[s-cars] Stromung Exhaust

[Postupack, Jeff]

Tom:
 
I'll have to call Marc to be sure because my memory recalls the bellows
in series with the 3" DP section.
 
There is a long mechanical lever from the DP-to-Cat Section  junction
back to the tail pipe even. Hangers are flexible.
 
It's tough to analyze the mechanical stress that caused your WG tube to
fatigue, Tom.. However your idea is quite interesting for sure!
A few others experienced this early on (Bangetek, A. Neckas, etc) on
what I believe are RS2 modified engines.
 
I am running IA Stage 3 for years now and have the most current Stromung
Gen #4 with double brace at the wastegate tube.
The leading edge of the Cat section #2 is bolted with a hanger to the
transmission. It's not firm  offers some 'flex'.
I inspect it periodically and see no signs of fatigue.
 
Now that we've got Ned Ritchie's attention these days, perhaps he can
add experience to this S-list analysis.
 
Drone: As for Ned's earlier request WRT drone, I can second Tom's
experience that the Stromung gen #4 with cat is the optimized acoustic
solution.
It also flows well for a ~1400 dollar system.

My acoustic reference is cruising at 75 MPH windows up, 5th gear, you
hear the engine purr in the drivers seat and not the exhaust.
I'll have to listen again at 55 MPH , 5th gear.
 
Questions: Does an RS2 configuration offer more heat and stress that my
setup?  

Jeff
 
 
 


________________________________

	From: Tom Mullane [mailto:tmullane at gmail.com] 
	Sent: Wednesday, February 08, 2006 7:30 AM
	To: Postupack, Jeff
	Cc: S-CAR-List at audifans.com
	Subject: RE: [s-cars] Stromung Exhaust
	
	
	Marc had mentioned this to me as well, but I took it mean
installing a bellows on the wastegate pipe to keep it from cracking off
the side of the main downpipe.  You are talking about a bellows at the
base of the downpipe where it meets the center/cat pipe, right?  If so,
I would argue that this is not needed; the factory system does not have
one.  
	 
	I also question whether or not a bellows would help at the WG
pipe.  The problem I see there with the current set up is that the
factory bellows between the WG and downpipe expands when the exhaust is
pressurized and tries to force the Stromung WG pipe toward the rear of
the car and away from the main downpipe.  A bellows here might
exaggerate this effect unless it is placed after the downward bend of
this small pipe.  Perhaps the factory bellows should be replaced with a
shorter bellows that expands less? 
	 
	Tom
	 
	Date: Tue, 7 Feb 2006 16:46:59 -0500
	From: "Postupack, Jeff" <Jeff.Postupack at analog.com >
	Subject: RE: [s-cars] Stromung Exhaust
	To: "Taka Mizutani" <t44tqtro at gmail.com>
	Cc: s-car-list at audifans.com, Kenneth Keith <auditude at gmail.com>
	Message-ID:
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8FDC0F9BE1F91D44BE964AA54AAA67B61A30C929 at wilmexm3.ad.analog.com
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	<snip>

	Recently Marc Swanson offered the idea to integrate a flexible
bellows
	device at the Downpipe.
	This reduces flex/stress at the DP due to the rearward steel
moving
	about.  Then I did the obvious thing
	and checked out the new Audi S4, A4 at Audi Nashua and damn,
that's
	exactly what Audi
	does.
	
	So if I DO open the product improvement process, I'll try to
address
	both issues posted today.
	
	All the best 
	Jeff