cwsttu

here is his reply to my letter when i asked if i could buy mufflers individually instead of buying the cat back

"Christopher,

There isn't a way to buy it that way. If you are planning on doing
something like that, I would just go to your local auto-parts store and
get
a couple of performance straight through mufflers. The full dual
exhaust
systems on the Rotary's will not give you a power increase. Many times
on a
properly tuned exhaust, the exhaust pulses will help draw the other
exhaust
pulses giving more power. If the pulses are independent, you do not get
that benefit.

Thanks,
Rocky"

WAYNE88N/A

I've dealt with Rocky before, he seems to be a fairly informed guy with our cars, and what he says does make sense, on a TUNED system that runs in a range of specific rpm's. On an untuned system (how many of us fall into this category?), the pulses could theoretically "fight" each other just as well as "draw" on each other. So what can we deduce from all this rambling? Absolutely nothing, lol...

Kungfupanda

He's right dual exhuast doest help rx7's much besides quiet down the noise, thats the only reason i buaght the dual greddy xtremes for my FC 13b DEI, the only engines that really use's duals to help are cars with V6 and up, basically becuase they run two difent exhuast pipes instead of one such as four cyclinders(ick) or rx7's

1987RX7guy

iTrader: (3)

To help bring out Wayne's point, As far as I know I have not see any single exhaust or dual for that matter that is "tuned" I always hear bitching and moaning about tuned versus uncollected. We have yet to see any back to back tests. Untill the time we are shown something solid on this he can't make that statement. If you buy say the cork sport turbo exhaust that doesn't mean because it is single sided it will give you more power the same goes for say a racing beat collected cat-back with header/pre-silencer. It doesn't mean otherwise either. It could be tuned by mistake but the chances of that are well? poor at best I would say.

cwsttu

guys im talking about TRUE DUAL exhaust... the RB ROAD RACE HEADER and then to two mufflers

SonicRaT

iTrader: (6)

Until someone dyno's the same car on the same day, at the same time, with both exhaust systems, nobody will know.

1987RX7guy

iTrader: (3)

I know what your talking about. Its been talked about a bagillionzillionmillion times! There is no proof eitherway.

WAYNE88N/A

I'd bet if we stick with the exhaust systems that were designed specifically for our cars, produced by reputable vendors (RB, etc...), then we probably can't go wrong...It's silly to envision one pulse "following" another when in reality the exact opposite also holds true...

Didn't somebody post on here a while back that the true duals gained something like 2 horses on the dyno?

Crash Test Joey

iTrader: (1)

Well it has been proven with piston engines that dual exhaust with a crossover pipe is the most effective way to build dual exhaust. Specifically, a X-pipe is more effective than an H-pipe.

I'm no rotary expert. Who can answer whether the rotors coils fire at the same time or not? If they alternate then the firing order would cause a similar exhaust setup to improve scavenging. One exhaust pulse would effectively siphon another from the other rotor through a crossover setup. This is how it works (effectively, too) with piston engines.

If on the other hand both rotors fire simultaneously the effect would be significantly less dramatic.

I can say also that with piston engines dual exhaust and a crossover makes the overall system SOUND much better. I see no reason it wouldn't work the same way for a rotary. The question is would the extra tubing weight negate any performance difference. Probably not, since rotaries make their power in the upper end of the rpm range, which is where dual exhaust is a good idea. Conversely, the same thing may cause a negative effect no low rpm power.

As mentioned above, it's got to be tested to be certain what happens. Are you volunteering to build systems both ways to try it out?

1987RX7guy

iTrader: (3)

Crash Test Joey

I understand that theory and it is a proven way of upping power. BUT my arguement is that NOT ONE of the exhaust setups sold for our cars are "tuned" if they were I am sure they would be advertised so. If your building a custom setup and do all the proper legwork with the mathematical equations and **** and do it right then its ok but until its proven that the setups out there are tuned they are not any better than uncollected setups.

I will say this though, Going from a racepiped collected exhaust to my true duals I dropped a second off my ET in G-tech trials.

Crash Test Joey

iTrader: (1)

It sounded in the original post that he was trying to build his own setup

And g-tech might be low tech compared to a chassis dyno, but it sounds like you've got conclusive enough testing results to me

MichaelFregoe

iTrader: (1)

http://www.mazdatrix.com/r-ex86nt.htm

Mazdatrix has numbers and the experience to back up there claims. Take a look

SPiN Racing

Not going to beat this dead horse.. but...

Buy your own two mufflers.. and slap em in place of the stockers.. that sounds like what you wanted.

If you short collect.. or Long collect.. if you follow some of the guidlines and read deply enough you should make more power than stock as has been proven in a bazilliongazillion whatever he said times.

Now.. UNCOLLECTED..... Racingbeat NOW carries a Uncollected system they call the "True Duals" setup.
They DIDNT POST HP NUMBERS last week when I looked at it.

Having raced motorcycles in the past I can guarantee you that a 2-stroke with individual pipes tuned properly with expansion chambers etc.. makes MAD power... Look at a 2 stroke dirtbike.. or go back to the H2 Tripple.. or the 3 cylinder 750 thing Kawi I believe made.. They all had individual pipes for each cylinder. Look back at the RX350 Freddy spencer race bike. Toomy Pipes.. /moan
They would hang with a ZX-7 on a road race track in the early 90s.

Now.. Rotary again... I think in my own mind you can make proper power with a "True Dual" system. BUT!!!..... You better make them the correct length with specific mufflers so that when the pulse exits the pipe the new one enters etc.. or however you need to do it so that it is tuned properly.. OR.. you will have issues of the reversion wave coming back and colliding at odd points at odd RPM's... and your power curve will look like ***.

Got a turbo? Ignore this thread.

Myself I will be Short or Long collected thank you very much... depending on room under the car, and muffler exit etc.

marlaman

I purchased the mazdatrix true dual setup for my 87 n/a originally and put it on my 90 vert when i purchased that and i drove the vert the same day after i had put the dual exhaust on her and compared to the drive about 5 hours before with a catback setup i was feeling quite a bit more pull. and my vert is currently an automatic and i still felt quite the increase in power. i'm not sure about other dual setups but the mazdatrix one is proven to be effective.

Matt

jg1bad10th

Hey Matt,the size of the pipping has alot to do with it .your pipping on the mazdatrix dual is probably alot bigger than the stock.I have a greddy n1 on my 10th which is a single setup and it flows great.same true with your mazdatrix with the size pipping it has.I hope that helps.also I'll p.m. you in a min.later

1987RX7guy

iTrader: (3)

There appears to be some misunderstanding about what I said in the eariler post.

I run the mazdatrix true duals. My current car 89GTU had a racepipe exhaust and I swapped it out for the true duals which I already had for a while and I did before and after runs. Using the true duals I dropped my time about a second.


Santiago

SPiN Racing

Define "Racepipe"

Is this just a pipe that goes back from a Turbo?
Is it a Pipe that goes back from a Thermo Reactor?
Is it a short collected RB header that has a pipe coming off it??

It sounds like a 1 Second improvement would be from a Thermo reactor (Stock chunk of cast iron) with a pipe running back to a muffler.
Then replacing it with a Uncollected system...
I really doubt a 1 second improvement from a full RB exhaust system to a uncollected one..
However.. if you had a uncollected header and tried to collect it yourself and as you mentioned earlier didnt collect in the right place.. you will really not do your engine any good.. and youre probably correct.. a Uncollected exhaust is very likely better than a Incorrectly collected one.

1987RX7guy

iTrader: (3)

Stock manifold with 2.5" pipe welded in to the Y pipe. The mufflers it had on were stock or stock replacement. I simply did it to illustrate the difference from a modified stock exhaust. Anyone with removed cats on a stock exhaust system would see the same gain. The gain would likely be much higher with cats installed on the car.

Santiago

SPiN Racing

Ahhh Yes.. Huge Improvement in that case.

That is the huge gain you read about in all the exhaust literature.

Big gain removing a bad cat.. big gain doing exhaust...

Installed a Wolf in a 1st gen that had a 6-port in it.. and I used to DESTROY it when it had a Jaytech intake and Carb setup. Did the wolf and a long collected system.. and he would walk away from my stock sport without a header but with a wolf.. from 2nd gear on up.

Course when the Sport gets done.. He will not be able to anymore