Spark-ignition refers to a type of internal combustion engine that uses a spark plug to ignite a mixture of air and fuel. This process occurs in the engine's combustion chamber, where the spark creates a small explosion that drives the engine's pistons. Spark-ignition engines are commonly found in vehicles powered by gasoline, making them a popular choice for cars and motorcycles. These engines operate on the principle of the Otto cycle, which involves intake, compression, power, and exhaust strokes. The efficiency and performance of spark-ignition engines can be influenced by factors such as fuel quality and engine design, impacting overall vehicle performance and emissions.