What type of engine relies on spark plugs for ignition?

A spark ignition engine is designed to rely on spark plugs to initiate the combustion process. In this type of engine, a mixture of air and fuel is drawn into the combustion chamber, where it is compressed. When the compression reaches a certain point, the spark plug generates a spark, igniting the air-fuel mixture and causing an explosion that pushes the piston down, thereby generating power.

This ignition method differentiates spark ignition engines from diesel engines, which utilize a compression ignition process where fuel is injected into highly compressed air, causing it to ignite due to the heat of the compression, rather than relying on a spark plug. Compression engines are a category of engines related to how they ignite fuel, but they do not specifically indicate the use of spark plugs. Similarly, while two-stroke engines can operate as either spark ignition or compression ignition types, the term itself does not directly indicate the use of spark plugs for ignition. Thus, the designation of a spark ignition engine is specifically tied to the operation using spark plugs.