Hi,

Planning to build my own muffler because nothing will fit my car (not an rx7). I picked up a stock muffler from an '84 GSL and hacked it up to see what was inside. It is a reverse flow, there's three chambers, no packing. The outer shell is double wall, plus there is a heat shield surround. Approximate chamber volumes from the inlet to the outlet side (negating the space taken up by the pipes): 250 cu inches, 475 , and 170.
In the pictures, you can see the exhaust is dumped into the middle chamber, it has to travel through the hole into the back chamber, then through a single pipe to the front chamber, then out the two outlet pipes. The two outlet pipes are both perforated, but only in a small area.

I'd sure like to see a cutaway of a RB muffler!

Hopefully someone finds this useful.

Cheers,

James

 

Nice! This helps me diagnose the strange noises my exhaust is making... I thought the muffler failed, but the way its built I don't think the muffler is the problem now, must be a loose gasket or something..

 

Huh,there must be variations to the stock mufflers.
Years ago,I chopped open my stock 84 muffler and it was fully lined with fiberglass between the outer walls.I assume not only for heat suppression,but also to keep vibration and secondary noise emissions down.The innards were similar,triple chambered,reverse flow....run of the mill muffler.

The RB mufflers,at least the modern ones....are simple, straight through units.
The reason they muffle so well is because they are as big as the stock units,so there is lots of packing material to absorb the noise.Most straight through glass-packs put their emphasis on compactness and "making" noise.The RB is nearly quiet as stock,and thats on a VERY loud engine.The extremely heavy wall,round construction also keeps them from buzzing and coming apart like other cheaper mufflers.

 

Cali emissions might be different. I am gonna replace mine too (it's Cali).

 

Also the difference could be a factory muffler vs a reproduction replacement muffler

 

The early RB were a reverse flow design as well. The new ones I still don't believe are straight through, they are far too quiet for straight through. The biggest magnaflows are bigger than a RB muffler and are still louder, so its not in the amount of packing, although that does help. Its simply not possible to have a straight through as quiet as the RB muffler. But I could be wrong.

 

very interesting

 

Well that explains why the stock muffler is so freaking heavy!

 

Someone did actually have a cutaway of one of the new racing beat ones. It is considered straight throught because it was just one long pipe bent up multiple times inside the chamber and covered with packing material IIRC from the picture that I saw.

 

Trust me,its straight through.

It might not be a straight line through the muffler body,the pipe has to angle a little to get from the top on the inlet side to the botton of the outlet side.....but the modern,RB mufflers are esscentially a glasspack. Just a very stout,well endowed glasspack.They arent made in Italy just to be expensive!
I did a full inspection on my SP version muffler when I got it in 01' and you can clearly see in one end and out the other.I cut the inlet pipe off and the RB tips in order to mate the muffler up to my 3" stainless system with an inlet flange and SS outlets........7 years of flowing 14psi, TO4B boosted, streetport 13BT exhaust gasses, cant be wrong.


http://smg.photobucket.com/albums/v2...evepics014.flv

 

Thanks for the info! Straight through, huh? I thought there was a chamber in the middle, but I don't know.
Believe me, I would love to just buy a RB muffler and be done, but it won't physically fit my application (not an RX7. Hell, not even a Mazda!)

James