Whats wrong with this turbo?
 

Hey guys, I know its been a while. Been inching away at the project Miata for a while now. I'm closer than i have ever been, however, i ran into a slight issue. The turbo just started making this sound just by idling the car and very very short drives to test out new components. Its has 100 miles on it, .030 restricter -4an oil feed line. Brand new mobile 1 synthetic 5w-30. It also leaks a very small amount of oil out the front of the compressor. Its a GT2860rs "disco potatoe" .86. Listen to the video and let me know what you think,

Thanks.



Imbed fail? Probably

sounds like the ball bearing center cartridge without oil.

It sounds the same on the car with oil.

What does it sound like when its on the car and actually spinning?

It sound like this, I can't copy the video but here is a link to the thread https://www.miataturbo.net/diy-turbo-discussion-14/grinding-scraping-noise-turbo-video-32958/

http:// www.youtube.com/v/nMc_KGN-omM&hl=en&fs=1

From information I've gathered online it seems that the turbo was starved for oil. It has a .030" restricter. I'm guessing even with the -4 AN line it couldn't squirt enough oil into the CHRA to maintain efficient cooling/lubricating and developed grinding/scraping. I'm going to drill out the oil feed fitting to .040 and see if it gets any worse. If it does get worse time to swap in a t25 or get a new CHRA.

This is what techguys@atpturbo.com said
Stan, Sounds like bearings are damaged from starvation. The leak you saw was not necessarily excessive oil pressure. It could have been leaking due to a turbo system configuration issue (ie. PCV or crankcase problem, or even engine piston ring blowby). When you decided to drastically drop the oil pressure to the turbo via the .030" restrictor, you may have inadvertantly cut a lot of oil supply to the turbo, especially if the noise started soon after that. The description you provided of the symptoms suggests that the bearings went dry. Spin turbo turbo by hand and see if it continues to spin freely for a few revs. If it does not, then that turbo is on the way out.

Savington and I have been running a .032" restrictor on our cars for the last two years with zero problems and we drive hard as hell. With the .064" restrictor I still blew smoke on start up and on the track.

However I agree that it sounds like it has no oil in it. If that were the case, it would melt-down and make really foul sounds. Are you sure there is no junk in the feed line and sure the fitting is clear? I was blowing tons of smoke on the track without the restricter. 30-minutes of 60psi oil pressure is not the answer. I had a funky knocking noise from the turbo and it turns out the heat sheild was not secure because the CHRA was loose. Make sure you're holding the heat sheild against the "frame" of the CHRA and see if it still makes the noise. Then, fill it with some oil and spin it, see if the sound changes.

Either way it's time for a CHRA exchange and on a street car I'd drive it until it grenades. If I were a betting man, which I am, I'd guess this turbo was run without water and the oil baked on the bearings

I sent those youtube links to my e-friend at TiAL to get his opinion.

I drilled a .040" in the feed fitting, going to see how long it lasts. Either way I'm delaying the inevitable. Going to check for clogged lines before put the car back together. Thanks for the suggestions.

No blockage on the oil lines, drilled restricter to .040. I believe the damage has already been done. The weird thing is on start-up it doesn't start scraping till i blip the throttle a couple times. Could this have something to do with spiking oil pressure?