Cold Engine Transient Fuel Control Experiments in a Port Fuel Injected CFR Engine

Abstract

Air-fuel mixture preparation is particularly challenging during cold engine throttle transients due to poor fuel vaporization and transport delays in port fuel injected (PFI) engines. In this study, a PFI cooperative fuels research engine is used to evaluate torque and to measure in-cylinder and exhaust CO, CO2, and unburned hydrocarbons during throttle transients at various early stages of engine warmup. Fast flame ionization detectors and nondispersive infrared fast CO and CO2 detectors are used to provide a detailed cycle-by-cycle analysis. Ttorque after cold throttle transients is found to be comparable to steady-state torque due to allowable spark advance. However, cold transients produce up to four times the unburned hydrocarbons when compared to steady-state operation. Finally, the x-tau fuel control model is evaluated in this challenging operating regime and is found to provide poor transient fuel control due to excessive fueling.