Eventually I'm going to do a TII swap and run a full 70mm exhaust (tanabe dp, mid pipe, Apexi N1). But in preparation for it, would 70mm be too big for an n/a with stock ports (RB headers, 70mm mid pipe, Apexi N1)?

 

should be ok if u rock the silencer on it
ur planing to eventually go turbo in the near future so why pay twice

 

You'll have to find some way to keep the 5/6 ports functional.

 

your going to lose some low end

 

70mm is the size of my friend's HKS downpipe on his FD

 

That's what I figured. But will I gain anything?

 

70mm is 2.75", which is right at the upper limit of what can be considered useful for an NA. You will get less low-end than you would have gotten with a properly-sized (2.5") NA exhaust, but believe me it will still be a lot stronger across the rev range than it was with the stock system, so long as you are able to keep the aux ports functional. It will also have a screaming top end.
BTW, I hope you aren't too attached to your hearing. That setup will be LOUD!!

 

Wouldn't the large piping compensate for how loud it is? Anyone have a video of this setup or something similar? Like an n/a with RB headers and Presilencer to an Apexi N1

 

All else being equal, a larger exhaust will be louder, and single exhaust will be louder than duals.

 

That's exactly right. I (very briefly) ran a MindTrain header to a Bonez High-flow cat to a big, nasty Corksport single. The exhaust note sounded awesome...through earplugs. Driving without earplugs and with the tip silencer removed was completely unbearable. I bought a Db meter at Radio Shack and measured 124Db at 10 feet while free-revving in neutral!
Later I put a pair of Racing Beat mufflers on it and measured 94Db at 18 inches. Granted, the y-pipe and RB mufflers are 50lbs heavier than the Corksport single, but that's a tradeoff I'll make every time on a street car. Keeping one's hearing and/or license is worth having a slightly slower car.
BTW, the RB mufflers have a super sexy tone and flow quite well.

 

I ran a 3inch o my NA before I got my turbo setup. It wasnt overly loud, just didnt have the turbo to quiet it down.

ALso I picked up nearly 20+ hp (160 to 180 if I remeber correctly) lol this is 10 yrs back now :P

Just do it, rotor's sound good anyway

 

lol. this thread makes me lol. you cant lose power from having too big of an exhaust on ANY car, as long as the headers are the right design. anyone who tells you different is just...not correct. (im in a nice mood today)

 

Then you'll be in an even worse mood when people start rolling in.

2/10

 

You sir make me el oh el.


I had an RB header, test pipe, resonator and a corksport catback on my NA for a while. I have a video of it somewhere. When I find it I'll post up. I would suggest keeping a cat on there instead of a test pipe though. It significantly dulled the noise. With the test pipe, people could literally hear me miles away.

 

What about an RB presilencer?

 

Not too sound like a ricer or w/e, but will this setup pop flames at higher RPMs?

 

i don't think it will, unless its a straight pipe or gutted cats. im not sure about the highflow cats tho

 

I meant a straight pipe, sorry.

 

oh yea it sure will. im running a borla xr1 exhauts rb header and straight pipe. its only 2.25in but if you are gonna do a straight pipe be ready to buy some earplugs. i can't even hear myself think.

 

So what do you reccommend would be a good exhaust with a 3" tip? I'm thinking of running headers, Bonez hiflow cat, and a straight, would that work? Not sure about exhaust systems totally but I think that could work? Looking for a single.. I want something that won't kill my low end, but will help my over all rev range..

 

i'm sporting a rb header and 2.5" straight pipes back to some rb mufflers, nice low rumble at idle, but she starts screamin' real quick, and yes i do pop some fireballs at higher rpm with a quick shift

 

your going to fine...your gong to lose some low end...run it strait al the way back put a pre-silencer in the middle at the same size to keep the flow flowing...

 

Does anyone make a 70mm presilencer?

 

address the 5th and 6th port issue. there are several "fixes"

 

You need to go back to school son, because that is just plain wrong.

Too large of an exhaust will result in lower exhaust gas velocity.

Lower exhaust velocity equals pooling of the exhaust gases in the exhaust pipe.

Pooling in the exhaust pipe acts like a clogged exhaust pipe... reducing the savaging ability of the exhaust... increasing the amount of exhaust gases forced to recycle with the incoming intake charge... reducing temp of the combustion event... reducing power... Kinda like running with an EGR valve on all the time and being 10 times the size it should be.

Now toss in how a rotary engine works with no exhaust valve (unlike a piston engine) and an incomplete burn with overlap from the intake, and you have a continued exhaust event up to the length of the exhaust system (depending on how much overlap and how incomplete the burn is (due to timing and engine speed)... This mixture is burning and can continue expanding up to three feet from the exhaust port. So you oversize here, and you can end up overheating the exhaust tubing, as well as having combustion events that could force the exhaust gases back into the engine.

Wait there is more. Now lets look at the 84-88 non turbos which use exhaust gas velocity/pressure to feed back up to the aux port actuators. Without sufficient exhaust gas velocity, there will never be enough pressure to activate the aux ports... further reducing the available HP and torque (in essence strangling the air into motor at higher RPMs).

So all those together show why a 2 inch exhaust on a non turbo will give you more power than a 3 inch.

This is not some piston engine that has a low simple exhaust temp... rotary exhaust temps can reach 1800F and burn out glass pack mufflers in a matter of hours.

On a non turbo ideally you want a 2" to 2.25" down pipe or header, but you do not want to be bigger than 2.5 inches until after the point where the back end of the cat would be. After the back end of the cat (or the front of the y-pipe) you can go up to a 3" single or two 2"- 2.5 inch duals. Anything bigger will reduce the power.