2nd Chance

iTrader: (1)

I pulled up all the custom exhaust threads in the second gen section and wasn't satisfied with what I learned. I want to do a full exhaust system with dual outs, looking to make good power and slightly less sound than my current setup. I'm trying to stay relatively cheap here too.

I am currently running a 2.5" straight pipe from the manifold back to a 12" Cherry Bomb and like it alright, but it was just a temporary fix after the OEM rusted off and tore up my bumper. I like it, but I want something a little more professional now.

Here's my idea:
RB disassembled header (just to save cash) going to a 2.5" pipe to a Cherry Bomb Extreme single 2.5" in/dual 2.25" out (Link - Cherry Bomb Extreme Skip the Y-pipe, save more cash + keep the Cherry Bomb tone I like) to two 2.25" pipes to B L A H mufflers.

I was thinking maybe the universal RB Power Pulse mufflers with dual twin tips but honestly I don't like what I have heard of their full systems from YouTube, it's too tame, I want something more aggressive.

Also:
I already have a cone intake.
Emissions are not governed in KY.
I live in a small country town so noise is not a big issue.
I will NOT be cutting, bending, or welding my own parts. I got a guy who has been doing quality exhaust work for longer than I've been living.

I'm looking for feedback on my setup. Possible improvements. Muffler suggestions. And advice on any problems I would run into trying to do this setup.

Dak

I would not use that Cherry Bomb. Flow would not be as good as with an actual Y-pipe and will hurt power because it doesn't merge the two streams properly. Read under the custom exhaust section in this link on how to properly merge them.
Rotary Tech Tips: Exhaust System Configurations
You could get away with something like the collector they use on their header even though it isn't necessarily what they call the proper way. Then the reverse of that to split it to your dual mufflers just as they describe. Though not cheap some thing like their presilencer from their true dual system is needed to help with getting sound down. Unfortunately to do it right will cost you. Not as much as buying their pre fabbed system but it will take some dollars for the pieces even if your buddy does the welding for free.Do some searching here:
Naturally Aspirated Performance Forum - RX7Club.com
and in the racing section for better results on custom fabrication.

marclong

iTrader: (1)

Fiberglass packed mufflers should be treated as disposable on a rotary. You would need a stainless steel packed muffler. Not sure what yours would be. Link doesn't say. FYI.

NativeBeggars

iTrader: (1)

I second the glasspack/Cherry Bomb exhaust. It's crazy loud and you'll probably burn it out.
Just go single and be done with it! Mine isn't obnoxious but it's not tame either.

Dak

From what I gathered in the link it is chambered. This has been my problem when looking for pieces to use in my next system besides R.B stuff. Everybody else uses fiberglass and if they don't like Burns stainless they are just as exspensive or the pipe size is wrong. Hard to find stainless packed resonators with 2" in/outs to put in the primaries.

If you follow his suggestion an go single you can make your primaries longer before you collect them. From everything I've read for a stock port or streetported motor the longer the primaries the better. The proper way of course is to tune the primary length and where you collect them on the dyno, but most of us don't have that luxury so you make them as long as possible for your planned configuration(dual or single outlet).

If you want dual outlets collect it mid chassis just prior to where the stock Y is with a collector. Then a short 2.5" section almost like an X-pipe( though I have wondered how an X-pipe would work or if you have to fullly merge the exhaust for a short distance) then split it with a Y to the rear mufflers of your chioce. Keep the primaries and any pre-silencers/resonators in them 2". Then back to 2" or 2.25" max from there to your mufflers.

j9fd3s

iTrader: (3)

my street exhaust recipe is the following:

RB downpipe, into either a cat or the RB presilencer, followed by the cat back of your choice.

the pros, its 100% bolt on, you get 90% of the power increase, and noise level is easy to control.


adding headers is ok, but you need to make sure that the inlet matches the outlet of the engine, and then noise can be an issue. power increase over the stock manifold will be small, as the manifold, by design, is not restrictive.

jjwalker

The link you posted, what the hell?

That cherry bomb muffler might as well be a brick in your exhaust system. Look at even the flow pattern they advertise, you will have more exhaust gas going out the left side than the right.

2nd Chance

iTrader: (1)

Okay, I need up to speed on the terminology I reckon... call me stupid. Hahah
I keep reading this term "primaries." What is that?
X-pipe?
Collector?

I guess none of that matters if I am not using the header though, right?

Oh yeah, thanks for the redirect to the NA performance forum too!
Sounds like I'll just go with the downpipe then.
I got a single now and really wanna get a dual system back, it looks so much better to me.

Also, what about piping? The stuff I got on there now looks like it came off a set of playground monkey bars. Is it worth buying a few pieces of SS pipe from RB?

Could I use a custom Y-pipe?

Is there any particular brand of muffler to stay away from?

I feel like such a noob for asking all this stuff, thanks so much for your help folks!

NativeBeggars

iTrader: (1)

I'm noob at it too, but I've done it. I wouldn't say to copy my exhaust, but it DOES work and doesn't leak. I have a turbo II CorkSport 3" SS driver-exit single that I got for dirt cheap. I had a spare CS 3" downpipe, so I cut one and made it reduce to the factory [railed out] precat section and manifold, as I don't have a header yet and I kept getting pulled over by the Black n Tans as we call the FHP here in FL, from all the noise I was making. But you can do anything with access to a welder. I personally haven't done much bending, so I'd leave that to someone else, but that's just my two cents.

Dak

On a header the two individual pipes running from each rotor to the point they collect are the primaries.
Here's an assortment of X-pipes, crossover and Y-pipes.
Magnaflow Tru-X, T, U, Y Crossover Pipes - Free Shipping on All Orders @ JEGS
Collector Unflanged Collector Assembly for RX7 1986-1992 - Racing Beat
No need for these( save for the Y-pipe) if you don't use the header kit or Road race header, or if you do use their streetable header( collector is built in) or the downpipe as j9fd3s suggested
Racing beat sells thick wall mild steel tubing as well which should work fine.
You can make a custom Y-pipe to split to the mufflers if you make your own custom rear section. If you buy a catback it will be part of it.

Stay away from mufflers with fiberglass packing for the most part. Some have gotten Magnaflows to work but I don't know for how long. Also don't use Flowmaster as I have read the rotaries exhaust pulses bust the internal baffles loose.

2nd Chance

iTrader: (1)

So, given this information I could build my exhaust any one these ways to do a dual system and it would turn out pretty good:

1. Road race header kit minus the outlet flange welded to a magnaflow tru-x cross-over with an adapter going down to 2" pipe on each side going to the universal RB power pulse mufflers

2. The streetable header going to a 2.5" pipe to a tru-y pipe splitting to 2" pipe back to RB universal power pulse mufflers.

3. The down pipe going to a 2.5" pipe to a tru-y pipe, etc.

4. The road race kit welded to the unflanged collector going to the tru-y pipe, etc.

It's obvious I don't want to spring the cash for that presilencer, huh? My car is loud now but I can tolerate it, wouldn't the dual exhaust, thicker piping and actual mufflers cut the noise level down considerably from the level it's at with a straight pipe with no cat to a 12"L 3" OD outlet Cherry Bomb? Or will the headers/down pipe make it that much louder?

My car shot a two foot flame out the exhaust today!

2nd Chance

iTrader: (1)

What about tips that have resonators in them?

Dak

Any of your options should work but they will all be loud, especially the ones that use a header. I think with any option you choose that includes a header you will want some sort of pre-silencer as the header will increase the noise. Also I wouldn't weld the whole system to be one solid piece. You want a flange on whatever header or downpipe you use and/or at a minimum one in the center of the car where the stock cat bolted to the stock Y section. Reason is if you don't and say you have to replace a driveshft you'll have to drop the whole exhaust header and all or cut and reweld vs. just unbolting and dropping the rear section of the exhaust. I like the way my old HKS sport system was setup with how just the short 14" or so Y section came out. I only have to remove that on piece to take out the driveshaft. This was a clone of it but I don't think they sell it anymore.Rotary Performance RP 50
You cuold use this Universal Muffler, 2.5-inch ID for RX7 1986-1992 - Racing Beat for options 2 and 3 and put flanges on it to save some cash.
Don't know about resonated tips. I don't think they'll accomplish the sound reduction you will need.

Dak

Go here and browse around for mufflers and such:
Exhaust Systems - Pipes - Pipe - Tubing - Headers - Car Exhaust Parts - Free Shipping on All Orders @ JEGS
http://www.summitracing.com/search/d...rder=Ascending
Find Custom Exhaust, Header Collectors, Race Mufflers & More | Burns Stainless