The Info List - Petrol Engine

A petrol engine (known as a gasoline engine in American English) is an internal combustion engine with spark-ignition, designed to run on petrol (gasoline) and similar volatile fuels. In most petrol engines, the fuel and air are usually mixed after compression (although some modern petrol engines now use cylinder-direct petrol injection). The pre-mixing was formerly done in a carburetor, but now it is done by electronically controlled fuel injection, except in small engines where the cost/complication of electronics does not justify the added engine efficiency. The process differs from a diesel engine in the method of mixing the fuel and air, and in using spark plugs to initiate the combustion process. In a diesel engine, only air is compressed (and therefore heated), and the fuel is injected into very hot air at the end of the compression stroke, and self-ignites.


1 History 2 Compression ratio 3 Speed and efficiency 4 Applications

4.1 Current 4.2 Historical

5 Design

5.1 Working cycles 5.2 Cylinder arrangement 5.3 Cooling 5.4 Ignition 5.5 Power measurement

6 See also 7 References

History[edit] Main article: History of the internal combustion engine The first practical petrol engine was built in 1876 in Germany by Nikolaus August Otto, although there had been earlier attempts by Étienne Lenoir, Siegfried Marcus, Julius Hock and George Brayton.[1] The first petrol combustion engine (one cylinder, 121.6 cm3 displacement) was prototyped in 1882 in Italy by Enrico Bernardi. British engineer Edward Butler constructed the first petrol (gasoline) internal combustion engine. Butler invented the spark plug, ignition magneto, coil ignition and spray jet carburetor, and was the first to use the word petrol.[2] Compression ratio[edit] Main article: Compression ratio With both air and fuel in a closed cylinder, compressing the mixture too much poses the danger of auto-ignition — or behaving like a diesel engine. Because of the difference in burn rates between the two different fuels, petrol engines are mechanically designed with different timing than diesels, so to auto-ignite a petrol engine causes the expansion of gas inside the cylinder to reach its greatest point before the cylinder has reached the "top dead center" (T.D.C) position. Spark plugs are typically set statically or at idle at a minimum of 10 degrees or so of crankshaft rotation before the piston reaches T.D.C, but at much higher values at higher engine speeds to allow time for the fuel-air charge to substantially complete combustion before too much expansion has occurred - gas expansion occurring with the piston moving down in the power stroke. Higher octane petrol burns slower, therefore it has a lower propensity to auto-ignite and its rate of expansion is lower. Thus, engines designed to run high-octane fuel exclusively can achieve higher compression ratios. Most modern automobile petrol engines generally have a compression ratio of 10.0:1 to 13.5:1.[3] Engines with a knock sensor can and usually have C.R higher than 11.1:1 and approaches 14.0:1 (for high octane fuel and usually with direct fuel injection) and engines without a knock sensor generally have C.R of 8.0:1 to 10.5:1.[4][5] Speed and efficiency[edit] Petrol
engines run at higher rotation speeds than diesels, partially due to their lighter pistons, connecting rods and crankshaft (a design efficiency made possible by lower compression ratios) and due to petrol burning more quickly than diesel. Because pistons in petrol engines tend to have much shorter strokes than pistons in diesel engines, typically it takes less time for a piston in a petrol engine to complete its stroke than a piston in a diesel engine. However the lower compression ratios of petrol engines give petrol engines lower efficiency than diesel engines. Typically, most petrol engines have approximately 20%(avg.) thermal efficiency, which is nearly half of diesel engines. However some newer engines are reported to be much more efficient(thermal efficiency up to 38%) than previous spark-ignition engines.[6] Applications[edit] Current[edit] Petrol
engines have many applications, including:

Automobiles Motorcycles Aircraft Motorboats Small engines, such as lawn mowers, chainsaws and portable engine-generators

Historical[edit] Before the use of diesel engines became widespread, petrol engines were used in buses, lorries (trucks) and a few railway locomotives. Examples:

Bedford OB
Bedford OB
bus Bedford M series
Bedford M series
lorry GE 57-ton gas-electric boxcab
GE 57-ton gas-electric boxcab

Design[edit] Working cycles[edit]

Four-stroke petrol engine

engines may run on the four-stroke cycle or the two-stroke cycle. For details of working cycles see:

Four-stroke cycle Two-stroke cycle Wankel engine

Cylinder arrangement[edit] Common cylinder arrangements are from 1 to 6 cylinders in-line or from 2 to 16 cylinders in V-formation. Flat engines – like a V design flattened out – are common in small airplanes and motorcycles and were a hallmark of Volkswagen
automobiles into the 1990s. Flat 6s are still used in many modern Porsches, as well as Subarus. Many flat engines are air-cooled. Less common, but notable in vehicles designed for high speeds is the W formation, similar to having 2 V engines side by side. Alternatives include rotary and radial engines the latter typically have 7 or 9 cylinders in a single ring, or 10 or 14 cylinders in two rings. Cooling[edit] Petrol
engines may be air-cooled, with fins (to increase the surface area on the cylinders and cylinder head); or liquid-cooled, by a water jacket and radiator. The coolant was formerly water, but is now usually a mixture of water and either ethylene glycol or propylene glycol. These mixtures have lower freezing points and higher boiling points than pure water and also prevent corrosion, with modern antifreezes also containing lubricants and other additives to protect water pump seals and bearings. The cooling system is usually slightly pressurized to further raise the boiling point of the coolant. Ignition[edit] Main article: Ignition system Petrol
engines use spark ignition and high voltage current for the spark 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. Power measurement[edit] The most common way of engine rating is what is known as the brake power, measured at the flywheel, and given in kilowatts (metric) or horsepower (Imperial/USA). This is the actual mechanical power output of the engine in a usable and complete form. The term "brake" comes from the use of a brake in a dynamometer test to load the engine. For accuracy, it is important to understand what is meant by usable and complete. For example, for a car engine, apart from friction and thermodynamic losses inside the engine, power is absorbed by the water pump, alternator, and radiator fan, thus reducing the power available at the flywheel to move the car along. Power is also absorbed by the power steering pump and air conditioner (if fitted), but these are not installed for a power output test or calculation. Power output varies slightly according to the energy value of the fuel, the ambient air temperature and humidity, and the altitude. Therefore, there are agreed standards in the USA and Europe on the fuel to use when testing, and engines are rated at 25 ⁰C (Europe), and 64 ⁰F (USA)[7] at sea level, 50% humidity. Marine engines, as supplied, usually have no radiator fan, and often no alternator. In such cases the quoted power rating does not allow for losses in the radiator fan and alternator. The SAE in USA, and the ISO in Europe publish standards on exact procedures, and how to apply corrections for deviating conditions like high altitude. Car
testers are most familiar with the chassis dynamometer or "rolling road" installed in many workshops. This measures drive wheel brake horsepower, which is generally 15-20% less than the brake horsepower measured at the crankshaft or flywheel on an engine dynamometer. A YouTube video shows workshop measurement of a car's power. The measured power curve in kW is shown at 3:39. See also[edit]

Bore Gasoline
direct injection Stroke Diesel engine Petrol


^ "Who Invented the Car?".  ^ "Hiram Maxim and Edward Butler:Two local inventors". Bexley. Bexley. Archived from the original on 15 February 2016. Retrieved 11 April 2016.  ^ "Compression Ratio Theory in Petrol
and Diesel Engines explained with Diagram -". CrankIT. 2014-04-03. Retrieved 2017-10-07.  ^ "Energy efficiency of vehicles". www.hk-phy.org. Retrieved 2017-10-07.  ^ "Direct Fuel Injection - What It Is and How It Works". ThoughtCo. Retrieved 2017-10-07.  ^ "Toyota Gasoline
Engine Achieves Thermal Efficiency Of 38 Percent". Green Car
Reports. Retrieved 2017-10-07.  ^ "Regulations and Standards". EPA. EPA. Retrieved 11 April 2016. 

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Automotive engine

Part of the Automobile

Basic terminology

Bore Compression ratio Crank Cylinder Dead centre Diesel engine Dry sump Engine balance Engine configuration Engine displacement Engine knocking Firing order Hydrolock Petrol
engine Power band Redline Spark-ignition engine Stroke Stroke ratio Wet sump

Main components

Connecting rod Crankcase Crankpin Crankshaft Crossplane Cylinder bank Cylinder block Cylinder head
Cylinder head
(crossflow, reverse-flow) Flywheel Head gasket Hypereutectic piston Main bearing Piston Piston
ring Starter ring gear Sump


Cam Cam
follower Camshaft Desmodromic valve Hydraulic tappet Multi-valve Overhead camshaft Overhead valve Pneumatic valve springs Poppet valve Pushrod Rocker arm Sleeve valve Tappet Timing belt Timing mark Valve float Variable valve timing


Air filter Blowoff valve Boost controller Butterfly valve Centrifugal-type supercharger Cold air intake Dump valve Electronic throttle control Forced induction Inlet manifold Intake Intercooler Manifold vacuum Naturally aspirated engine Ram-air intake Scroll-type supercharger Short ram air intake Supercharger Throttle Throttle
body Turbocharger Twin-turbo Variable-geometry turbocharger Variable-length intake manifold Warm air intake

Fuel system

Carburetor Common rail Direct injection Fuel filter Fuel injection Fuel pump Fuel tank Gasoline
direct injection Indirect injection Injection pump Lean-burn Stratified charge engine Turbo fuel stratified injection Unit injector


Contact breaker Magneto Distributor Electrical ballast High tension leads Ignition coil Spark plug Wasted spark

Electrics and engine management

Air–fuel ratio meter Alternator Automatic Performance Control Car
battery (lead–acid battery) Crankshaft
position sensor Dynamo Drive by wire Electronic control unit Engine control unit Engine coolant temperature sensor Glow plug Idle air control actuator MAP sensor Mass flow sensor Oxygen sensor Starter motor Throttle
position sensor

Exhaust system

emissions control Catalytic converter Diesel particulate filter Exhaust manifold Glasspack Muffler

Engine cooling

Air cooling Antifreeze
(ethylene glycol) Core plug Electric fan Fan belt Radiator Thermostat Water cooling Viscous fan (fan clutch)

Other components

Balance shaft Block heater Combustion chamber Cylinder head
Cylinder head
porting Gasket Motor oil Oil filter Oil pump Oil sludge PCV valve Seal Synthetic oil Underdrive pulleys

Portal Category

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By size

Microcar City car Kei Subcompact Supermini Family car Compact Mid-size Full-size


Hot rod Lead sled Lowrider Street rod T-bucket


Compact executive Executive Personal luxury car


Compact MPV Mini MPV


Compact SUV Crossover SUV Mini SUV


Grand tourer Hot hatch Muscle Pony Sport compact Supercar

Antique Classic Economy Leisure activity vehicle Ute Van Voiturette

Body styles

2+2 Baquet Barchetta Berlinetta Brougham Cabrio coach Cabriolet / Convertible Coupé Coupé
de Ville Coupé
utility Drophead coupe (Convertible) Fastback Hardtop Hatchback Landaulet Liftback Limousine Multi-stop truck Notchback Panel van Phaeton Pickup truck Quad coupé Retractable hardtop Roadster Runabout Saloon / Sedan Sedan delivery Sedanca de Ville ( Coupé
de Ville) Shooting-brake Spider / Spyder (Roadster) Station wagon Targa top Torpedo Touring car Town car ( Coupé
de Ville) T-top Vis-à-vis

Specialized vehicles

Amphibious Driverless (autonomous) Hearse Gyrocar Roadable aircraft Taxicab Tow truck


Alternative fuel Autogas Biodiesel Diesel Electric (battery NEV) Ethanol (E85) Fuel cell Gasoline / petrol (direct injection) Homogeneous charge compression ignition Hybrid (plug-in) Hydrogen Internal combustion Liquid nitrogen Steam

Drive wheels

Front-wheel Rear-wheel Two-wheel Four-wheel Six-wheel Eight-wheel Twelve-wheel

Engine position

Front Mid Rear

Layout (engine / drive)

Front / front   Front mid / front   Rear / front   Front / rear   Rear mid / rear   Rear / rear   Front / four-wheel   Mid / four-wheel   Rear / four-wheel 

Engine configuration (internal combustion)

Boxer Flat Four-stroke H-block Reciprocating Single-cylinder Straight Two-stroke V (Vee) W engine Wankel

Portal Category

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Heat engines

Carnot engine Fluidyne Gas turbine Hot air Jet Minto wheel Photo-Carnot engine Piston Pistonless (Rotary) Rijke tube Rocket Split-single Steam (reciprocating) Steam turbine Stirling Thermoacoustic

Beale number West number

Timeline of heat engine technology

Thermodynamic cycle

Authority control

GND: 4044196-9 N