I am specifically asking about the piping after the cat or racepipe, I think most of you knew that already. Gonna get headers as well. The exhaust is corksport header back, it is offered in 2.5 inches or 80mm (3.15 in.), so which is best for an NA, thanks.

 

I run a 2" header(2.5 at the collector) on my streetport 87n/a.. its loud.. I can't imagine going larger. I run a high-flow cat(2.5" in and out) then split to the dual mufflers all 2.5" was a huge improvement. I can't see the need to go larger unless your running something more than streetport or custom carbs etc. what mods on the engine? that would help to know....

I'm thinking of removing the cat as i no longer have to get smogged

 

3" would be obnoxiously loud

 

Many people advise against anything bigger than 2.5" for n/a. I don't feel like searching and finding specifics, but I don't think you'll find anyone wholeheartedly suggesting the 3.15".

 

it is a NA '91 currently all stock with only apexi power intake. Planning on the exhaust, haltech for a little tuning and than sometime down the road a large pineapple street port (portland based rotary shop) and probably 720 injectors, all with the haltech so somebody should be able to fine tune everything. so i assume the 2.5 but welcome all comments i really appreciate feedback

 

I personally would not go any bigger then 2.25inch ID on the piping.
Larger pipes allows larger volume of air to exit with the accompany of loud sound but that doesnt help any if the velocity is low.
Then theres the exhaust pulses from collected headers which is basically a forum in itself lol.
There are lots of threads about it, you can search and read up on them if you like.

 

alright cool, no 2.25 available from corksport but the 2.5 isn't too much bigger and more than half inch smaller than the 80mill

 

2.5 inch is perfect and Corksport doesn't offer an 80mm header back, just a turbo back.

 

They have an 80mm header back assuming you buy their headers. If i recall it changes to 80mm on the outlet of the presilencer.

2.5" is best for anything non-turbo south of a p-port engine...

 

yeah 2.5 is good for a street car. the racers use a 3" generally don't care about anything except power over 5000rpms, and noise to a point (we've gotta be under 103db).

 

Like everyone else said go with 2.0" header and 2.5" header back, as for the rest of the setup, haltech is a bit over kill for an NA, for tuning go with the Rtek 2.1, and there really isn't any need for 720cc injectors as the stock fuel system will handle anything an NA can put down ( besides a PP and IDA's).

 

I run a 2" straight pipe with no cats and stock headers.

I think it sounds good, real loud and deep sound

 

im going to run a 4-4.5in quad exhaust with glasspacks just to **** people off.

 

Glasspacks have been known to melt.

 

If they are packed with stainless steel instead of glass, it'll be fine. Magnaflow makes some nice stainless packed silencers.

 

it all depends man. ask rotary god.

 

you mean Fiberglass
just making sure other people understand, because glass melting temp are higher then fiberglass.

 

is "rtek" the brand or name of ecu-rtek 2.1? or is the rtek 2.1 made a by a different brand?

 

^ http://www.pocketlogger.com/index.php?pid=rtek7

 

Yep, I used one for years, great product!

 

thanks for the link absence

 

I meant fiberglass when I said "glass".

As far as linkage, go to summit racing and look for their magnaflow straight through stainless mufflers.