So Im putting on my racing beat road race header and I think to myself.......... Self, what would this bad *** header sound like if you just ran your car open header. Well, after running it open header I found that 1. It gurgles like a mother ******, definately a rotary engine, 2. Its louder than a mother ******, reminds me of the dragsters I see running at the tracks. Now for the reason I actually made this post, do you think from the header I should run true dual or have the pipes collect into one and use the Y pipe that come with my N1's?

 

true duals would be really cool and better performance over the other way. I vote go for true duals.

 

I am leaning towards the true duals as well. The only reason I wasnt sure is because of the noise factor, but when talking to a friend he pointed out something pretty obvious that I didnt even think of......silencers for the N1's. Heh so Im probably going with the true dual.

 

yeah, but those silencers kill the horsepower you gained by going true dual. Just a thought.

 

yeah that i know, but i would only use them if im going on a long trip or into a town where the cops are ********, like lets say in rowlett

 

ahhh....I get ya

 

true duals is a dumb idea. it will sound like **** because the exhaust pulses will go from left muffler to right. (sounds retarted) also, rotarys like a little bit of back pressure, and true duals don't do ****. Run you "fake" dual system and i guarantee you will be very happy. Even racing beat or rotary performance would agree.

Enjoy your new exhaust!!
- Curt

 

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

 

Actually, a true dual sytem gives you maximum HP across the entire powerband, and also flattens out the torque curve. The exhaust pulses are very fast, also there is a downloadable sound clip on Mazdatrix's website of a FC running true duals, it doesnt sound like ****. Yes, rotaries need backpressure to open the 5/6th ports, but they can be wired open, or actuated some other way. A silencer may give you the backpressure needed. And I bet if you called up rotary performance or racing beat, they'd tell you that for maximum power on a N/A, true duals would be the way to go.

*edit*- I see that he has a S5 N/A, so he doesnt have to worry about backpressure since the ports are opened by the airpump.

 

So, why are all the IT racers running singles?

Just food for thought.

Remeber they tune for max power in a given RPM range!

 

Well, as I understand it, a true dual sytem will give you maximum across the board powerband, and increased low end , and midrange torque. Best thing for a street-driven car. On a IT car, where it is basically going to stay at a high RPM, a single can give most peak HP, higher in the RPM range, which is better for race applications. Also a single system will be lighter. Am I pretty close on this?

 

Do you even own an Apex exhaust? They do nothing to drain HP but just as they do almost nothing to quiet the sound. They WILL NOT drop your HP enough to offset the dual system.

My '86 has a RR header that collects into a single pipe just before entering the Apex N1 (single, passenger side outlet). No extra mufflers or pre-silencers. With the ported engine it is a nice soft rumble at idle and very loud at WOT. I cannot tell a difference in HP or noise with the silencer in or out while driving. The exhaust note changes with it at idle but that is about it.

 

Well, that's a matter of taste. I think it sounds oh-so-super-p1mp. Have you ever heard a V8 with a true dual exhaust system? Much the same - the exhaust pulses bounce back and forth from left to right... except on a rotary it's "balanced".

No engine "like[s] ... back pressure". They like exhaust gas flow velocity, which, in a badly tuned system on an N/A car, is often mistaken for backpressure. The key to a good exhaust is to maximise gas velocity while minimizing backpressure. True dual exhaust is an excellent compromise.

Enjoy your new exhaust!!
- Curt [/B][/QUOTE]

Well, I think he'll be happy either way - but a true dual system sounds neater and is more unique. Oh, and Racing Beat or RP wouldn't agree without a lot more info - like budget, desired powerband, application, etc.

Brandon

 

Good question. The answer is that they can do things that we (street cars) cannot. Well-built IT cars use very long headers followed by very long exhaust tubing that very very gradually expands in diameter. The IT cars I've seen have exhausts that snake all around the underside of the car, in order to reach the "magic" lenth. They're tuning for maximum torque at high RPMs - thus all the trouble they go to.

Just FYI, the turbo exhaust theory is a little different. The higher the pressure differential across the turbine, the more efficiently a turbo operates. Thus, the "best" TII exhaust is one that is very short, and very large diameter - you can't rely on scavenging nearly as much, since the turbo smoothes out the exhaust pulses.

Brandon

 

That's interesting - I've seen dyno charts from the Pensacola guys (Jay's car - drftkng on the forum, but he's not on much) that shows a 75 hp drop with the silencer in. This is while making about 250 rwhp on the stock turbo. Things might be different in N/A land, but afaik there's a very very definite hp drop - almost like driving w/ the AC on, in my experience.

Brandon

 

I have true duals that I bought from Mazdatrix, definate improvement over stock
TD is way to go IMO. Except for the weight factor.

 

WooHoo!!! way to dispell the myth!!
backpressure = bad.... always....

Damn, your AC kills 75hp?
Good thing mine's coming off...

 

I was not referring to a turbocharged car. And anyone concerned with putting on Road Race headers is not either. A turbocharged car is a completely different ballgame. 75HP sounds a bit ridiclious but not unbelieveable. But that 75 HP loss is not caused directly by the restriction in the exhaust but would be caused by the boost loss from the small amount of backpressure created. (BTW: in most cases unless the turbo is huge the turbo itself chokes the motor's exhaust more than the rest of the exhaust system) And if there is that much of a drop in power by the little amount of backpressure the silencer creates it indicates that the wastegate/exhaust design on that car could be improved.

 

oh... my vote goes for the duals... my money goes for the duals too... eventually...

 

true duals man. i wonder whats the tq difference though between them??

 

true duals are pimp and a half in a N/A car in my opinion, I say go for it.

 

Ive decided to go with true dual, Im just waiting for my flange to get here so I can take it to Don Marvel to have him make me the custom pipes. Thanks for everyones suggestiongs but I was pretty set on true duals from the start. Oh and to the guy that said "fake" true duals, how do you figure that it is fake? Each rotor housing has its own pipe and muffler for exhaust to exit out of, thus making it a true dual system.

 

I have had both systems so here is my PERSONAL take on both. If you disagree with me is cool We each have different tastes. On my '88 I had a short primary collected system that split back apart through two Brullen mufflers, no cats. The collector pipe was 2 1/2" and the primaries are the standard 2". Car sounded awesome. Alot like an F-1 car. I loved it but really loud. I then changed to the true dual system still utilizing my Brullen mufflers and no presilencers. Car gained alot of lowend and a decent amount of midrange power as well. Top end power suffered though. For street use the dual was better. Daily driving was easier and gas mileage went up by an impressive margin. It was really loud though. Louder than the collected but this is to be expected. The downside is that it sounded absolutely horrible. I hated it. Tone was all wrong and no longer sounded like a rotary (or any other engine for that matter). The collected system was faster on the top end. Power on a collected system gets even better if you collect it to a 2.5" pipe and then gradually expand it to a 3" pipe. Great power here and my personal favorite. I really love the sound of a collected system. My GSL-SE has such a set up except it is a long primary system.

Decide what you want to do with the car. If it is a racer I say go collected. If it is a daily driver then dual may be the thing for you.

 

Thanks man. Im starting to get sorta worried about the tone of the true dual. Im going to be driving it around town a lot and its my daily driver.

 

Would anyone happen to have a sound clip of a RX7 running true duals and one running collected?