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

A petrol engine (gasoline engine in American 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 co ...

designed to run on

petrol Gasoline (; ) or petrol (; ) (see ) is a transparent, petroleum-derived flammable liquid that is used primarily as a fuel in most spark-ignited internal combustion engines (also known as petrol engines). It consists mostly of organic c ...

(gasoline). Petrol engines can often be adapted to also run on fuels such as liquefied petroleum gas and ethanol blends (such as ''E10'' and ''E85''). Most petrol engines use spark ignition, unlike

diesel engine The diesel engine, named after Rudolf Diesel, is an internal combustion engine in which ignition of the fuel is caused by the elevated temperature of the air in the cylinder due to mechanical compression; thus, the diesel engine is a so-ca ...

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

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 engine A V engine, sometimes called a Vee engine, is a common configuration for internal combustion engines. It consists of two cylinder banks—usually with the same number of cylinders in each bank—connected to a common crankshaft. These cylinder ...

s. 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 current for the spark may be provided by a

magneto A magneto is an electrical generator that uses permanent magnets to produce periodic pulses of alternating current. Unlike a dynamo, a magneto does not contain a commutator to produce direct current. It is categorized as a form of alternator, ...

or an ignition coil. In modern car engines the

ignition timing In a spark ignition internal combustion engine, ignition timing is the timing, relative to the current piston position and crankshaft angle, of the release of a spark in the combustion chamber near the end of the compression stroke. The need f ...

is managed by an electronic Engine Control Unit.

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 th ...

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

Applications

Applications of petrol engines include

automobile A car or automobile is a motor vehicle with wheels. Most definitions of ''cars'' say that they run primarily on roads, seat one to eight people, have four wheels, and mainly transport people instead of goods. The year 1886 is regarded ...

motorcycle A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle steered by a handlebar. Motorcycle design varies greatly to suit a range of different purposes: long-distance travel, commuting, cruisin ...

aircraft An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines. ...

motorboat A motorboat, speedboat or powerboat is a boat that is exclusively powered by an engine. Some motorboats are fitted with inboard motor, inboard engines, others have an outboard motor installed on the rear, containing the internal combustion ...

s and small engines (such as lawn mowers, chainsaws and portable generators).

History

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

References

{{Authority control Internal combustion piston engines Gasoline engines