Causes of turbocharge exhaust wheel damage

Image C is a damaged exhaust wheel, the red circle indicates the damaged area.

Image A is a turbocharger section cut out. Image B is a section cut out for exhaust side of a turbocharger.

In image B, yellow circle indicates the part where most of the turbocharger dialed from. Many claim that is the caused by bad bearing. But it is not always true. The black circle shows a smaller gap between the impeller and the housing. The damages caused by bearing failure would cause the black area to get hit first. On contrary, damages found only on yellow areas will indicated the cause came from objects shot out from engine.