What causes this?

[M13]

your exhaust was swinging and that cast piece couldn't handle the weight swinging back and forth.

How does your engine blow from an exhaust leak though? Looks like you had the knock issue and lean issues that also contributed to this crack (making metal weaker due to high temps)

This wouldn't cause engine to blow lol.

[quadracer111]

It got a nasty knock... I found a longblock with 56k on it and had it swapped, it runs stronger than the old engine ever did. Also a new turbo.

[Snow]

Sorry so you blew the engine then?

[Skym]

Could be the metallurgy. Or that piece of metal was machined too thin and exhaust swinging too much on it. A flexi placed in front pipe should help stop it from happening again. Or exhaust manifold, turbo, exhaust got too hot due to rich, retarded tune (antilag???) and combo of the above.

[quadracer111]

A td05 turbo from my subaru, exhaust side. What made my engine blow up...

Anyone have an idea how this happens? Is it simply heat and age?