930 Muffler Design #2 (Pix)

RarlyL8 · RarlyL8's Garage

Took all of your suggestions from my previous design faux-pa and came up with this.

Muffler case is similar in configuration to stock. Internals are 3'' S/S going into a split 2.5" S/S dual outlets. All pipes are perforated and muffler will be packed with S/S wool. Tail pipes will be added.

Any issues glare out at you?

Where can I buy rock wool or other muffling material?

Jim2 · Jim2's Garage

Looks good!

I built a similar one using single in and out, but it's a little too loud. Apparently, the dishes rattle in the kitchen cupboards (hehe).

I was also intested in packing material but unable to find anything convenient. Years ago I saw a race shop build a muffler and wrap the internal pipes with header wrap tape and stainless lock wire. Their internal pipes had lots of large perforations, est 3/8".

MotoSook · 04-05-2005, 08:23 PM

That's going to be loud. The perforations are small and not as numerous. Fiberglass material can be bought from motorcycle muffler retailers. They sell them to repack canister mufflers. Might just use house insulation if you have some around. Make the hole a bit larger and use the f-glass...should quiet it some, but allow for decent flow off idle..nice boost ramp

Why not use CherryBombs? I cut one up to make a pre-muffler.

A good book for intake and exhaust design is out there. Smith&Morrison.

Loud can be fun

..esp. at 10,000 RPM with a burnt out canister

YermanCars · 04-05-2005, 08:37 PM

no muffler thats what I did

use one for the exhaust and one for the wastegate dump

David · David's Garage

I've got some ceramic wool insulation we use for heat treating. It's very friable since it's not long strands like fiberglass. I've used it in mufflers with larger holes than you have and after awhile it started snowing out of the exhaust, but it is made for high temp. Let me know if you want a piece of it.

H20911 · 04-06-2005, 05:51 AM

It looks like most of the exhaust will ignore the right side (due to the lack of a pure "T" ) the left is much more free flowing. It is easier to flow through an "S" rather than to make the sharper "U" turn .

I would definatly agree that the holes will need to be enlarged if you want to deaden the sound a bit.
It will be loud, but I like a little noise

RickM · RickM's Garage

FWIW, here's a paper (from 1954!) on Muffler design basics. Perhaps some beneficial tidbits to influence your design. http://naca.central.cranfield.ac.uk/reports/1954/naca-report-1192.pdf

MotoSook · 04-06-2005, 08:13 AM

Dang Rick! That's a good find....good companion to Smith and Morrison.

RarlyL8 · RarlyL8's Garage

Thanks for the link!

The hole sizing was taken directly from a MagnaFlow straight-through unit that I have. According to everything I have read a turbo application requites as staight-through path as you can give it. No baffles, no expansion chmbers.

One thing you can't see is the deviding plate between the twin 2.5" pipes. It is shaped to allow more even flow.

What about long narrow slits on the 3" pipe? Would that be effective in releaving pressures to be muffled?

David - I'll gladly pay shipping if you can supply me with the material. Shoot me an e-mail at rarlyl8@yahoo.com

RarlyL8 · RarlyL8's Garage

Here's a pic of the dividing plate between the two outlet pipes. It is designed to direct flow to the driver's side path to even things out. The "plate" is an extension of the contour of that pipe.

Any issues I might have with this part of the design?

David · David's Garage

I think the best flow would be with equal flow into each pipe. Like a splitter between the two with the center of the splitter carved out to allow good flow (hard to explain without pencil and paper).

Something like on a high end collector:
http://www.burnsstainless.com/MergeCollectors/mergecollectors.html

strokher racing · 04-12-2005, 06:35 PM

You are correct turbo's like straight thru designs. Want to loose 25-50hp? I have seen this much of a loss on the dyno from swapping to a flowmaster on a turbo engine that was 347 cubic inches.

RarlyL8 · RarlyL8's Garage

Straight through would be perfect if I had room to do it right AND make it quiet. That's a tuffy. This attempt uses volume to make up for a less-than-ideal path.

David - I received your ceramic wool today. Thank you so much!!

You really need to see the pipes above in 3-D to do it justice. It's as good as I can get to smooth flow given the constraints within the muffler case. It is all I can do to get the 3" inlet pipe to mate up with two 2.5" outlet pipes. I tried the dual curve method you are speaking of, there simply is not enough room in the muffler case to allow for it.

The real question is resonance. I don't want any. None. My last attempt was a dismal failure, hopefully this design will accommodate that requirement.