cracked UrQ EM

[SIMON HOLTBY]

--- isham-research.freeserve.co.uk at pop.pol.net.uk, quk at isham-> 

Warping on WR motors is rare - it's common on MBs.  I wonder often if
> this is because of ECU control of fuel mixture on the MB - the WR is
> entirely mechanical.  I've never studied how the WX's fuel management
> works - can the ECU cause the mixture to go very lean at high revs.
> If, for example, you take your foot of the gas to decelerate at high
> speeds?  Lean running 'heat bursts' are my favorite explanation for
> warping.
>
Phil,
 
Here are a few more ideas (or guesses)

1.
The head on an MB engine is a different casting to that of a WR and so the
the area where the manifold studs are mounted may be weaker. This may be
due to an oil/water way being closer. The manifold(steel) expanding at a
different rate to the head(alloy) is strong enough to pull a stud from the
head.

2.
The MB engine has a watercooled turbo which continues to run after engine
shut down, this cools the turbo and manifold which it is bolted to quicker
than a WR. The resulting quicker contraction of the manifold warps it.

3.
The MB engine runs hotter than a WR possibly due to a higher compression
ratio. So causing a higher risk of warping


OK so a Dialynx manifold is more prone to warping on an MB is this also
true with an original Audi manifold?  What milages could the original
owners of an MB and WR quattro expect before it cracks or warps?


I believe that cracked manifolds on the 20v turbo engines are very rare.
Is this because Audi learned from the 10v motor and over engineered the
manifold.

The same is true with SAAB turbo engines 16v engine manifolds are far
better than 8v. Maybe it is due to the multivalve engines being crossflow
allowing better air circulation around the manifold.

Simon Holtby

88' Camaro (no turbo no problems)
 

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