Power to weight ratio
The power -to-weight ratio (also mass-performance ratio ) is the quotient of the mass and the power of a vehicle , an engine , a battery , a machine or for humans and animals. It is usually given in kilograms per kilowatt.
The reciprocal value is the power density , also called “specific power”, in kilowatts per kilogram. Both terms are sometimes referred to area or volume instead of weight. The term performance indicator is also used in the railway sector and is usually given in kilowatts per ton.
In the case of drives , a low power-to-weight ratio is generally sought, since a smaller mass or a higher power enables higher acceleration and thus counteraction to obstructive natural forces such as inertia , gravity or the moment of inertia . For example, a lower power-to-weight ratio of a vehicle allows a higher speed on inclines.
A low mass-performance ratio is also aimed for in accumulators for traction or for transportable devices; However, the stored energy per mass (joules per kilogram) usually plays a role here and should be as high as possible. See also energy density .
Examples and meaning on vehicles
Motor vehicles
The acceleration typically specified for motor vehicles , for example in "X seconds from 0 to 100 km / h", depends on a number of parameters (such as torque curve , gearshift , traction , air resistance ) and can therefore not be derived directly from the power to weight ratio. Basically, however, the following applies here: a lower power-to-weight ratio enables greater acceleration.
For trucks, buses and similar vehicles, minimum engine power based on weight is prescribed under German law, and consequently a maximum power-to-weight ratio.
Typical power weights in motor vehicles:
- Formula 1 car: 1 kg / kW
- GP motorcycle: 0.8 kg / kW (with driver, as of 2012)
- Sports motorcycle: 1.3 kg / kW (with driver, as of 2019)
- Sports car: 4.2 kg / kW ( Porsche 911 Turbo S , 2009)
- Common cars: 14.7 kg / kW
- Leopard 2 tank : 56 kg / kW
- Last tricycle Goliath Goli , fully loaded 164 kg / kW
Selection of some vehicles:
| vehicle | Empty weight in kg |
Power in PS (bhp) |
Power- to-weight ratio in kg / PS (bhp) |
|---|---|---|---|
| Keating Bolt (Biturbo) | 990 | 2,534.6 (2,500) | 0.39 (0.40) |
| Keating TKR | 995 | 2,027.7 (2000) | 0.49 (0.50) |
| F1 Benetton B186 BMW (1986) | 540 | 900 | 0.67 |
| F1 Red Bull Racing RB8 Renault (2012) | 640 | 750 + 80 | 0.89 |
| Motorcycle Ducati 1299 Superleggera | 162 | 220 | 0.76 |
| Porsche 956 C (1984) | 820 | 620 | 1.32 |
| VW Golf VII GTI | 1351 | 220 | 6.28 |
| VW Golf I GTI | 810 | 110 | 7.36 |
| VW Polo V | 1100 | 105 | 10.48 |
| Motorbike MZ ETZ 125 | 120 | 10.2 | 12 |
| Opel Corsa D 1.2 ecoFLEX | 1120 | 70 | 16 |
| Simson S51 moped | 78.5 | 3.7 | 21st |
With light vehicles, the weight of the people being transported is becoming more important.
Rail vehicles
The tensile force typically specified for rail vehicles in kN or acceleration in m / s² depends on a number of parameters (e.g. torque curve , rail conditions ( slip ), traction , air resistance ) and can therefore not be derived directly from the power-to-weight ratio. Basically, however, the following applies here: A lower power-to-weight ratio enables greater acceleration, greater excess tractive power on inclines and a higher top speed.
Particularly in the case of locomotives that are supposed to pull non-powered wagons , however, a high weight is necessary so that the locomotive has high static friction on the rail. High performance with low weight would only lead to spinning wheels.
Examples of electric multiple units (Germany)
Long-distance transport
| vehicle | Mass 1 in kg | Power 2 in kW | Power to weight ratio in kg / kW | Performance indicator in kW / t |
|---|---|---|---|---|
| ICE T | 273,000-368,000 | 3000-4000 | 91.00-92.00 | 10.87-10.99 |
| ICE 1 | 849,000 | 9600 | 88.44 | 11.31 |
| ICE 2 | 412,000 | 4800 | 85.83 | 11.65 |
| ICE 4 | 670,000 | 9900 | 67.68 | 14.78 |
| ICE 3 | 409,000-454,000 | 8000 | 51.13-56.75 | 17.62-19.56 |
Regional traffic
| vehicle | Mass 1 in kg | Power 2 in kW | Power to weight ratio in kg / kW | Performance indicator in kW / t |
|---|---|---|---|---|
| Stadler Kiss | 170,100 - 305,000 3 | 2000-4500 | 56.70-68.60 | 14.58-17.64 |
| Stadler flirt | 100,000 - 170,000 | 1300-2600 | 38.46-65.38 | 15.29-26.00 |
| Siemens Desiro HC | 200,000 | 3290 4 | 60.79 | 16.45 |
| Alstom Coradia Continental | 141,000 - 168,000 | 2160 - 2880 4 | 48.96-58.33 | 17.14-20.43 |
| Bombardier Talent 2 | 85,000 - 173,000 3 | 2020 - 3030 4 | 42.08 - 57.10 | 17.51-23.76 |
| Siemens Desiro ML | 132,000 | 2600 4 | 50.77 | 19.70 |
Train
| vehicle | Mass 1 in kg | Power 2 in kW | Power to weight ratio in kg / kW | Performance indicator in kW / t |
|---|---|---|---|---|
|
DB class 481 (2-part) (S-Bahn Berlin) |
59,000 | 594 4 | 99.33 | 10.07 |
|
DB class 472 (3-part) (S-Bahn Hamburg) |
114,400 | 1500 4 | 76.27 | 13.11 |
|
DB class 420 (3-part) (S-Bahn Munich old) |
129,000 | 2400 4 | 53.75 | 18.60 |
|
DB class 430 (4 parts) (S-Bahn Stuttgart) |
118,800 | 2350 4 | 50.55 | 19.78 |
|
DB class 425 (4 parts) (S-Bahn Hanover) |
114,000 | 2350 4 | 48.51 | 20.61 |
|
DB class 423 (4-part) (S-Bahn Munich new) |
105,000 | 2350 4 | 44.68 | 22.38 |
Examples of combustion engine railcars (Germany)
| vehicle | Mass 1 in kg | Power 2 in kW | Power to weight ratio in kg / kW | Performance indicator in kW / t |
|---|---|---|---|---|
| Regioswinger (611) | 116,000 3 | 1080 | 107.41 | 9.31 |
| Regioswinger (612) | 116,000 3 | 1120 | 103.57 | 9.66 |
| Pendolino (610) | 95,350 3 | 970 | 98.30 | 10.17 |
| ICE TD | 219,000 | 2240 | 97.77 | 10.23 |
Footnotes
1 - unless otherwise stated, the empty weight without passengers; 2 - unless otherwise specified, the maximum traction power; 3 - service mass; 4 - hourly output
Planes
In the case of aircraft , a low mass-performance ratio or high thrust-to-weight ratio means higher climbing performance and a shorter take-off taxi distance .
Aircraft with a low power-to-weight ratio, in particular combat aircraft , can also fly long-lasting, tight turns with high g-forces , as the drag caused by the high lift (which is necessary to overcome the centrifugal force ) is countered by a large thrust ( curve combat ). For this reason, aircraft have a particularly low power-to-weight ratio; Fighter aircraft are often also equipped with afterburners , booster engines or launchers in order to be able to increase the thrust for a short time. A thrust-to-weight ratio that is greater than 1 enables acceleration in a vertical climb.
Examples and meaning on engines
For engines, the power-to-weight ratio is given with and without gearbox, clutch, cooler, etc. In the case of piston engines, often also the calculated power-to-weight ratio per cylinder. Selection of some internal combustion engines with a wide range of performance:
Piston engines
| engine | Working principle | Rotation frequency in 1 / min |
Dimensions | Power in kW |
Power density in kW / kg |
Power to weight ratio in kg / kW |
cylinder | Power per cylinder in kW |
|---|---|---|---|---|---|---|---|---|
| G95ME-C9 | Two-stroke diesel | 70-80 | 2400 t | 82440 | 0.034 | 29.1 | 12 | 6870 |
| G40ME-C9 | Two-stroke diesel | 125 | 173 t | 8800 | 0.051 | 19.7 | 8th | 1100 |
| S30ME-B9 | Two-stroke diesel | 150 | 86 t | 5120 | 0.060 | 16.8 | 8th | 640 |
| V48 / 60B | Four-stroke diesel | 500 | 250 t | 20700 | 0.083 | 12.1 | 18th | 1150 |
| L21 / 31 | Four-stroke diesel | 1000 | 20 t | 2000 | 0.100 | 10.0 | 9 | 222 |
| DENQBAR | Four-stroke diesel | - | 25 kg | 3.1 | 0.12 | 8.1 | 1 | 3.1 |
| EL 308 (old) | 2T Otto | 3000 | 30 kg | 4.5 | 0.15 | 6.66 | 1 | 4.5 |
| DENQBAR | 4T Otto | - | 17 kg | 4.8 | 0.28 | 3.5 | 1 | 4.8 |
| Delta Hawk V | Two-stroke diesel | 2650 | 142 kg | 135 | 0.95 | 1.05 | 4th | 33.75 |
| Shepherd 3702 | 2T Otto | 5000 | 45 kg | 65 | 1.44 | 0.7 | 3 | 21.66 |
| FE (3.46 cm³) | Two-stroke glow igniter | 32000 | 0.45 kg | 1.4 | 3.1 | 0.32 | 1 | 1.4 |
See also
literature
- Hans-Hermann Braess, Ulrich Seiffert: Vieweg manual automotive technology. 2nd edition, Friedrich Vieweg & Sohn Verlagsgesellschaft mbH, Braunschweig / Wiesbaden, 2001, ISBN 3-528-13114-4 .
Individual evidence
- ↑ Maximum power-to-weight ratio for trucks, buses, etc. Ä .: § 35 StVZO
- ↑ Motorization - time series 2003 to 2012; New car registrations ( Memento of the original from November 22, 2013 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , kba.de, accessed on November 23, 2013
- ↑ Keating Bolt Specifications ( Memento of the original from May 23, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , keatingsupercars.co.uk, accessed May 11, 2015
- ↑ Keating TKR Specifications ( Memento of the original from January 11, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , keatingsupercars.co.uk, accessed March 7, 2015
- ↑ Data from the Benetton B186 BMW , ultimatecarpage.com, accessed on May 20, 2013
- ↑ Data from the Red Bull Racing RB8 Renault , ultimatecarpage.com, accessed on May 20, 2013
- ↑ Technical data Porsche 956 C) , Porsche.de, accessed on May 24, 2013
- ↑ Technical data of the Golf VII GTI , volkswagen.de, accessed on May 19, 2013
- ↑ Corsa Technische Daten , Opel.de, accessed on May 20, 2013
