Exhaust questions!
 

Ok, I'm bound to get the search button flame on this one, but I've searched and found nobody who has ran true straight pipes. Just a downpipe into a 2.5" y, with 2.5" duals out the back. No mufflers, no cats, no silencers. Anybody do it, and what would be problems other than noise? (Noise doesn't bother me too much) How many decibles you think that would be? :) Or would it be too free and cause the turbo to spool to hell?

You've never found anyone because the noise burst their eardrums and caused internal bleeding in the cranal area. Mmm, maybe not but still, not too many people have done it. I do remember someone having it. Might wanna title the thread sumin like "who has straight pipes?" because not everyone looks at every "exhaust question" thread because there are so many.

That's because with the turbo there, there is in effect, no duals! Best would be a single 3" all the way down the car to the bumper....IMHO...no splits, just smooth flow.

I had heard that too much flow on turbo's is not all to good, thus my reason for 2.5" and the Y pipe to add some pressure in there. I guess I can give it a try and see how it sounds, just wondering what side effects this may have.

I've ran mine straight through, and with open manifold as well for a short period of time...I got WAY too many complaints with the open manifold. This was all on my N/A by the way. But yeah, it's loud either way. I had no cats, mufflers, anything....just pipe. It's loud, but it's fun! You can also shoot a lot of flames with it that way. Anyway, I say go for it, but I recommend it for people who live in the country like me where nobody is around to care. But then, I still got complaints, so either way, you're gonna get some whiners thinking your car is too loud, but try it. I didn't have any problems with my car when I did that. I just had problems with people whining about how loud it got. Oh, and by the way...open manifold is just WAY too loud for even me. I couldn't handle it...it sounds neat, but I was afraid I would go deaf, so I went ahead and had them aim it out the back of the car ;). Enjoy!

<>< <>< Matt ><> ><>

Well, my brother has a '91 Chevy 350 with glasspacks and no cats, and so does my '86 Chevy 396, so we're used to waking up our neighbors. Does a Y under the passanger seat sound like a good idea then run to duals? I don't want one single big pipe hanging out the back, that looks terrible imho. Especially when it has the dual cutouts already! I'm not crazy enough for open manifolds, I have run my truck with open headers and god did I almost die! How loud do you think 2.5's off a turbo would be? :)

You can never have too much flow on a turbo. Mine is 3'' to the Y and splits off into a 60mm HKS catback. No silencers or anything. It sounds fine. It would sound like ass with no mufflers at all.

I made a video of me running 1st-3rd gears, but my capture card is broken.

If you're refering specifically to FC RX-7's with stock turbos, then yes, the wastegate is too small for high flow.
If you mean turbos in general, that's completely wrong. As long as your wastegate can handle it, more flow = more power, always! That's why so many Jap exhausts are available in 90mm (3.5").

I meant the stock FC turbo. What do you think would be a good muffler/cat less setup? 2.5" 3.0" 3.5" ? :)

If you're worried about too much flow, why the hell do you not want a muffler?

well, for one I'm cheap. For two I like loud things, and for three I plan on swapping the turbo soon. So I guess too much flow isn't all that big a worry. I was more concerned with why nobody else has run true straights.

Plenty of cars over here (not just 7's) run systems consisting of only straight-through mufflers, and they're nor excessively loud. You just have to make sure you get quality mufflers, and they won't necessarily be cheap!. Remember the larger the can, the quieter it'll be (more sound absorbing material), so get the biggest you can fit/afford.

Didn't you read? I said no mufflers, as in, true straight pipes, just pipes, no mufflers, no cats, no nothing, just the pipe!

Yeah, and my point was use straight-through mufflers. These have practically zero restriction (if they're built right) but are effective mufflers.
Running no mufflers at all is just plain stupid. You obviously have no idea how much noise an engine produces (turbo or not) or you wouldn't have even suggested it. You'll get pulled over by every cop in a half mile radius. Silly idea; forget it.

I don't believe the rotory's going to be much louder than a 454 with open headers. Half the people here run straights and open headers and never get pulled over. Calm down already.

Hmm, perhaps maybe you are calm, and just calling me stupid in a calm suave sort of way, but in that sense, lighten up and let me get my own tickets? :)

Hey, every now and then, you just gotta rant!
If you drove a 454 with open headers over here you'd probably be thrown in jail! You must have nicer cops.
But to answer your original question...
...the big problem you'll almost definitely encounter is not the noise level, but resonance. I put a full 3" exhaust on my last rotary turbo with just a single back-and-forth type muffler. The noise level was OK (some disagreed, I loved it!), but at a constant 65-75mph, the resonance was incredible. After a 30 min drive at that speed I felt physically sick and had to stop! The next day I had a long 3" bullet muffler installed mid-system and that only had a small effect on volume but cured the resonance completely.
If you dead set on this, and think you'll get away with it, just do it. When (not if!) the noise and resonance drive you nuts, at least you're not throwing out any components, just inserting some mufflers!
:D

That was my main concern for the moment. I don't plan on taking too many far trips with it, going to be my solo car and thats about all. My truck has a funky resonance to it at low speeds and low rpm, kind of gets on most peoples nerves, but I enjoy it, I guess it depends on the person!