i kno alotta pple say that 3" piping is optimal for cars with turbo, but i was thinking, is 2.5 that bad? you'll still feel gains over stock rite? and will it be louder or quieter than the 3"? and will custom piping welded to universal muffler definitely be cheaper than buying a full catback? thanks


[Modified by Pengo, 11:03 PM 5/17/2002]

 

well i have a sohc vtec..and i went w/a 2.5 in greddy piping to an apexi dunk...if i were to have like a gsr turbo or si turbo i'd go w/3" unless u only want to run like 6-7 psi..then go w/2.5....i went w/2.5 cause im gonna be boosting less then 10 psi for now so its cool...

 

In almost all cases, 3" will give you more power, and will also be louder.

 

i'm contemplating the same thing. i really really want a quiet exhaust, as quiet as stock. but i dont think that is achievable with a 3" exhaust... unless the whole piping back is a straight-through 3" resonator?

 

Even then it still won't be as quiet as stock.

 

Nope, if you want all the power 3" gives you will sacrifice some noise level for that!

 

3" all the way... the exhaust has plenty of restriction with that big turbo in the way, so by freeing up the exhaust as much as possible, you will get better flow. Also, the fact that on turbo cars, you dont utilized the scavenging effect and there is no exhaust pulse, there really is no need for any smaller sized diameter exhaust to promote scavenging. Noise level is lowered by the turbo due to the turbo restriction in the exhaust flow. The main reason why noise would be a concern is due to lack of sound deadening. I'm pretty sure that if you ran a pre-muffler in addition to the rear muffler, sound levels will be much lower. AND as long as there are not bottlenecks or louvers or other restrictors, you will retain just as much power as if you had a straight pipe... only factor would be the extra weight of another muffler, but that is really minimal.

 

hey guys, whats the difference between mandrel bent piping and crush bent piping? i'm gonna get a custom 3" exhaust too, but the local muffler guy says he does crush bent..

 

crush bent

they crush the steel to make bends. this causes turbulence, reduces diameter of piping, and in all reduces flow MAJORLY!

mandrel bent

smooth flow, smooth transitions, no turbulence caused. SUPERIOR!

Comparison of flow between a crush bent and mandrel bent - 3" crush bent is maybe equal to 2.25" mandrel bent in terms of flow. This does NOT factor in the turbulence caused by the crush bends.

 

crush bent sucks. If you look at a crush bent pipe, you will see ripples that cause exhaust flow disturbances. If you look at a mandrel bent pipe, the bend is smooth.

 

how much more is mandrel bends?

 

3" mandrel bent is the way to go

 

not much if anything... Click Here To Find A Good Shop

 

This actually is a touchy subject, it also depends on the type/displacement of the engine...at least that's what some tech's told me...2.5' isn't gonna hurt...but definetly 3" if you want the car to breath...plus it does sound better, and if you really want it to sound stock, get a muffler with a silencer...Apexi has a model, I cant remember what it is, but with the silencer you can't hear anything...I had one on my old hatch, cause my girlfriend didn't like the sound of the exhaust...It might cause slight back pressure, but I'm sure it will run fine...just my .02 bro...good luck...

 

For turbo, you don't want any back pressure. That hurts a turbo more then anything. And, with a turbo on a car, your exhaust will sound quiet anyways, unless you use straight piping and no muffler.

Get 3"

 

Ohh, ok...yep just another motor guy over here, thanks for the info...but quiet??? I'm not totally sure on that...got anything to back that up with? The more air, the louder right???Vibration, etc.

 

turbo's will make it quieter than an all motor car... but it still wont be quiet...

 

Even with a small turbo like greddy for sohc? I thought 2.5 was good enough. Does anybody have a dynochart on 2.5 and 3 piping?

 

yea i was thinkin the same thing. except if u plan on running really high boost with a kit like the greddy, i figured 2.5 would be a good mix of power and sound cuz the greddy is made to work well with stock piping already. if nething i'd like to see a real comparison between 2.5 and 3