Hi,

I've got a streetported 12A in an Opel GT, and I'm running a stainless header with a magnaflow resonator and a magnaflow muffler. I think it sounds allright, but I doubt the local police will (especially considering the 'pull-me-over red' paintjob). I would like to run a racing beat muffler, but I just don't have the space. I mocked one up out of cardboard and stuck it under the car: left about 1 inch of ground clearance without the suspension being compressed. I think the only way I can get it to a reasonable decibel level and have something that fits is to make it myself.
So... does anyone know what the internal construction of the RB powerpulse muffler is? I phoned racing beat, but all they could tell me was perforated tube with stainlees steel wool. Anyone have any more detail? (I did try searching...)

Thanks,

James

 

This thread may be of some help to you. It's worth reading anyhow...

https://www.rx7club.com/showthread.p...ler+steel+wool

Jamie

 

One pipe enters, two pipes leave. They are perforated. The outer shell is packed with stainless steel wool. It is very solid sounding when you knock on it. The middle chamber is where the sound cancelation occours. It is also the hottest part. Ever see an RB muffler with paint missing from the center section? That's why.

If I were you, I'd consider a Borla Pro XS with offset pipes. It is quieter than the straight through and can fit in tighter spaces.

The RB muffler is 8" diameter and 18" long not inclusing the pipes. TRhe Borla is 14" long and I think 4" thick by maybe 9" wide (oval). If this will give you better ground clearance, go for it.

 

It's the opposite of Thunderdome!

Basically this is all there is to it. It's one chamber packed with steel wool with perforated pipe through it. One 2.5" inlet splits internally with a smooth properly done branch to 2-2" outlets. It's very simple. It's not quite straight though as the pipes flow downward slightly due to the inlet and outlet locations not being centered. It's a good muffler that does it's job well. It's decently quiet. The hardest part of trying to build a muffler like this is acquiring the perforated core tubing and then splitting it into 2 smaller perforated core pipes.

 

Ah you got the joke!

As for the internal construction, I think it is more like this. The one pipe that enters is either 2" for the '79-'80 and '83-'85 models. The '81-'82 (their 'streetport' model) actually has two 1 7/8" pipes which collect into an approximately 30° Y which flows into a 2.25" pipe, not a 2.5", and then enters the muffler.

Inside, the single pipe is welded to a flat plate and is forced to flow into a perforated tube of slightly smaller diameter. This perforated tube extends into the center chamber where it either ends or continues through another plate. Can't recall. The two outlet perforated tubes begin in th ecenter section, I think, and wrok their way through the rear flat plate at the back of the muffler. They are also of a slightly smaller diameter than the inlet pipe. Where the perforated tubes end, some rear tubes begin which carries the exhaust gasses out of the muffle through a set of chormed or stainless steel pipes, depending on when the muffler was constructed. Some had slant cut tips while the newer models have a small inned pipe and a stainless outer pipe with a rolled inward edge that is straight.

That's the inner construction of an RB muffler to the best of my knowledge.

 

Wow!

Fast replies with good information, thanks!
I forgot to mention I'm running 2.25" tubing, which probably doesn't help the noise level. I will look into the borla, I see they have been mentioned in other threads as well.
As long as I have the guru's attention, do you think that there would be a big difference between the racing beat mini-presilencer (10") and the 14" long magnaflow resonator I currently have? They are both the same outside diameter. I'm guessing that they are both perforated tube in a cylindrical can with SS wool packing. I can't fit the longer presilencer.

Thanks again!

James

 

The RB is designed for a rotary and will last for decades. The Magnaflow is not.