Particulate Matter Emission During Start-up and Transient Operation of a Spark-Ignition Engine (2): Effect of Speed, Load, and Real-World Driving Cycles

Previous research into Particulate Matter (PM) emissions from a spark-ignition engine has shown that the main factor determining the how PM emissions respond to transient engine operating conditions is the effect of those conditions on intake port processes such as fuel evaporation.

The current research extends the PM emissions data base by examining the effect of transient load and speed operating conditions, as well as engine start-up and shut-down. In addition, PM emissions are examined during “real-world” driving conditions - specifically, the Federal Test Procedure. Unlike the previous work, which was performed on an engine test stand with no exhaust gas recirculation and with a non-production engine controller, the current tests are performed on a fully-functional, production vehicle operated on a chassis dynamometer to better examine real world emissions. PM emissions prior to and after dilution are examined, and the results are discussed in the context of a previously developed PM formation and emission model. The results show that the greatest increases in PM emissions come directly after start-up, and when load is increased - either when the load is increased at constant speed, or when the vehicle accelerator is depressed to change speed while maintaining nominally constant intake pressure. Engine shut-down can cause a brief, small peak in PM emissions, for reasons that will be discussed.