If it's a 2.5" straight through exhaust (making assumption from thread title) it'll be loud as hell. Need more details... is it an off-the-shelf exhaust or custom? Hi flow cat? What sort of headers?
your intake will generate the sound - Ram Pod = louder / CAI = quiter.
Then your headers/extractors will then flow the noise to your 2.5 system.
If you dont have a resonator then the noise will still continue to travel to the muffler.
depending on your muffler - cannon = loud as hell or twinloop = nice quite sound.
Saying that - a resonator depending on size/quality should be able to shut the fhukker up but yet again a str8 thru cannon will definately make the incabin noise annoying.
Power vs sound = what is it that your after?
2.5 will give you abit of lag from 0-80 but after that it should flow nicely as the engine is working harder.
for a daily - i would recommend 2.25 rather than a 2.5..
but this will depend again on what bolt on mods you have.
2.5 is too big for a "dc2" (assuming its a vtir with the usual mods....) full stop.
IF you have heavy work , or supercharged etc 2.5 is great. But the usual intake/header mods do not justify a larger than say 2.25inch system
Noted that the cat-back piping should match the outlet size of the cat itself - which should also match the collector size of the header too.
IMO if it must be a 2.5 inch , use a standard ITR muffler or similar to tighten the sound and aid throttle response both down low and mid range. Back pressure is real and is needed on smaller engines.
2.5 is too big for a "dc2" (assuming its a vtir with the usual mods....) full stop.
IF you have heavy work , or supercharged etc 2.5 is great. But the usual intake/header mods do not justify a larger than say 2.25inch system
Noted that the cat-back piping should match the outlet size of the cat itself - which should also match the collector size of the header too.
IMO if it must be a 2.5 inch , use a standard ITR muffler or similar to tighten the sound and aid throttle response both down low and mid range. Back pressure is real and is needed on smaller engines.
Back pressure is not real, and by smaller engines you're talking 4stroke dirtbikes.
Some sort of flow velocity must be kept however, and if you can't move the gas through the pipe as fast as you should.. Then you're got nothing left to gain out of that oversize piping.
"N/A cars: As most of you know, the design of turbo exhaust systems runs counter to
exhaust design for n/a vehicles. N/A cars utilize exhaust velocity (not backpressure)
in the collector to aid in scavenging other cylinders during the blowdown process. It
just so happens that to get the appropriate velocity, you have to squeeze down the
diameter of the discharge of the collector (aka the exhaust), which also induces
backpressure. The backpressure is an undesirable byproduct of the desire to have a
certain degree of exhaust velocity. Go too big, and you lose velocity and its
associated beneficial scavenging effect. Too small and the backpressure skyrockets,
more than offsetting any gain made by scavenging. There is a happy medium here."
Originally Posted by bennjamin
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