[s-cars] Stromung Exhaust

[Tom Mullane]

If a bellows is to be added on the downpipe, you would want it to be
directly after the hanger that attaches it to the trans.  Since the
transmission is rigidly bolted to the engine and moves with it, the exhaust
hanger at the trans should only flex as the downpipe expands and contracts
with heat.  To provide flex between the engine/downpipe and the body/rest of
the exhaust, you'd want that bellows between the downpipe and the center/cat
pipe.  I'm not sure it's needed, unless there have been complaints of
exhaust contact with the body on acceleration or deceleration.  You would
know better than I, but I have not heard of this being a problem, nor have I
heard about any fatigue related Stromung failures other than the WG pipe.
As you say, the WG pipe issue has been addressed with stronger bracing to
the main pipe.

Tom


On 2/8/06, Postupack, Jeff <Jeff.Postupack at analog.com> wrote:
>
> 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:
>        < 8FDC0F9BE1F91D44BE964AA54AAA67B61A30C929 at wilmexm3.ad.analog.com>
> Content-Type: text/plain;       charset="us-ascii"
>
> <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
>
>
>
>