Foreign object damage in BKD turbo - how?

[efeballi]

Hello all,

My 2005 SEAT Altea with BKD engine had a problem with the turbo, sometimes shuddering, low low-end power, sometimes turbo cr@pping out completely and leaving the car with 70 hp. Anyway, I called sticky valves, off came the turbo and went for a clean. The turbine screw had pits on the outside edge of the blades, which did look like sand particles hit the turbine.
Anyway, turbo core was swapped, valves and VNT actuation cleaned and the car now works fine, but I can't help but wonder what hit the turbine. I can't recall any specific event that could result in the turbo ingesting something, no siren sound, nothing.
What could it be?


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[imo000]

The air filter wasn't sealing well or had a hole in it at some point.

 

[efeballi]

The FOD is on the turbine side.


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[imo000]

The compressor wheel blades were intact?

 

[efeballi]

Yup. That's what boggles me.


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[imo000]

Well then carbon from the combustion chamber or from the EGR is the likely source.

 

[efeballi]

EGR strikes again...


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[efeballi]

Nope, it's bone stock. We did run a 170hp tune for some time (it's 140hp stock) but that was a two week period and it was a year ago.

I don't know if that would increase EGT by so much. I have the damaged core with me, any other way I can see if the temps have gone so high?

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[efeballi]

Very late addition:
Symptoms such as high vacuum noise, black smoke under acceleration and excessive turbo lag (well actually my added knowledge that these are related) led me to search for a boost leak. Shop checked all hoses and fittings, tightened a hose clamp on the intercooler (it wasn't very slack though) and all these problems are now solved. I believe that due to the boost leak, the turbo was commanded to work harder to reach the boost demanded by the ECU, and this overworked the turbine and the excessive pressure and temperatures melted the turbine blade tips. I ran a required/actual boost log on VCDS and all looks good for the moment.
Old turbo core now lives as a paperweight on my desk.

 

[Kravt]

Thanks for the update on this. I had a similar problem with the VNT system in my turbo locking up from heat damage, not soot. I had an audible boost leak when it went down. Must have been the cause. Seems to be easy to toast a turbo this way, even on a stock tune.

 

[zzdiesel]

Turbos melt from high exhaust temperatures caused by excessive lugging of the engine for to long a time.

 

[efeballi]

Turbos melt from high exhaust temperatures caused by excessive lugging of the engine for to long a time.

Well, in this case, I wasn't pushing the car particularly hard, no tuning, no towing, no track time, mostly tootling around in traffic. The turbo worked hard to compensate for the boost leak, that's why the turbine blade tips melted.