gco_shift

Hey everyone!!!

So I am thinking about going to a single exhaust route for the type of street tuning on my car. I have an NA 2nd gen rx7 and want to change my exhaust a bit. But before I do the change I wants some real general info.

First off, I want to make exhaust a single so what size would I have to make it to make the flow just enough so that there won't be any lag but not small enough that air is not flowing through. I was thinking about going 2 1/2in or maybe even 2 3/4in but not really sure what will do the job I want.

So please let all the knowledge pour out from those that may know how to help with this debate or if there is even any debate at all.

any suggestions are welcome and Thanks for the help

also note this is going to be a street tune for the state of CA so lets try and keep it a smog legal

jjcobm

iTrader: (18)

Without going into details:

2.5" for N/A is a decent size. 3.0" for turbo. As far as exhausts "legal" in cali. You will have to see that for your self.

BlackRexx7

i second what the other guy says, im pretty sure the dimentions are correct. but if you want, i've found a few things online about rx7 exhaust lengths diameters etc. I'd check out the rx7 performance handbook i believe it mentioned this in it.

canonize-ryda

your piping should be ok till the y-pipe then it goes down half an inch. i would just go back up half an inch with the one new pipe. then it would be the same the whole way. get hi flow muffler and keep the cat.

Cordt

you should make it a true dual 8)

canonize-ryda

true dual without proper back pressure loses alot of torque. specially on a NA. its ur call. what year is your fc. i think at 25 years old u no longer have to follow emissions. mines an 86 and its 25 years old this year.

gco_shift

Thanks for all of your responces they all were all very helpful in this dilema I was having I think that I will be going with a 2.5" exhaust piping with a CA legal high flow cat with an apexi N1 mufler. Hopefully it will not have to much of turbulence. I just wanted to make sure that the set up is going to be good because I am changing the set up to a single since it is an NA model and there is really no need to have a dual exhaust being that the tuning I will do is just a simple street tune

But if anyone has any other oppinions I am very willing and open to hear them out.

canonize-ryda

does cali do the cars without emission 25 years or older? or is that only certain places(i realize everything in cali is wrong and can kill u according to the fcc)

Gryffinwings

iTrader: (3)

California no longer does the rolling 25 year rule, I believe it's anything 1976 and earlier that's smog exempt. Catback exhaust are legal, some high flow cats you can get away with like the bonez. I plan on using the Apexi GT Racing Exhaust myself.

Cordt

just my opinion but i think there is really no reason for it. change the cat out and you will be fine. losing a muffler just makes it look stupid because you have a spot on your bumper for a second one. keep the dual outlets or shave the 2nd indentation on the bumper IMO.

Gryffinwings

iTrader: (3)

Of course the counter argument here is that dual exhaust tend to be heavier. Personally the only way I can see an single exit exhaust looking stupid is if it exits on the passenger side, I think that looks really wierd.

canonize-ryda

true driver side exhausts look alot better, funny u say that i never noticed i thought there was a difference.

gco_shift

I actually like how the single looks even though there would be an empty outlet for the passenger side exhaust. I could easily fabricate a cover to fill in the gap; I could be wrong but is there really any need for the second muffler??? I mean if you increase the size of the piping and just not create a Y junction it will have a similar flow because instead of breaking it off into two after the cat the flow will be constant till the outlet. There might be slight increase in back pressure but it won't be big enough to notice with an NA setup as opposed to the turbo because a higher flow is a good idea when running a turbo application. but like i said I could be wrong.

But idk I guess in the end it is really all up to the tuner and the tuning setup for the specific application for the vehicle. But please keep the info coming it is really good to get other peoples insight on a topic such as this.

gco_shift

I wish California did not have such a strict emissions law and it is kind of sad that they changed it so that if the vehicle is 75 of older it is exempt from smog as well as hybrid and diesel engines. As far as high flow cats they have to be made to specific emission standards and only a few companies make them for California specific.

Does anyone on this forum have any high flow cat on there set up in Cali or does anyone know a good brand that has pretty good results I am just a bit curious as to what is on the market? I saw some made by Flowmaster but I don't know if they are good.