This thread popped up at a concerning time for me. My exhaust flanges finally shipped yesterday and I was planning on installing my new exhaust next week (using the new RB muffler). It's going on a daily and if it ends up as loud/tinny as some folks have said you can count one more unhappy camper on the list (not to mention my neighbors)...

I can vouch that there is a "baffle" although it's not truly a baffle as it does not impede the air flow directly. RB calls it an expansion chamber - what it looks like to me is that the inlet dumps into a hollow cavity walled off (via said baffle) from the rest of the muffler, and then it exits this chamber through dual perforated pipes with stainless packing (although that's only what it looks like, I haven't actually pulled one apart to see for certain).

From what I can deduce, the muffler itself (sans eternal piping, etc) may not be made in house. On their site (and I was told this via email as well) they mention waiting for the muffler canisters to arrive for the 83-85 power pulse muffler. Perhaps that's only referring to the can and not the internals, although I couldn't say. Finally assembly is in-house however; that's essentially certain.


Hey GSLSEforme, I've seen you mention this often but I can't recall if you were ever specifically regarding RB's "new" stainless mufflers. Is that the case? Curious for clarification sake.

My experience with exhaust restrictions on "normal" vehicles says otherwise. It isn't from running lean that far back, man, it's high pressure!

​​​​​I'm not inventing bullshittium here, it's an effect I have seen multiple times, and quantified with pressure gauges. And no it has nothing to do with material, but it is a sign of an internal failure.

Peejay, he's referring to my picture I posted (muffler hanging in a garage). I had a vac-leaky used holley and on initial startup the exhaust got neon-hot idling in my garage for about 1/2 hour (see avatar pic). Muffler got that discoloration from that incident. That's what GSLSEforme was referring to.
Sorry I confused the issue, but I am in the market for a new full exhaust so... I hope RB straightens things out.

Now, did you jumping your car around in a field have anything to do with the damage? It shouldn't have broken like that, but most of us won't punish our cars like your racing does.

I have zero interest in getting a replacement unless the design as changed. I still have an "old" RB muffler system on my '81, it is very nice. For this car, I will try to make my own setup, and if that can't be done to my satisfaction, because I want the bridgey back in the car, then it is Duratec or K24 time. Probably Duratec because the transmission issue isndead simple and junkyardable.

Ah, so this was on your rally car?

RallyCROSS car.

And most of why I barely drive it anymore is the loud exhaust.

Aside from the header, any NA exhaust is easier and cheaper to just have made by a local exhaust shop. Plus, you can provide them your specifications (tuning exhaust length for bridge or peripheral ports).

And what mufflers would you suggest?
Application would be a 270hp bridge port. Will regularly be driven on 2-16 hour trips.

As for mufflers? Dealer's choice. Get a large straight through Magnaflow or some other brand (anything with a stainless steel perforated core). If you plan on long drives in addition to racing the vehicle, put an electronically controlled valve in the system. That's my plan with the new exhaust I'm having made. This way highway trips don't murder my ears with drone and I can still open it up when at full chat.

That's not acceptable, I have played the exhaust cutout game and with a rotary it requires retuning because the engines are so sensitive to backpressure. Especially with a bridge port, if you want a good idle and good fuel economy you NEED a free flowing exhaust.

I got 24mpg with the bridge port and the original RB long primary exhaust system. Sometimes as high as 29 when all the stars were aligned correctly (long trip, no cold start enrichment, all highway, 90+ degrees outside, no hills).

Every NA race engine I build uses a Borla XR-1, and if I need to meet sound restrictions such as Laguna seca I stack them. I haven't been disappointed.

Then don't use an cutout valve? For me, it seems feasible as I can run two maps on my car. May not be the case for you.

My other plan was to use two small hot dog resonators on the primaries and a standard straight through muffler at the end (like the RB first gen system). The benefit of having it made locally is that I can choose the components and not pay a premium for parts that seem to have diminished quality.

I also don't want to wake the neighbors when I leave at 4 in the morning.

Darn, there goes that whole "rotary" thing.

You're asking to make more than double the horsepower in an NA application to be quiet without making concessions? K.

https://www.erc-rotary.com/sa22c

i think having it quiet (enough) can be done. you need a really big muffler, i have a Japanese Rx7 magazine and they did a muffler test, they did hp, dp, and frequency. basically the bigger the muffler the quieter it was.
so you could roll your own. the competition muffler was 8" by 20", which is larger than anything i can find in the USA

plan C, my friend made 231rwhp on this setup, and its quiet. RB header, to 2 x 2.25 straight through glasspacks (if you can find SS ones all the better), into 2 x 2.5" turbo style mufflers.

@peejay
What's the tranmission solution for that motor?
Thanks

NC Miata 5-speed. It's a smoothcase.
I have not had one apart but I bet it still has a provision for a speedo gear, so just slap in the appropriate tailhousing for your chassis and away you go. Locate the engine mounts by where the trans puts it.

Ahhh... that duratec. Thanks.

yeah that would work. the 2006-2015 miata 5 speed has the same guts as the 1994-2005 miata 5 speeds...

Maybe its just because I never see salt on the roads, but I don't see the allure to a stainless steel exhaust. I mean its a tube that dumps unwanted gasses and silences the engine pulses; it lives UNDER a car. Why does it have to be shiny? Who is looking under their car all day long?

IDK, Vin Diesel?

I spent 4 hours under my car this weekend. and stainless is stainless so it the metal doesn't oxidize and fall off.

I mean...it IS significantly lighter.

Like I said I don't experience salt. and I have a cutoff wheel just in case. (or oxy)

Seems like the problem on this thread is that it is more venerable to breakage and excessive noise because of that.

:lol: Ah Vinny the reason why there are so few stock FDs