Quote:
Originally Posted by te51levin
I'm going to disagree with this. A local friend (unfortunately, not someone on this board) and I spent a day with his stock '85, comparing exhaust systems. We used Streetdyno to test the results and found that replacing the stock muffler and cat with a test pipe and SC muffler gained five peak horsepower and eight at redline. A much louder setup with a small glasspack was worth seven peak horsepower and eleven at redline compared to the stock cat and muffler. So there are definately tangible power gains to be had by making intelligent changes to a naturally aspirated AW11!
One important note to add is that we found NO LOSS in low-end or midrange power with either setup. That is solidevidence against the old muffler-shop myth that you need backpressure to make torque. It's not the backpressure you need; it's reasonably sized header tubing. Big headers will kill velocity at low RPM, and that hurts torque. Small headers that provide good velocity at low engine speeds will add backpressure at high speeds and kill horsepower. Everything's a compromise.
For those who don't know what Streetdyno is, please read up before attacking. It's not a real dyno, but it does the same thing in much the same way by recording acceleration via the ignition signal and calculating that into a full-spectrum horsepower and torque plot.
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if you read the guy's post, he said "maybe ten hp". you said 11. not that much of a difference in ten or even 15 hp, thats quite a gain in my opinion for a 1.6 liter (as opposed to gaining maybe 30 on a 5.0 for instance)
just clearing things up, i think you both were saying the same thing