Power-to-weight ratio

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Power-to-weight ratio

Power-to-weight ratio (specific power) is a calculation commonly applied to engine

Engine

An engine is a mechanical device that produces some form of output from a given input.An engine whose purpose is to produce kinetic energy output from a fuel is called a Wiktionary:prime mover; alternatively, a motor is a device which produces kinetic energy from a preprocessed "fuel" ....
s and mobile power sources to enable the comparison of one unit or design to another. Power-to-weight ratio is a measurement of actual performance of any engine or power sources. It is also used a measure of performance of a vehicle as a whole, with the engine's power output being divided by the curb weight of the car, to give an idea of the vehicle's acceleration.

Power to weight (specific power)
The power-to-weight ratio (Specific Power) formula for an engine (power plant) is the power

Power (physics)

In physics, power is the rate at which mechanical work is performed or energy is transmitted, or the amount of energy required or expended for a given unit of time....
generated by the engine divided by weight

Weight

In the physical sciences, weight is a measurement of the gravitational force acting on an object. Near the surface of the Earth, the Earth's gravity is approximately constant; this means that an object's weight is roughly proportional to its mass....
of the engine as follows:

A typical turbocharged V-8 diesel engine might have an engine power of and a weight of , giving it a power to weight ratio of 0.56 kW/kg (0.25 hp/lb).

Examples of high power to weight ratios can often be found in turbines.

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Encyclopedia

Power-to-weight ratio (specific power) is a calculation commonly applied to engine

Engine

Power to weight (specific power)

The power-to-weight ratio (Specific Power) formula for an engine (power plant) is the power

Power (physics)

Weight

Space Shuttle

NASA's Space Shuttle, officially called the Space Transportation System , is the spacecraft currently used by the United States government for its human spaceflight missions....
's main engines use turbopump

Turbopump

As the name suggests, a turbopump comprises basically two main components: a rotodynamic pump and a driving turbine, both mounted on the same shaft....
s (machines consisting of a pump driven by a turbine engine) to feed the propellants (liquid oxygen and liquid hydrogen) into the engine's combustion chamber. The liquid hydrogen turbopump is slightly larger than an automobile engine (weighing approximately ) and produces nearly 70,000 hp

Horsepower

Horsepower is the name of several non-International System of Units units of power . It was originally defined to allow the output of steam engines to be measured and compared with the power output of draft horses....
(52.2 MW) for a power to weight ratio of 164 kW/kg (100 hp/lb).

Examples

Engines

Engine	Power to weight ratio
Turbocharged V-8 diesel engine	0.25 hp/lb / 410 W/kg
Boeing 777 GE90-115B Jet Engine	7.63 hp/lb / 12,513 W/kg
Space shuttle turbopump	100 hp/lb / 164120 W/kg

Vehicles

Vehicle	Power	Weight	Power to weight ratio
Subaru R2 Subaru R2 The Subaru R2 was announced in Japan on December 8 2003. It is Subaru's re-entry in the Japanese kei car market.The R2 name was inspired by the Subaru R-2, the kei car model that was produced between 1969 to 1972.... type S 2003	47 kW / 63 bhp	830 kg	57 W/kg
Subaru Legacy Subaru Legacy The Legacy is a mid-size car introduced by the Japanese automaker Subaru in February 1989 as a larger companion to the company's Subaru Leone/Subaru Loyale.... 2.0R 2005	121 kW / 162.3 bhp	1370 kg	88 W/kg
Subaru Outback Subaru Outback The Subaru Outback is an all wheel drive crossover manufactured by Subaru since 1995 in sedan and station wagon body styles.All vehicles with an "Outback" badge are equipped with AWD; there were no versions built with only front wheel drive.... 2.5i 2008	130.5 kW / 175 bhp	1430 kg	91 W/kg
Ford Focus Ford Focus (North America) The Ford Focus is a compact car sold in the North American market. It was introduced in 1999 as a 2000 model year as a replacement for the Ford Escort and the Mercury Tracer.... 2.0 auto 2007	104.4 kW / 140 bhp	1198 kg	94 W/kg
Artega GT Artega GT The Artega GT is a RMR layout 2-seat sports car produced by Germany manufacturer Artega Motors. The GT is currently Artega's first and only model for sale....	220 kW / 300 bhp	1100 kg	200 W/kg
Lotus Exige Lotus Exige The Lotus Exige is a two-door, two-seat sports car made by Lotus Cars. It is essentially a coupe version of the Lotus Elise, which is a roadster.... GT3 2006	202.1 kW / 271 bhp	980 kg	206 W/kg
Chevrolet Corvette C6 Chevrolet Corvette C6 The Chevrolet Corvette C6 is the sixth and current generation of Chevrolet Corvettes. It was introduced in 2005, and according to several issues of Motor Trend magazine, will be superseded by the C7 Corvette in the 2012 calendar year....	321 kW / 430 bhp	1441 kg	223 W/kg
Chevrolet Corvette C6 Chevrolet Corvette C6 The Chevrolet Corvette C6 is the sixth and current generation of Chevrolet Corvettes. It was introduced in 2005, and according to several issues of Motor Trend magazine, will be superseded by the C7 Corvette in the 2012 calendar year.... Z06	337 kW / 505 bhp	1421 kg	265 W/kg
McLaren F1 McLaren F1 The McLaren F1 is a sports car designed and manufactured by Gordon Murray and McLaren Automotive. On March 31, 1998, it set the record for the fastest production car in the world, 240.1 mph , which it held until the introduction of the Bugatti Veyron in 2005.... GT 1997	467.6 kW / 627 bhp	1220 kg	403 W/kg
Ultima GTR Ultima GTR The Ultima GTR is a sports car manufactured by Ultima Sports Ltd of Hinckley, Leicestershire, England, and described by commentators as a supercar.... GTR720 2000	257.3 kW / 345 bhp	1048 kg	480 W/kg
Honda CBR1000RR Honda CBR1000RR The CBR1000RR is a liquid-cooled inline four-cylinder Honda sport bike that was introduced in 2004 to replace the Honda CBR954RR.... 2009	133 kW / 178 bhp	199 kg	668 W/kg
MTT Turbine SUPERBIKE 2008	213.3 kW / 286 bhp	227 kg	940 W/kg
Formula One Formula One Formula One, abbreviated to F1, and currently officially referred as the FIA Formula One World Championship is the highest class of auto racing sanctioned by the F?d?ration Internationale de l'Automobile .... 2006	582 kW / 780 bhp	605 kg	962 W/kg

Batteries

Battery Battery (electricity) In electronics, a battery or voltaic cell is a combination of one or more electrochemical cell Galvanic cells which store chemical energy that can be converted into electric potential energy, creating electricity.... type	Power to weight ratio
Nickel hydrogen battery Nickel hydrogen battery A nickel hydrogen battery is a rechargeable electrochemical power source based on nickel and hydrogen. The difference with a nickel-metal hydride battery is the use of hydrogen in a pressurized cell of up to 1200 Pounds per square inch ....	75 W/kg
Nickel-cadmium battery Nickel-cadmium battery The nickel-cadmium battery is a type of rechargeable battery using nickel oxide hydroxide and metallic cadmium as electrodes.The abbreviation NiCad is a registered trademark of SAFT Corporation and should not be used to refer generically to nickel-cadmium batteries, although this brand-name is genericized trademark to describe all ni...	150 W/kg
Lead acid battery	180 W/kg
Nickel metal hydride	250 (market) –980 W/kg (lab)
Lithium ion battery Lithium ion battery Lithium-ion batteries are a type of rechargeable battery in which a lithium ion moves between the anode and cathode. The lithium ion moves from the anode to the cathode during discharge and in reverse, from the cathode to the anode, when charging....	1700 W/kg (lab)

Electric motors

Motor type	weight	power	Power to weight ratio
Himax HC6332-230	0.69kg	2.2kW	3188W/kg
Hi-Pa Drive	120kg	235kW / 320 bhp	1958W/kg

Fuel cells

Fuel cell Fuel cell A fuel cell is an Electrochemistry conversion device. It produces electricity from fuel and an Oxidizing agent , which react in the presence of an electrolyte.... type	Power to weight ratio
PEMFC	967 W/kg (market) - 1,500 W/kg (lab)

The inverse of power-to-weight, weight-to-power ratio (power loading) is a calculation commonly applied to aircraft, cars, and vehicles in general, to enable the comparison of one vehicle performance to another. Weight-to-Power ratio is a measurement of the acceleration capability (potential) of any land vehicle or climb performance of any aircraft or space vehicle.

Power-to-weight ratio

Power to weight (specific power)

Examples

Engines

Vehicles

Batteries

Electric motors

Fuel cells

See also