horsepower & torque (question for adsayer maybe)

1. Noesph L-plater Joined: Sep 2009 Surrey Posts: 41 106 Indy

   #1 4th March 2010, 01:39

   ok, I was told.....
   
   bhp= lbft of torque x rpm / 5252
   
   1.1 (mpi) engine says it's got 70lbft of torque
   
   peak power is at 5500 rpm
   
   so
   
   70lb x 5500rpm / 5252 = 73.30 bhp
   
   to be 60bhp according to that equation it would have to be
   
   70lbs x 4500rpm / 5252 = 59.97.
   
   is it that the engine has 73hp, but it loses 13hp through the gearbox, driveshafts etc, or that equation just doesn't work with tu engines.
2. Toad Saxperience Post Whore Joined: Mar 2007 Reading Posts: 8980 French tin can

   #2 4th March 2010, 08:51

   I think you're confusing the RPM range of where peak power and peak torque are achieved, as they're rarely identical.
   
   If your engine has "70lbs of torque" it will be at a specific RPM range. Your last calculation is just a guess, where there happens to be a calculation which equals to 60bhp. So your second to last calculation is incorrect, as you've mistaken peak power's RPM range to be equal to peak torque's RPM range, hence the increased calculation of BHP you've got. At 5500rpm, your engine will have less than 70lbs of torque, but due to the amount spreading to a higer RPM range, max BHP is achieved.
3. yr51ocw Frequent Poster Joined: Oct 2005 Posts: 751

   #3 4th March 2010, 09:16

   toad has it bang on there. peak torque and power do not usually occur at the same engine rpm.
4. Noesph L-plater Joined: Sep 2009 Surrey Posts: 41 106 Indy

   #4 4th March 2010, 11:23

   yeah, peak torque is at 3500 rpm. So your saying torque goes down from there.
5. Toad Saxperience Post Whore Joined: Mar 2007 Reading Posts: 8980 French tin can

   #5 4th March 2010, 13:18

   If peak torque is at 3500rpm, then yes, it will begin to drop off after then. Depending on how quickly it drops off will determine your max BHP rpm.
6. Noesph L-plater Joined: Sep 2009 Surrey Posts: 41 106 Indy

   #6 4th March 2010, 15:36

   yeah, so it would be producing something around 57 lb ft of torque at 5500rpm to work out at 60 bhp
7. Jigg Infrequent Poster Joined: Dec 2009 newport, south wales Posts: 155 saxo 1.6 vtr

   #7 4th March 2010, 16:04

   just use a dyno easier lol
8. Toad Saxperience Post Whore Joined: Mar 2007 Reading Posts: 8980 French tin can

   #8 4th March 2010, 20:16

   I think you've got it.
9. Noesph L-plater Joined: Sep 2009 Surrey Posts: 41 106 Indy

   #9 4th March 2010, 22:30

   Cool. Thanks.