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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