Here is the layout of the RX-8 exhaust system, any ideas about how to route a hi-flow system from you guys with experience?

How about removing the secondary cat? That should give slightly better exhaust flow.

what about retaining the cats, or replacing with a high-flowcat.. :)

trying to stay legal...

--- what about that big honking muffler back there..

The muffler design look similar to the one on the corvette and I have seen many aftermarket ones to replace it.

Depending on how much space there is down there with the driveshaft and rear axle, might be able to split off to dual pipes earlier, eliminating any sudden 90 degree turns.

i'm not going to guess at how much improvement over stock you can get and still stay legal, but certainly you could save some pounds by gettin' rid of that huge dual tipped muffler and switched it for (some kind of) regular one-in-one-out...

How about placing a hiflow muffler in the spot with the secondary cat is and having just pipes to the rear.

Seems efficient and probably would be pretty loud.

How about this... 2 small straight through mufflers (had theses on my old FC.. very loud!)

I'd like to see how much room there is under the car... (I didn't see one on a lift or anything at Laguna Seca) so the Y pipe could be made straighter, and start further up towards the engine.

and get rid of the cat :) ... for racing purposes only .

nice PS job Dan..

I like that.. :)

I still hate that alst 90 degree bend tho'

Actually, I use the Gimp... Remember, I'm a Linux only operation.

And, yes, I hate the 90 bend too.. maybe something like this...

it depends on where the O2 sensors are placed too

it'll be very likely to be put on the second cat. we can use a high flow cat and some kind of electronic fix (reisistor fix)

depends how much space you get at the cavity, you might fit a small muffler in the center section, making it 1 in 2 out?

btw, doesn't it mess up the weight ratio? cuz removing that big o' can means your back end is now 40lbs lighter

also, what's the exhaust diameter? seems like 2.5"

that means aftermaket is going to sell us 3" mendrel bend big muffler with 2 tips at round $1200

i think i'll opt of a hi flow cat / 2.75" crash bend piping and some kind of dual exhaust can?

From the literature in the press kit there are actually 2 O2 sensors one before and one after the cat I believe. There is also just one cat. The piece you see at the header position is actually a resonator. I would say make a set of headers to a straight pipe back to a single tip high flow muffler. We can't be as bad as a damn SUV for the environment plus in Indiana we have no tests, so na na aboo boo.
Save weight and get a high flow system. Also the weight you loose in back I don't think will hurt to much especially if you replace the resonator with a real set of headers, so you lose weight on both sides of the car..

Maybe we can get someone to make a trick rear valance for a single center pipe configuration, can someone alter a photo of the MazdaSpeed rear photo (I am at work with no photo editor here) with one single pipe out the center, kinda curious how that would look

btw, what does the rotory headers look like?

normal headers, only there are only 2 pipes, similare to a 2 cylinder engine

BTW Fritts, all new cars have to have 2 O2 sensors to be ODB2 compliant.

Originally posted by fritts
... There is also just one cat. The piece you see at the header position is actually a resonator. ...

Thanks for clearing that up. I have a resonator on my Probe that looks exactly like that. I thought about asking about it but I wasn't sure and I didn't want to look stupid like I didn't know what a cat looked like. :)

We have emission testing every three years. I would not want to run a "straight" cat in this or any other vehicle just to gain 10hp.. It's really bad for the environment.. It's already hard to breathe in Toronto during the smog alert days, no need to contribute to that just to gain a bit of hp which really is meaningless..

Finally a voice of reason, not that it would change those people's mind

Well I'm all for a more free flowing exhaust to get more power, I have one on my car right now. But at least with my engine, running a "straight" cat does not make any worthwile gains.. maybe 1-2hp. With the Renesis you might gain more since it's a rotary engine.. but really, is the extra 5-10hp worth all that pollution? For what? A little more power? I'd sacrifice that in a flash for a breathe easy summer.. No cats is a very irresponsible proposition imo.

That said the 90 deg turn can definitely be improved on.

I agree with the leaving of the cats in... the exhaust options I am looking at are in line with keeping the car in the vague realm of manufacturers warranty if possible.. so pretty much anything rearwards of the cat. convertor is fine.


* However I have to tell you that adding a "test pipe" (removing the cat) and freeflowing exhaust to my 1991 non-turbo car gained a heck of a lot more power than 10 hp.

I guess if I lived in a polluted city I would have an issue with it. But when SUV's and trucks are running down the road with large displacement engines, the overall volume of crap they put out has to be much higher than anything the renesis even without a cat would put out. I will remove my cats..

i have a feeling that you could (if you wanted to) easily burn more gasoline than any SUV with a few races per week... remember that you're not getting 20mpg at 8k WOT... ;)
without that cat there, your HC emissions are gonna go through the roof, and i've heard all sorts of horror stories from guys with 13B's and no cats (like how bad the exhaust stinks, and how bad it'll make you choke when you walk 'round behind your car)... you might be advised to get rid of the resonator, the muffler, and get a "high flow" (:p) exhaust system to go around the cat... these days, the catalytic converters aren't the same kick-in-the-nuts the air-pumped systems from the 80's were... you're not gonna see the same gains without a LOT of front end (ie: serious FI) improvement... leaving everything stock except for "high performance" (:p) filters and an exhaust, maybe a chip (which can't change nearly as many things in this engine as it could in high-tech piston engine), i'd say you're not gonna do much other than make yourself sick by guttin' or removing your cat.
rotary or not (whatever QL meant by that), it's not gonna see you big gains with mostly stock mechanicals.

The gains we see from high flow exhaust systems remain to be seen so I would not say that you will not see them. My choice to do what I wish anyway so just make sure your not behind me...

Also how much of your normal day driving do you find yourself racing during normal driving your emission can't be terrible.
Most likely still doing better than large displacements you see running around..

*shrug* okay. you are right. :)

Originally posted by fritts
The gains we see from high flow exhaust systems remain to be seen so I would not say that you will not see them. My choice to do what I wish anyway so just make sure your not behind me...

Also how much of your normal day driving do you find yourself racing during normal driving your emission can't be terrible.
Most likely still doing better than large displacements you see running around..

Very incorrect. Just because the SUV's burn 20L/100km that doesn't automatically mean that they are terrible pollutants. Cars from 20/30 years ago pollute as much as 20 or 50 modern cars.. not quite sure about the number. If you take off the cats on the Renesis I'd wager any money that you will pollute a LOT more than any properly tuned SUV.

Btw, I believe that removing emission equipment on any vehicle is AGAINST the law.. maybe I'm wrong there.. Either way it's very irresponsible and ignorant.

I have a hard time believing that the shear volume of exhaust coming from a 6 liter engine when properly tuned is going to be that much better. Also to this how many people right now are running around with straight pipes on the their Rams, F150s, and Sonomas. I know I am from hick country but its quite a few around here. Not to mention the Diesel trucks running around. I don't really care about legal issues or environmental. All I'm getting at is that there are much worse polluters out there than I am ever going to be. So rag on me if you want but if you want to stop pollution there are way bigger hitters than me in the line up. Let also not forget how the government is trying to put cats on all motorcycles, even though the average trip driven by a motorcycle is less than the distance usually needed for a cat to even warm up.

I understand that but this is a case of "hey everyone else is doing it, why can't I?". It maybe so but that doesn't make it right for you to do it... Do you really have people running straight pipes down there? :confused: Are there NO emission laws/controls? In the end my point is that the gains realized from this mod do not outweigh the cons of polluting the environment.. Of course in the end you will do what you want. Beauty of free will vs social responsibility.

In Indiana there are the same laws that apply to almost every state, not sure about canada. Except in Indiana we do not have any type of inspection. The only thing I know that is anywhere near exhaust related that would get you in trouble would be for having an overly loud exhaust. Which is something I encounter every day on the highway or in town. I am not saying that because others do it, it is ok, I am just saying that there are other fish bigger than me to fry first.

Originally posted by fritts
I guess if I lived in a polluted city I would have an issue with it. But when SUV's and trucks are running down the road with large displacement engines, the overall volume of crap they put out has to be much higher than anything the renesis even without a cat would put out. I will remove my cats..

Actually, all auto emmission test are based upon an allowed amount of emmissions per mile driven. Therefore, an SUV with 50% of the fuel efficiency does not necessarily create more pollutants. The exception is carbon dioxide emmissions, which are directly proportional to fuel efficiency, but are not considered as pollutants by many peeps.

I can guarantee that the removal of catalytic converters will make your car much dirtier than any properly functioning regulated vehicle in the last 20 years. Plus just because someone else is worse is that a reason to slack off? I think not.

How about this guys I have major quams about start up emissions. I don't think it should be required so bye airpump. But you have somewhat convinced me that I could get a high flow cat without gaining to much weight and decreasing performance. I have no Idea what the cost will be but if its not terribly cost prohibitive I'll definetly look into it. Sound better guys.

The problem is not always what cars spew the most crap either. You can't assume the your car is the only one putting out pollutants.

To get an accurate idea of how much pollution results from removed equipment you would need to take the number of antisocial irresponsible self-important ignorant sheltered spoiled American daddy-pays-for-my-stuff punk twerps and multiply that number by the amount of extra emissions produced. It is hard to say how much extra emissions there would be so I recommend using 2 cars, on modified and one not, and two ignorant fools. You put their mouths over the tail pipes and wait an hour. Then scrape their lungs and weigh the crud that comes out.:(

Of course I am just a jerk for saying this since everyone knows these days that you have the right to do whatever you want without thinking about or understanding the consequences and you can figure "screw anybody that doesn't like it." It's the American way.:mad::( :mad:

Looks like this thread has been Thoroughly hi-jacked.
Lets get back to discussing the possibility of improving the exhaust in the RX-8.

We can start a virtual lynch mob for the emissions scuff-laws in a new thread, cant we?

i'm with you.. about getting the discussion back on track...

Actually , I am awaiting an email from Racing Beat about aftermarket exhaust options right now.








FWIW > if you wanna save the enviornment go ride a bike or drive a Honda Insight... I will try to keep my car within the "federal" guidelines set forth, nuff said.

Originally posted by DrKillJoY
FWIW > if you wanna save the enviornment go ride a bike or drive a Honda Insight... I will try to keep my car within the "federal" guidelines set forth, nuff said.

I apologize for my contribution to keeping the thread off topic. I just want to say that I agree with the quoted statement. In fact the regulations might even be too restrictive. My point is simply that we are part of a community and while most of us are responsible, some of us are not. I hate to see enthusiasts get a black eye from a few people breaking the law.

Well we are still talking about the exhaust. :) Believe I also want to extract the maximum available amount of power out of any mod but removing cats is a pet peeve of mine. Sorry. :)
Incidentally, why do you guys think that Mazda chose the T design for the exhaust? I'm no expert but like others commented before that 90deg turn cannot be very good for flow.. Unless they know something we don't?

they knew people would be looking for a way to upgrade the car so gave the enthusiasts an obvious one to start with?;) :D

ill leave mine stock and just work with the front end, any aftermarket ones are too loud for me and I want to stay legal.

I'm not sure if you can get it done where you are but in the GTA we have a custom exhaust shop, Brullen. They can make the sound tailored to your preference. A free flow exhaust does not automatically have to be loud.

Personally, the exhaust is too quiet for me. I like to be able to hear it, maybe not as ear pearsing as my FC was (that was L-O-U-D), but enough to be able to ehar it with the windows down.

I use the exhaust note as another form of input on how the engine is operating. In my FD, i can immediatly tell by the exhaust sound when something is amiss... (not that I expect anything to go wrong with the RX-8) I also use it as a shift point indicator... when i hear it reach this sound, shift.

if i can get a higher flow without failing emissions tests than I may or maybe just change for a lighter one.

On older rotaries there was a lot of power to be gained by going to a single high flow cat instead of the triple cat stock setup. Evn more can be gained by removing it altogether, though certain exhaust combinations would simply be too loud. Unless you went with Racing Beat mufflers, oftentimes a header and presilencer with a catback was too loud on an N/A FC.

In my part of the world, it's "technically" illegal to remove your emissions equipment, i.e., most shops won't do it for you but they don't make you actually have one come inspection time and many places don't do emissions tests.

Personally I think exhaust notes generally sound better without a cat, with the mufflers regulating the exhaust note - you get a purer, more vintage sound. I don't care about the "moral" ramifications, I live in a place where the thing resembling smog is when people burn their trash (yes that's legal here!) and cats don't do anything to reduce greenhouse gas (CO2) emissions. If they crack down hard enough I'll just drive cars old enough not to need to be tested (can't wait to get an RX-3!)

As for the tight bend in the exhaust, I think it's pretty simple. With only a single cat on the RX-8, and being a naturally aspirated rotary and therefore LOUD, the restrictive catback is in place to keep the car quiet in stock form. They figure most people who want a louder note will spring for an aftermarket piece, which Mazdaspeed will probably sell sooner or later.

From what I can tell, the header and resonator are tuned to just about max.
The cat is a matter of your conscience and local enforcement.
But – Oh yeah – loose that big can in the back.
Two small straight-through’s should be about perfect.

{edit} Referring to smokingclutch's comment about loud:
It is NA, but the 4 side port arrangement gives a softer pop than a peripheral port.

If the constriction on the exhaust on the 8 is anything close to what it was on the 2nd Gen 7's then if you are brave enough to do it, dropping the cats and running two straight pipes all the way back should make the car FLY.

I used a setup Racing Beat was providing through MazdaTrix and did that with my 89 and it was like driving a completely different car after I mod'ed it. Night and day difference, like the difference between driving a Civic and a Camaro SS. I even passed E-Check 2 years in a row, by some miracle of GOD, with no cats on the car...

I am sure they have improved the whole exhaust setup and all, but that used to be the best way to get more power out of the NA's, at least it was with the 2nd Gen. [Well that is other than being an idiot an trying to put a supercharger on that engine and wind up buying a new one every 20K miles ;) ].

Quick

A rotary engine is very similar in working with a two stroke engine: intake, compression and outlet. No valve's like a four stroke engine. But the exhaust mounted on a rotary engine is the same as on a four stroke engine. So I was thinking about this: a two stroke engine needs an expansion exhaust system to build up the right pressure at the right rpm's. Now I was wondering what such an exhaust would do in combination with a rotary engine... :confused:
Maybe this can gain a lot more power and torque?

O.S. Engines, a famous R/C engine manufacturer, also produces a rotary engine. It also uses an expension exhaust/muffler:

An engineering marvel
Here's another O.S. "first"-the first rotary engine for R/C models. The O.S. .30 Wankel produces tremendous horsepower for its size. In addition to being compact and highly power efficient, the .30 Wankel is smooth-running and quiet. It includes two needle bearings and one ball bearing. It's perfect for .25-.35 applications. The engine includes an expansion muffler and a glow plug.

http://www.osengines.com/engines/osmg1400.jpg