|
I can chime in here with my four hundred bucks worth having just been down this road. When I got my K27S from UMW, it was "as new.". I am pretty certain that it was not brand new, but freshly rebuilt, and looked brand new to my untrained eye.
Anyhow, I noted immediately that the turbine wheel did not spin as free as the 3DLZ it was replacing. It wasn't rough feeling, but would only turn for 3 or so revolutions with a good snap. The 3DLZ would spin like a bicycle wheel by comparison. I'd never had a fresh turbo in my hands before so figured that some break-in period was required.
The K27 lived on the car for 6 months or 3k miles before I tore the engine down for a rebuild last fall. I noticed at that point that the turbine wheel had not "loosened up" like the 3DLZ, and I also noted some play in the turbine wheel that was worrisome, but in my haste to get the car back on the road I bolted it back up as is.
Fast forward to a few weeks ago, I decided to pull the turbo and sent it off for a rebuild. I had been seeing a smoke puff on startup more frequently than ever before, plus I convinced myself that the "draggy" turbine wheel could be the reason why the turbo could not maintain even 10psi past about 4500rpm on a 3rd gear dyno pull (I've modded this engine to 3.5 liters and enlarged intake ports to 37mm, FYI). I also theorized that a draggy turbine wheel could contribute to what I feel are higher than expected oil temps (its debatable, however whether my temps are higher than normal given my build).
Well, the rebuilder said I could have ran it for a while longer but that it was a good idea to rebuild it now. I got a 360 degree thrust bearing to replace the 270 that was in there. The turbine side shaft bearing was a bit cooked but I've seen worse ones posted in photos on this forum. The rebuilder told me that I shouldn't expect the turbine to freewheel on the bench. When I compared to the 3DLZ he stopped me and said that they have a completely different bearing design.
I looked at dozens of forums (both Porsche and DSM/Supra/RX7) and there is a lot of conflicting info out there.
I can't really evaluate yet whether the rebuilt turbo is performing better than before. Literally within days of installing it I put the car up for a suspension refresh.
|