ch0g0nda

My car needs a new catback system and I can get a really good deal on a muffler with a 2.5" inlet.

All I wanna know is if having 2.5" pipes from the cat will be too wide?

steve84GS TII

Nah.Thats about the outlet size of a RB header.
Rotaries move a lot of air for their size,so larger piping is OK compared to piston engines of comparable HP levels.
Just be sure the muffler is capable of surviving behind a rotary.No fiberglass and prefferably no baffled mufflers(Flowmaster,ect)The best mufflers are straight through types, with stainless steelwool construction,although they can be loud......but then again,all mufflers are loud behind a rotary,except a RB Powerpulse.

Siraniko

iTrader: (13)

what mods do you have? because it makes a difference. Im assuming you have a N/A, not a turbo.

ch0g0nda

1984 GSL. Bone stock; not really sure what direction I wanna go with it either.

vipernicus42

iTrader: (4)

Here's a tip:

Rotaries don't need backpressure, so it doesn't really matter what sized pipe you have. However rotaries also eat through conventional mufflers, silencers, resonators, glasspacks etc... because of the extreme heat and powerful pulsing of the exhaust. So unless this is a very high quality muffler, a rotary-specific muffler, or a muffler cheap enough that you won't mind replacing it when it fails, don't bother with it.

Oh.. and rotaries are loud... very loud indeed when used with no cats. (unless you get a good muffler/presilencer like the set that racingbeat.com sells)

Jon

ch0g0nda

Well really it's only gonna be a temp deal till I can afford something that isn't 100% rust.

So if it only lasts a few months I'm ok with that.

therotaryrocket

can you get the exhaust in a different size? I'm pretty sure that 2.5" would'nt be the best choice, although it holds a lot of volume it doesn't have as good velocity as say a 2". I think you'll make more power going smaller than 2.5", even if you don't you'll probably make the same power...and 2.5 will only make more noise...I think, im not sure just my 2 cents.

FB II

well, i ran 2.5" on mine and it was fine. i even still had pretty damn good low end (compared to stock). if it's temp yea, hit it up. although, i believe 2.25" is the best medium for an n/a 12a.

ch0g0nda

Well I'm gonna look around and see who can do the 2.5" piping the cheapest. I'd like to keep this all under $130 CAD but we'll see...

Thanks for the advice guys.

RandyTibbles

I did the same to my 85 gsl-se...2 new cats and no muffler!all i have is a 5 in tip

jason_child

man you should run about 2.25 and just get the to stretch it to fit your muffler and as for a great deal on mufflers out by lougheed you should try revs off of revscene he sells great apexi n1 replicas for 100 dollars they last well on the rotary and have a nice deep sound well as deep as a rotary gets if you wanna no more email me i have this setup on my seven in victoria b.c.

Moonchopper

Good god jason child, use some punctuation, PLEASE!

Anyways, I would think that 2.25" would be ideal for a n/a 12a.

I might be wrong, but isn't backpressure somewhat associated with torque? Or am I just thinking of my Jeep's inline 6?

d0 Luck

you need backpressure on any car. i ran 3" on my stock old style 4 port 13b and sure it revved freely, but i lost a good amount of torque fr. idle to 4k.

disclaimer for my 3": i was going BP, but never hard chance to

ch0g0nda

Well I didn't know they could stretch the pipe to fit. I"ll definatly look into having some 2.25" stretch fit, low end torque is good.

As for the muffler, I picked up this cheap one off ebay... I just needed something fast, don't anymore but hey, the muffler should already be in my mailbox in the states. Just gotta go pick it up.

9d7gst

What about these spiral mufflers?

http://www.jegs.com/cgi-bin/ncommerc...38&prmenbr=361

Mabey a little expensive......and doesnt have the flash of the fart cans. But, should do nicely.

calvinpaul

iTrader: (2)

Sorry to jack your thread, but I thought that you needed NO backpressure on a 12a NA. Did I just misread someone somewhere?

ch0g0nda

Uh yeah, the link I posted to the ebay auction was won by me. The muffler is here.

I'm not gonna go shopping for another.

9d7gst

Uh yeah.........DUH. I was asking for a opinion.

Aus 12a Series II

I've got a 2.5'' full system with a 3" tip and its great... alot ov noise though it gets really loud which can be anoying if you want to hear anything besides your car say a sound system. You make alot of power and it does sound good. Its really personal preferance, i would advise though if you want to hear you sound system with out it having to be at 100% to go for something small and less noisey maybe.

Good Luck

Michael

ch0g0nda

Anyway Noise is an issue, I don't mind the sound of an engine but I don't always wanna have it drowning everything out. Anyone got any noise complaints concerning 2.25"?

9d7gst

EVERYBODY FREEZE!!!! DONT NOBODY MOVE!!!!

How hard is it? hummm 2.25.....2.5..... ok low end torque or a little less with more high end power.... Geeze make up your mind. If your bitching about me making a statement in your thread, your gonna bitch about the noise anyway you go.

ch0g0nda

Bitching? Sounds like your the one who's bitching.

How hard is what? I don't give a rats *** about the power. Oh noes, I lose 1/2hp below 4500rpm but gain a 1/2 above... LIFE AND DEATH!

I just wanna know if there's a noticable difference between the sound a 2.5" and 2.25" pipe will make.

Oh and about your first post, perhaps if it was a question, you should have posted it as such. You know, instead of as a suggestion.