10v header: Downpipe

[JShadzi at aol.com]

<<  My question is about headers and turbos.  I was under the impression that
 turbos generate too much heat for headers to stand up to, and that cast iron
 manifolds were preferred.  I know that my Porsche 944 turbo has a stainless
 header, but the turbo is quite aways away.  I am curious for your thoughts
on this.>>

Well, yes, it is generally considered that cast iron manifolds are stronger,
but that does not mean a tube runner manifold cannot be even stronger than
that if though is put into the design and construction of it.  You are right,
though, that a thin-walled mild steel header will self destruct in no time,
as the heat and expansion caused by a turbo are severe.  Even thin-walled 304
stainless is not considered ideal, as it will weaken over time at the levels
of heat in a turbo application, over 1000 degrees!  Aircraft quality 321
stainless is considered ideal, as it contains some titanium that gives it
much better heat stability and strength.  In a thin walled header
application, 321 is the material of choice, but its very expensive, about
twice the cost of 304.  To build a header like mine out of 321 would have
cost over $500 in just tubing!

So, I looked for another material that would be suitable, and I found thick
walled hydraulic tubing, often referred to as WeldEls.  These are cast steel
elbows and drawn pipe that come in all kinds of shaped and sizes.  I used a
thick walled 304 stainless schedule 10 WeldEl, with a wall thickness of .109"
(16g is about .058").  These, because of their thickness, will hold up well,
while still not making a tank compared to the stock manifold.  When finished,
my header weighed about 10lbs.

So, with the proper material and thickness, a header can be designed for any
application.

 <<Keep up the great work... and may we, that only dream of building similar
 beasts, live vicariously through you and your turbo Audi. :)>>

Get out there and do it!

Javad
80tq.com