I hear alot of people saying things like "A 2.5" exhaust loses low end torque". Well, here is my theory on this. How much pound feet do you think you will lose? 20? 30? 50??. Maybe 10 at the most and an average of maybe 6 from idle to 3Krpm. Its not a major difference from stock, but you might feel the difference. Will your car actually be slower? Maybe, but read on...

Its dyno proven that a high quality cold air intake adds torque, and so will pulleys and cams. So, if you were to combine those mods with a 2.5" exhaust, the torque that you would of lost will probably be retained and the car will feel like stock from idle to 3K, BUT PULL from 3K to redline. If you were to simply bolt on a 2.5" exhaust on a stock car and drive it, yeah, it will probably feel slower to 3K, but install a CAI, and you could probably retain the "lost" torque. With that being said...

I was going through an old Car Craft magazine and came across some interesting facts. HP is the primary exhaust pipe determinant. Hp rely's on pipe size. Engines of equal power output, regardless of displacement, generally require the same size pipe. So a 2L I-4, 3L V-6 or a 5L V-8 with 140hp all need the SAME exhaust pipe size. Ok. Now, here is the "suggested" pipe diameter for our 140hp, 2L I-4: 2.5". What? 2.5"???? Yes. For engines with 200 to 300hp, a single 3" exhaust is needed, for engines with 100 to 200 hp, a single 2.5" exhaust is NEEDED. Our cars come with a single 2" pipe, which is severely restricting power. That might be ok if we had sub 100hp, but we don't. What is surprising is that the Turbos still have 2 inches with 210hp. They COULD of been faster with 2.25 or 2.5 from the factory. Dam you Mitsu/Chrysler. So back to my point. I think that this info is correct in some respect. I think that the Domestic guys are very truthful(theve been doing this for half a century) and I honestly believe that a 2.5" exhaust for our NT's are required. I know alot of people say that 2.5" exhausts "lose torque, go with a 2.25", but I think this might change their mind. It did for me. So in short, and Im not THE automotive authority, a 2.5" with not lose torque unless you combine it with other torque building mods, ie. CAI, pulleys, Cams, compression. Its probably a better choice over a 2.25", which might not lose torque, but will hinder midrange and high end power. And for the people here wanting to add a dual exhaust with 2.5" pipes, go for smaller. A dual 2.5" pipe configuration is good for 300-400hp. Unless you are packing a huge turbo, go for it, but I would suggest 2.25".

Soniclipse
1997 Black Mitsubishi Eclipse RS A-4
Mobil 1, Valvoline Synpower PS fluid, Bosch Plat. plugs, clear bumpers, Ractive Fusion headlights, more to come.

I'm going to have to disagree with this through personal experience.

As you can see from my list of mods, I have enough "torque adders" that should have equated back to stock low RPM grunt. Didn't happen. There should also be an IceMan intake on their. ANYTHING under 3k RPMs really isn't worth a damn. Once it hits 3k, it's normal. Once it get's past 4k, that's when the fun starts.

I would have to make a guess that I lost over 20ft/lb of torque under 3k RPMs. But have probably gained well over 15hp at the top end. That's where I wanted it, so that's what I get to live with.

SEA97GS - 15.785@88.20MPH
NW.DSM.ORG
HotShot Headers-Custom 2.5" exhaust-MSD 8.5mm plug wires-NGK Plugs-Nitto NT555R Drag Radials on RX-7 wheels-Eibach ProKit Springs-Tokico shocks-front upper STB

97 Eclipse GS-15.463@88.57MPH - RIP
92 Talon TSi AWD-12.927@105.47MPH

Hmm, maybe you were running too lean/rich.

Soniclipse
1997 Black Mitsubishi Eclipse RS A-4
Mobil 1, Valvoline Synpower PS fluid, Bosch Plat. plugs, clear bumpers, Ractive Fusion headlights, more to come.