Do you talk power or drive torque?

[HDi fun]

What's your take on this;-

'We all talk power but we all drive torque.'

The two are inextricably linked, and different engine configurations (fuel type, air delivery etc.) give massively different numbers for each.

In which camp do you sit?

[fingers]

I personally talk both. Having a V8 (when it works) I have oodles of BHP and torque. I often find it difficult getting it through to some people having power coming out of your ears is all good and well but if you have little torque to go with it the engine will struggle to pull the weght of the vehicle.

[Doughnutter]

The old saying "BHP figures sell engines, torque wins races" is spot on in my opinion.

[Freddie]

I think BHP takes the spotlight, only because this is where the bragging rights lie.

[vr1066]

I'm still trying to fully understand it all :s

Am I correct in saying torque is what pins you to the seat when you accelerate? (very technical :P )

[waynne]

Here is me being controversial or trying to.

Torque is a measure of bhp and RPM. If you have a 400bhp tractor which only revs to 2500rpm it will be much slower than a 400bhp Car with a 6000rpm redline.... Discuss and ponder. let battle commence etc....

[HDi fun]

BHP is a derivitive of torque and revs. You can't have one without the other.

It is torque that shoves you in the seat when you accelerate. Torque is twisting force. So more torque is more twist which means more acceleration.

It's the lack of revving ability that makes diesels feel breathless as revs rise hence the constant gear changing.

[waynne]

BHP is like PMPO wheras Torque is like RMS! Both describe loudness but 1 is a better measure of the effect of loudness. BHP and Torque both measure power but Torque is the better description of the effect of power

[pgarner]

Horsepower = Torque x rpm / 5252.

if an engine if in good running order HP, not bhp but the engine actual hp and torque lines should cross at 5252rpm ( must be in bhp and foot pounds or watts and newton meters not a combination of ether otherwise it wont work)

another thing a lot of cars now especially continental are expressed as PS (PferdeStarke the german version of horsepower ) however they are quite often expressed as having the same bhp there is a slight difference

1 PS = 1.014 BHP

[HDi fun]

That's an interesting point PG, proving that BHP is a function of torque and revs. I've taken the numbers from my car last time on the dyno and plugged in 331 (lbft) at 2500 rpm. That suggests that at 2500rpm my engine's dishing out about 157bhp. I'll do some more arithmetic and see what the torque figure is at 4300rpm (where power is recorded at 192bhp).

Kind of shows where diesel strengths and weaknesses are.

[pgarner]

using it the other way then
Torque = Horsepower x 5252 / rpm

192 x 5252 / 4300 =
234 lbft

going to have a look myself next time the laptps connected to the car to find out my own reading it gives me a engine torque reading but nthing about power

[HDi fun]

PG, your numbers sit with the dyno plot very closely. It shows that torque falls off quite steeply as revs rise with my (diesel) car. And it drives as such. Loads of torque in the midrange - so much so that you can accidentally get some wheelspin in third or even fourth gear on a slippery road.

A large capacity petrol engine with good turocharging and supercharging might be the best on all fronts. ie. A flat torque graph. Imagine having 300 lbft from idle and all the way up to 7000rpm. with 300bhp at 7000rpm.

Anyone said 'Honda'?

[waynne]

Hondas tend to peak late when it comes to Torque. They are nice high revving engines though.

[pgarner]

well at least i know now it works came across it last year in a mag but a never had any figures to work with

yeah hondas are torque shy its all up high. really after the vtec kicks in. nice revving fun but a pain when you have to drop it all the time to pass

[HDi fun]

Most Japanese fours are that way. I had a Primera 2.0 which is a 16v twin cam effort and that revved to about 7600 before the red. Great fun, but basically lifeless below 5000rpm.