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how do dynos work?

Discussion in 'Dyno Figures' started by 17UCK!, Sep 13, 2008.

  1. 17UCK!

    17UCK! New Member

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    i see/here people sayin i went in n got my car dyno tuned n they got 40kws out it.. just wondering exactly how it works? and dose it work on a vs commo lollllll:thumbsup:
     
  2. adamc11

    adamc11 Donating Member

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    To put it simply... you drive your car up onto the dyno and put your rear wheels (for rwd car) on a set of rollers. When you accelerate though the gears, the rollers spin and the dyno measure the power your car has at the wheels :D
    To say someone got 40kw out of it (they probably mean 40rwkw (rear wheel kw as dynos measure in kw at the wheels)) it means that they probably had a tune at the same time... i.e. dyno tune... a professional tuner tunes your vehicle on the dyno so you get the most amount of power out of it.
     
  3. 17UCK!

    17UCK! New Member

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    yeh but like how do they " tune " it?? wat do they axully do 2 make u get more kw? thats wat i dont understand.:bang:
     
  4. impulsesv6

    impulsesv6 Alloytec Garage

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  5. greenfoam

    greenfoam New Member

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    Mostly the extra power is from more spark advance, the factorys don't tune cars to all their potential for various reasons. So most cars can have the spark advance increased so that by the time the piston reaches the top of it's stroke the burn is allready well underway and so you get more pressure, more effciency and more power. On modified cars that have had parts changed to get more effciency from the motor they can have more fuel added in those areas to gain a bit more power again. That's about it
     
  6. Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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    Beat me to it.

    Power is just a calculation. It doesn't really exist. James Watt thought it up when wanting to talk about the effort required from a pony to move coal in a coal mine. At best it was an estimation because horse couldn't sustain the effort over a period of time at the figure that Watt came up with.

    It has been passed on through the years as a figure that people use to rate the available power of a machine. An engine doesn't produce power at all, it produces torque (twisting effort), this is measured and converted to hp or kW.

    To answer the OP's question a bit more, a dyno loads up the engine by providing resistance to the rollers and measures peak torque. This is when the engine loses it's ability to spin the rollers at certain revs.
     
  7. 17UCK!

    17UCK! New Member

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    cheers greenfoam . that was the kinda answer i was lookin 4 lol..:thumbsup:
     
  8. Weekend Warrior

    Weekend Warrior Waghoon

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    torque is actually "turning force" and is calculated by the force x radius :D hahah good old physics class taught me that one
     
  9. Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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    Turning force twisting force, same thing. The effort required that causes something the turn or twist.
     
  10. davey g-force

    davey g-force I'm a sceptic...

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    Not sure if I mis-read your post but I'm not sure what (watt?) you're trying to say here. Of course power exists and it is very real.

    Power (measured in watts) measures the rate of energy use or production per unit of time; i.e. 1 watt = 1 joule of energy per second.

    An engine produces BOTH power and torque - hence why all vehicle manufacturers quote both kW and Nm figures. Also why two cars can have the same power, but one can be quicker than the other due to it having more torque.
     
  11. Not_An_Abba_Fan

    Not_An_Abba_Fan Exhaust Guru

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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
     
  12. davey g-force

    davey g-force I'm a sceptic...

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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.
     
  13. impulsesv6

    impulsesv6 Alloytec Garage

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

    there is a calculation
     
  14. burnz

    burnz dah dut dut da dah

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    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.
     
  15. commsirac

    commsirac Banned

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    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)
     
    Last edited: Sep 18, 2008
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  16. greenfoam

    greenfoam New Member

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    : ) This thread is classic ( :
     
  17. 17UCK!

    17UCK! New Member

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    yeh go me i started it lol.. but u gave me an answer forwat i asked:p
     
  18. VSIIBerlinaL67

    VSIIBerlinaL67 New Member

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

    Swordsy mmmm beer....

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    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.
     
    Last edited: Sep 28, 2008
  20. vt748

    vt748 New Member

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    Sorry Davey G is wrong


    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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