ICE-10 — The Gasoline (Petrol) Engine

ASSUMPTION — This lesson covers general architecture; no specific OEM engine code or exact values are given.

In this lesson you will learn:

• The working principle
• Injection methods
• Emissions and knock limits

1. Working Principle

The gasoline (Otto) engine inducts an air-fuel mixture, compresses it, ignites it with a spark, and extracts work from the expanding gas.

FACT — Ignition is initiated by a spark plug and propagates as a flame front, hence “spark ignition” (SI).

2. Injection Methods

• Port injection (MPI) — fuel is sprayed into the intake port and mixes before entering.
• Direct injection (GDI) — fuel is sprayed directly into the cylinder at high pressure.

FACT — GDI allows higher compression ratio through charge cooling and better fuel economy, but is prone to particulate (PN) formation and may need a GPF (ICE-12, ICE-22).

3. Lambda Control

FACT — The gasoline engine is kept near stoichiometric (λ ≈ 1) for efficient three-way catalyst (TWC) operation. The lambda sensor measures exhaust oxygen and the ECU adjusts fuel accordingly.

4. Knock Limit

FACT — Compression ratio and spark advance are limited by knock. The ECU detects knock via the knock sensor and retards spark (ICE-27, ICE-28).

5. Emissions Control

• CO, HC, NOx → three-way catalyst.
• Particulates (GDI) → GPF.

6. Summary

• Gasoline engines are spark-ignited (Otto).
• MPI vs GDI injection.
• λ ≈ 1 control is critical for the TWC.
• Knock limits compression ratio and advance.

7. Sources

• Bosch, Gasoline-Engine Management
• Heywood, Internal Combustion Engine Fundamentals

Next Lesson

• ICE-11 — The Diesel Engine.