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Power Transmition System Problem

  1. Nov 16, 2006 #1
    Hi Guys and Girls

    I have a tutorial question that requires me to calculate the efficiency of the power transmittion system in coverting engine power to vehicle motion.

    I have the rolling resistance at a specific speed and the required information to calculate the power required to overcome the drag.

    I thouught to calculate the power require to overcome the rolling resistance and the drag but i am not sure where to go from here!

    Any help would be great!
     
  2. jcsd
  3. Nov 16, 2006 #2

    brewnog

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    You quite rightly state that the power required will balance the rolling resistance and the drag, at a constant speed. Power is force times velocity.

    Do you know how to calculate the drag? If so where are you getting stuck?
     
  4. Nov 17, 2006 #3
    Well the rolling resistance at 140mph is 200N and this results in an additional power required of 16.78hp.

    The power required against the drag of the car at 140mph is 159.57hp.

    The maximum power of the car is 190bhp at 7800rpm.

    So how do i calculate the efficiency of the power transmittion system?
     
  5. Nov 17, 2006 #4

    brewnog

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    Either you're missing information, or you've not copied your question fully.

    Does it say the maximum power of the car is 190bhp or the engine?
     
  6. Nov 18, 2006 #5
    The exact question is -

    A new sports car has the following published specifications and performance when fitted with a 1.8 litre, 16 valve, double overhead cam, turbocharged engine.

    Maximum Power: 190bhp at 7800rpm
    Maximum Speed: 140mph (level road,sea air)
    Mass: 1200kg
    Chassis Dimensions: 1.7 x 1.4 x 4.2 (widthxheightxlength)
    Coefficient of drag for the vehicle is 0.34
    Sea air density is 1.2 kg/m*3

    If the rolling resistance of the vehicle at 140mph is 200N, estimate the efficiency of the power transmition system in converting engine power to vehicle motion.
     
  7. Aug 18, 2011 #6
    Hi guys, i have a very similar problem to the one described here, could anyone provide insight into how to complete this?

    Is there a need to take into account a gain in potential and kinetic energy of the car for efficiency?
     
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