Factors affecting torque.

[Ads4]

I know that we all (pretty much) crave more BHP, and with it torque, but does anyone specifically tune their car for torque and then the BHP that comes with that?

I'm trying to understand, as the subject title says, the factors that affect torque figures. I've looked at a few signatures and see that the torque figures aren't always proportionate to the BHP figures, namely Doug 399bhp 464 ft-lb , Leon 503bhp 475ft-lb , and Mihneah 511BHP 505ft-lb.

Although Doug's S4 is over 100bhp down on Leon's, it's only 10 down on torque. And Mihneah's is only 8bhp more yet 30ft-lb torque more than Leon's.

I presume this is down to exhaust types, flywheels etc, but explanations in laymans terms are most welcome

[S4TAN]

A lot of that could be down to rolling-road differences Adam ... results can vary wildly from place to place or machine to machine from what i've been told ...

[yorkie]

I think Doug is the only person who can answer this as I think this can be set by the re-map.

[GrahamS4]

Interesting. If (could be a when) I go K04 I'd rather as much torque as possible keeping the feel of the mapped K03 car alive.

[GrahamS4]

Also have it in my mind from somehwere that while Mihnea and leon's K04s have clearenced/ported hotsides, Dougs are a K04 hybrid. Could of course be wrong.

[buzzard]

custom remap allows alteration of values affecting pwer/torque

more low down boost /timing/fuel input/cam timing/compression ratios all at different RPM
all limited by detonation levels.
its very deep at this level.

[MarkB]

Torque is a factor of horse power derived from an equation relating to rpm. Depending where the power is in the rev range will depend how much torque/power you have.

The equation was posted the other day.

[philipwalker]

Air speed into the cylinders affects torque. Big ports air speed can slow down at low revs.

Think back to Webber carbs long trumpet/inlet pipes, small chokes more torque. Also some modern engines have variable length inlet pipes for ths reason. Motorbikes hae a valve to reduce the flow of the exhaust at low speed.

On N/A engines this can be assisted with a longer exhaust camshaft duration creating a vacume in the exhaust

[JDB]

Is there anyway to work out the torque from the peak MAF reading?? I know BHP is MAF /8 but it there something similar for torque?

[S4TAN]

MAF/8 won't give you much of a bhp figure .... try MAF/0.8 ...

[Dippy]

You are looking at peak figures in isolation. It will make more sense if you look at some graphs instead. For a turbo engine it is possible to map for a different profile torque curve by simply varying the boost settings throughout the rev range. However the details of this are far beyond me.

I hope I don't insult you by being too layman...

Torque is the force of the engine. If you are riding a bicycle it is how hard you push the pedals.
Power is the rate at which the engine does work. If you are riding a bicycle the faster you pedal, the more power you generate.

[Ads4]

Torque is the force of the engine. If you are riding a bicycle it is how hard you push the pedals.
Power is the rate at which the engine does work. If you are riding a bicycle the faster you pedal, the more power you generate.

Fine. I'm with you with that. What I don't get is why then we are so bothered with BHP. Why have an MRC 400/500 BHP. Why not an MRC 475ft-lb. It's the differences I don't get-ok it could be down to mapping but all three cars I've mentioned are MRC tuned. Is it purely the different maps that are creating the torque figure differences, or is it parts installed that are giving a major diference. Or just that you get a 'lucky' car?

[JDB]

Cheers Julian!!! Sorry to digress slightly from the torque/ bhp question how accurate is the MAF/0.8?

[S4TAN]

I think it's just a good approximate formula based on the observed relationship between air flow and crank bhp for these cars (+/-5% tolerance maybe?) - which gives a co-efficient of 0.8 ...

[kjrsc05]

Torque is the force of the engine. If you are riding a bicycle it is how hard you push the pedals.
Power is the rate at which the engine does work. If you are riding a bicycle the faster you pedal, the more power you generate.

Fine. I'm with you with that. What I don't get is why then we are so bothered with BHP. Why have an MRC 400/500 BHP. Why not an MRC 475ft-lb. It's the differences I don't get-ok it could be down to mapping but all three cars I've mentioned are MRC tuned. Is it purely the different maps that are creating the torque figure differences, or is it parts installed that are giving a major diference. Or just that you get a 'lucky' car?

from my experiance its the fact that 'most' people know that high bhp figure is good for performance, but the same people dont understand the relationship between torque and acceleration.


i have only ever been asked once to build an engine with a torque figure in mind, (just so happens to be my brothers GT-4), every one else wants an engine ' that will do 200 bhp' etc.

so i think the answer is the old qoute of bhp sells engines - torque wins races can be applied here lol