I'm Having loads of issues with noise at the minute.

I have currently have Racing Beat Header, Agency power Daul Res mid pipe and Race Roots single exit. Static the car reads 99DB on a drive by im hitting 102-105 depending on the conditions which is far too loud. I've had the exhaust modified so it's 3inch form the Manifold back with no flanges and welded sleeves. (I mainly had this done for ground clearance)

I recently found out that the Race Roots back box is hollow. (it you tap it with something metal it make a hollow 'ting' noise.) the last event i done there was a company on site which sell exhausts, i tested one of there back boxes on my current exhaust (slip the sleeve into my tail pipe and the car read 86DB Static at 4.5k

I'm going to cut out the Race Root's box, install this one and have a 3 inch tail pipe at 45 degree angle.

New Back box = https://www.merlinmotorsport.co.uk/p...3-inch-u327600

 

Should have gotten the HKS instead of the shitty knockoff from Race Roots.

 

Sure, if you want to pay more for the identical muffler that Coast Fab sells.

That you would recommend aluminum in general and on a rotary in particular is apparently not direct experience based.

 

I'm sure it would still be too loud and I've learnt my lesson from buying cheap.

 

With 3" tubing, 200 CPI Cat, 3" Vibrant Resonator (short one) and 3" Flow Master Hushpower / Laminar Flow muffler I was mid to high 90's at 50 feet. It's somewhat of straight through design using perforated cones internally. This was with an open intake element that increased sound considerably. Did not find a measurable power difference when testing back to back with and without muffler so I can only assume it's not very restrictive. What's pretty neat is the outside of the muffler doesn't get hot. No burning myself any longer when adjusting the shocks or rear sway bar. It does drone badly though.

 

Good thread with good info. Has anyone considered running Racing Beat presilencers in place of a cat or resonator? I'm considering running the RB race midpipe with a custom catback using either a titanium or stainless canister style muffler (HKS or JIC) with one of the RB presilencers at the flange where it bolts to the midpipe. Also plan on having the exhaust tip cut off, cut into pieces, and rewelded as a lobster tail turndown. I'm hoping that will keep the car at a reasonable tone without being too heavy.

Edit: This is the muffler I'd run were I to go titanium. And yes, I know some folks who can weld titanium, which is going to make life much easier for me because I have never worked with it lol.

http://thmotorsports.com/jic_magic/j.../i-109814.aspx

 

How much does exhaust length effect the RX8? I assume it has some effect being that everyone is running the exhaust out the back of the car, versus dumping it in front of the diff.

I'm a complete newb to the rotary world, so please bear with me. I just bought a RX8 and am in the process of setting it up for STX next year. I plan to build a custom exhaust like I have on all my previous race cars, so I'm sucking in as much information as possible.

 

My initial thought was to build an exhaust similar to the one I built for my M3.


100 cell 3" Magnaflow Spun Metallic Cat
18awg 3" tubing
Hushpower muffler

This combination on my M3 was 24lbs from the header back.

For the RX8, I was planning on putting in a Moroso spiral flow muffler as a resonator.

Good start or back to the drawing board?

 

My brother's 8 has a turndown after the diff- no muffler, no cat, single resonated midpipe. It is EXTREMELY loud at every RPM in the cabin, and that's with full interior. Outside is loud too, but not as bad as you'd think after hearing inside. That said, his entire exhaust system weighs around 20lbs from the manifold back, so there's that. Performance wise, I didn't really notice much difference, but it might have been due to the fact that I was too distracted by how much louder it was LOL

 

One issue would be overheating your diff; however, the rules you will have to abide to will most likely determine where you dump it.

 

dumping it underneath is louder inside & out rather all the way out the back. If you don't have a helmet on it is unbearable IME for long distance rides - been there, done that and many years later my ears are still ringing ...

You can control the heat the diff will experience from the exhaust, there are plenty of various products for this

OE manifold - 15 lbs
OE Cat pipe/resonator - 23 lbs
OE Catback muffler - 39 lbs

mine is almost entirely 20 Ga., forgot that I did dump the heavy mesh muffler inserts after I had previously weighed it, likely closer to 30 lbs now, think you'll have a hard time getting any where near what you are claiming for the M3 exhaust without blowing the meter off the stand ...

 

Reviving an old thread....

Getting ready to start building my STX exhaust and have a question.

I know Stainless is required due to the heat, but does the entire system have to be stainless? If not, where can I transition to mild steel components. Can I use a mild steel resonator and/or muffler after the SS cat?

 

After the cat you should be fine to use a mild steel muffler/resonator I'm sure. Mine is for sale if you want it...new engine setup next year and requires a larger diameter

 

I think you need to re-read your post again. Team's comment was "Supposedly the BHR one is more rugged." and your response confirmed that.


Please don't respond and turn this thread into another Team vs. Charles debate. This thread is good information for people like me building an exhaust system.

 

the Moroso unit continues to work fine for the dummy with the super lightweight professional quality exhaust, otherwise I'm confused about how a disappointing string of suspension issues & inconsistencies has anything to do with building an exhaust system

 

Mark, are you using one? Simmons is looking into them. By design they looked to restrict the exhaust flow. I remember seeing flow bench tests demonstrating the same thing.

 

Relative to what exactly? Moroso rates it for up to 850 CFM. A full-on NA Renesis will not generate much more than half that rate. I switched from a straight-thru 3" ID x 6.5" OD x same length repackable racing muffler several years ago and noticed no performance differance. The sound was the same, the smaller OD just didn't hang down and hit bumps etc. it was a bit lighter too.

The stainless version is recommended for durability. The steel version will yield at a much lower temperature.

I really have no personal issue with BHR. Several attempts to work together resulted in delays/excuses. Not saying they weren't justifiable or unavoidable on their end, but rather that I have no patience. I was an early adapter for some of the ignition solution parts (not the full kit), but after having some issues and the early plug wires not being removable/servicable from the coils without returning them and waiting I just sent it back and said forget it. I think they took it personal, though I wasn't upset. Later I just made my own. Had the opportunity to get a new/unused BHR ignition from another member, installed it, and shotly thereafter had a failed coil issue. From which I pioneered the DIY ignition troubleshooting thread. It was replaced no problem, but I saw no benefit over my homemade kit and promptly sold it. About the same time I figured out there was a misunderstanding about setting proper dwell in the PCM and nobody seemed interested so I just kept it to myself until others finally caiuht on too (Oltmann). I just prefer to establish my own destiny rather than be beholden to someone else. I don't play suck-up well ....


.

 

Here's what I ended up with.... (Please note this is for a STX autocross car)

Bought an OBX header off ebay and gave it a little trim.






Extended the runners 16 inches







Built a custom 3in exhaust using most of ScubaSteve's original exhaust.











I ended up with:
Long tube header
100 cell 5in body cat
2- spiral flow mufflers

Don't know anything about weight or sound yet. I did fire it up last weekend and it is somewhat loud, but that was in a garage with the door open. Hopefully it's less than 100db. It did have a much deeper tone, kinda nasty sounding.

 

Diverging collector = fail

But you aren't the first and likely not the last either ...

 

Most recently discussed here if you're open minded enough to look ...

https://www.rx8club.com/series-i-aft...-256531/page2/

 

Also if I'm seeing it correctly in the limited photo angles, the cat converter appears to be located further back than the ST rules allow ... has to be within 6" of OE pipe flow position from where the OE cat exits. It appears to be in the OE resonator position which is not in compliance to the rules wording as I recall ...

 

That would be a negative....

"The inlet of the single replacement converter may be located no further downstream than 6” (152.4 mm) along the piping flow path from the original exit of the final OE converter."

The inlet to the new converter is ~5.5in downstream from the exit of the OEM converter.

 

The intent of my build is the most bang for the buck. You'll notice that you don't see any Burns Stainless or Coastal Fab type of components in my build. I have less than $300 invested in this header and I'm pretty confident it is better than the stock manifold.

Are there better options, likely yes, but this works for me.

 

I did the same thing to my racing beat header - cut it and added about a foot of length. Seems to work fine and no issues yet. Got popped and DQd last weekend for too much power. Put down 225hp at the rear wheels (on a dynojet) with a stock series 2 motor! Oops.

 

Was it that stupid MCE mobile dyno? That thing seems to read high and just DQ's people that I know are legal on the local dynojet we use for classing...