Gasoline fuel injection delivers precise fuel quantity via port fuel injection (PFI) or gasoline direct injection (GDI). The ECU calculates injector pulse width based on air mass, target lambda, fuel pressure, and multiple correction factors.

Overview

Modern gasoline engines often use GDI for efficiency and power, sometimes combined with port injection for cold start and high-load enrichment. The ECU manages injection timing, pulse width, and fuel pressure.

Controlled Signals

• Injector pulse width
• Injection timing (GDI)
• Fuel rail pressure (GDI)
• Air mass / MAP
• Battery voltage compensation

Maps Involved

• Base Fuel Maps (VE or mass-based)
• Injector Flow Characterization Maps
• Fuel Pressure Target Maps (GDI)
• Cranking Enrichment Maps
• Warm-up Enrichment Maps

Logic Sequence

Air Mass Calculation → Target Lambda
         ↓
Base Fuel Calculation
         ↓
Temperature & Transient Corrections
         ↓
Injector Dead Time Compensation
         ↓
Final Pulse Width → Injector Driver

Calibration Objectives

• Accurate fuel delivery across all conditions
• Maintain target AFR
• Minimize fuel trim deviations

Calibration Strategy

• Verify injector characterization if upgrading injectors
• Adjust fuel maps to match actual airflow changes
• Monitor STFT and LTFT for calibration accuracy

Diagnostics

• Injector circuit faults
• Fuel trim out of range
• Fuel pressure deviation (GDI)

Best Practices

• Match injector size to power goals
• Always verify AFR after fueling changes
• GDI systems require quality fuel to prevent carbon buildup