Exhaust Manifolds - long

QSHIPQ at aol.com QSHIPQ at aol.com
Tue Jan 8 08:47:34 EST 2002

The subject of EM's is interesting, difference of opinion and experience
varies widely.  The 20vt EM doesn't bolt up to the 10v head, the "ease" of
install of esp the RS2 EM makes the 10vt a piece of cake.  I have modified a
few tools to install just the RS2 EM.  It's quite interesting to me what audi
has and hasn't done to address the EM's on various cars.

 The one that seems to have gotten the best, but only partial solution, is
the 10vt cars.  The 2pc manifold is without question a work of art, and sound
in engineering and practice.  What it lacks is twofold, block to
turbo/manifold support, and slotted manifold bolt holes to allow expansion.
Interesting to note, if you take a gander at the v8 tubular headers, audi
slotted the holes at the head/manifold mates, it's not even turbo'd.

No question in my mind that audi knows what the problems are/were with the
10vt EM's.  They correctly designed EM's (in different ways as well) on the
v8, 10v N/A, 20vt and N/A, the v6tt...

Motor mount failure adds additional stress to any exhaust system, so do bad
exhaust mounts themselves.  *Any* failure of any exhaust component that adds
additional movement or stress on the head/EM/Turbo manifests itself in the EM
in terms of cracking and warping, TURBO OR N/A.  Remember too, that N/A 10v
heads constantly get leaks and pop #1 exhaust studs as well.  That indicates
to me that this is a design problem inherent to long cast iron log style
manifolds.  This conclusion is supported by any documentation wrt EM theory
and design.

The dialynx manifold is a brick house, IMO/E. When it's built that way, it
will abuse the head, instead of audis design which does more damage to the EM
itself.  Phil's *opinion* that it's a POS is only opinion, if it doesn't
detract from performance (I actually understand it has gains), it is a viable
and good alternative to the 1pc manifolds.

The major problems with EM's on audi turbos in general, is that the head
mating surfaces and stud mounting varies widely head to head.  I've had some
(all heat cycled) manfolds that have no interference on the studs of one
head, pulling on some when place on another.  This indicates to me that the
*best* thing you can do for ANY EM, is to slot and/or progressive bore (see
Corky Bell) the mounting holes, use a heat cycled EM, machine both the EM and
the head flat.  Support to the turbo/EM would help emmensely as well, it's
really not that hard to do (Javad), and can save the damaged caused by the
missed bad motor mount.

Clearly audi has taken steps to correct the design problems inherent in the
1pc EM.  The 2pc was a great step in the right direction, just incomplete
(needs slots and support).  WRT Phil's comments on the "dimple" causing flow
problems, I just don't buy it.  The reason you run into this on the urq, is
that the downpipe is 6mm bigger than the 5ktq/200tq 10vt downpipe.  So you
can either direct bolt in the 200tq downpipe without dimple, or dimple the
urq one.  Me, I'd choose the latter, the restriction in the downpipe is
upstream of any dimples you choose to put in it (or just look at the dimples
in the dowpipe under the driveshaft arch, road rash "dimples" would be an

My .02 arbitraged thru the peso

Scott Justusson
QSHIPQ Performance Tuning

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