Richie1

Hi,

Its always intrigued me when looking at the power charts/results of Impreza Turbos that they almost always seem to have peak BHP values way higher than their respective peak torque values.

Example - POC's result from Power Engineering = 298bhp / 242 lb/ft


Other examples arent as much of a diff with around 20BHP more than the peak torque value figure.

For my own curiousity, can anyone explain why this happens a lot on these cars (and possibly others) All the other cars I have seen seemt to have a larger peak torque value than they do BHP e.g. 239BHP and 243lb/ft or 204BHP and 218lb/ft


Cheers

Hoppy

Torque and bhp figures are meaningless without the context of rpm, and even that can be misleading unless you can see the whole plot on a graph. Having said that, rolling-road measurements are prone to huge relative innacuracies, but the shape of the torque curve will tell you most.

Richard.

Cosie Convert

Impreza's have an ECU that is quite 'reserved' with the midrange torque. If you look at some of the LINK ECU results they are producing loads more torque.
Did you see Dave Brown's result ? 300+ torque and 250 bhp !(approx)
that was running 1.7 bar boost.

It can also depend on the engines cams, my bike produces only 62lbft torque but 110 bhp !(at 10,000 rpm)
A big V8 may produce in the region of 500lbft torque with 300 bhp.

Torque output always equals Power at 5250 rpm. Generally speaking, if you make your peak power above 5250rpm it will exceed your torque and vice versa.

As usual there are exceptions such as world rally cars but they run with restrictors so that kills the power.

Hope this is helpfull but probably just more confusing !!

SimonJM

Hi Richie,

If you want to find out about torque and bhp check out the following:

www.scoobmania.freeserve.co.uk/tuning/torque_vs_hp.html

Needs a bit of thought to understand some of it, but quite good.

Just for interst mine is 281 ftlb and 276bhp

Cheers

Simon

POC

Hi Richie, a very good explaination from Cosie Convert there....

Basicaly, my car runs a 3in BPM twin dump downpipe, and a 3in HKS Hiper exhaust system. The result of the 3in bore is a large drop in back pressure.... this results in a loss in torque. If I were to run a 2.5in system, the back pressure would be inmproved and the torque fig would rise...

Swings and roundabouts.....

I am v happy with the power figure though

Paul

Richie1

Cheers

Just all the other 2 litre turbos I have seen were the opposite but for some reason I noticed a lot of Imprezas were like this (peak BHP more than peak torque)

Hope you didnt mind me using yours as an example POC.... was the best example I could see at the time

Rich

POC

No problems Rich....

Paul