how can you change the torque but not nec the bhp? just wandered as my car seems to have a fair bit of torque but not so much bhp, thought they would go hand in hand.:confused:

Air filter / exhaust / porting - all will increase the amount of air getting in - which in turn will create more torque - and as a consequence you'll get more horsepower.

 

Basically anything that can get more air/fuel mix into the chamber will increase your torque.

 

Tricky subject really - since the science behind it is mind boggling. Different engines will exhibit different torque curves - an NA Z will probably show more torque than a TT in the 750rpm - 1,200rpm - since the turbo can't produce any positive boost until after this (dependant on turbos of course), and the higher compression on the NA will be an advantage.

 

If you wanted loads more torque low down - i.e. if you were trying to improve your 1/4 time - getting nitros inj. at low revs until the blowers really kick in will really help.

 

This is just the tip of the iceburg really - different camshafts for example can really alter you torque curve.

 

Si.

power is torque times revs. So you can have a lot of torque low down at not many rpm but none at the top of the rpm band and a high bhp. A diesel is like this. What it can mean is almost the same max bhp at 4000rpm and at 6000 rpm. Many hot engines have no torque low down but enough at high rpm to give big tested bhp figures. However driveability is better with the car with a flat bhp curve and big torque low down.

 

If you see some of the rolling road charts you'll understand as they chart torque and bhp against rpm. You can see the power curve drops off when the torque is already well on its way down the hill. This is also the point of max transmission loss as well.

 

Also a big bhp motor isnt necessarily quicker as you cant keep the rpm at the big bhp point without lots of gears and gearchanges.

Torque makes the car go forward. Torque is just the circular equivalent of a good old shove.

 

BHP is just (badly) applied maths and doesn't actually tell you much about how the car drives. Tells you lots about how much energy you're using over time, but who cares?

 

Peak BHP and 0-60 are both bloody useless as indicators of performance, but the market's obsessed with them!

 

A high BHP figure just means you've got a middling amount of torque at high revs (which is good because the gearbox can turn that into performance) or that you have a high amount of torque at middling revs (which is good because it means you don't have to drive at the redline everywhere.) You can't tell which from the figure.

 

If you've got a car with whanging torque in the middle and lots of power at the top (like a Z) then it'll be faster in practice than many other cars with just the high peak power at high revs, but you can't tell that from looking at BHP figures.