BHP and Torque corrolation

[Guest JMW]

I've been trying to get a handle on this for a while. I spent a few hours dyno-ing 5 2 stroke spannies and after looking at the torque and BHP figures and comparing them to other bikes I've run, there doesn't seem to be a direct relationship between the two values.

EG..

A bike making 80bhp delivers 65Mn's of torque yet a similar bike making 85bhp delivers 60Mn's of torque.

With no discernable difference, what would cause the torque figure to drop when outright engine power is up ?

Any takers ?

J

[gavin]

ive already explained ths one to you once before, on aleks forum, in a thread you started

http://www.yamaha-rd.com/forum/viewtopic.p...t=5250&start=36

power = torque x revs/5250

so, by calculation a bike making 80bhp at 10,000rpm has 42lb-f of torque.

but another bike making 80bhp at 9000rpm has 46lb-f of torque.

the higher up the revs it makes the power, the less torque it has. there is also a difference between torque at peak power, and actual peak torque. its quite possible for a bike that maks loads of power on a dyno at sky high revs to have bugger all torque, and so never actually make that power on the road, because it will never be able to overcome the rolling and wind resistance.

just proves you never listen

[gavin]

just for my amusement ive been playing with your numbers

65Mn (Mewton Neters? ) is 47.94lbf

60Nm is 44.25lbf

so assuming you havent just plucked these numbers out of your head

bike no1 makes peak power of 80bhp at 8,761rpm or thereabouts

bike no2 makes peak power of 85bhp at 10,085rpm or thereabouts

right?

i say thereabouts, because theres a little rounding in the calculation.

[johnalpi]

LOL @

bike no1 makes peak power of 80bhp at 8,761rpm or thereabouts  

8,761rpm or there abouts? +/- 1rpm,

[gavin]

LOL @

8,761rpm or there abouts? +/- 1rpm,

maybe...whats your point?

[johnalpi]