Jehuty77

With the hope that one day our RX7 will move, we need to look at building a proper exhaust.

Right now what my buddy has on the car is a straight pipe with a rice cannon on the end, its deafening just working on the car and its also pissing off every neighbor in the area.

We don't care about the 2 horse power gain of a free flowing exhaust, what is your guys recommendation for building an exhaust that is quiet while still sounding respectable that can stand up to a Rotary.

Part Names + Numbers would be helpful if you know them

This is for an N/A S4 RX7

Thanks

KNONFS

iTrader: (14)

After having numerous exhausts on my NA and then Turbo FC; I can only recommend the racing beat catback. It lasts a lifetime, and its not a loud exhaust system for an aftermarket setup.

It douns like you are trying to build your own exhaust, if so, go with the RB mufflers:

Universal Muffler, 2.5-inch ID for RX7 1986-1992 - Racing Beat

pre silencer:

Universal Presilencer , 2.5-inch ID for RX7 1986-1992 - Racing Beat

If you would rather buy mufflers from a widely know brand in the states, then I would choose Borla. I had good results with Borla XR1 mufflers when I was running a single exhaust.

My advised, add all materials costs and time that will take you to build an exhaust sytem, AND then gauge the quality of the product. In the long run, it might be cheaper to go with an off the shelve proven system.

MIDNFauciUSN

iTrader: (8)

Bonez High flow cat from rotary performance, with the Racing Beat cat back...

j9fd3s

iTrader: (3)

the cheap exhaust recipe is;

stock exhaust manifold -> into this Down Pipe / Presilencer Kit for 86-88 RX-7 NT - Manual - Racing Beat -> into the cat back of your choice, RB, or an Apexi, or even custom.

alternatively you can buy just the DP Down Pipe for 86-91 RX-7 - Racing Beat into a cat, into a cat back of your choice. after a cat you could even run this muffler, Dynomax 17733 Dynomax Super Turbo Mufflers

Trigger Happy

This is all very good information in this thread, thank you everybody! One question though...

So having a cat in there would allow even fiberglass mufflers to survive? What's your experience with magnaflow hi-flow spun cats on rotaries?

I've personally used this cat on a couple exhausts I've welded up for my own cars and they work great, but that's on piston engines. I'm not sure if they'd survive a rotary. Thoughts?

RotaryEvolution

iTrader: (30)

the recipe is keeping it dual over a single exit exhaust, end of story.

some turbo cars can get away with single exhaust and be reasonable, non turbo cars simply cannot.

i also don't really agree that a cat will save a glass pack muffler, in fact most cars heat up the catback even more when a cat is present than not. i just smogged my car and had to reinstall my cat for testing, when running with the resonator there was no problem but as soon as i put the cat on the oil that had accumulated from my pinion seal leak began to smolder on the catback, indicating the exhaust temps at the back of the car were quite a bit higher. the only way it could possibly save the mufflers is due to slightly less airflow due to the restriction and the cat sacrificing itself by burning oil before it got to the cans. i would rather sacrifice the mufflers than deal with a failing cat. good quality cans will not burn out, like the RB power pulse, borla XR series or RB catbacks.

Hazard15301

iTrader: (5)

Fiberglass won't hold up to a rotary exhaust's high temps. Period. I've had kids tell me they run off the shelf part store mufflers no problem, but it's only a matter of time before they blow out.

RotaryEvolution

iTrader: (30)

well, i have one customer who had some cheapo off the shelf cans put on and they haven't been doing too bad. they did manage to hold up 230whp on the dyno behind a 9.4:1 6 port stock turbo.

it was probably the quietest tuning experience i can remember.

but once they do give up, unless you can weld on your own it's going to cost more than a good quality cat back would eventually.

Trigger Happy

So cats aren't the solution. In that case what did Mazda pack their factory mufflers with and expect them to survive?

In any case it looks like I'll be getting him to buy the RB stuff, I only want to weld it up once

j9fd3s

iTrader: (3)

we're not allowed to run that cat in CA, because it doesn't have the right bribe number, i mean CARB number on it.

there are two problems with the exhaust on the rotary, 1. is that its a little hotter than a piston engine, although not hugely so.

the second is that the exhaust ports have no valve, so every time the exhaust opens you get an uninterrupted blast of exhaust gasses, that at some point is breaking the speed of sound.

this pounding is why the rotary is so hard on exhaust components.

however, the stock exhaust manifold is designed to dampen these pulses, and then the cat will dampen it further enough, that you don't need a special muffler in the rear on a street car.

Trigger Happy

Good thing we live in Ontario, Canada where CARB doesn't apply, however we are not allowed to remove any emissions equipment that came from the factory. We don't have to pass emissions if the car was built before 1988, but all the EGR/cats/PCV/airpump(in the case of rotaries) still has to be there if we get pulled over and a cop/ministry official checks for it.

So basically it's like trying to muffle a howitzer, with the shell and everything coming out. I thought it was the heat I had to worry about more so than anything. I can definitely see how those pulses would literally blow out a muffler.