I know that the exhaust must exit behind the driver.

But is it legal to remove the exhaust completely for scca autox events, and then reattach it with some type of flange after (since my car is a daily driver)? Has anyone ever done this and is it possible?

Just trying to get down my budget racing car to race weight as much as possible without coughing up the cash for a ti exhaust. Thanks.

It's legal as long as it meets sound requirements........Give it a shot:smoker:

Both Geoke and Davis had a flange installed right at the muffler, they can just pull the exhaust and bolt on a turn down at the track.

Both Geoke and Davis had a flange installed right at the muffler, they can just pull the exhaust and bolt on a turn down at the track.

So is a turn down necessary to keep it legal? Or is it just for sound purposes? Does anyone know how loud (db) our car is without the muffler or with a straight pipe?

So is a turn down necessary to keep it legal? Or is it just for sound purposes? Does anyone know how loud (db) our car is without the muffler or with a straight pipe?

Heat and sound. The turn down will knock the sound down a tiny bit, mostly what you hear in the car because it is aimed at the ground. Also if you just leave the exhaust open under the trunk area it can get hot enough to melt your bumper, mp5 had part of his melt and fall off at the Wendover Prosolo.

^^^^ +1 on that.

If you don't care about the sound you could do what I did and picked up another cat to muffler section (i got one from teamrx8) took my stock peices off and hung them on the wall. All i did was just cut the part that pointed up towards the muffler/undertray and turned it down towards the ground and welded it there.

Does anyone know how loud (db) our car is without the muffler or with a straight pipe?

I can only imagine it's not real quiet.....Previous rotaries were almost unbearable without any muffling.....I cannot say that about the Renesis but I wouldn't bet on it.

In the end, it's probably easier to just fab up a light weight exhaust for the summer season that you can leave on.....Putting parts on and off your car before and after events gets to be a real pain and I doubt you'll notice the extra 15-20lbs.

So is a turn down necessary to keep it legal? Or is it just for sound purposes? Does anyone know how loud (db) our car is without the muffler or with a straight pipe?

I don't have a db figure for you, but I can compare the FD to the RX-8.

A kid running his FD (no cat, dump pipe) got kicked out for being to loud in a Houston-area SCCA event I attended about a year ago, and as a rule of thumb, turbo'd engines are generally quieter than N/A.

Imagine putting your ear next to a chainsaw, that's about what standing next to a catless//exhaustless rotary should sound like.

In addition, if you really must know - search for a thread that discusses a e-cutout or manual cutout - if there's a video in one of them you'll at least be able to hear something that would sound similar to what you want to do.

Edit - not sure if you'd be leaving the cat on...

I've heard a few RX8's run in BS with no muffler, but with the stock cat and mid pipe and they aren't all that much louder than the Isley set up which many of us now use...louder, for sure, and with no redirection of the exhaust outlet probably not going to pass sound, but not ohmygod loud.

Anything is better than the hybrid Evinrude/electric motor stock sound, though :lol2:

+1 on that mwood had brandon at one of our local events get in to take a run in my car and he tried to start it again :banghead: not realizing it was running because it was so quiet. Had a lot of people at events ask me at times if it is running. There is no mistakening that it is running now though :lol2:


If i remember right isley told me his setup comes in just under the SD legal limit of 91 so I am guessing it would be 92-94 maybe.

If i remember right isley told me his setup comes in just under the SD legal limit of 91 so I am guessing it would be 92-94 maybe.

Mine comes in at 89-91 @ 50'. NO WAY you will meet sound in SD, limit is 93 @ 50', with just a turn down. Barbara's car with a single exhaust and 12" Borla, mine is 16", was 91-93 @ 50' so with no muffler I would expect you will be in the 95 db range.

:D good thing I don't run there very often

fwiw, we were recording 91 - 93 dB @ 50 ft with an open catback pipe

to play it safe for San Diego we installed a Supertrapp disc-set only with enough discs to equal an open pipe and were below 89 dB ...

understand there are a lot of factors on what any given reading will be; wind direction, atmospheric conditions, etc. etc.

or you could play the directional coffee can game like the evos where doing :yelrotflm

By the way mark where can I pick up a supertrapp disc setup?

http://store.summitracing.com/partdetail.asp?autofilter=1&part=SUP%2D444%2D2503&N=700+115&autoview=sku

and you'll need another disc set too

http://store.summitracing.com/partdetail.asp?autofilter=1&part=SUP%2D404%2D6512&N=700+115&autoview=sku

I recommend running the pipe all the way out the back shroud with the disc muffler on the end, it will be waaaaaaay quieter inside the car and the extra pipe weight is worth it for a street driven car

thanks everyone. I'm gonna look for a muffler or welding shop around here and see what I can do about cutting off my muffler... no noise limits around here that I know of...

I would love to have a more pemanent solution like ULLLOSE's or Team's setup since my stock exhaust is way too quiet anyway...

but the cheapest method (and more painful) is simply to take the muffler on and off for each event.

Thanks to Team, my supertrapp is coming in tommorow, and I'll get it installed either this week or next. I'll be running a single exhaust supertrapp though... so we'll see how it sounds compared to Team's...

Depending on how it sounds, I'm actually considering just forgetting the flange, and having the shop weld the straight pipe and supertrapp together. Do you guys think the supertrapp with a few discs (which makes it quieter) is daily driveable? I would obviously put on all 18 discs for autox purposes...

It's probably going to be pretty loud.......My issue with running a single supertrapp on a rotary has always been the amount of heat involved. Make sure you use lots of anti-seize on the bolts before installing them or you'll end up with warped and stripped out threads. Obviously the fewer discs you use the more heat you're going to trap. Don't under estimate this, just for grins go out and put your hand on one side of your factory muffler after you've been on the highway......:flamed:

^you probably don't have enough experience to say for sure ...

^you probably don't have enough experience to say for sure ...

You're right, I've only had them installed on three previous RX7's........That's the beauty of this forum. I can act like an engineer without actually doing any of the work..:)

"loud" is a personal preference

some people think anything other than OE is loud

other people don't think a catback straight pipe is loud

only the owner can say what's acceptable ...

"loud" is a personal preference

some people think anything other than OE is loud

other people don't think a catback straight pipe is loud

only the owner can say what's acceptable ...

You're right....."Loud" is a personal preference and on a stock car with a stock cat it might not be so bad. I had this setup on my 82 RX7 and really enjoyed it. Of course, I was in high school at the time so anything that made the car more loud and obnoxious was okay in my book....

Still, I think the bigger issue is trapping all the heat into a very small space.....But then again, I probably do not have enough experience to comment on this.....:rolleyes:

lol, me either

http://www.rx8club.com/showpost.php?p=1873441&postcount=517

but my recommendation was for a disc-only setup

the disc set gets hot, but there is no buildup per se as you get quite a bit of airflow through the shroud, my use is mainly WOT only and other than the disc cap turning a fluorescent purple color there hasn't been any heat issue at all

You DO know how much power you're giving up with the disc muffler, right? ;)

or gained ;), as always it just depends on the specifics

So my straight pipe w/ a Supertrapp is finally on. Muffler weighed about 32 lbs. Supertrapp and piping weighed about 6 lbs. So I figure my exhaust weighs around 13-14 lbs. Cost was $62 supertrapp, $30 extra discs, $20 mandrel bent U-pipe, $70 install. Its loud, but quiter than I expected with 18 discs, probably because I have it sticking way out the back.

Quick question for Team or anyone, how many discs do you need to add to approx = straight pipe? I think Team mentioned that he used 18 discs; was that 18 on each side for your setup?

I'm considering running no discs at all at my next event making it true straight pipe, hehe...

So did you create a flange for the exhaust so you can put the stock muffler back on? If so, how long do you think it would take to swap out exhausts?

it should take 16 - 18 of the 4" ST discs to equal the full flow of the RX-8's OE exhaust pipe, however you may want to run some tests with more or less to see if it makes any difference

I only have 12 discs on each of my dual Supertrapps, but that equates to 24 total which should approximate the flow of my 3" single feed pipe, my exhaust output is greater than a Stock setup

the OE cat-back muffler exhaust should be around 38 - 39 lbs total

and for events that don't have sound control you can always pull the discs or just the end cap off and run less on the street for additional noise control, at some point it will start hissing loudly and lose top end power with too few discs tho

OEM exhaust = OEM Muffler + OEM pipe from cat to muffler
OEM exhaust ~ 39 lbs = OEM Muffler ~ 32 lbs + X
X = OEM pipe from cat to muffler ~ 7 lbs
My Supertrapp + mandrel bent U pipe = 6.3 lbs
My custom ghetto exhaust = 7 lbs + 6.3 lbs = 13-14 lbs for under $200

I didn't get the flange because I ended up going with the supertrapp to adjust my sound. To remove the stock exhaust for each event would require jacking up the car, removing the flange, removing the 4 hangers, and bolting on the turn down. And repeating it to go home. My guess is that with practice that could be done in about 20 min or so. I figured it would be too much of a pain on top of the tires for each autox.

The supertrapp requires six small bolts to remove. Like Team suggests, for every event where noise isn't limited, I plan on removing the end cap to simulate a straight pipe. For the street I'll use 6-12 discs (right now, I'm using 18), but what hissing are you talking about? Is it from too much backpressure created with too few discs?

fyi, for anyone that doesn't know, supertrapp discs aren't intuitive. More discs = more flow. Less discs = less flow.

yes, with too few discs there is excess backpressure and the gas velocity through the minimal openings is high causing a hissing sound, you probably won't want to go less than 12 discs

I agree that swapping out the muffler would be a PITA

I agree that swapping out the muffler would be a PITA

That's why I just run straight pipe :) Complete stock exhaust is sitting in the garage thanks to team for hooking me up with another peice from cat to muffler.

Probably put the stock exhaust back on for the drive to topeka though as I doubt the fiance could handle 18 hours with it like that :lol2: