American Motors AMC modern era inline six on stand at Rambler Ranch

A petrol engine (gasoline engine in American and Canadian English) is an

internal combustion engine An internal combustion engine (ICE or IC engine) is a heat engine in which the combustion of a fuel occurs with an oxidizer (usually air) in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal comb ...

designed to run on

petrol Gasoline (North American English) or petrol ( Commonwealth English) is a petrochemical product characterized as a transparent, yellowish, and flammable liquid normally used as a fuel for spark-ignited internal combustion engines. When formul ...

(gasoline). Petrol engines can often be adapted to also run on fuels such as

liquefied petroleum gas Liquefied petroleum gas, also referred to as liquid petroleum gas (LPG or LP gas), is a fuel gas which contains a flammable mixture of hydrocarbon gases, specifically propane, Butane, ''n''-butane and isobutane. It can also contain some ...

and ethanol blends (such as '' E10'' and '' E85''). They may be designed to run on petrol with a higher

octane rating An octane rating, or octane number, is a standard measure of a liquid fuel, fuel's ability to withstand Compression ratio, compression in an internal combustion engine without causing engine knocking. The higher the octane number, the more compres ...

, as sold at petrol stations. Most petrol engines use spark ignition, unlike

diesel engine The diesel engine, named after the German engineer Rudolf Diesel, is an internal combustion engine in which Combustion, ignition of diesel fuel is caused by the elevated temperature of the air in the cylinder due to Mechanics, mechanical Compr ...

s which run on

diesel fuel Diesel fuel, also called diesel oil, heavy oil (historically) or simply diesel, is any liquid fuel specifically designed for use in a diesel engine, a type of internal combustion engine in which fuel ignition takes place without a spark as a re ...

and typically use compression ignition. Another key difference to diesel engines is that petrol engines typically have a lower compression ratio.

History

The first practical petrol engine was built in 1876 in Germany by Nicolaus August Otto and Eugen Langen, although there had been earlier attempts by Étienne Lenoir in 1860, Siegfried Marcus in 1864 and George Brayton in 1873.

Design

Thermodynamic cycle

Most petrol engines use either the four-stroke Otto cycle or the two-stroke cycle. Petrol engines have also been produced using the Miller cycle and Atkinson cycle.

Layout

Most petrol-powered piston engines are straight engines or V engines. However, flat engines, W engines and other layouts are sometimes used. Wankel engines are classified by the number of rotors used.

Compression ratio

Cooling

Petrol engines are either air-cooled or water-cooled.

Ignition

Petrol engines use spark ignition.

High voltage High voltage electricity refers to electrical potential large enough to cause injury or damage. In certain industries, ''high voltage'' refers to voltage above a certain threshold. Equipment and conductors that carry high voltage warrant sp ...

for the spark this may be provided by a magneto or an ignition coil. In modern car engines, the ignition timing is managed by an electronic Engine Control Unit. Ignition modules can also function as a rev limiter in some cases to prevent overrevving and the consequences of it, such as valve float and connecting rod failure.

Primer

Primers may be used to help start the engine. They can draw fuel from fuel tanks and vaporize fuel directly into piston cylinders. Engines are difficult to start during cold weather, and the fuel primer helps because otherwise there will not be enough heat available to vaporize the fuel in the

carburetor A carburetor (also spelled carburettor or carburetter) is a device used by a gasoline internal combustion engine to control and mix air and fuel entering the engine. The primary method of adding fuel to the intake air is through the Ventu ...

Power output and efficiency

The power output of small- and medium-sized petrol engines (along with equivalent engines using other fuels) is usually measured in kilowatts or

horsepower Horsepower (hp) is a unit of measurement of power, or the rate at which work is done, usually in reference to the output of engines or motors. There are many different standards and types of horsepower. Two common definitions used today are t ...

. Typically, petrol engines have a thermodynamic efficiency of about 20-30% (approximately half that of some diesel engines).

Applications

Applications of petrol engines include

automobile A car, or an automobile, is a motor vehicle with wheels. Most definitions of cars state that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, peopl ...

motorcycle A motorcycle (motorbike, bike; uni (if one-wheeled); trike (if three-wheeled); quad (if four-wheeled)) is a lightweight private 1-to-2 passenger personal motor vehicle Steering, steered by a Motorcycle handlebar, handlebar from a saddle-style ...

aircraft An aircraft ( aircraft) is a vehicle that is able to flight, fly by gaining support from the Atmosphere of Earth, air. It counters the force of gravity by using either Buoyancy, static lift or the Lift (force), dynamic lift of an airfoil, or, i ...

motorboat A motorboat or powerboat is a boat that is exclusively powered by an engine; faster examples may be called "speedboats". Some motorboats are fitted with inboard engines, others have an outboard motor installed on the rear, containing the inter ...

s and small engines (such as lawn mowers, chainsaws and portable generators). Petrol engines have also been used as "pony engines", a type of engine used to start a larger, stationary diesel engine.

References

{{Authority control 1876 introductions Internal combustion piston engines Gasoline engines German inventions