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Spark-ignition engine
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<p> A spark-ignition engine (SI engine) is an <a href="/facts/Internal_combustion_engine/Ju4BXzj0">internal combustion engine</a>, generally a <a href="/facts/Petrol_engine/oj3XzkQU">petrol engine</a>, where the combustion process of the air-fuel mixture is ignited by a spark from a <a href="/facts/Spark_plug/Y9lG10hg">spark plug</a>. This is in contrast to <a href="/facts/Compression-ignition_engine/9B9opxvA">compression-ignition engines</a>, typically <a href="/facts/Diesel_engine/9B9opxvA">diesel engines</a>, where the heat generated from <a href="/facts/Compression_ratio/QNJXIT08">compression</a> together with the injection of fuel is enough to initiate the combustion process, without needing any external spark. </p>