Re: 2-piece EM: even more questions...

[OorQue@aol.com]

>  However, to me it seems the thing hangs onto the heat too long and that is 
a major factor in the cracking and
>  warping of the unit.

The major factor here is that Audi chose to build an in-line 5-cylinder 
engine ... because of this, the manifold has to be quite long and convincing 
it to expand equally across its entire length is next to impossible, 
especially when there is a turbo hanging off one end of it.  By re-designing 
it as a two-piece manifold -- two cylinders on one side, three cylinders on 
the other -- and connecting them together with a flexible stainless-steel 
bellows, Audi solved the problem as best it can be solved while still using a 
cast manifold instead of a fabricated header with five individual pipes.

> Maybe the unit should have been cast in a material more suitable to getting 
rid of any absorbed heat.

This is one of those chicken-and-egg things -- is the problem the design or 
the material its cast from? -- but according to my neighbor across the 
street, who's a metallurgist for Boeing, the material Audi used should work 
just fine for this application.  (He tested a piece from a broken manifold 
for me in order to determine whether it was worth welding it up as well as 
the correct rod and pre-heat procedure to use ... nice guy, eh?)

The bottom line here is that you shouldn't have any problems with the stock 
two-piece manifold, coated or otherwise. 

JG