dB and loudness question for a 944 exhaust I'm building

[TheStig]

Hey guys. I'm going to be acquiring a Dynomax Magnum bullet muffler that is 2.5" dia. which I will be constructing a cat back with myself. This cat back I'm making will be used for the autocrosses. I have a question regarding a sound issue though. Right now I have a straight pipe on my car connecting to a factory muffler for street and track.

Would a straight pipe and a bullet style muffler (lol might as well call it a resonator honestly) be sickening loud for the autocross course?

[Jad]

I think you will have to try it and see what happens, but in general 944s sound pretty bad with most of the aftermarket exhausts, and that is assuming they sound OK to begin with.

Ask Ralph and Dan C how much trouble they had when they changed the exhaust.

[TheStig]

oh boy I hear you on that one when it comes to sound. I'm actually considering now just leaving the factory catalytic converter on and using this bullet muffler.

[harnishclan]

I am very interested in seeing how that comes out. I currently have the MSDS header tapered down to a stock diameter straight pipe and finally into a stock muffler. But I have been looking at pretty much the same thing as you except using 3" pipe. And really the only reason for 3" is because that is the dia of the header. Are you doing this before next AX?

[MVZ944T]

If you have a turbo, I suggest that you do not use the very small diameter mufflers with the louver type holes intruding in the inside. Turbos's do not like back pressure. On my turbo at Laguna Seca last year, I had two, 6"x16" Magnaflow mufflers, a 90 degree diverter, and I still got black flagged. Typically, I can run one 16"x6" magnaflow at Qualcom.

[TheStig]

Hey Harnishclan, I should have it on before June 25. To prevent a whistle between the cat back flange and catalytic converter, I'm going to use the same flange from the factory muffler (I learned my lesson from an aftermarket cat-back that whistled due to the larger diameter piping and the donut gasket not fitting correctly) but expand it to the 2.5"

Before working on a new cat, I'm going to run the factory cat to see how loud it will be. Hopefully I won't be buzzing all around the Northern end of the Q's West lot.

[harnishclan]

Great! I look forward to "hearing" from you. I don't have any whistling noise at all. Used a Mr Gasket header gasket between flanges and it is working just fine.

[TheStig]

Harnish I don't think I got the chance to look at your car really. Are you running a Bursch header or still factory manifold and downpipe? I didn't know Mr. Gasket made a similar flange gasket for our cars. Perhaps I should consider using a Mr. Gasket if I were to have a whistle issue.

[harnishclan]

Andy, I am using ceramic MSDS header and that has a 3" collector. That uses the standard 3 bolt triangle common to many headers. I also bought a 3" to 2 1/2" reducer and just welded that to a straight pipe that is welded to the the stock flange which is bolted to the stock muffler.

Brian

[TheStig]

doh I just saw your other post up there about your exhaust upgrades... time to get some coffee

[Dan Chambers]

Hey guys:

Just to let you know, most, if not all "after-market" mufflers are somewhat loud on 944's. If you use an after-market Cat. with an after-market muffler, you're in for some reall "blappy" noise. The 92-decible limit is easier to exceed that you think.

Andy and Brian, I still have my Stainless-Steel cat-back 2.5" Danske muffler for sale. If either of you want to bolt it up and check out the noise-factor before a possible purchase, I'm game. (I'm selling it for $200.00 ..... and would entertain $150.00 cash to get it out of my storage unit asap )

Let me know, drop me a PM to discuss .......

Dan C.

[TheStig]

Hey Dan, someone off of Rennlist has a Dansk muffler too! He was telling me they are pretty loud when hooked up to a straight pipe on the car, and you guys already know I like loud things

I got my Dynomax Magnum muffler yesterday and it looks like I should this bad boy together next week. I'm going to use the stock cats at Qualcomm to avoid exceeding the 92 dB limit.

I do need a new muffler too and would like to get rid of the slightly rusty one on my car....if its possible, you think you have enough space to fit in your 944 and bring to the auto-x on June 25? I might be interested

[Dan Chambers]

Andy:

I'll bring it on the 25th, somehow. You're welcome to check it out.

[TheStig]

okie dokie guys tomorrow at 8 am I'm off to my buddies shop to construct my auto-x muffler. I should have it on for the June 25th event

[TheStig]

WOHOO!!!! I got my megaphone all put together this morning!!!! IT'S LOUD!!!!!!



I don't think I'll fail the dB-meter because I still have the cat on but chances are the Southern part of the West Lot will hear me zip around the North part of it.


enjoy the pix guys! You'll hear it first hand next weekend!