Looking to remove the stock exhaust. Dedicated race car.

Looking for exit on passenger side for weight distribution.

Must comply with SCCA sound limit: 103db

sblethen: Saw you custom made yours. Where'd you have it done?

I just got enough points back to do the exhaust.

 

Stock header? Stock midpipe? 103 db @ what distance?

Building your own will be the lightest. How much muffler you need will depend on the above.

 

Stock header
Straight midpipe (no cat)

Unfortunately, these sound limits are quite vague. Differ by tracks. I've seen 92db at 30 ft to 108 at 50ft.

Probably safest bet is better than 95db at 50 ft.

I know the answer is unclear, but so is any rules search. This is a changing area, and from what I understand will worsen as more people move closer to tracks.

 

You'll need a strong muffler to stay below 95 db @ 50 ft with no cat. I don't have a ton of applicable experience, but I'll share a few tidbits of information:

An RX-8 showed up to a local autocross with an HKS Hi-Power with a stock header and cat-delete and was well over our limit of 90 db at 75 ft (approximately equivalent to 94 db @ 50 ft).

I'm currently running a high-flow cat, two very small Coast Fabrication mufflers, and a Borla 40474, and I'm well below our local sound limit. As a test, I tried the same setup without the Borla, and it was loud enough free-revving that I knew it would fail sound at our local venue.

I'd suggest reading about some of the custom exhausts people have made for BS/CS autocross, particularly those who have competed in San Diego (90 db @ 50 ft limit). Keep in mind that they were all behind a stock cat and cat-pipe muffler. Something like the Isley/Borla might work.

What brand of muffler to use comes down to personal preference, experience, budget, recommendations, etc... I have had good luck with Borla and Coast Fabrication. The Coast Fabrication stuff is pricey, but they are very light, the packing material is easy to replace (or they have high-temp options), and they have fantastic customer service. I'd call them up and talk to Gary Donahoe to see what he recommends.

I hope that helps. Hopefully someone else with more directly applicable experience will chime in. Good luck.





EDIT: One more (somewhat obvious) note - most of your weight will be exhaust tubing. Heavy-gauge tubing will hold in more sound. Running a better muffler will allow you to run thinner-gauge tubing at the expense of more sound transmitted into the cabin.

If I redid my exhaust, I'd also add a couple V-bands to make removing and reinstalling the exhaust quicker / easier.

 

With stock header, no cat, the big heavy racing beat dual outlet muffer my RX-8 was just barely under the 92db limit at Laguna Seca.

How about the Racing Beat single outlet racing muffler? It should be fine.

 

If it exits out the side and the meter is on that side then your job is 10x harder to accomplish

 

That's gonna be tough. I failed a sound test with my car when it had a dual resonated midpipe (brand new so resonators were still intact) and an Espelir catback which is not a whole lot louder than stock if you keep the cat. Car clicked 99.6dB at 50 feet. Interesting part was though on a different pass, it ran 94.1dB but at 8,300RPM when I passed the sound meter. The 99.6 reading was at 9,000RPM.

Needless to say I'm banned from running the car at that track now lmao.

 

The Racing Beat race exhaust tested below 92 db @ 50 ft with the stock cat-pipe. Replace the cat with a straight-pipe, and my guess is that you will gain more than 3 db. I could be wrong, but that race muffler doesn't look any bigger than the one on the HKS Hi-Power.

 

Sound readings in general are not consistent. Atmospheric conditions, wind direction, driver inputs, site specific anomalies etc all play a role. What RB tested or what somebody else pulled is often not relevant to what your own reading might be.

 

Side doesn't matter direction does

Our original exhaust with a regular Borla muffler had our exhaust coming straight out the back on the passenger side and failed DB at NHMS. I think it was 103 with a limit of 102. We went to the local store and purchased a 90 degree elbow that pointed it in the opposite way for the afternoon and came in at 91db. same day, same track ,same spot, same temps, same readings ect. all documented by the person reading sound. he re-measures all those unique pressures and wind direction each session to my understanding.

I am now running a custom pipe in stainless (stainless will help with heat a lot near the tranny and rear end!) We then ran a custom Borla muffler that they (Borla) made for me. Supposedly they used to make them a while ago specifically for the RX8 but no longer do. I have a contact for it if your interested, I will be ordering another one soon. It did take about 3 months to get though. I also took the tip and stretched it in an upward angle to allow the exhaust to go up rather than back. this helps a lot actually, however I have no factual data to share since I do not have before and after measurements. This is a common practive in our area and has been tested by others. I am no running 92-94db depending on weather. I have a long header and 3" all the way to the rear muffler with as minimal turns as possible. I will try to post up pics and the muffler itself.

Stephen

 

Here is what I think is a pretty informative thread for you. Sadly as any newbie knows the search engine on this site sucks so I spent a little while going through my old posts to find it.

https://www.rx8club.com/aftermarket-...-borla-216122/

 

This is the old exhaust with original Borla Racing muffler that most "racers" are using. Regular XP1 I think is what it is called (Not specific to a rotary)

 

here is the new Borla Muffler that is specific to the Rotary. Notice the upward flare. Also check out the inside of this thing, strange but effective...

No Dyno Numbers. Sorry

 

I can build you one Mark, just give me a ring

 

I'm looking for the same thing except I don't care about sound levels at all besides it has to have some type of muffler. Not a fan of straight pipe.

 

Stephen or Don; It seems that there are a few of us interested in this. Stephen you said you're going to order another one. Perhaps we can make a mini group buy for 3 or 4 or 5 of these if someone is going to custom make them. Perhaps we can get a better price that way?? Stephen talk it over with your contact. I'm definitely in.

 

I have no issue providing a "group buy" of several exhausts assuming everyone is understanding of the timeline involved during the end of the race season. The way the exhaust works on my cars is that while it is two pieces, it is a complete system from header to tailpipe. We currently use two small "race" mufflers that weigh almost nothing but actually do help with the sound, and we use a "diffuser" at the rear if we need to point the noise away from sound control. It is very effective at its job. All my exhausts are stainless, and if you are really concerned about weight we can use thin gauge tubing for the tailpipe section. I highly suggest wrapping the tailpipe section of the exhaust where it passes the diff, and it is not a bad idea to wrap almost the entire thing to control heat and keep it away from the gearbox etc. Obviously coatings are an option as well.
Lots of cool stuff, anyone interested feel free to give me a ring.

 

Personally, I'm not totally concerned about weight, more weight distribution. I'm already ballasting the car, so total weight doesn't matter, and having the weight low, midline, and passenger side is perfect.

Other's may have more concern. I could take 200 lbs off the car is I ran SCCA instead of NASA.

Would have to fit stock header, can't relocate that according to the rules.

 

you cant use a proper header? I know the car which has run PTD/PTC has always had a header on it.

 

Aftermarket or modified header +2 points
Line C.23.

 

Also interested.

 

+1 group buy!

 

On my phone so this is short... I just want to clarify that the only thing borla was my muffler. The rest of the exhaust was custom fit into the car with engine, transmission, and header installed. Fit it tight for maximum ground clearance. As Don said make sure you wrap it and keep the heat Shields near the gas tank installed as well.

Stephen

 

why dont you custom fabricate your own that exits by the heat shield and have it pointing down.. I BELIEVE this is something that teamrx8 did, way back when.. it was an old post IIRC..

or do something like the Screen FD

 

I'm interested in the Borla rotary specific muffler for my N/A RX-7. I was about to purchase another XR1 but if Borla can make these again, would be great.