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986Jim · 03-31-2006, 07:57 AM

You don't technically lose bottom end Umph, what happens is the power is moved higher in the band which is desirable from a speed standpoint.

It's absolutly proven that on any motor N/A, Turbo/Supercharged whatver, that the best exhaust is the lowest back pressure no matter what. You may lose torque at the lower rpm range (well it's moved higher technically) but that will make the car faster.

Integra Type-R completly stock with an open DC Sports header header (meaning nothing after the header no cat no exhaust etc. made an additional 14hp at the wheels over having the exhaust system hooked up. It was all top end and the dyno graph shows less torque down low, but it still doens't matter, the car is faster.

Look at the S2000 as an example. 240hp at 8800rpm. Sounds like it won't have much bottom end, and it doesn't but you don't stay at 4000rpm for long when you mash the throttle, and the S2000 with it's 170ish ft/lbs is more than 30 less than the lest powerful boxster, but the S2000 is still faster in straight line acceleration by almost a half second over the 2.5. Why? Because higher HP no matter where it is, makes for faster acceleration.

Our all motor honda race car makes 274whp @ 9900rpm (all motor meaning Normally Aspirated no nitrous etc.) and 181 ft/lbs of torque at 7600rpm. It still pulls 1.41 60ft times and runs the 1/4 mile in 10.74 @ 124mph. 181ft/lbs doens't sounds like much but it doesn't matter it makes 274whp which makes it fast.

This muffler bypass will likely not give any performance increase as the flow is coming off the pipe at a hard 90* angle and going out the tip at a hard 90* angle. If anything you would probablly lose whatever you gain because of the cross-flow effect at the muffler enterance and tip. All that's really happening is sounds is being by-passed the muffler, thats all. If you did have a gain, it would just move the power higher in the band, which from a straight line acceleration point is a good thing.

A car with 500 ft/lbs of torque at 3000rpm is way slower than a car with 250hp at 9000rpm. Think Diesel for example, lots of torque, but no rpm or HP so they are slowwwwww...

here is the race car i was talking about:
http://www.etdracing.com/team/vibrant/finished4.jpg
http://www.etdracing.com/team/vibrant/finished6.jpg
http://www.etdracing.com/vibrant.html

ralegen · 04-14-2006, 10:26 PM

Wow... Well said 986Jim. As for the muffler, I like the throttle "growling" sound.

eslai · 04-15-2006, 11:55 AM

However, that does depend on how you plan to drive it. Yes, if you're going to rip it to redline at every stoplight, less exhaust restriction is the way to go. On street driven cars, it may not be.

Your argument sounds suspiciously like "no exhaust is the best exhaust" and completely disregards cylinder scavenging, etc. Instead, I'd like to say that yes, you can go bigger, but there's a sweet spot for pretty much any setup.