What are the advantages/disadvantages of both of these exhausts? I have seen long primary exhausts on FB's, and it works quite well. But I havent seen it on an FC yet. The short primary system is the common collected exhaust on FC's.


I emailed racing beat and mazdatrix to see what they have to say, but Im curious what the consensus here is.

 

are you talking about the length of the header pipes?

 

I'm sure it has to do with torque, I wonder if people even make long runners for fc's?

 

I remember reading about this kind of thing a while back, but my memory is a bit fuzzy. I think that it has to do with the 6 ports on an FC. Because of them, I think that you loose torque, (especially low-end) when you have a true dual long header. From what I remember, this is exagerated when you have a ported motor. I'm sure that in a race aplication, it would be different though. I could be wrong, so if I am - free bump.

 

The 6 ports only decrease low end torque when theyre NOT working. The reason they were designed to be closed until 3800 rpm was because they hirt the bottom end. You might be thinking of the people who have dirty or stuck 6 ports, and the true dual exhaust doesnt have enough back pressure to open the 6 ports, so they wire them. Kinda OT, but true dual exhaust has PLENTY of back pressure to open PROPERLY functioning and clean 6 ports.

Back to the exhaust itself. From my general knowledge of exhaust tuning, moving the collector farther from the motor moves the torque peak lower in the rev range, and moving it closer to the engine moves the torque peak higher.

BTW, I called mazdatrix, and whoever answered the phone was useless. He basically told me to buy their true dual system and was totally useless as far as answering any of my questions.

 

This link was given in a similar discussion once before: http://www.nsxprime.com/FAQ/Miscella...austtheory.htm
Also, do a search in the forum and I'm sure you'll find more info.

 

I believe a long primary system (tuned correctly) on an NA 2nd gen would be benificial. but you would only get a single exit exhaust. you will need to know the correct length.. (which should be the same length on the FB)

-Zach

 

I already knew everything in there. Whil eit may be a good read for someone who cant tell amuffler from a turbo, it didnt help me at all.

Anybody else want to chime in, and confirm or deny my thoughts that a long primary system will have a better low end, but not as mcuh top end, and a short primary will be just the opposite?

 

short headers for high rpm power, long for torque. Same with intake manifold...
But from what iv heard, short headers are pretty useless, Overall power gains where very small. Long tubes had better overall performance. But this was for piston engines, dont know if it would be much different on a rotary engine.

 

anybody else? Evil aviator, Im calling you

 

Everyone is pretty much right. I've had both systems. I had a short primary and a dual setup (obviously not at the same time) on my 2nd gen. Torque was impressively increased with the short primary system over stock. Factory shoebox manifold sucks! It got even better with the dual however it sounded like ***! (Don't use dual if your engine is ported!) Long primary makes more power everywhere in the powerband. Most people don't do it on 2nd gens since there are no pre made kits and you would lost an exhaust tip.

 

Thanks, thats exactly what I wanted to hear. I have the true dual right now, and it definately sounds like ***. Im going to start making my long primary exhaust in about a week. Ill be sure to post how it turns out.

 

Shoot Rob@Pineapple a e-mail. Duel is the way to go. CJ

 

I already have a true dual. I cant stand the sound. And its about to get a WHOLE lot worse with my ported motor Ill have in within a week.

 

there is a thread somewhere in the RP forum that goes into good detail. talk to Paul Yaw. I'll see if i can fish it up.

 

ok here it is
https://www.rx7club.com/forum/showth...hreadid=120200

 

Hmmm....thats funny. I get more comments about my cars exaust (not one bad yet.) note than I do on the looks of my 3rd gen! O-well. To each his own.
Ther is also a guy in rpnw, that has true duel....and i think its sounds pretty good...almost as good as mine.

Are you still using the stock mufflers?

CJ

 

Dual is NOT the way to go for a ported rotary. Anyone who says it is has never tried it. I have! It doesn't work as good. Not even Rob at Pineapple can convince me. E-mail Paul Yaw on his thoughts about true duals. I already know what he'll say because I spoke with him on the subject a long time ago. Collected is the ONLY way to go on any form of ported rotary.

 

Hey mazdaspeed7? I thought you were going to dyno your motor before the porting?

Its obvious that a very short system that collected early would make the most top end. If I could have a shop make me some I would because everytime I shift (racing) im in the high rpm band and torque becomes useless. I think the RB headers are desined for an everage power band tuned to the stock power / torque curve. But I think a full single exaust with RB street headers will give more top wich is what im looking for. Im doing a before after dyno asap with autoteck motorsports very soon.

 

Its along story, but to make it short, Justin(rx7impreza) broke down ont eh way to NOPI. I went to go take him the tols an parts he needed to fix it, and I hit a trailer fender in the road. My car got FUCKED up. It busted my radiator, and the sudden loss of coolant overheated my coolant seals. So my motor is currently apart, and getting ported, and waiting for the gasket kit so I can put it back together. I cant wait to get to the dyno. Im going to blow away the common idea here that n/a's cant bust 200 rwhp

On your exhaust. Theres 2 things that are not going to quite work out how you want. First, the RB single header uses 2.5" pipe. Youll never make the power you want with that. And you can forget about a ported motor with a 2.5" single exhaust. Your exhaust will be a restriction. Second, a short primary system has a very narrow powerband. It creates a lot of turbulence when its not in its sweet spot. So youll have good power within a very narrow range at the top of the rpm band, but your low end and midrange will suffer, and your drivability will really suffer.

PP13Bnos, what kind of mufflers do you have?

rotarygod, hit me up on AIM, af24179

 

Well, there's already quite enough BS in this thread, so I'm not sure if my additional opinions will help much. To respond to the original question posed in this thread, here is a quote from Racing Beat: "The Long Primary system typically adds 5% or more horsepower over a Short Primary system on a street ported engine at higher RPMs". I think that I will limit my reply to the above published info on this subject.

 

Did you ever get my PM? I would really like to hear your thoughts on exhausts, since you have helped me out before. Like I said, if you dont want to post it here, reply in a PM. Im really interested in what is BS in this thread, and yout thoughts on what exhaust is best for me. I have pics of my porting to show you, but I dont want to post them here.

If anyone wants to see some BS deep enough you can drown in, go read the "street port vs bridgeport" thread

 

Mazdaspeed7. Sorry but I didnt quiete understand what you are telling me.

Are you saying that 2.5 inches CAT-BACK ( single) and 2.5 inch headers are going to restrict my top end with a non street ported engine??? And is the Street header considered long or short??? I think anything will give better top end than my stupid stock muffler dont you think?

 

I had my 89 gtu with true duals, one header pipe to one mufflers, the other to the other muff, I noticed a gain in low end torque from, what wasn't there when I had the stock setup(collected), way louder, gain in hp 6K+

 

I'd like to know what length primaries some people (RB, Rob Golden or Paul Yaw) have tried, and what type of results they've gotten.