Wouldn't bother welding it, chances are it cracked because of differential expansion from poor mix of materials, be hard to weld for that reason. It's not total junk, the exhaust housing on the turbo can be replaced but is normally really expensive. Get a quote from VW/Audi for the exhaust housing first and go from there really.
I think what rockmonkey is saying is that the housing probably cracked because it had a poor mix of metals, which expand and contract at diffeent rates, that in itself will make it really hard to weld because some metals require a completely different style of welding to others.
It probably can be welded but not sure how long it would last, if a poor mix is the cause of the crack.
Guess you could run it cracked but it depends how bad it is, is it on the surface that mates to the gasket or is it actually running through the inserts where the threads are?
Remember though normally once cracked it will only get worse with more heat cycles. If your turbo's not going just try and hold out a bit longer and get a new exhaust housing fitted before you put the turbo on, alot less trouble in the long run.
im going for whatever i can reasonably afford but given the space issues I have and not having squillions to spend on 4wd systems and LSD's i figure a nice 250-260 brake in a car that weighs just over a tonne should see me right.
(260 bhp and 1100 KG gives the same power to weight at an RS4)
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