Hiya,

I'm sure this is a virgin question, but could someone please put my mind at rest and explain the proper difference between BHP and torque when comparing the power/speed etc of a vehicle.

Thanks,

Mark.

 

Torque is force (measured value), BHP is power (calculated value).

A car's speed/acceleration is down to torque and torque spread (over rpm range) only, given a certain set of gear ratios.

Peak BHP is used to sell cars.

 

OK, so the performance of a high torque (maybe even diesel) low BHP would be better than low torque, high BHP (if this is possible) ?

 

Nope. I said Torque AND Torque spread over rpm!

Chances are, you won't get a really fast car if you can only make torque at low RPM.

 

Hopefully this click me should help you mate.

 

Great, thanks to the both of you

 

Sorry to link to a Vauxhall forum article, but one of our members covered this for an A-Level project and trimmed it down for the site (still was 9 pages). The article covers pretty much everything and is designed to be understood by non technical people.

Have a look here:
http://www.migweb.co.uk/forums/showthread.php?s=&threadid=597

 

I will see if I can dig up the website I found which explained the differences of power and torque in real terms. eg 1/4 mile etc.

 

That is an excellent link but in the simplest terms, if you regard torque as the amount of twisting force exerted per engine revolution, it is easy to see that the more revolutions per minute you can generate, the more power (bhp) is available. Which is why when you change down, torque is multiplied by the gear ratio and you have more accelleration.

I think the confusion arises when people tend to talk about low-end power as torque, and high-end as bhp. In both cases, the more bhp you have available at any given engine speed, REGARDLESS OF TORQUE OUTPUT, the faster you will go.

Cheers,

Richard.

 

"the more bhp you have available at any given engine speed, REGARDLESS OF TORQUE OUTPUT, the faster you will go."

Yes, but don't forget that BHP is a product of TORQUE, you can't have one, without the other.

BHP = RPM x ftlbs div' 5252.

So the higher the torque, the higher the BHP. If you want "BIG" BHP no.s, you need to maintain your torque as high up the rpm's as possible.

Mark.

 

"The higher the torque, the higher the bhp." At a given engine speed - agreed. But equally, the higher the revs the higher the bhp, at a given torque output

As you say, it is important to appreciate that torque and bhp are inextricably linked. Check out any torque/bhp curves and you'll notice how peaks and troughs in one curve are directly reflected in the other.

Richard.

PS Mark, love my hybrid TD04L turbo and the Spin Doctor's mapping is sweet. I think you do a slightly bigger one, don't you? Hhmmm. Can always use more torque...

[Edited by Hoppy - 6/27/2002 9:38:14 AM]

 

How come on an S2000 there a piddly torque figure and a huge bhp figure way up the rev range???
If it was a simple calculation then cars with VTEC would have low low bhp figures? Where's the catch that makes them high bhp runners?
Oh the confusion. I'm going back to bed.

I'm over the water this weekend visiting some mates in Londing (one of them just bought a loverly 993 and I need to take it for a spin ) so get them Scoobys out and showing off the torque and bhp for me please so I don't miss my baby while I'm away.

 

You only have to look at the equation to realise why you can have relatively high bhp, at high rpm, but still have a low torque figure.

15,000rpm x 350ftlbs div' 5252 = 1000BHP !!!! or,

200bhp x 5252 div' 9000rpm = 117ftlbs. But, if you had 200bhp at 5000rpm, you would also have 210ftlbs.

Mark. Looking for 450ftlbs @ 7500rpm.......

 

Mark, I think you'll be looking for a new gearbox as well

Best regards,

Richard.

 

Richard,

I didn't say I "had" 450ftlbs @ 7500rpm, or anywhere near it, BUT, I wouldn't complain

Mark.

 

 

BIG torque wrench, 600ftlbs of torque.

Not very good for 1/4 mile runs though....

Paul