2.1.1 Internal Combustion Engines Explained

Key Concepts

• Four-Stroke Cycle
• Fuel and Air Mixture
• Ignition System
• Exhaust Emission Control

Four-Stroke Cycle

The four-stroke cycle is the fundamental operation of an internal combustion engine. It consists of four distinct processes: intake, compression, combustion (power), and exhaust. Each stroke is essential for converting fuel into mechanical energy.

Example: When you start your car, the engine goes through the four-stroke cycle repeatedly. The intake stroke draws in a mixture of fuel and air, the compression stroke compresses this mixture, the combustion stroke ignites it to produce power, and the exhaust stroke expels the waste gases.

Fuel and Air Mixture

The fuel and air mixture is the combination of gasoline (or diesel) and air that is compressed and ignited in the engine's cylinders. The correct ratio of fuel to air is crucial for efficient combustion and optimal engine performance.

Example: Think of the fuel and air mixture as the ingredients in a recipe. If you add too much of one ingredient, the dish won't turn out right. Similarly, if the fuel-to-air ratio is off, the engine won't run efficiently, leading to poor performance and increased emissions.

Ignition System

The ignition system is responsible for creating the spark that ignites the fuel and air mixture in the combustion chamber. This system includes components like spark plugs, ignition coils, and distributors (in older engines) or spark plug wires (in newer engines).

Example: Imagine the ignition system as the match that lights a campfire. Without the spark, the fuel and air mixture won't ignite, and the engine won't produce power. Regular maintenance of the ignition system is essential to ensure reliable engine performance.

Exhaust Emission Control

Exhaust emission control systems are designed to reduce the harmful pollutants released by the engine. These systems include catalytic converters, oxygen sensors, and exhaust gas recirculation (EGR) valves. Proper functioning of these systems is crucial for environmental and regulatory compliance.

Example: Think of the exhaust emission control system as a filter that cleans the air before it leaves the car. Just as a filter removes impurities from water, these systems remove harmful gases from the exhaust, reducing the impact on the environment.