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Conrod equal more torque?

  1. Jul 29, 2015 #1

    Sorry if this is in the wrong thread I'm new to the forums. I was recently talking my mate about how engines produce power and torque and how there's so many factors in it. I mentioned the length of conrod would be a factor but my mate disagreed that it has no effect on torque. To my understanding this is why I see it effects torque.

    If you have a bolt and you have a short wrench it's difficult to undo the bolt. If you increase the length of the wrench you increase the torque and less force is required. However he made a valid point that the conrod is pushing or pulling the crank not twisting it as it's still linear motion. So with the example of the wrench and bolt does the length of conrod still effect torque in the same way? If not what is the effect of different length conrods I've struggled to come across any decent information online.
  2. jcsd
  3. Jul 29, 2015 #2

    Ranger Mike

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    this question comes up from time to time
    go into Search and type in con rod length and you will find several threads posted here
    short reply is - we run longer con rods to take advantage of a slight increase in power gained by mechanical advantage. The piston remains at Top Dead Center slightly longer in crank shaft degrees. You must use custom pistons with wrist pin located closer to the deck ( top of Piston) and this means the piston is lighter Mass. We use a smaller wrist pin than usual so the over all reciprocating mass is lighter and spins up RPM quicker. You are not making more power as such, you are making more effective use of the power that is available as the leverage is slightly better. There are longevity issues as sidle loading and long life will be reduced but you are spinning past 5000 RPM so what the hey-hay??
    thats racing!


    Last edited: Jul 29, 2015
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