Petrol engineThailand
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151. Petrol engine
A petrol engine is an internal-combustion engine that normally uses spark plugs to ignite a mixture of air and petrol. For this reason, it is also known as a spark-ignition or positive-ignition engine.
Petrol engines convert the energy released by combustion into mechanical power that drives the vehicle. Modern petrol engines use electronic engine management and emissions-control systems such as catalytic converters to improve efficiency and reduce harmful exhaust emissions.
Wikimedia.org • Florian Lindner • CC BY
How does a petrol engine work?
A petrol engine draws or injects fuel and air into the engine, compresses the mixture and ignites it using a spark plug. The resulting combustion produces pressure that moves the pistons and generates mechanical power.
What is the difference between a petrol and diesel engine?
A petrol engine normally uses spark ignition, while a diesel engine uses compression ignition. The two engine types also differ in fuel, combustion characteristics and emissions-control systems.
What emissions can a petrol engine produce?
Petrol-engine exhaust can contain pollutants such as carbon monoxide, hydrocarbons, nitrogen oxides and, particularly with some direct-injection engines, particulate matter. Modern emissions-control systems are designed to reduce these pollutants.

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