Alright so here's the long and short of it. I've had a nagging issue with my 2007 MCS for nearing a year now. It's sounding like super knock, however I've not been able to find a fix that actually works. You can see some of my struggles HERE

Well just recently I reinstalled my stock Cat to see if my Catless DP was the culprit. Surprise, surprise I can still duplicate the hesitation and smoke (however it has lessened). But that's not the point of this post. I decided to take a quick peek at the insides of my turbo to see what it looked like. It looked quite dirty. But then I thought maybe it's normal for a turbo with 71k to look like it does.

Well I took a couple of photos. Not very good photos so hopefully you all can shed some light on my concerns.

Here is one with the flash:



And one without:


So tell me, is my turbo on the outs? Or is it just a normal 71k dirty turbo?

 

Based on patterning it looks like you may have oil leaking from the rear bearing seal. Could be caused by seal wear or coking in the oil drain plenum inside the turbo causing excessive oil pressure against the seal. I remember discussing turbo longevity with my SA and being told if I get over 70K out of one I'm doing good. Hows the shaft wobble?

This however would not cause the sound your hearing. Has the ECU stored any superknock codes? Blue/grey smoke oil, Black smoke fuel.

 

Zero codes stored that I can see. I work at a shop so I have access to a good scan tool that has BMW and MINI. And thinking back, I've seen both colors. The really bad instances it was fairly black. When it seemed not as bad of a 'hiccup' it would be greyish. Never any blue however. So I'd be more inclined to say black smoke is the color I've seen.

If it's a fuel issue, where would I start looking? I've had different plugs, different coils, and has continued to happend after walnut shell blasting my intake valves. I've also been using BG 44k recently thinking maybe I should try to clear out my combustion chambers. It happens rarely, but I can reproduce it with ease and if I'm running my tune, it makes it worse. (I assume the added boost on exacerbates things).

I didn't think the shaft wobble was too bad, but I'm very green when it comes to turbos, so who knows.

 

black soot coming out of the tail pip is usually an indication that your running rich, if it comes out with the catless DP when you boost, theres usually too much fuel before the air mixes. when the cat is it, it catches some of that. im not aware of how much shaft play there should be in a turbo, but working in the industry that makes turbine parts, there is no play. we most work with air bearings.


im not sure of the bearings on these turbos, there could be some play. you do have some carbon buildup.


also judging by the distance between the eye of the turbine and the shroud, that there is a tolerance if things get a little whacky.


have you tried going back to stock tune and stock DP?

 

It has happened recently. I'm currently running the stock tune and have the original cat. installed. It can still happen, albeit a lesser amount comes out and the hesitation is less as well. But yes stock tune, stock DP, it still happens on a hill and in a higher gear.