Spark ignition identifies internal combustion engines that use spark plugs to initiate combustion, distinguishing them from compression ignition engines. These powerplants compress a homogenous mixture of fuel and air, requiring a precise high-voltage spark to trigger the power stroke. The term frequently appears in engineering literature and emissions regulations to categorize gasoline, ethanol, and natural gas engines.
The emissions standard for heavy SI engines changed again this year.
Do not mix it up with
- Diesel engine: An SI engine uses spark plugs to ignite fuel, while a diesel engine uses the heat of compression.
Related terms
Petrol engine
An internal combustion engine that generates power by igniting a mixture of gasoline and air with a spark.
Diesel engine
An internal combustion engine that uses high compression to ignite fuel without spark plugs.
Ignition timing
The exact moment a spark plug fires relative to the position of the piston during the compression stroke.