Altered torque curve?

646 Views 3 Replies 0 Participants Last post by scoobymike, May 29, 2001

Discussion Starter · May 27, 2001

Am seriously considering fitting a new exhaust on my E5, since so many folk here have experienced real gains versus stock. But have heard that this may alter the torque curve. Acceleration (esp. for overtaking purposes) is more important to me than top-end grunt, so the torque coming-on around 3000 RPM's is very usable for me. Do the aftermarket exhausts move this significantly higher up (say, above 4000)? This would be a bit of a negative for me...

Thanks, and cheers!

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Discussion Starter · #2 · May 27, 2001

Hi there

yes if you fit a bigger exhaust, the torque will be higher up, by how much depends on the diameter. Scoobymike said that a Evo 6 with Supersprint exhaust and Sports ECU had 432,4 Nm (instead of 380) at... 5190 rpms! and 354 bhp at 6610 rpms.

For drivability you need torque, but for acceleration you need power. There's a technical explanation for this on autospeed.com. Personally I like torquy engines with a lot of power

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Discussion Starter · #3 · May 28, 2001

I think the general idea is that a perfomance exhaust will shift the maximum torque up the rev range a bit/a lot depending on the car and zorst.

This sort of thing:

The trick is trading as little low down grunt for your maximum gain at higher revs. The car may well fell less responsive and might even feel 'quicker' with the standard exhaust if the losses at lower revs are unacceptable.

As you say it is probably preferable to have better low-end characteristics for everyday driving, sod the [email protected] power figures, but a good exhaust's benefits should outweigh any minor drop ( and amp;lt;15%) in torque at lower revs.

With just an exhaust, my car went from 185lbs/ft @ 3000rpm to 220lbs/ft @ 3840rpm, with the torque at the previous peak (3000rpm) being a good 15-20lbs/ft higher. In my case a win:win scenario, but then my car came with a particularily restrictive exhaust. The V will be better in this respect but all road cars have compromised exhausts to some degree.

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Discussion Starter · #4 · May 29, 2001

Claudius is absolutely right. Just check Blow Dogs dyno chart. The power gain is impressive considering it's just a simple exhaust swap but peak power is a little bit above 7000rpm. So you always have to rev it to the redline to get out the maximum.
So to improve torque in lower revs aswell a remap is unavoidable.

Cheers

Mike

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