In a petrol engine, a compressed mixture of air and fuel is ignited by a spark plug. The injection system injects fuel into the intake manifold (indirect injection) or directly into the combustion chamber (direct injection). The ignition coil provides the energy with which the spark plug generates a spark. When the engine speed increases, the ignition timing is advanced. When the load increases (e.g. due to headwind or driving uphill), the ignition is retarded again.
