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how do dynos work?

Not_An_Abba_Fan

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I am referring to the term horsepower and how it relates to an engine. An engine doesn't produce power, all it does is create a twisting (or turning) force. Which is torque. The power figure is calculated using a formula based on torque and RPM.

Without going into too much detail here is a site that explains it pretty well. http://www.vettenet.org/torquehp.html
 

davey g-force

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Yeah, that's all fine, but your comment "an engine doesn't produce power" is not correct.

Sure a dyno measures an engine's torque and then calculates its power, but that's not to say the engine isn't producing power. It is expelling energy over time, thus it's producing power.
 

burnz

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how do you calculate rwhp into fwkw, and torque for that matter

there is a calculation
in short NO only estimates, unless you remove the motor and measure on a power absobsion engine dyno.


and the other post abba i think, james watt. one BHP= 3000 Lbs per foot/ per minute.
and torque is 5252 or 5454 one of the two.
 

commsirac

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I am referring to the term horsepower and how it relates to an engine. An engine doesn't produce power, all it does is create a twisting (or turning) force. Which is torque. The power figure is calculated using a formula based on torque and RPM.

Without going into too much detail here is a site that explains it pretty well. http://www.vettenet.org/torquehp.html
Im with Davey G force here

NAAF, engines are devices that can do mechanical work, the faster they do that work the more power they have. They do "work" because they provide a turning force and they are able to turn. I can provide just as much torque as the worlds best production car V8 by standing on the end of a metre spanner, but can I make a car move along at any where near the rate of an engine producing 500kW? of course not.
Power is simply the product of torque and how fast the engine is spinning.
You can have a small amount of one and a large amount of the other to produce the same effect
ie a v8 producing 300Nm at 2000rpm will produce the same power as a smaller engine producing 100Nm at 6000rpm. Either one will produce the same effect on the vehicle, given that the gearing is adjusted accordingly.
You are correct in that power is merely calculated on the dyno. The force that is used to move the rollers is calibrated and controlled and the power is then calculated by the speed at which they are spinning, the torque figures for the engine can only be worked out if the rpm of the engine is known. Power from the engine is transferred to the dyno and the surroundings(heat in the tyres etc). The power developed could be measured by looking at how much energy the dyno gains/produces per unit time, it depends on how it is braked, but is not as easy to do as measuring/monitoring the resistance force.

For those that care:
power can be calculate by the force x speed
The effective turning force at 1m from the crankshaft is given as the torque in Nm. The speed has to be in metres per second and it it is the speed that an object would be going if it were attached at a metre radius from the crankshaft.
1rpm is equivalent to a distance of 2 x Pi metres per 60 seconds.
or 1rpm is equivalent to 0.105m/sec

the v8 producing 300Nm at 2000rpm can be calculated to be producing:
300 x 2000 x 0.105 = 63kW

or more simply
9549x power(kW)/rpm = torque(Nm)
 
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greenfoam

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: ) This thread is classic ( :
 

17UCK!

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yeh go me i started it lol.. but u gave me an answer forwat i asked:p
 

VSIIBerlinaL67

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how about diesel cars that have fk all power but make heaps of torque
 

Swordsy

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how about diesel cars that have fk all power but make heaps of torque
Because they generally don't rev as high.

Horsepower = (Torque * RPM)/5252

KW is just replacing the number at the bottom to the measurement(foot pounds to nm) that torque is in.
 
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vt748

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Im with Davey G force here
Sorry Davey G is wrong


Power from the engine is transferred to the dyno and the surroundings(heat in the tyres etc). The power developed could be measured by looking at how much energy the dyno gains/produces per unit time, it depends on how it is braked, but is not as easy to do as measuring/monitoring the resistance force.
Torque is tranferred to the dyno.

Power is calculated from the torque value. The engine produces torque and engineers have come up with a calculation (power) that helps them compare different engines. ;)
 
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