Turbo Exhaust Piping Size??????

Until you are certain that you'll eventually be boosted, don't buy anything w/ a diameter larger than 2.5". Of course, for our cars, this isn't an easy thing to do since most companies use 60mm piping. If you intend not to remove your air conditioner compressor, your downpipe will likely be no bigger than 2.5" in diameter. If that is the case, at no point in your exhaust system will you want the diameter to be smaller than that. Also, if you are to have the system custom made, it would be to your benefit to have it mandrel bent.

Thermal Research and Development makes an exhaust specifically for forced induction Acura's and Honda's. Click here for more info., part numbers or to contact TR&D.

No matter what diameter you choose, if you decide the exhaust note is too loud, there is a relatively easy and inexpensive remedy. Purchase a good ol' glass pack (I like the Cherry Bombs personally.) from your local automotive parts store. They can be had in diameters of 2.5", 2.75", and 3" and typically cost no more than 20 USD's. Next, weld it in backwards on the B-pipe, the section between the catalytic converter and the muffler. You don't have to put in on backwards but I find that it does not disrupt exhaust flow and also quiets things down a bit more than positioning it the "correct" way.

I HTH and if you have any more questions, don't hesitate to ask.

OK....lets say you have an 2.5" exhaust on an NA application...it will be loud because there is little to no backpressure...when you add a turbo, exhaust will be quieter because there is more backpressure...the more backpressure you have, the less sound will come out.

The exhaust does more than just emissions stuff....when the high pressure waves travel down the exhaust, some reflect back as a low pressure waves....low pressure waves help create the scavenging effects that draw the exhaust out of the cylinder...don't want that spent exhaust to dilute the fresh intake charge....if the turbine is creating to much backpressure, then it isn't big enough....our small engines make power higher in the rpm range so there is no need for such a small turbine inducer unless your trying to reduce turbo lag

I'm not a very turbo knowledgable guy, but that is my take on it.

3" is too big....when you start to push 300whp start to look into 3" piping.

an exhaust is an exhaust, just because a company deems it a turbo exhaust, does not mean that it's the best exhaust for a turboed car.

2.65" or so would be good for a boosted Si....you start to go bigger, the exhaust gas moves slower...when it moves slower, it cools off and thus becomes denser, heavier air.....this is not a hard concept to understand...which would you rather push to a gas station, an f350 or a metro....get it, good....not only that, but like I said before...the exhaust gas comes out in pulses...the head of the pulse is a high pressure, the tail end is a low pressure....high pressure goes to low pressure, so the head of the next pulse will be sucked out by the tail end of the previous pulse....if you go to big, the pulses don't line up (higher entropy) and the sucking doesn't quite work.....me, I like it when sucking goes good, I'm sure most of you can appreciate a good sucking too

it's hard to figure out the ideal exhaust diameter...a lot of it has to do with design, bents, dents, etc.