A couple days ago my friend picked up a s5 turbo to replace his s4 turbo.
It had more shaft play than his s4 turbo so we decided to swap just the Hotside and manifold from the s5 onto the s4.
Upon start up there was a grinding sound coming from the turbo that went if the engine was revved, either it went away or we just couldn't hear it while the engine was revved.
But when the engine returned to idle you could hear the grinding.
We checked both the center sections from both turbos and they are the same so it is not a early s4 turbo with the double heatshields or whatever. And when bolting the Hotside on we made sure it went on straight so it wasent cocked or crooked or anything like that.

Any ideas what we did wrong?

Thanks



-Kyle

 

it may be just the way you TQ it down,,especially if the inside had some cracks

i have done countless hotside swaps and there is no issue unless you have one CHRA that was intended for the early s4

when you do get it wrong,, one way will seat the CHRA but not tighhten up
and vichy versa is a CHRA that does not seat fully into the step relieved into the hotside

 

the hotside needs to be cleaned thoroughly, if it does not sit flush then the CHRA may **** to one side and cause the turbine wheel to rub on the housing. also if there is alot of buildup in the housing and the old turbine was worn, the new wheel may be running on all that old buildup.

best bet is to just have the whole hotside bead blasted to get rid of any scale and deposits, this should also allow the CHRA to drop in easily versus having to tighten it down into place.

 

Okay Thank you guys for the replies, it is appreciated.

 

s4 has a thicker heat shield lip, you have to keep the lip and the turbine housing matched. s4 turbine housing with a s5 heat shield will result in grinding. if thats not the case, its probably just dirty, not tighrened all the way down, or bent shaft