More 2pc manifolds

Fri Oct 26 14:19:05 EDT 2001

A couple of points to ponder Phil.  You have deleted or don't consider the 2 
pc or superceded 1 pc manifold support bracket necessary.  FYI, ALL 10v N/A 
cars use EM support brackets.  If N/A cars use them, all we turbo guys are 
adding is more weight.  Hmmm.

Hydraulic motor mounts were on all 44 chassis cars since 1985.  1985, 86 or 
87 10v non turbo cars consistently spit out exhaust manifold studs, when the 
motor mounts fail.  Usually in the following order 1 upper, 5upper, 2 lower, 
1 lower, following that rule of thumb is the turbo cars as well.  N/A cars 
don't crack manifolds.  It would be my conclusion then, that it's not the 
hydraulic motor mount that's the problem, it's the heat that's the problem.  
Add in lack of EM support, heat becomes more critical.

RE:  No cooling ducts on urq's motor mounts.  It was added to the 44t to help 
cooling of the motor mount located next to a hot turbo.  FYI, non turbo 10v 
cars also have an exhaust system and heat shield close to the motor mount, 
and that motor mount fails too.  Hence, cooling ducts to the motor mount are 
a good idea.  Hydraulic mount failure is not limited to turbo cars at all.

The 2pc manifold is a good upgrade to all 10vt cars.  Downpipe?  Ding it, 
grind it, heat fit it.  100,000 rpm vortex?  The urq downpipe is larger in 
diameter than the 200tq already (and part of the problem in 2pc urq fitment). 
 Phil, you have posted before, that to clear the 2pc manifold you need 6mm 
clearance into the urq downpipe.  Guess what?  The urq downpipe is exactly 
6mm larger than the 200tq downpipe.  Sooooo, the ding might affect 
performance, but I'd expect no less performance than the 200tq downpipe.  To 
really address the restriction in the downpipe, the turbo vortex is messed up 
at the cast flange at the front end of the downpipe anyhow.

The N/A cars have the same problems with failed hydraulic mounts popping 
manifold studs, not cracking manifolds.  The 10v N/A cars also support the 
EM, all of them.  Not supporting a 10vt EM manifold causes heat failures, and 
more of them.  

IME, anyone claiming motor mounts causing EM stress cracking, hasn't looked 
at a N/A car with a failed motor mount.  Failed motor mounts cause stud 
failures in manifold attachment, heat cycles cause stress fractures in the 

My .02 arbitraged thru the peso.

Scott Justusson

Phil writes:
Yes.  It doesn't bother you, but Audi has deleted the one-part manifold
originally fitted to the MB and MC engines, replacing it with the one-part
fitted to the WR and WX.  The difference is in wastegate control - the WR/WX
uses exhaust gas pressure conveyed from an orifice just above the turbo
mount and the MB/MC use (depending on engine level) either unthrottled or
throttled inlet manifold air.  If you're ordering a one-piece for an MC, you
have to order the plugging screw - it's listed on the FPA, though not
clearly.  Otherwise a normal stainless bolt will do.

We see about five ur-quattros a week in the workshop.  Two will usually be
for cracked manifolds.  We've never fitted a two-part.  It doesn't fit
anyway - you have to bash one hell of a dent in the downpipe to clear it,
centimetres from the turbo exit with the´gasflow in a 100,000rpm vortex.

No cooling duct on an ur-quattro - that's a Type 44 issue.

I'm buying another Type 44 next week with a cracked manifold, and I'll
probably put a one-part on even though officially it should have a two-part.
I know the engine mount is gone.

> Do they not have problems after that?  Assuming a good engine mount. I
know Aelred can't say the same - I've got the proof.

Never seen a problem - never had a customer come back.

> In that regard, not that I would want to let the mount go bad and
> transmit those shocks, the cryogenic treatment would help prevent the
> cracking due to relieving stresses and increasing strength.  I "was"
> thinking mostly heat expansion at different rates was causing the
> cracking, not so much shock.  But now I can see where both are
> potential problems.

The quick test is a piece of paper.  Get under the car and see if you can
slip it round on top of the subframe.  If it gets stuck, the engine is on
the subframe.  With practice, you can spot it from the front of the car by
the shape of the sump protrusion - a couple of years ago I spotted about
fifteen in an hour when we brought 240-odd ur-quattros together at
Silverstone - I think all also had cracked manifolds.  I keep meaning to
take a 'good' and 'bad' front picture - if the car is cresting a slight rise
it's incredibly easy to see.

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