Horsepower
Encyclopedia
Horsepower is the name of several units of measurement
of power
. The most common definitions equal between 735.5 and 750 watt
s.
Horsepower was originally defined to compare the output of steam engine
s with the power of draft horse
s in continuous operation. The unit was widely adopted to measure the output of piston engines, turbines, electric motors, and other machinery. The definition of the unit varied between geographical regions. Most countries now use the SI unit watt
for measurement of power. With the implementation of the EU Directive 80/181/EEC on January 1, 2010, the use of horsepower in the EU is only permitted as supplementary unit.
provided a reason to compare the output of horse
s with that of the engines that could replace them. In 1702, Thomas Savery
wrote in The Miner's Friend: "So that an engine which will raise as much water as two horses, working together at one time in such a work, can do, and for which there must be constantly kept ten or twelve horses for doing the same. Then I say, such an engine may be made large enough to do the work required in employing eight, ten, fifteen, or twenty horses to be constantly maintained and kept for doing such a work…" The idea was later used by James Watt to help market his improved steam engine
. He had previously agreed to take royalties of one third of the savings in coal from the older Newcomen steam engine
s. This royalty scheme did not work with customers who did not have existing steam engines but used horses instead. Watt determined that a horse could turn a mill wheel 144 times in an hour (or 2.4 times a minute). The wheel was 12 feet in radius; therefore, the horse travelled 2.4 × 2π × 12 feet in one minute. Watt judged that the horse could pull with a force
of 180 pounds. So:
This was rounded to an even 33,000 ft·lbf/min.
Others recount that Watt determined that a pony could lift an average 220 lbf (0.9786087553 kN) 100 ft (30.5 m) per minute over a four-hour working shift. Watt then judged a horse was 50% more powerful than a pony and thus arrived at the 33,000 ft·lbf/min figure.
Engineering in History recounts that John Smeaton
initially estimated that a horse could produce 22,916 foot-pounds per minute. John Desaguliers increased that to 27,500 foot-pounds per minute. "Watt found by experiment in 1782 that a 'brewery horse' was able to produce 32,400 foot-pounds per minute." James Watt and Matthew Boulton standardized that figure at 33,000 the next year.
Most observers familiar with horses and their capabilities estimate that Watt was either a bit optimistic or intended to underpromise and overdeliver; few horses can maintain that effort for long. Regardless, comparison with a horse proved to be an enduring marketing tool.
A healthy human can produce about 1.2 hp briefly (see orders of magnitude
) and sustain about 0.1 hp indefinitely; trained athletes can manage up to about 2.5 hp briefly and 0.3 hp for a period of several hours.
In certain situations it is necessary to distinguish between the various definitions of horsepower and thus a suffix is added: hp(I) for mechanical (or imperial) horsepower, hp(M) for metric horsepower, hp(S) for boiler (or steam) horsepower and hp(E) for electrical horsepower.
Hydraulic horsepower is equivalent to mechanical horsepower. The formula given above is for conversion to mechanical horsepower from the factors acting on a hydraulic system.
(1901, CR 70) definition of standard gravity
, gn=9.80665 m/s2, is used to define the pound-force as well as the kilogram force, and the international avoirdupois pound (1959), one mechanical horsepower is:
Or given that 1 hp = 550 ft·lbf/s, 1 ft = 0.3048 m, 1 lbf ≈ 4.448 N, 1 J = 1 N·m, 1 W = 1 J/s: 1 hp = 746 W
in the 19th century and became popular across Europe and Asia. The various units used to indicate this definition (PS, CV, hk, pk, ks and ch) all translate to horse power in English, so it is common to see these values referred to as horsepower or hp in the press releases or media coverage of the German, French, Italian, and Japanese automobile companies. British manufacturers often intermix metric horsepower and mechanical horsepower depending on the origin of the engine in question. Sometimes the metric horsepower rating of an engine is conservative enough so that the same figure can be used for both 80/1269/EEC with metric hp and SAE J1349 with imperial hp.
Metric horsepower, as a rule, is defined as 0.73549875 kW, or roughly 98.6% of mechanical horsepower. This was a minor issue in the days when measurement systems varied widely and engines produced less power, but has become a major sticking point today. Exotic cars from Europe like the McLaren F1
and Bugatti Veyron
are often quoted using the wrong definition, and their power output is sometimes even converted twice because of confusion over whether the original horsepower number was metric or mechanical.
DIN 66036 defines one horsepower to lift a mass of 75 kilograms within one second against the earth gravitation over a distance of one metre. Similar definitions were already common to the time of James Watt
.
The PS was adopted by the Deutsches Institut für Normung
(DIN) and then by the automotive industry throughout most of Europe, under varying names. In 1992, the PS was rendered obsolete by EEC directives, when it was replaced by the kilowatt as the official power measuring unit. It is still in use for commercial and advertising purposes, in addition to the kW rating, as many customers are still not familiar with the use of kilowatts for engines.
In addition, the capital form CV is used in Italy and France as a unit for tax horsepower
, short for, respectively, cavalli vapore and chevaux vapeur (steam horses). CV is a non-linear rating of a motor vehicle for tax purposes. The CV rating, or fiscal power, is
, where P is the maximum power in kilowatts and U is the amount of CO2 emitted in grams per kilometre. The term for CO2 measurements has only been included in the definition since 1998, so older ratings in CV are not directly comparable. The fiscal power has found its way into naming of automobile models, such as the popular Citroën deux-chevaux
. The cheval-vapeur (ch) unit should not be confused with the French cheval fiscal (CV).
In the 19th century, the French had their own unit, which they used instead of the CV or horsepower. It was called the poncelet
and was abbreviated p.
The term was originally developed at the Philadelphia Centennial Exhibition in 1876, where the best steam engines of that period were tested. The average steam consumption of those engines (per output horsepower) was determined to be the evaporation of 30 lb/h of water, based on feedwater at 100 °F (37.8 °C), and saturated steam generated at 70 psi (482.6 kPa) gauge pressure. This original definition is equivalent to a boiler heat output of 33485 BTU/h. In 1884, the ASME redefined the boiler horsepower as the thermal output equal to the evaporation of 34.5 lb/h of water "from and at" 212 °F. This considerably simplified boiler testing, and provided more accurate comparisons of the boilers at that time. This revised definition is equivalent to a boiler heat output of 33469 BTU/h. Present industrial practice is to define boiler horsepower as a boiler thermal output equal to 33475 BTU/h, which is very close to the original and revised definitions.
The amount of power that can be obtained by a steam engine or steam turbine based on boiler horsepower varies so widely that use of the term is entirely obsolete for these purposes. The term makes no distinction as to the steam pressure or temperature which is produced (both of which significantly influence engine/turbine output); it merely defines a thermal output of a boiler. Smaller steam engines often require several boiler horsepower to make one horsepower, and modern steam turbines can make power with as little as about 0.15 hp (boiler) thermal output per actual horsepower developed.
and speed, the power may be calculated; the relationship between torque in foot-pound
s, rotational speed in rpm and horsepower is:
Where
is power, 
is torque, and 
is rotations per minute.
The constant 5252 is the truncated value of (33,000 ft·lbf/min)/(2π rad/rev).
The standard equation relating torque in inch pounds, rotational speed in rpm and horsepower is:
Where
is power, 
is torque, and 
is rotations per minute. The constant 63,025 is the truncated value of (33,000 ft·lbf/min) × (12 in/ft)/(2π rad/rev).
See torque.
Drawbar horsepower (dbhp) is the power a railway locomotive
has available to haul a train
or an agricultural tractor to pull an implement. This is a measured figure rather than a calculated one. A special railway car called a dynamometer car
coupled behind the locomotive keeps a continuous record of the drawbar
pull exerted, and the speed. From these, the power generated can be calculated. To determine the maximum power available, a controllable load is required; it is normally a second locomotive with its brakes applied, in addition to a static load.
If the drawbar force (
) is measured in pounds-force (lbf) and speed (
) is measured in miles per hour (mph), then the drawbar power (
) in horsepower (hp) is:
Example: How much power is needed to pull a drawbar load of 2,025 pounds-force at 5 miles per hour?
The constant 375 is because 1 hp = 375 lbf·mph. If other units are used, the constant is different. When using a coherent system of units, such as SI
(watts, newtons, and metres per second), no constant is needed, and the formula becomes
.
in Britain
and was used to denote the power of early 20th century British cars
. Many cars took their names from this figure (hence the Austin
Seven and Riley
Nine), while others had names such as "40/50 hp", which indicated the RAC figure followed by the true measured power.
Taxable horsepower does not reflect developed horsepower; rather, it is a calculated figure based on the engine's bore size, number of cylinders, and a (now archaic) presumption of engine efficiency. As new engines were designed with ever-increasing efficiency, it was no longer a useful measure, but was kept in use by UK regulations which used the rating for tax purposes
.
This is equal to the displacement in cubic inches divided by 10π then divided again by the stroke in inches.
Since taxable horsepower was computed based on bore and number of cylinders, not based on actual displacement, it gave rise to engines with 'undersquare' dimensions (i.e., relatively narrow bore), but long stroke; this tended to impose an artificially low limit on rotational speed (rpm
), hampering the potential power output and efficiency of the engine.
The situation persisted for several generations of four- and six-cylinder British engines: for example, Jaguar's
3.4-litre XK engine of the 1950s had six cylinders with a bore of 83 mm (3.3 in) and a stroke of 106 mm (4.2 in), where most American automakers had long since moved to oversquare (wide bore, short stroke) V-8
s (see, for example, the early Chrysler Hemi).
In the case of an engine dynamometer, power is measured at the engine's flywheel
(i.e., at the crankshaft output). With a chassis dynamometer or rolling road, power output is measured at the driving wheels. This accounts for the significant power loss through the drive train.
In general:
All the above assumes that no power inflation factors have been applied to any of the readings.
Engine designers use expressions other than horsepower to denote objective targets or performance, such as brake mean effective pressure (BMEP). This is a coefficient of theoretical brake horsepower and cylinder pressures during combustion.
used to estimate the power of steam engines.
nhp = 7 x area of piston x equivalent piston speed/33,000
For paddle ships the piston speed was estimated as 129.7 x (stroke)1/3.35
For the nominal horsepower to equal the actual power it would be necessary for the mean steam pressure in the cylinder during the stroke to be 48 kPa (7 psi) and for the piston speed to be of the order of 54–75 m/min.
s in the 19th century but is misleading because the actual power output may only be 70% to 90% of the indicated horsepower.
invention of the late 18th century), and later by means of a De Prony brake
connected to the engine's output shaft. More recently, an engine dynamometer
is used instead of a De Prony brake. Although the output delivered to the driving wheels is less than that obtainable at the engine's crankshaft, a chassis dynamometer gives an indication of an engine's 'real world' horsepower after losses in the drive train and gearbox. This gives a reasonably accurate indication of how a wheeled vehicle engine will perform once on the road.
shafts of a steamship (or one powered by diesel engine
s or nuclear power
), or an aircraft
powered by a piston engine or a gas turbine
engine. This shaft horsepower can be measured with instrument
s, or estimated from the indicated horsepower and a standard figure for the losses in the transmission (typical figures are around 10%). This measure is not commonly used in the automobile
industry, because there, drive train losses can become significant.
) in lieu of the OEM
exhaust manifolds. The atmospheric correction standards for barometric pressure, humidity and temperature for testing were relatively idealistic.
A few manufacturers such as Honda and Toyota switched to the new ratings immediately, with multi-directional results; the rated output of Cadillac's
supercharged
Northstar V8 jumped from 440 hp under the new tests, while the rating for Toyota's
Camry
3.0 L 1MZ-FE V6 fell from 210 hp. The ES330 and Camry SE V6 were previously rated at 225 hp but the ES330 dropped to 218 hp while the Camry declined to 210 hp. The first engine certified under the new program was the 7.0 L LS7 used in the 2006 Chevrolet Corvette
Z06. Certified power rose slightly from 500 hp.
While Toyota and Honda are retesting their entire vehicle lineups, other automakers generally are retesting only those with updated powertrains. For example, the 2006 Ford Five Hundred is rated at 203 horsepower, the same as that of 2005 model. However, the 2006 rating does not reflect the new SAE testing procedure as Ford is not going to spend the extra expense of retesting its existing engines. Over time, most automakers are expected to comply with the new guidelines.
SAE tightened its horsepower rules after some engineers noticed parts of the old test could be subjected to different interpretations. Under the old testing procedures, there were small factors that required a judgment call: how much oil was in the crankcase, how the engine controls were calibrated and whether a vehicle was tested with premium fuel. In some cases, such can add up to a change in horsepower ratings. A road test editor at Edmunds.com, John Di Pietro, said decreases in horsepower ratings for some '06 models are not that dramatic. For vehicles like a midsize family sedan, it is likely that the reputation of the manufacturer will be more important.
DIN
regarding road vehicles. Because the German
word for horsepower is Pferdestärke, in Germany it is commonly abbreviated to PS. DIN hp is measured at the engine's output shaft, and is usually expressed in metric (Pferdestärke) rather than mechanical horsepower.
of 16 December 1980 is a European Union standard for road vehicle engine power.
s or truck
s having a spark ignition, diesel engine
, or fuel injection engine.
Units of measurement
A unit of measurement is a definite magnitude of a physical quantity, defined and adopted by convention and/or by law, that is used as a standard for measurement of the same physical quantity. Any other value of the physical quantity can be expressed as a simple multiple of the unit of...
of power
Power (physics)
In physics, power is the rate at which energy is transferred, used, or transformed. For example, the rate at which a light bulb transforms electrical energy into heat and light is measured in watts—the more wattage, the more power, or equivalently the more electrical energy is used per unit...
. The most common definitions equal between 735.5 and 750 watt
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...
s.
Horsepower was originally defined to compare the output of steam engine
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...
s with the power of draft horse
Draft horse
A draft horse , draught horse or dray horse , less often called a work horse or heavy horse, is a large horse bred for hard, heavy tasks such as ploughing and farm labour...
s in continuous operation. The unit was widely adopted to measure the output of piston engines, turbines, electric motors, and other machinery. The definition of the unit varied between geographical regions. Most countries now use the SI unit watt
Watt
The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:...
for measurement of power. With the implementation of the EU Directive 80/181/EEC on January 1, 2010, the use of horsepower in the EU is only permitted as supplementary unit.
Definitions of term
Units called "horsepower" have differing definitions:- The mechanical horsepower, also known as imperial horsepower, of exactly 550 foot-pounds per second is approximately equivalent to 745.7 watts.
- The metric horsepower of 75 kgfKilogram-forceA kilogram-force , or kilopond , is a gravitational metric unit of force. It is equal to the magnitude of the force exerted by one kilogram of mass in a gravitational field...
-m per second is approximately equivalent to 735.499 watts. - The boiler horsepower is used for rating steam boilerBoilerA boiler is a closed vessel in which water or other fluid is heated. The heated or vaporized fluid exits the boiler for use in various processes or heating applications.-Materials:...
s and is equivalent to 34.5 pounds of water evaporated per hour at 212 degrees FahrenheitFahrenheitFahrenheit is the temperature scale proposed in 1724 by, and named after, the German physicist Daniel Gabriel Fahrenheit . Within this scale, the freezing of water into ice is defined at 32 degrees, while the boiling point of water is defined to be 212 degrees...
, or 9,809.5 watts. - One horsepower for rating electric motorElectric motorAn electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
s is equal to 746 watts. - Continental European electric motors used to have dual ratings, using a conversion rate of 0.735 kW for 1 HP
- The Pferdestärke PS (German translation of horsepower) is a name for a group of similar power measurements used in Germany around the end of the 19th century, all of about one metric horsepower in size.
- British Royal Automobile ClubRoyal Automobile ClubThe Royal Automobile Club is a private club and is not to be confused with RAC plc, a motorists' organisation, which it formerly owned.It has two club houses, one in London at 89-91 Pall Mall, and the other in the countryside at Woodcote Park, Surrey, next to the City of London Freemen's School...
(RAC) horsepower is one of the tax horsepowerTax horsepowerThe tax horsepower or taxable horsepower was an early system by which taxation rates for automobiles were reckoned in some European countries, such as Britain, Belgium, Germany, France, and Italy; some US states like Illinois charged license plate purchase and renewal fees for passenger...
systems adopted around Europe which make an estimate based on several engine dimensions.
History of the unit
The development of the steam engineSteam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...
provided a reason to compare the output of horse
Horse
The horse is one of two extant subspecies of Equus ferus, or the wild horse. It is a single-hooved mammal belonging to the taxonomic family Equidae. The horse has evolved over the past 45 to 55 million years from a small multi-toed creature into the large, single-toed animal of today...
s with that of the engines that could replace them. In 1702, Thomas Savery
Thomas Savery
Thomas Savery was an English inventor, born at Shilstone, a manor house near Modbury, Devon, England.-Career:Savery became a military engineer, rising to the rank of Captain by 1702, and spent his free time performing experiments in mechanics...
wrote in The Miner's Friend: "So that an engine which will raise as much water as two horses, working together at one time in such a work, can do, and for which there must be constantly kept ten or twelve horses for doing the same. Then I say, such an engine may be made large enough to do the work required in employing eight, ten, fifteen, or twenty horses to be constantly maintained and kept for doing such a work…" The idea was later used by James Watt to help market his improved steam engine
Steam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...
. He had previously agreed to take royalties of one third of the savings in coal from the older Newcomen steam engine
Newcomen steam engine
The atmospheric engine invented by Thomas Newcomen in 1712, today referred to as a Newcomen steam engine , was the first practical device to harness the power of steam to produce mechanical work. Newcomen engines were used throughout Britain and Europe, principally to pump water out of mines,...
s. This royalty scheme did not work with customers who did not have existing steam engines but used horses instead. Watt determined that a horse could turn a mill wheel 144 times in an hour (or 2.4 times a minute). The wheel was 12 feet in radius; therefore, the horse travelled 2.4 × 2π × 12 feet in one minute. Watt judged that the horse could pull with a force
Force
In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...
of 180 pounds. So:
This was rounded to an even 33,000 ft·lbf/min.
Others recount that Watt determined that a pony could lift an average 220 lbf (0.9786087553 kN) 100 ft (30.5 m) per minute over a four-hour working shift. Watt then judged a horse was 50% more powerful than a pony and thus arrived at the 33,000 ft·lbf/min figure.
Engineering in History recounts that John Smeaton
John Smeaton
John Smeaton, FRS, was an English civil engineer responsible for the design of bridges, canals, harbours and lighthouses. He was also a capable mechanical engineer and an eminent physicist...
initially estimated that a horse could produce 22,916 foot-pounds per minute. John Desaguliers increased that to 27,500 foot-pounds per minute. "Watt found by experiment in 1782 that a 'brewery horse' was able to produce 32,400 foot-pounds per minute." James Watt and Matthew Boulton standardized that figure at 33,000 the next year.
Most observers familiar with horses and their capabilities estimate that Watt was either a bit optimistic or intended to underpromise and overdeliver; few horses can maintain that effort for long. Regardless, comparison with a horse proved to be an enduring marketing tool.
A healthy human can produce about 1.2 hp briefly (see orders of magnitude
Orders of magnitude (power)
This page lists examples of the power in watts produced by various sources of energy. They are grouped by orders of magnitude, and each section covers three orders of magnitude, or a factor of one thousand.-zeptowatt :...
) and sustain about 0.1 hp indefinitely; trained athletes can manage up to about 2.5 hp briefly and 0.3 hp for a period of several hours.
Horsepower from a horse
In 1993, R. D. Stevenson and R. J. Wassersug published an article calculating the upper limit to an animal's power output. The peak power over a few seconds has been measured to be as high as 14.9 hp. However, Stevenson and Wassersug observe that for sustained activity, a work rate of about 1 hp per horse is consistent with agricultural advice from both 19th and 20th century sources.Current definitions
The following definitions have been widely used:| Mechanical horsepower hp(I) |
≡ 33,000 ft-lbf/min 745.699872 W Watt The watt is a derived unit of power in the International System of Units , named after the Scottish engineer James Watt . The unit, defined as one joule per second, measures the rate of energy conversion.-Definition:... |
|
| Metric horsepower hp(M) |
≡ 75 kgf Kilogram-force A kilogram-force , or kilopond , is a gravitational metric unit of force. It is equal to the magnitude of the force exerted by one kilogram of mass in a gravitational field... ·m/s ≡ 735.49875 W |
|
| Electrical horsepower hp(E) |
≡ 746 W | |
| Boiler horsepower hp(S) |
≡ 33,475 BTU/h 9,809.5 W | |
| Hydraulic horsepower | = flow rate (US gal/min Minute A minute is a unit of measurement of time or of angle. The minute is a unit of time equal to 1/60th of an hour or 60 seconds. In the UTC time scale, a minute on rare occasions has 59 or 61 seconds; see leap second. The minute is not an SI unit; however, it is accepted for use with SI units... ) × pressure (psi) × 7/12,000 or 745.699872 W |
|
In certain situations it is necessary to distinguish between the various definitions of horsepower and thus a suffix is added: hp(I) for mechanical (or imperial) horsepower, hp(M) for metric horsepower, hp(S) for boiler (or steam) horsepower and hp(E) for electrical horsepower.
Hydraulic horsepower is equivalent to mechanical horsepower. The formula given above is for conversion to mechanical horsepower from the factors acting on a hydraulic system.
Mechanical horsepower
Assuming the third CGPMGeneral Conference on Weights and Measures
The General Conference on Weights and Measures is the English name of the Conférence générale des poids et mesures . It is one of the three organizations established to maintain the International System of Units under the terms of the Convention du Mètre of 1875...
(1901, CR 70) definition of standard gravity
Standard gravity
Standard gravity, or standard acceleration due to free fall, usually denoted by g0 or gn, is the nominal acceleration of an object in a vacuum near the surface of the Earth. It is defined as precisely , or about...
, gn=9.80665 m/s2, is used to define the pound-force as well as the kilogram force, and the international avoirdupois pound (1959), one mechanical horsepower is:
| 1 HP | ≡ 33,000 ft·lbf/min | by definition | ||
| = 550 ft·lbf/s | since | 1 min | = 60 s | |
| = 550×0.3048×0.45359237 m·kgf Kilogram-force A kilogram-force , or kilopond , is a gravitational metric unit of force. It is equal to the magnitude of the force exerted by one kilogram of mass in a gravitational field... /s |
since | 1 ft | = 0.3048 m and | |
| = 76.0402249068 kgf·m/s | 1 lb | = 0.45359237 kg | ||
| = 76.0402249068×9.80665 kg·m2/s3 | g | = 9.80665 m/s2 | ||
| = 745.69987158227022 W | since | 1 W | ≡ 1 J Joule The joule ; symbol J) is a derived unit of energy or work in the International System of Units. It is equal to the energy expended in applying a force of one newton through a distance of one metre , or in passing an electric current of one ampere through a resistance of one ohm for one second... /s = 1 N·m/s = 1 (kg·m/s2)·(m/s) |
|
Or given that 1 hp = 550 ft·lbf/s, 1 ft = 0.3048 m, 1 lbf ≈ 4.448 N, 1 J = 1 N·m, 1 W = 1 J/s: 1 hp = 746 W
Metric horsepower
Metric horsepower began in GermanyGermany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
in the 19th century and became popular across Europe and Asia. The various units used to indicate this definition (PS, CV, hk, pk, ks and ch) all translate to horse power in English, so it is common to see these values referred to as horsepower or hp in the press releases or media coverage of the German, French, Italian, and Japanese automobile companies. British manufacturers often intermix metric horsepower and mechanical horsepower depending on the origin of the engine in question. Sometimes the metric horsepower rating of an engine is conservative enough so that the same figure can be used for both 80/1269/EEC with metric hp and SAE J1349 with imperial hp.
Metric horsepower, as a rule, is defined as 0.73549875 kW, or roughly 98.6% of mechanical horsepower. This was a minor issue in the days when measurement systems varied widely and engines produced less power, but has become a major sticking point today. Exotic cars from Europe like the McLaren F1
McLaren F1
The McLaren F1 is a supercar designed and manufactured by McLaren Automotive. Originally a concept conceived by Gordon Murray, he convinced Ron Dennis to back the project and engaged Peter Stevens to design the exterior of the car...
and Bugatti Veyron
Bugatti Veyron
The Bugatti Veyron EB 16.4 is a mid-engined grand touring car. The Super Sport version is the fastest road-legal production car in the world, with a top speed of . The original version has a top speed of...
are often quoted using the wrong definition, and their power output is sometimes even converted twice because of confusion over whether the original horsepower number was metric or mechanical.
PS
This unit ( = horse strength) is no longer a statutory unit, but is still commonly used in Europe, South America, Japan and India especially by the automotive and motorcycle industry. It was adopted throughout continental Europe with designations equivalent to the English horsepower, but mathematically different from the British unit.DIN 66036 defines one horsepower to lift a mass of 75 kilograms within one second against the earth gravitation over a distance of one metre. Similar definitions were already common to the time of James Watt
James Watt
James Watt, FRS, FRSE was a Scottish inventor and mechanical engineer whose improvements to the Newcomen steam engine were fundamental to the changes brought by the Industrial Revolution in both his native Great Britain and the rest of the world.While working as an instrument maker at the...
.
The PS was adopted by the Deutsches Institut für Normung
Deutsches Institut für Normung
is the German national organization for standardization and is that country's ISO member body. DIN is a Registered German Association headquartered in Berlin...
(DIN) and then by the automotive industry throughout most of Europe, under varying names. In 1992, the PS was rendered obsolete by EEC directives, when it was replaced by the kilowatt as the official power measuring unit. It is still in use for commercial and advertising purposes, in addition to the kW rating, as many customers are still not familiar with the use of kilowatts for engines.
pk, ch, hk, hv, LE, k/ks, KS, KM, CP, PS
The Dutch paardenkracht (pk), the French chevaux (ch), the Swedish hästkraft (hk), the Finnish hevosvoima (hv), the Norwegian and Danish hestekraft (hk), the Hungarian lóerő (LE), the Czech koňská síla and Slovak konská sila (k or ks), the Croatian and Serbian konjska snaga (KS), the Macedonian Којнска сила (KC), the Polish koń mechaniczny and Slovenian konjska moč (KM) and the Romanian cal-putere (CP) all equal the German Pferdestärke (PS), and are approximately equal to 735.5 W.CV and cv
In Italian (Cavalli), Spanish (Caballos de vapor), and Portuguese (Cavalo-vapor), CV is the equivalent to the German, PS. It is also used as the French term for the Pferdestärke, but in French, this should be written in lowercase letters as cv.In addition, the capital form CV is used in Italy and France as a unit for tax horsepower
Tax horsepower
The tax horsepower or taxable horsepower was an early system by which taxation rates for automobiles were reckoned in some European countries, such as Britain, Belgium, Germany, France, and Italy; some US states like Illinois charged license plate purchase and renewal fees for passenger...
, short for, respectively, cavalli vapore and chevaux vapeur (steam horses). CV is a non-linear rating of a motor vehicle for tax purposes. The CV rating, or fiscal power, is
, where P is the maximum power in kilowatts and U is the amount of CO2 emitted in grams per kilometre. The term for CO2 measurements has only been included in the definition since 1998, so older ratings in CV are not directly comparable. The fiscal power has found its way into naming of automobile models, such as the popular Citroën deux-chevauxCitroën 2CV
The Citroën 2CV |tax horsepower]]”) was an economy car produced by the French automaker Citroën between 1948 and 1990. It was technologically advanced and innovative, but with uncompromisingly utilitarian unconventional looks, and deceptively simple Bauhaus inspired bodywork, that belied the sheer...
. The cheval-vapeur (ch) unit should not be confused with the French cheval fiscal (CV).
In the 19th century, the French had their own unit, which they used instead of the CV or horsepower. It was called the poncelet
Poncelet
The poncelet is an obsolete unit of power, once used in France and replaced by cheval vapeur . The unit was named after Jean-Victor Poncelet....
and was abbreviated p.
Boiler horsepower
One boiler horse power unit or BHP is equal to a boiler thermal output of 33475 BTU/h, which is the energy rate needed to evaporate 34.5 lb (15.65 kg) at 212 °F (100 °C) in one hour. The unit is not current outside of North America.The term was originally developed at the Philadelphia Centennial Exhibition in 1876, where the best steam engines of that period were tested. The average steam consumption of those engines (per output horsepower) was determined to be the evaporation of 30 lb/h of water, based on feedwater at 100 °F (37.8 °C), and saturated steam generated at 70 psi (482.6 kPa) gauge pressure. This original definition is equivalent to a boiler heat output of 33485 BTU/h. In 1884, the ASME redefined the boiler horsepower as the thermal output equal to the evaporation of 34.5 lb/h of water "from and at" 212 °F. This considerably simplified boiler testing, and provided more accurate comparisons of the boilers at that time. This revised definition is equivalent to a boiler heat output of 33469 BTU/h. Present industrial practice is to define boiler horsepower as a boiler thermal output equal to 33475 BTU/h, which is very close to the original and revised definitions.
The amount of power that can be obtained by a steam engine or steam turbine based on boiler horsepower varies so widely that use of the term is entirely obsolete for these purposes. The term makes no distinction as to the steam pressure or temperature which is produced (both of which significantly influence engine/turbine output); it merely defines a thermal output of a boiler. Smaller steam engines often require several boiler horsepower to make one horsepower, and modern steam turbines can make power with as little as about 0.15 hp (boiler) thermal output per actual horsepower developed.
Electrical horsepower
The horsepower used for electrical machines is defined as exactly 746 W. The nameplates on electrical motors show their power output, not their power inputRelationship with torque
For a given torqueTorque
Torque, moment or moment of force , is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist....
and speed, the power may be calculated; the relationship between torque in foot-pound
Pound-foot (torque)
A pound-foot is a unit of torque . One pound-foot is the torque created by one pound force acting at a perpendicular distance of one foot from a pivot point....
s, rotational speed in rpm and horsepower is:
Where
is power, is torque, and is rotations per minute.The constant 5252 is the truncated value of (33,000 ft·lbf/min)/(2π rad/rev).
The standard equation relating torque in inch pounds, rotational speed in rpm and horsepower is:
Where
is power, is torque, and is rotations per minute. The constant 63,025 is the truncated value of (33,000 ft·lbf/min) × (12 in/ft)/(2π rad/rev).See torque.
Drawbar horsepower
- See also Power at rail
Drawbar horsepower (dbhp) is the power a railway locomotive
Locomotive
A locomotive is a railway vehicle that provides the motive power for a train. The word originates from the Latin loco – "from a place", ablative of locus, "place" + Medieval Latin motivus, "causing motion", and is a shortened form of the term locomotive engine, first used in the early 19th...
has available to haul a train
Train
A train is a connected series of vehicles for rail transport that move along a track to transport cargo or passengers from one place to another place. The track usually consists of two rails, but might also be a monorail or maglev guideway.Propulsion for the train is provided by a separate...
or an agricultural tractor to pull an implement. This is a measured figure rather than a calculated one. A special railway car called a dynamometer car
Dynamometer car
A dynamometer car is a railroad maintenance of way car used for measuring various aspects of a locomotive's performance. Measurements include tractive effort , power, top speed, etc.-History:...
coupled behind the locomotive keeps a continuous record of the drawbar
Drawbar (haulage)
A drawbar is a solid coupling between a hauling vehicle and its hauled load. Drawbars are in common use with rail transport, road trailers, both large and small, industrial and recreational, and with agricultural equipment.-Agriculture:...
pull exerted, and the speed. From these, the power generated can be calculated. To determine the maximum power available, a controllable load is required; it is normally a second locomotive with its brakes applied, in addition to a static load.
If the drawbar force (
) is measured in pounds-force (lbf) and speed () is measured in miles per hour (mph), then the drawbar power () in horsepower (hp) is:Example: How much power is needed to pull a drawbar load of 2,025 pounds-force at 5 miles per hour?
The constant 375 is because 1 hp = 375 lbf·mph. If other units are used, the constant is different. When using a coherent system of units, such as SI
Si
Si, si, or SI may refer to :- Measurement, mathematics and science :* International System of Units , the modern international standard version of the metric system...
(watts, newtons, and metres per second), no constant is needed, and the formula becomes
.RAC horsepower (taxable horsepower)
This measure was instituted by the Royal Automobile ClubRoyal Automobile Club
The Royal Automobile Club is a private club and is not to be confused with RAC plc, a motorists' organisation, which it formerly owned.It has two club houses, one in London at 89-91 Pall Mall, and the other in the countryside at Woodcote Park, Surrey, next to the City of London Freemen's School...
in Britain
United Kingdom
The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
and was used to denote the power of early 20th century British cars
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
. Many cars took their names from this figure (hence the Austin
Austin Motor Company
The Austin Motor Company was a British manufacturer of automobiles. The company was founded in 1905 and merged in 1952 into the British Motor Corporation Ltd. The marque Austin was used until 1987...
Seven and Riley
Riley (automobile)
Riley was a British motorcar and bicycle manufacturer from 1890. The company became part of the Nuffield Organisation in 1938 and was later merged into British Leyland: late in 1969 British Leyland announced their discontinuance of Riley production, although 1969 was a difficult year for the UK...
Nine), while others had names such as "40/50 hp", which indicated the RAC figure followed by the true measured power.
Taxable horsepower does not reflect developed horsepower; rather, it is a calculated figure based on the engine's bore size, number of cylinders, and a (now archaic) presumption of engine efficiency. As new engines were designed with ever-increasing efficiency, it was no longer a useful measure, but was kept in use by UK regulations which used the rating for tax purposes
Tax horsepower
The tax horsepower or taxable horsepower was an early system by which taxation rates for automobiles were reckoned in some European countries, such as Britain, Belgium, Germany, France, and Italy; some US states like Illinois charged license plate purchase and renewal fees for passenger...
.
- where
- D is the diameter (or bore) of the cylinder in inches
- n is the number of cylinders
This is equal to the displacement in cubic inches divided by 10π then divided again by the stroke in inches.
Since taxable horsepower was computed based on bore and number of cylinders, not based on actual displacement, it gave rise to engines with 'undersquare' dimensions (i.e., relatively narrow bore), but long stroke; this tended to impose an artificially low limit on rotational speed (rpm
Revolutions per minute
Revolutions per minute is a measure of the frequency of a rotation. It annotates the number of full rotations completed in one minute around a fixed axis...
), hampering the potential power output and efficiency of the engine.
The situation persisted for several generations of four- and six-cylinder British engines: for example, Jaguar's
Jaguar (car)
Jaguar Cars Ltd, known simply as Jaguar , is a British luxury car manufacturer, headquartered in Whitley, Coventry, England. It is part of the Jaguar Land Rover business, a subsidiary of the Indian company Tata Motors....
3.4-litre XK engine of the 1950s had six cylinders with a bore of 83 mm (3.3 in) and a stroke of 106 mm (4.2 in), where most American automakers had long since moved to oversquare (wide bore, short stroke) V-8
V8 engine
A V8 engine is a V engine with eight cylinders mounted on the crankcase in two banks of four cylinders, in most cases set at a right angle to each other but sometimes at a narrower angle, with all eight pistons driving a common crankshaft....
s (see, for example, the early Chrysler Hemi).
Measurement
The power of an engine may be measured or estimated at several points in the transmission of the power from its generation to its application. A number of names are used for the power developed at various stages in this process, but none is a clear indicator of either the measurement system or definition used.In the case of an engine dynamometer, power is measured at the engine's flywheel
Flywheel
A flywheel is a rotating mechanical device that is used to store rotational energy. Flywheels have a significant moment of inertia, and thus resist changes in rotational speed. The amount of energy stored in a flywheel is proportional to the square of its rotational speed...
(i.e., at the crankshaft output). With a chassis dynamometer or rolling road, power output is measured at the driving wheels. This accounts for the significant power loss through the drive train.
In general:
- Nominal is derived from the size of the engine and the piston speed and is only accurate at a pressure of 48 kPa (7 psi).
- Indicated or gross horsepower (theoretical capability of the engine) [ PLAN/ 33000]
- minus frictional losses within the engine (bearing drag, rod and crankshaft windage losses, oil film drag, etc.), equals
- Brake / net / crankshaft horsepower (power delivered directly to and measured at the engine's crankshaft)
- minus frictional losses in the transmission (bearings, gears, oil drag, windage, etc.), equals
- Shaft horsepower (power delivered to and measured at the output shaft of the transmission, when present in the system)
- minus frictional losses in the universal joint/s, differential, wheel bearings, tire and chain, (if present), equals
- Effective, True (thp) or commonly referred to as wheel horsepower (whp)
All the above assumes that no power inflation factors have been applied to any of the readings.
Engine designers use expressions other than horsepower to denote objective targets or performance, such as brake mean effective pressure (BMEP). This is a coefficient of theoretical brake horsepower and cylinder pressures during combustion.
Nominal horsepower
Nominal horsepower (nhp) is an early Nineteenth Century rule of thumbRule of thumb
A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation. It is an easily learned and easily applied procedure for approximately calculating or recalling some value, or for making some determination...
used to estimate the power of steam engines.
nhp = 7 x area of piston x equivalent piston speed/33,000
For paddle ships the piston speed was estimated as 129.7 x (stroke)1/3.35
For the nominal horsepower to equal the actual power it would be necessary for the mean steam pressure in the cylinder during the stroke to be 48 kPa (7 psi) and for the piston speed to be of the order of 54–75 m/min.
Indicated horsepower
Indicated horsepower (ihp) is the theoretical power of a reciprocating engine if it is completely frictionless in converting the expanding gas energy (piston pressure × displacement) in the cylinders. It is calculated from the pressures developed in the cylinders, measured by a device called an engine indicator – hence indicated horsepower. As the piston advances throughout its stroke, the pressure against the piston generally decreases, and the indicator device usually generates a graph of pressure vs stroke within the working cylinder. From this graph the amount of work performed during the piston stroke may be calculated. It was the figure normally used for steam engineSteam engine
A steam engine is a heat engine that performs mechanical work using steam as its working fluid.Steam engines are external combustion engines, where the working fluid is separate from the combustion products. Non-combustion heat sources such as solar power, nuclear power or geothermal energy may be...
s in the 19th century but is misleading because the actual power output may only be 70% to 90% of the indicated horsepower.
Brake horsepower
Brake horsepower (bhp) is the measure of an engine's horsepower before the loss in power caused by the gearbox, alternator, differential, water pump, and other auxiliary components such as power steering pump, muffled exhaust system, etc. Brake refers to a device which was used to load an engine and hold it at a desired RPM. During testing, the output torque and rotational speed were measured to determine the brake horsepower. Horsepower was originally measured and calculated by use of the indicator (a James WattJames Watt
James Watt, FRS, FRSE was a Scottish inventor and mechanical engineer whose improvements to the Newcomen steam engine were fundamental to the changes brought by the Industrial Revolution in both his native Great Britain and the rest of the world.While working as an instrument maker at the...
invention of the late 18th century), and later by means of a De Prony brake
De Prony brake
The de Prony Brake is a simple device invented by Gaspard de Prony to measure the torque produced by an engine. The term "brake horsepower" is one measurement of power derived from this method of measuring torque...
connected to the engine's output shaft. More recently, an engine dynamometer
Dynamometer
A dynamometer or "dyno" for short, is a device for measuring force, moment of force , or power. For example, the power produced by an engine, motor or other rotating prime mover can be calculated by simultaneously measuring torque and rotational speed .A dynamometer can also be used to determine...
is used instead of a De Prony brake. Although the output delivered to the driving wheels is less than that obtainable at the engine's crankshaft, a chassis dynamometer gives an indication of an engine's 'real world' horsepower after losses in the drive train and gearbox. This gives a reasonably accurate indication of how a wheeled vehicle engine will perform once on the road.
Shaft horsepower
Shaft horsepower (shp) is the power delivered to the propellerPropeller
A propeller is a type of fan that transmits power by converting rotational motion into thrust. A pressure difference is produced between the forward and rear surfaces of the airfoil-shaped blade, and a fluid is accelerated behind the blade. Propeller dynamics can be modeled by both Bernoulli's...
shafts of a steamship (or one powered by diesel engine
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...
s or nuclear power
Nuclear power
Nuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...
), or an aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft 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.Although...
powered by a piston engine or a gas turbine
Gas turbine
A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between....
engine. This shaft horsepower can be measured with instrument
Instrument
Instrument may refer to:* Instrument , a documentary of the band Fugazi, directed by Jem Cohen* Instruments , a performance visualizer-Science and technology:...
s, or estimated from the indicated horsepower and a standard figure for the losses in the transmission (typical figures are around 10%). This measure is not commonly used in the automobile
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
industry, because there, drive train losses can become significant.
Engine power test codes
Engine power test codes determine how the power and torque of an automobile engine is measured and corrected. Correction factors are used to adjust power and torque measurements to standard atmospheric conditions to provide a more accurate comparison between engines as they are affected by the pressure, humidity, and temperature of ambient air. There exist several standards for this purpose, some described below.SAE gross power
Prior to the 1972 model year, American automakers rated and advertised their engines in brake horsepower (bhp), frequently referred to as SAE gross horsepower, because it was measured in accord with the protocols defined in SAE standards J245 and J1995. As with other brake horsepower test protocols, SAE gross hp was measured using a stock test engine, generally running with few belt-driven accessories and sometimes fitted with long tube (test headersExhaust manifold
In automotive engineering, an exhaust manifold collects the exhaust gases from multiple cylinders into one pipe. The word manifold comes from the Old English word manigfeald and refers to the folding together of multiple inputs and outputs.In contrast, an inlet manifold is the part of an engine...
) in lieu of the OEM
Original Equipment Manufacturer
An original equipment manufacturer, or OEM, manufactures products or components that are purchased by a company and retailed under that purchasing company's brand name. OEM refers to the company that originally manufactured the product. When referring to automotive parts, OEM designates a...
exhaust manifolds. The atmospheric correction standards for barometric pressure, humidity and temperature for testing were relatively idealistic.
SAE net power
In the United States, the term bhp fell into disuse in 1971-72, as automakers began to quote power in terms of SAE net horsepower in accord with SAE standard J1349. Like SAE gross and other brake horsepower protocols, SAE Net hp is measured at the engine's crankshaft, and so does not account for transmission losses. However, the SAE net power testing protocol calls for standard production-type belt-driven accessories, air cleaner, emission controls, exhaust system, and other power-consuming accessories. This produces ratings in closer alignment with the power produced by the engine as it is actually configured and sold.SAE certified power
In 2005, the SAE introduced "SAE Certified Power" with SAE J2723. This test is voluntary and is in itself not a separate engine test code but a certification of either J1349 or J1995 after which the manufacturer is allowed to advertise "Certified to SAE J1349" or "Certified to SAE J1995" depending on which test standard have been followed. To attain certification the test must follow the SAE standard in question, take place in a ISO9000/9002 certified facility and be witnessed by an SAE approved third party.A few manufacturers such as Honda and Toyota switched to the new ratings immediately, with multi-directional results; the rated output of Cadillac's
Cadillac
Cadillac is an American luxury vehicle marque owned by General Motors . Cadillac vehicles are sold in over 50 countries and territories, but mostly in North America. Cadillac is currently the second oldest American automobile manufacturer behind fellow GM marque Buick and is among the oldest...
supercharged
Supercharger
A supercharger is an air compressor used for forced induction of an internal combustion engine.The greater mass flow-rate provides more oxygen to support combustion than would be available in a naturally aspirated engine, which allows more fuel to be burned and more work to be done per cycle,...
Northstar V8 jumped from 440 hp under the new tests, while the rating for Toyota's
Toyota Motor Corporation
, , , commonly known simply as Toyota and abbreviated as TMC, is a multinational automaker headquartered in Toyota, Aichi, Japan. In 2010, Toyota Motor Corporation employed 317,734 people worldwide, and was the world's largest automobile manufacturer by production.The company was founded by...
Camry
Toyota Camry
The Toyota Camry is a series of mid-size automobiles manufactured by Toyota since 1982, and sold in the majority of automotive markets throughout the world...
3.0 L 1MZ-FE V6 fell from 210 hp. The ES330 and Camry SE V6 were previously rated at 225 hp but the ES330 dropped to 218 hp while the Camry declined to 210 hp. The first engine certified under the new program was the 7.0 L LS7 used in the 2006 Chevrolet Corvette
Chevrolet Corvette
The Chevrolet Corvette is a sports car by the Chevrolet division of General Motors that has been produced in six generations. The first model, a convertible, was designed by Harley Earl and introduced at the GM Motorama in 1953 as a concept show car. Myron Scott is credited for naming the car after...
Z06. Certified power rose slightly from 500 hp.
While Toyota and Honda are retesting their entire vehicle lineups, other automakers generally are retesting only those with updated powertrains. For example, the 2006 Ford Five Hundred is rated at 203 horsepower, the same as that of 2005 model. However, the 2006 rating does not reflect the new SAE testing procedure as Ford is not going to spend the extra expense of retesting its existing engines. Over time, most automakers are expected to comply with the new guidelines.
SAE tightened its horsepower rules after some engineers noticed parts of the old test could be subjected to different interpretations. Under the old testing procedures, there were small factors that required a judgment call: how much oil was in the crankcase, how the engine controls were calibrated and whether a vehicle was tested with premium fuel. In some cases, such can add up to a change in horsepower ratings. A road test editor at Edmunds.com, John Di Pietro, said decreases in horsepower ratings for some '06 models are not that dramatic. For vehicles like a midsize family sedan, it is likely that the reputation of the manufacturer will be more important.
Deutsches Institut für Normung 70020
DIN 70020 is a standard from GermanGermany
Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...
DIN
Din
DIN or Din or din can have several meanings:* A din is a loud noise.* Dīn, an Arabic term meaning "religion" or "way of life".* Din is one of the ten aspects of the Ein Sof in Kabbalah ....
regarding road vehicles. Because the German
German language
German is a West Germanic language, related to and classified alongside English and Dutch. With an estimated 90 – 98 million native speakers, German is one of the world's major languages and is the most widely-spoken first language in the European Union....
word for horsepower is Pferdestärke, in Germany it is commonly abbreviated to PS. DIN hp is measured at the engine's output shaft, and is usually expressed in metric (Pferdestärke) rather than mechanical horsepower.
Economic Commission for Europe R24
ECE R24 is a UN standard for the approval of compression ignition engine emissions, installation and measurement of engine power. It is similar to DIN 70020 standard, but with different requirements for connecting an engine's fan during testing causing it to absorb less power from the engine.Economic Commission for Europe R85
ECE R85 is a UN standard for the approval of internal combustion engines with regard to the measurement of the net power.80/1269/EEC
80/1269/EECDirective 80/1269/EEC
Council Directive 80/1269/EEC of 16 December 1980 on the approximation of the laws of the Member States relating to the engine power of motor vehicles is a European Union law concerning measurement of engine power in motor vehicles intended for road use with at least four wheels and a maximum speed...
of 16 December 1980 is a European Union standard for road vehicle engine power.
International Organization for Standardization
- ISO 14396 specifies the additional and method requirement for determinating the power of reciprocating internal combustion engines when presented for an ISO 8178 exhaust emission test. It applies to reciprocating internal combustion engines for land, rail and marine use excluding engines of motor vehicles primarily designed for road use.
- ISO 1585 is an engine net power test code intended for road vehicles.
- ISO 2534 is an engine gross power test code intended for road vehicles
- ISO 4164 is an engine net power test code intended for mopeds.
- ISO 4106 is an engine net power test code intended for motorcycles.
- ISO 9249 is an engine net power test code intended for earth moving machines.
Japanese Industrial Standard D 1001
JIS D 1001 is a Japanese net, and gross, engine power test code for automobileAutomobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
s or truck
Truck
A truck or lorry is a motor vehicle designed to transport cargo. Trucks vary greatly in size, power, and configuration, with the smallest being mechanically similar to an automobile...
s having a spark ignition, diesel engine
Diesel engine
A diesel engine is an internal combustion engine that uses the heat of compression to initiate ignition to burn the fuel, which is injected into the combustion chamber...
, or fuel injection engine.
See also
- Brake specific fuel consumptionBrake specific fuel consumptionBrake Specific Fuel Consumption is a measure of fuel efficiency within a shaft reciprocating engine.It is the rate of fuel consumption divided by the power produced. It may also be thought of as power-specific fuel consumption, for this reason...
—how much fuel an engine consumes per unit energy output - Horse power (machine)Horse power (machine)A horse power is a now largely obsolete machine for using draft horses to power other machinery. It is a type of animal engine somewhat more sophisticated than a horse mill. A common design for the horse power was a large treadmill on which one or more horses walked. The surface of the treadmill...
- Horsepower-hourHorsepower-hourA Horsepower-hour is an outdated unit of energy, not used in the SI system of units. The unit represents an amount of work a horse is supposed capable of delivering during an hour...
- European units of measurement directives