Is 2.5" exhaust piping too big?
Flaccid Member
Joined: Jul 2002
Posts: 571
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From: Seattle
Originally posted by qtiger
The common aftermarket has produced bolt on parts, not horsepower. Good dyno gains have been seen moving to 2.5" exhaust systems on B series engines. I can't see how an engine with a larger displacement and high valve lifts can possibly benefit from a smaller exhaust system.
AN-R produces a header with 2" primaries and a 2.5" collector. Hytech, SMSP, and Burns Stainless are other good choices.
The common aftermarket has produced bolt on parts, not horsepower. Good dyno gains have been seen moving to 2.5" exhaust systems on B series engines. I can't see how an engine with a larger displacement and high valve lifts can possibly benefit from a smaller exhaust system.
AN-R produces a header with 2" primaries and a 2.5" collector. Hytech, SMSP, and Burns Stainless are other good choices.
dyno gains on 2.5" systems with NA motors are based on highly modified powerplants, from high lift cams, porting, increased compression, increased head component strength, and higher rpm allowances.
any motor pushing more air requires increased exhaust size to handle increased exhaust volume properly. but in the case of a stock H22A motor, 2.5" is overkill. stock tubing diameter it 2.25" with crush bends and a very restrictive baffle chamber muffler... going with a freer flowing muffler and less resistive piping is more than sufficient unless the motor has received significant buildup to warrant the larger piping.
by going with larger diameter piping, you sacrifice low-mid range efficiency due to decreased exhaust velocities. if your motor is significantly modified to increase top end power, you'll need an exhaust system that can function properly at those ranges... thus justifying a sacrifice to your low end for a larger, more significant, topend gain. of course in this case, you sacrifice mid-range driveability for top-end power... *if* your motor is modified to make use of all the extra volume available in the exhaust system.
