martwrxsl

I know this has been discussed to death but I still don't get it.

Ok as an example, if a car has lots of bhp like the new BMW M3 414bhp and not as much torque 295lbs/ft I think. Then as a comparision the BMW 335d 281bhp and 428lbs/ft of torque. Sorry I own a scooby but it's easier to do the comparison this way.

The M3 will beat the 335d if driven to it's potential every time. The 335d has huge amounts of torque why should this happen. I thought that torque gave you the acceleration? The M3 is also heavier than the 335d! The transmission losses are the same! Yet the M3 beats the 335d to 60!

I know diesel people are going to say well you can leave the 335d in 5th gear but I'm not talking about that. Gear for gear if you give it everything the M3 will win. Fuel consumption figures ignored for this please!

Is it to do with diesel cars not having the torque range of revs of petrol cars?

subaruturbo_18

i think the power comes into play at a later rev range. a diesel can rev to say 4-5k? where as the m3 will rev to about 7-9k? that aside i thought that the m3 would have had more torque as its a v8???.

i was taught that in a gear box u put in so much torque and depending on the ratio, out the other end comes less torque but more horsepower, or something along those lines. and yes the torque curve would die out as the revs went up, and the power starts to kick in. thats why on a rolling road print out the torque will kick in first, that wil give you your initial grunt to move, then as the revs go up the power will keep it going as it already has momentum and the revs on its side. so although it is the torque that gives acceleration, the power will come into play also. hope that helps and is not too confusing

Dracoro

A torque figure by itself is meaningless.

If I stand on a pushbike and push on the pedal, I'm generating more torque than a Bugatti Veyron!!!

However, multiply that torque through a gearbox and it starts to have some meaning. This is expressed in BHP at given revs.

BHP is a product of torque, gearing and revs.

At 2000rpm the TD is probably producing more BHP than the M3.
At 7000rpm the M3 will be producing more BHP than the TD.

Many TDIs produce MORE torque than a Formula 1 car.

It's not so much how much torque, but rather how those torque are used/multiplies etc. that really matters. We have a handy figure for all this and it's called BHP.

There's plenty of reading on t'internet (see the external links section at the bottom of wikipedia: Horsepower - Wikipedia, the free encyclopedia )

Remember:

HP = Torque x RPM ÷ 5252

subaruturbo_18

much better explanation than mine lol. i did this all at college about a year ago but its starting to slip already.