The Effects of Injector Targeting and Fuel Volatility on Fuel Dynamics in a PFI Engine During Engine Warm-up: Part I - Experimental Results

This study was performed to quantify the effects of injector targeting and fuel volatility on transient A/F excursions and fuel film mass in a port fuel injected (PFI) engine. Two injector targeting positions as well as injection timing and four different fuels were studied. Warm-up tests were performed with the throttle ramped between two positions over a one second interval to provide smooth changes in airflow and injected fuel. The exhaust A/F was recorded for each transient and fit using the X-τ model to estimate the change in the liquid fuel stored in the port and cylinder due to the throttle ramp. The change in fuel stored in the films was:

• ∼20% less with valve targeting
• ∼30% less with IVO injection timing
• 50-100% higher for hesitation fuel