Overspeed on Rear Turbo

[rudypoochris]

Hey Guys,

Did some maintenance today and finally got an endoscope down the intakes to see what 86k miles (60k at 17.5psi) looks like. Need some advice/opinions on how bad the overspeed is at the rear turbo. Maybe @VargasTurboTech can chime in.

Thanks!

FRONT:

















REAR:















I am assuming the oil on the rear turbo is from the PCV. Hoping anyway... When knocking the turbos (front and rear) with the endoscope they didn't seem to have play, but I did get them to rotate some.

I adjusted the rear wastegate tighter by 2 turns a long time ago to get rid of some rattle. It worked, but likely it has been driven harder than the front turbo. I will need to tighten the front up.

[Tony@VargasTurboTech]

You emailed me, I have no idea what you are asking though. I do not see any evidence of overspeed, overspeed shows itself with failed turbos over time. Sticking a camera in there isn't going to tell you much besides you have no compressor wheel damage, but if you did your turbo would fail shortly after. From what I see, they look fine.

[SCGT]

Looks good to me too.

http://garrettbyhoneywell.com/turbo-...oubleshooting/

[rudypoochris]

You emailed me, I have no idea what you are asking though. I do not see any evidence of overspeed, overspeed shows itself with failed turbos over time. Sticking a camera in there isn't going to tell you much besides you have no compressor wheel damage, but if you did your turbo would fail shortly after. From what I see, they look fine.

Thanks for the advice. I was referring to the build up of metal on the rear turbos compressor blades. Looked like the compressor was maybe contacting the housing. Originally I stuck the camera down there because I had pumped 1.2L/min of water preturbo while doing some testing. I was concerned about impingement of which there appears to be none.

[lfelunden]

These turbos at 16psi is nothing, alpina b3 biturbo runs 16.5 psi stock, b3s 18 psi stock - SAME turbos!

[SCGT]

I see no signs of compressor/housing contact. Maybe need better pics to see if it is there but I don't see signs of it.

[rudypoochris]

These turbos at 16psi is nothing, alpina b3 biturbo runs 16.5 psi stock, b3s 18 psi stock - SAME turbos!

Yeah, I am at 17.5psi. They are basically maxed out at 18psi. You can get a little more, sure, but its going to take a lot of pwm...

[rudypoochris]

I see no signs of compressor/housing contact. Maybe need better pics to see if it is there but I don't see signs of it.

Awesome. Thanks!

[Sticky]

I'm not sure what signs to look for regarding contact and I'm no turbo expert but does this picture not show some contact/damage?

[SCGT]

No. I agree there is something there though.

Contact between the compressor wheel and the housing will tend to occur at the knee of the bend in the housing first. In other words, 1/2 way through the curve. As such, you would not be able to see it from this angle. If you WERE able to see housing/compressor rub right from the front it would be very bad, it would mean your clearances through the turbo had gone to hell, the compressor wheel would have -at best- developed a peeled back edge, your efficiency would have gone to hell and this would have shown in logs for sure, unless you're running very conservative boost. Hint: You're not.

That aside, the artifact circled in red is not typical of the housing being even kissed by the compressor wheel. A minor kiss tends to look like a buff mark at best, or maybe some slight polishing, not the little snake bite type thing we see there. This is intuitive if you think about it. The mark shown could have been anything but I'd bet an orange soda that it wasn't from the wheel. Maybe some piece of dirt or large grain of sand made it through. Same thing for the compressor wheel. The artifact shown was likely a small foreign object. Keep in mind the size of these things means the indications shown are tiny.

This is nothing to be concerned with.



Edit: This is what < 0.003" rub did to a housing. You can see where there compressor hit, then skipped and hit again. This is typical minor rubbing/kissing. Note where it is with respect to the knee of the curve. Hope this is helpful.

[Sticky]

That aside, the artifact circled in red is not typical of the housing being even kissed by the compressor wheel. A minor kiss tends to look like a buff mark at best, or maybe some slight polishing, not the little snake bite type thing we see there.

Yep, that's exactly what I was referring to.

[rudypoochris]

Thanks for the comments. This is what I was going off of:



Failed turbo:

[J1gilles]

Thanks for the comments. This is what I was going off of:

http://www.60-130.com/images/im...c09128fb-1.png


http://www.60-130.com/images/im...2ab067b4-1.png

Failed turbo:
What you are showing with the above picture (top one) is very common with higher mileage turbos. Increasing the boost over "stock" levels can accelerate this process. This does not really cause any significant issues and I assume you are having no trouble building or maintaining boost so I wouldnt worry about it. Now the bottom picture is a whole different story...

[rudypoochris]

Yeah, the curling of the metal I thought was an indication that it was rubbing against the housing, but it may not be. Who knows! It will blow up eventually.

[Tzu]

What is also present in the "failed turbo" photo is obvious blade tip overtemperature, which in itself will also degrade the rotor clearance to the inlet.