Internal Combustion Engine Basics

Engine Overview

• The engine is a complex machine that converts heat from burning gas into force that turns the road wheels.
• It is called an internal combustion engine because the combustion process takes place inside the engine.

Engine Structure

• The engine has two basic parts: the cylinder block and the cylinder head.
• The cylinder block is the lower, heavier section that houses the crankshaft and sometimes the camshaft.
• The cylinder head contains valve-controlled passages for air and fuel mixture entry and gas expulsion.

Engine Types

• The most common type of engine is the in-line engine, with cylinders arranged vertically in a row.
• The V-engine is a more compact type, with cylinders arranged opposite each other at an angle.
• The horizontally-opposed engine is an extension of the V-engine, with cylinders arranged at a 180-degree angle.

Power Creation

• The conversion of fuel energy into power starts when petrol is mixed with air in a carburettor.
• The mixture is drawn into the cylinders, compressed, and then ignited by a spark plug.
• The rapid expansion of the burning gas drives the piston down the cylinder, which is then converted into rotary motion by the crankshaft.

Four-Stroke Cycle

• The four-stroke cycle consists of induction, compression, power, and exhaust strokes.
• The induction stroke draws the fuel mixture into the cylinder through the inlet valve.
• The compression stroke compresses the mixture to about an eighth or ninth of its original volume.
• The power stroke drives the piston down the cylinder as the ignited gases expand.
• The exhaust stroke allows waste products to escape through the exhaust system.

Compression Ratio

• The compression ratio is the difference between the volume of the air and fuel mixture and its eventual volume when compressed.
• A compression ratio of 9:1 means the mixture is reduced to one-ninth of its original volume.

Firing Order

• The firing order is the sequence in which the spark plugs ignite the mixture in each engine cylinder.
• The distributor directs the flow of current to each spark plug at the correct time during the four-stroke cycle.
• The spark occurs just before the piston reaches top dead centre (TDC) on the compression stroke.

Learn about the internal combustion engine, a complex machine that converts heat from burning gas into the force that drives a car. Understand the chain of reactions initiated by a spark and the process of petrol vapour burning rapidly within a cylinder to generate power.