I would love to have a custom exhaust made instead of getting the racing beat full system. Why? I want it a little louder than the rb system, I’ve seen threads of custom exhausts making a bit more power and maybe save a little money. So my question is, what are some good specs for a custom Na exhaust? I know 2.5in pipes are pretty accepted. I’m thinking racing beat header and maybe going catless? What mufflers, presilencers, dual or single? More detail the better!

 

also stock port and will stay that way for long enough that im not worried about having to buy another setup later

 

Hello!

One thing about rotaries is that they can be loud. I recommend a good muffler/mufflers on the end. Something like Racing Beat, Borla, or Dynamax,or Magnaflow. Below I'll have some links on stuff people have used.

If you use two mufflers, it'll be a bit quieter, but remember that with rotaries being loud, the better muffler and having two will make it quieter. Personally I prefer NA's with a little more hushness considering Racing Beat can be throaty while being fairly free flowing.

I used to use a single "Corksport" and it was incredibly loud, requiring me to go into neutral around police officers and an exhaust ticket. The exhaust ticket was $200, so spend that on a muffler and you'll avoid that scenario.

Magnaflow I have used:

2.5" in/out mufflers, 7" round = part #14716 (two of them)
4" tips = part #35136 (two)

I did use this on an LS1-T56, but it sorta sums it up, you'll need a y-pipe as well if needed.



Racing Beat: Universal Muffler, 2.5-inch ID for RX8 - Racing Beat

Dynamax: https://www.summitracing.com/parts/w...xoCM8sQAvD_BwE

Borla: Many have used XR-1 series mufflers.

 

i did some measurements and stuff a while ago, and i'm hazy on the numbers (you can search), but a good street exhaust is the following.

Stock manifold. It flows enough, and it acts with the exhaust port inserts to de-couple any tuning, so you have more freedom to pick a muffler/cat without hurting power, which is nice.
Pipe Size, Mazda got this right, i think its 50mm OD, and 48mm ID, however the S5's are welded on the inside, so they end up being like 44-46mm which is too small. going up to the next bigger size would be ok, probably wouldn't do much.
grinding it out to 48mm, or this Down Pipe for 86-91 RX-7 - Racing Beat
for the center you can run a cat, and it cleans up the smell and knocks down some noise, or you should run a muffler there (RB offers the dp/presilencer as a kit,

for the rear, either a single in the same diameter as the front, or a Y in 40-50mm. the stock Y is fine, the RB y is probably nicer.
for a rear muffler it is up to you. with a stock manifold and a car/center muffler just about anything will be streetable
or there have been a TON of cat backs offered for the FC, and you could use any of them

make sure your fab guy uses all the hanger points

basically you end up with 90% of the power gains, but its easy to keep it quiet enough, and its potentially emissions friendly too

 

I like my setup using the collected RB header/ presilencer set up but as others said noise can be an issue. I originally had a 50mm HKS sport catback which is NLA. It's a touch quieter than the RB though. The pipes finally got rusted out and I put some 2.5in. id ebay mufflers with barely any packing on it. Was to loud overall and I eventually got new piping and fixed the HKS since the mufflers were still good. My point is louder than RB sounds good until you have to drive and live with it everyday. As for power a long primary system is best but I imagine is hard to quiet down due to only using a single muffler. You would basically collect it just before the muffler. For max power the collection point has to be tuned on a dyno. That said a RB road race header and presilencer from their true dual system collected and into a 2.5" muffler would be the best you could do with out the dyno. It will be louder than a dual muffler setup. You could use the same header presilencer but collect it mid chassis and then out to dual mufflers. In theory should make less power but how much I don't know. Whatever you do if you use a header use muffler whit SS packing and plenty of it. All that said with the setup j9fd3s suggested those Ebay mufflers I had would've probably been fine.

 

i was thinking about this, and you might double check my numbers, i'm going from memory. the factory pipe size was good, that was the takeaway. going the next size up wouldn't hurt, and then going bigger than that would probably just be loud