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Re: Factory exh performance?

On 10 May 1995 glen.powell@smc.com wrote:

>   You claim that sleeving a cat makes a big enough difference in
>   flow to be worth the effort Vs an empty cat, but then you claim that
>   replacing all the stock mufflers with straight pipe has no benefit?
>   Your positions appear to be in direct conflict.....

	This is not necessarily in conflict.  I think that Scott is 
saying that the cat is the biggest restriction, so changing the cat has a 
much bigger result than changing the mufflers.  Then, if you do change 
the cat, the best way to do it is to sleeve it, since that makes the cat 
flow like a straight pipe.  Now, in regard to the mufflers, I get the 
impression that Scott has found that the flow of the stock mufflers is 
only marginally worse than a straight pipe, so changing them would result 
in gains, but much smaller than would be found by sleeving the cat.
	It seems to make sense to me, but to verify it, we would have to 
go out and actually flow test the components.  I really wonder about 
Scott's muffler claims, because I know that Suppertraps can be quite 
freeflowing, but until I actually test the pieces, I'll defer to Scott's 
experience, tempered by what everyone else says.
	BTW, I put a pair of Flowmasters on an '87 RX7 a couple weeks 
ago, just because they were there, and cheap.  They seem to present very 
little restriction, (based on my previous experience trying to quiet the 
hot breath of a rotary) and have a very menacing hollow sound.  I heard 
them on a Corvette once also, and they gave it almost a Ferrari-like sound!
	It might be interesting to try one on the Audi.  I might also try 
one of my Carbon Fibre mufflers if I can get e bigger one made up.  The 
one i have is too small for a car.

Graydon D. Stuckey