" On a rotary engine, the exhaust is also very crucial. While exhaust changes can make a five to 10 horsepower difference on a piston-engined streetcar, it is not uncommon for exhaust changes to make a 30-horsepower improvement on a rotary-powered streetcar. High-flow catalytic converts help, as does enlarging and tuning the exhaust.

For better torque, run two long, straight pipes as far as you can. For maximum top end, you will want to add a crossover pipe in your system. Be aware that rotaries are insanely loud and exhaust temps should be in the 1600-1800 degree area, so play safe when messing with exhaust. Most of the companies listed in the source box sell a street exhaust for these cars. "

This is an excerpt from a Grassroots Motorsports article (June '98), that's just more proof that these cars are very dependant on intake and more importantly exhaust mods!

 

Damn, you're so full of useful information!


-Ted

 

" Much of a rotary’s power is made by improving the exhaust. The collector’s design, size and location directly affect torque, throttle response and top end. Speedsource sells an exhaust system that maximizes power for IT racing. "

Another quote from a pole winning driver and 7 tuner (Sylvain Tremblay)

Man do you think all these people are lying...maybe racing beat, mazdatrix, and rx7.com are all together on this?!?

 

Ok well thats really interesting but how about answereing the age old question of weather or not dual is better for an FC than single?? Weather or not you can achieve the same power gain through a single larger diameter exaust versus having a dual smaller diameter exaust
WAIT im not trying to start a DEBATE here just wondering what those guys that wrote that quote would have to say about it

 

IMO running a single straight exhaust is the simplest way to acheive maximum top end power from a rotary.

 

I heard duals collecting near the rear axel is optimal. Whether we're running a sp, bp, pp or stock port motor and where we want peak power could determine the shape and size of the exhaust.

 

They're not talking 'duals' as in dual tail pipes. The stock FC exhaust is a single collected out from the log-type exhaust manifold, split into two tailpipes.

They are talking about using headers and collecting the dual header primaries as far back as possible from the exhaust ports to gain more power. The 'dual' exhaust they are talking about almost always exits through a single tail pipe.

Crawl under an ITA RX-3 or an IT7 first gen next time you're at the road races to see what they mean...

 

I thought I was pretty clear in stating that the dual(meaning an aftermarket race header) not collecting until near the rear axel, would mean converging into a single muffler. Otherwise I would've said true duals as in Mazdatrix $1300 system (which I had at one time back in 1996, which by the way offered me very little performance gain over a well designed single system).

 

Let me bet the first to say what everone else is already thinking...

Well Duh!!

 

I race in IT7 and i have two pipes all the way back to a single supertrapp. loud as hell but within noise regs. but...the IT7 racers said that it's an old road race system and there is better stuff out now. I don't know if they're on the net but the company that makes IT7 stuff is ISC Racing Services. Mike VanSteinberg is the man to talk to. they made the old exhaust system and have come up with a new design but since i already have a race exhaust, i wouldn't see the benefits like others would.

 

I remember reading that two things are important in exhaust design: Thermal effeciency and Volumetric effeciency.

Go figure....

 

I agree exhaust mods indeed make the largest single gain for a tII. Add an $80 homemade intake system and that will push a serious limit!

That k&n filter is 9 inches long!!! Fits perfectly!

 

I thought the main reason rotaries make so much power on exhausts is because the boost is raised when the exhaust is installed ?

 

thats what I thought too.

 

so on a street 7 w/ stock ports..... a headerwith the end of it having the collector and a good 2.5 inch piping to one muffler is the max power i will gain ?

 

you can get very impressive power gains from n/a with single or dual, and even more so with turbo. i know the mazdatrix system can push out 33.5rwhp gain on an n/a because i had a friend that put the system on with a before/after dyno, i think a well tuned single system would make at least 5-10 more hp than a dual, but its yet to be seen, maybe one day rotaries rule

 

The dual vs single argument has been going on forever for these cars. Someone needs to go get like 15 exhaust systems and dyno them all on an NA and a T2. Then that same person shoud proceed to scan and post them in the forum . If you do it I'll be your bestest friend forever promise

 

.....BUT, I have always loved and read everything I could about rotaries, I think the reason for all the debate is that rotories and the power gains/curves are alien compared to a regular piston engine. I say forget what you know about exhaust and look at what the actual old experienced racers at the track are actually using. They have tried it all, and from what I have read, headers that are collected as far back as possible into a single exhaust out the back is the best. It has something to do with the pressure and timing WHEN the collection is done so that one side sucks the others exhaust out with maximum efficiency. This is not my idea, it is just what I have read in Grassroots, and other mags that are not only printed to sell neon kits and crome Honda oil caps to kids who like to LOOK fast.

Just my .02, turbos may be different,

John

 

I have long dreamed of running, or at lease working for, my own RX7 mag. Kind of like Sport Compact Car meets Grass roots motorsports. Anything do do with rotary power. We test and tune and start new projects. and everyone on this forum has a subscription at $4.99 an issue, for 12 issues. Or have a by-monthly at 7.99 an issue.
This is my dream. we get to build our own cars. make our own go fast parts. better than whats out there now.
any way if I were rich...

 

I've got the same dream tweaked...maybe one day. Either way I'm working on something that I hope will give me great results (intake side). I've been doing an INSANE amount of research lately (not that I'm not always researching something, besides cars are my life , but I'm talking STOOPID amounts of hours working and researching on the intake system in the 7 and any other car I think has relevance to that car...wish me luck guys

 

rotaries get a lot of power from exaust n/a or t2, t2 gets more from the raised boost, but the gains of an n/a are exceptional as well, bottom line rotaries love to breath, a 4 cylinder w/open exaust can loose a lot of power due to it's need for back pressure

 

Do tell more we are here to help. I am trying a couple of things to get the n/a to breathe better. perhaps we could colaberate