is burned directly inside the engine itself. Most automobile engines work on a 4-stroke cycle. A cycle is one complete sequence of 4 strokes of the piston in the cylinder. The operation cycle of the four-stroke petrol engine includes : inlet stroke ( intake valve opens), compression stroke, power stroke (both valves are closed), exhaust stroke.
To describe the complete cycle , let us assume that the piston is at the top of the stroke and the inlet valve , as well as the exhaust valve, is closed.. When the piston moves down the inlet valve opens to intake a charge of fuel into the cylinder. This is called the inlet or intake stroke.