infinitepat

look here

http://home.att.net/~mazdarx8/901-0184_IMG.JPG

Looks like a typical POS facotry log syle manifold. I think a good tube style header, perhaps even one desiged with a dual exhaust in mind, will be one of the fisr bolt ons available. And I bet it makes some good gains.

fritts

Holy crap!

That is a terrible design. Makes me wonder if the production version will have a better design or if that's it. Seems like all the design work they went through on the intake to give us a variable runner system, they would put some time into the exhaust system.

Here is another thought, could it possible that the header is like that to actually lower the performance. This may sound dumb but here it is. The first versions of the Renesis were rated at 280 hp. Now if Mazda knew they were going to go ahead and produce a Mazda speed version they may have detuned the renesis so that the MPS version would have its place above the regular 8. Now, as for the runner system since it really is designed to help with the torque through out the power band. This was designed for the driveability of the car, as they did not want an S2000 engine in the 8.

I'm sure my theory is out there but who knows.

I would like to find some better pics of the exhaust header if there are any so that we can confirm that this is the one on the production version.

infinitepat

Its almost certianly designed like that for emision reasons. It probley goes straight into a single cat, real close to the engine so the gass's are stioll hot, then splits after that for the dual exhaust. Though its possible that it stays a single exhuast untill the muffler, then splits into the dual - ALA cheap trans-am's. But I think there is lil question that a good x-pipe setup, and true dual exhaust would probley add a fair bit of power. Admitidly I'm no rotory expert, but I seem to recal the old rx7's seeing substantial improvemnts with lil more than a free flowing exhuast.

fritts

With a design like that there should be some extra horsepower in aftermarket headers. I am not sure if you would loose torque or not though. Lord knows that we don't need that. Another place of improvement seem to be the air box. As the airbox is almost an inline system. The runners that go to the airbox are pretty long from what I have seen on the press pack. Seems like it would pretty easy to install an after market airfilter right in place of where the airbox is. Another point would be the y-pipe and the runner system. I would like to see what happens to torque down low without the runner system. See how much it really affects it. With as many tubes as there are in the runner system seems like a direct system would definetly help the top end. I guess time will tell.

CraziFuzzy

It may be that a header would not change the performance characteristics as much as on a piston engine. Due to the smoother opening and closing of the Exhaust ports, there is less pressure surges in the exhaust manifold for the header to smooth out.

justinm2

In the past rotaries have always responded very well to exhaust changes, of course that was also before they changed the location of the exhaust ports.

PsYcHo_Pilot

I really hope the Renisis hasnt been screwed up with the new ports, <can they me extended or briged??> hopefully wont effect any mods such as intercooled turbo's or a supercharger option. i hope it has the same soup up options at the old 7 engines.

any one got any answers ??

justinm2

According to the mazda people the guys at rotarynews.com spoke with the renesis is designed to take boost.

RX - 8

the 3rd gen rx7 got an ample boost with an aftermarket exhaust...i think that the current exhaust design of the rx8 is probably more helpfull in the torque area rather then horsepower...a friend of mine had an Apexi exhaust on his fd...with the silencer in the exhaust he got +2ft/torque...and thats on the dyno...

N20SA22C

Crazifuzzy- Rotaries do very well with exh mods becuase they have many powerfull exhaust pulses, it is also the reason why they spin a turbo quite well for such a small motor.

PhychoPilot- The Renesis should be anle to hold at leaste 8lbs of boost and be quite healthy. It has a little more compression than a 91 non turbo which did fine under 10lbs tuned well. Go with N2O because it is only used some time, and comes out of the bottle very cold(free intercooler). A direct port setup can easily net 65-75 hp and maintain excellent reliability. We'll see

Kyle Lancaster--Double Agent Saleman

CraziFuzzy

I realize previous rotaries had very strong pulses, this was mostly because of the rapid opening/shutting of the exhaust ports. The Renesis should have a much smoother exhaust, due to the fact that the ports are opened up much more gradually as the rotor uncovers it.

wakeech

i can't remember the # of degrees of e-shaft rotation, but i'm pretty sure that the expiration stroke on the RENESIS is shorter (?) and opens later than on perhipherally ported 13B blocks IIRC.
obviously, i can only make a guess as to how this would effect the force of the pulse, but it would certainly make it shorter in duration.

CypherNinja

I'm pretty sure that the speed of the side exhaust ports opening (while being slower than the peripheral exhaust) is still quite a bit faster than most piston engines.

dIe 4 da 8

i know these arent the best but its the ones i gotta work wid seeing dat i dnt have lots of money...but i want opinions which one u think is better?............GReddy sp2 eshaust? or Tanabe super medallion hyper exhaust? wut u guys think? they both cost the same but i ono which one is better... thanks guys.

RotaryNoob

Another Resurrection... Maybe in spirit of the holiday's?