| The future SULEV hydrocarbon (HC) emission standard is much more stringent than the current LEV standard for port-fuel-injection gasoline SI engines. Reduction of the cold start engine-out HC emissions is the key to meet this challenge. The goal of this work is to identify the sources of HC emissions during cold start, and provide an efficient simulation tool to help the cold start fuel calibration.; Cold and hot start tests were conducted on a fully instrumented new Chrysler 2.4-L, 4-cylinder, 16-valve, DOHC, multipoint-port-fuel-injection gasoline engine. Based on the experimental findings, theories of mass transfer and thermodynamics were applied to establish a generic simulation model for the cold start fuel calibration (CSFC) in port-fuel-injected gasoline engines. Different liquid fuel evaporation mechanisms in the engine intake port were identified and quantified.; The model was applied to a 2.4 L Line-4 DOHC engine and a Chrysler 3.3 L V6 pushrod engine. This CSFC model can handle different cold start soaking temperatures and any combinations of fuel components easily. Based on the findings of the simulation, important cold start fuel calibrations were proposed to improve the cold startability and reduce HC emissions. This model has a great potential to benefit lots of port-fuel-injection gasoline engine cold start fuel calibration work. |
