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

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.