924Board.org

[IXLOR8]

My car is coughing up fur balls.

The sound material in the muffler is coming out. I have been thinking about taking to Midas or a shop like that. Any suggestions on what works good for performance and noise control. Size of pipes, length of muffler, diameter of shell?

I am not real interested in the "fart pipe" sound.
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Wisconsin

[timstar92404]

I'm going to have a costum exhaust shop replace my entire exhaust except the manifold and I also don't know what muffler to put on the car.

My car doesn't have a cat and I don't want one. So I"m looking for a mulfler that will be quieter than my flowmaster (don't know which model) but still sounds nice...

I don't want the custom exhaust shop to fit a ricer exhaust on my car.

don't know if I can find a quiet performance muffler that sounds like the flowmasters but much quieter.
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78 924 sold.
85.5 944

[CBass]

If it's mandrel bent, 2.25" exhaust is the way to go. Crush bent, 2.5" pipe is the way to go. You have a couple choices when it comes to cats and mufflers.

If you are going to be tested for emissions, you'll most likely need a cat. You can get aftermarket cats for less money than an OEM replacement, in common imperial tube sizes. For a little bit extra, you can get high flowing performance catalytic converter.

For a muffler, the first thing to consider is flow. Flowmasters, despite their names, flow like crap. A good bargain muffler is the Dynomax Turbo muffler, it flows great and doesn't sound too bad. Use a 2.5" inlet/outlet muffler, regardless of whether you're using 2.25 or 2.5" exhaust tube, as a 2.25" muffler will be a significant flow restriction over the 2.5" on either pipe.

If you have a little more money to throw at it, and you're going all stainless, spend the extra cash and get a Borla oval muffler, or a stainless Magnaflow oval. You can get a nice Borla or Magnaflow on Ebay for under $100 USD, just keep your eye out for one.

A good option is to cut off the downpipe's end just past where the two pipes merge, taking a die grinder/dremel to the inside and grind the welds smooth. Weld a reducing coupling to the end to increase the diameter to whatever you want it to be, 2.25 or 2.5, etc. Don't worry about a reduction in pipe diameter for an inch or so before the reducing coupling, as long as it's short and a gradual transition, you'll actually pick up a little flow from the venturi effect. It's called a merge collector by header builders.
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'81 931 in various states of assembly

[CBass]

http://cgi.ebay.com/ebaymotors/XL-MagnaFlow-Stainless-Steel-Muffler-5x8x18-21-2-13950_W0QQcmdZViewItemQQcategoryZ33636QQitemZ7991216204QQrdZ1

Good muffler, think it'll fit the 924 but I'd measure first to be sure. Good deal regardless.
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'81 931 in various states of assembly

[timstar92404]

do you think the 60 series flowmaster would sound good?

they have sound clips on the flowmaster website and the 60 series doesn't sound good it sounds like honda/ jap car muffler.


I think I have a 40 series muffler and its too loud without a cat.

what about the 50 series? its sounds good from the clip but don't know if it will actually be noticably quieter than the 40 series.
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78 924 sold.
85.5 944

[CBass]

Forget about flowmasters, they're junk. They don't flow very well, and they do very little to supress sound. They sound awful on everything except for V8s. The only flowmasters that do flow do next to nothing for sound supression, and have very large inlet diameters that would require significant stepping of tube diameter to fit them.

Now for starters, you have a 110hp 924. It's not likely that any previous owner has done anything to the head or internals of your engine that will result in any significant power gains, so we'll assume that your engine is stock. You need around 2.5cfm of exhaust flow for every hp, roughly. That's very roughly, by the way, just a good rule of thumb, and something that can be fine tuned by dyno testing for each engine. 2.5cfm/hp is a bit more flow than absolutely necessary, but it's usually wise to go with a little more flow and a little less sound supression, since it's hard to estimate every flow restriction in the system.

Given that, 110 x 2.5 = 275cfm. 2.25" mandrel bent tube will support this kind of flow, as will a decent 2.5" inlet muffler such as a Dynomax or Cherry Bomb Turbo muffler. You should be able to pick up a CB Turbo almost anywhere, they stock them at Canadian Tire for about $40 CDN. This is obviously more flow than the factory needed to make 110hp, but it does leave room for future improvement, such as headwork or a hotter cam, higher compression, etc.

You'll want a resonator to kill pressure waves, 26-28" past the merge of the downpipe tubes, that'll keep your pulse tuning around 4000rpm.
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'81 931 in various states of assembly

[IXLOR8]

What is the stock pipe size going into the muffler?


I went to a Midas Shop today. . . They wanted $150 to install a universal muffler.

I said the word Porsche.
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Wisconsin

[alxch1n15]

hey ixlor8, what color porsche do you have, and are you downtown? ive seen two around, a copper color one, and a red one with a black hood. either of them yours?
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'81 924 n/a

[IXLOR8]

My car is Indigo Blue. I live in Stoughton. See pictures at link below. What 924 do you have? Do you have it down town? I saw one around University and Park Street about two weeks ago. I did not remember what color.

Rick
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Wisconsin

[Rooy]

If you are going 'no cat', just be aware that all shops may not do this for you if the car was originally equipped with a cat. They are required by law to install one. So I would be a little suprised if a big chain outfit would do this.

Andrew
Neenah, WI

[alxch1n15]

i have a light blue 81, i havent been driving it down town, but around the middleton area.

hey rooy, do you drive on hwy 151 often? i see a good looking red 924 there when i go up the girls house in menasha. we're going to all have to get together sometime for a wisco meet...or something.
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'81 924 n/a

[timstar92404]

my car passed emissions without the cat so I don't feel like paying 400 bucks (midas quote) for a cat.

the thing about mufflers is you don't know how they sound before they go on your car and you may hate it but then you're stuck with it.

not sure about the canadian tire mufflers.

I'm looking for a quieter muffler w/o cat.

maybe I need them to install a resonator as I don't have one now.
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78 924 sold.
85.5 944

[CBass]

I have a 2.25" cherry bomb turbo on my GTI, on a 2" pipe. It's louder than a stock economy type muffler, but it has a really deep tone to it. It doesn't sound fartcanny, and sounds really nice above 2000rpm. Below 2000rpm, it sounds like it's bellowing, very deep and a little unpleasant to listen to. Still, for $40, it was cheap and it flows better than the 2" crush bent system with a 4-1 "toilet bowl" exhaust manifold.

Turbo mufflers cancel out a lot of undesirable sound waves, so they don't sound too bad... I still love the sound of a good reflection type muffler on most engines, but that's my personal taste. A lot of Honda guys love the sound of an absorbtion "straight through" muffler on their cars...
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'81 931 in various states of assembly

[Rooy]