ICE-36 — Fuel Control

ASSUMPTION — This lesson covers fuel control conceptually; specific ECU model details are not given.

In this lesson you will learn:

• How fuel quantity is calculated
• Gasoline vs diesel
• Transient control

1. Fuel Quantity Calculation

The ECU computes the fuel mass needed for the target lambda (or target torque) and converts it to injection duration.

FACT — Fuel mass ≈ air mass / target AFR. Gasoline targets λ ≈ 1 (stoichiometric); diesel follows a lean target that varies with load/speed.

2. Gasoline vs Diesel

• Gasoline — air (throttle) + fuel quantity together; λ ≈ 1 target.
• Diesel — air is generally free; load is set by fuel quantity; λ always > 1.

FACT — This difference fundamentally changes the strategy: gasoline centers on mixture, diesel on injected quantity.

3. Transient Control

FACT — Under fast throttle changes, the intake-wall fuel film (wall film) and air-measurement delay disturb the mixture. The ECU applies transient compensation (e.g., acceleration enrichment) to correct it.

4. Summary

• Fuel mass = air mass / target AFR.
• Gasoline λ ≈ 1; diesel lean targets.
• Transient compensation keeps the mixture stable.

5. Sources

• Bosch, Gasoline-Engine Management and Diesel-Engine Management

Next Lesson

• ICE-37 — Idle Control.