate the emissions. There can be a 12% variation in the NOx, over 50% variation in PM, 40% variation in CO, and 17% variation in HC emissions due to fuel differences. Environmental changes were shown to cause a 12% variation in the NOx, 46% variation in PM, 11% variation in CO, and 30% variation in HC emissions. As heavy duty engine manufacturers are faced with in-use emissions testing, compensation for future fuel composition will impact engine manufacturers' designs.