rppngears

Hi, I don't have an Rx7, but I'm not too far from it. I have an '04 rx8 with a Greddy turbo and Interceptor/Microtech ecu. Lately alot of Greddy turbos have been dying, myne included, and I'm still trying to figure out why before I reinstall my rebuilt turbo. Few of the people on the 8 forum have alot of experience with turbos, so I was hoping someone here could help.

The info I have is as follows:
-Turbo had 1500 miles on it, was running at 5psi. A significant number of others have failed under similar circumstances. The failure was indicated by loss of boost at high rpms - <2psi at 6krpms. Also, there was alot of oil in the intake tract and in the turbo itself. Some smoking under deaccel - as expected with all that oil.

-The rebuilder didn't see anything that definitely identified the cause of death, but the shaft had been blued, indicating it could have been running hot. I called Greddy about this though and they claimed it is perfectly natural for a shaft to have some blueing. Bearings and seals were bad.

-I cranked the engine over without the turbo installed to look for oil flow through the supply line. After a few seconds of cranking, I couldn't get any flow. May not have cranked long enough to build up sufficent pressure though. I pulled the line off and was able to easily blow through it, so it seemed fine. Reinstalled it.

-I do have a bov.

I suspect the problem has been caused by the location of the wastegate signal. Greddy taps it at the intake manifold after the throttle body. This leads to being able to create full boost 5-7psi in the manifold at 30% throttle. Since the throttle plate is only 30% open, it is a huge restriction and on the other side of it the boost level could be considerably greater. So the turbo compressor may be seeing large amounts of boost, but only 7pounds is being crammed into the manifold. This seems like it could lead to overspeeding the turbo and possibly to surge since when under part throttle, the turbo is producing alot of pressure with very little flow.

But wanted to get some more experienced opinions on it.

-Thanks

GUITARJUNKIE28

if the shaft were blued, i'd think oil starvation. pop the supply line off again and crank a little longer to make sure you don't have a clog somewhere.

what size is the supply line? restrictor?

alwaysboostin

what is the mitsubishi part number on that turbo? ie td04,5,6 18t, 20t etc
if the bearings are dark in color along with the shaft then it sounds most like you have an oiling issue that does not allow the oil flow to remove the heat from the bearings. what size oil drain and feed do you have installed?

rppngears

Its a Mitsubishi TD06-18g turbo, although its a Greddy kit, so it is likely modified from stock Mitsubishi specs. I'm not sure of the oil supply and drain line diameters, but they came with the kit from Greddy. I'd hope they'd know how to properly size their parts, but you never know.

GUITARJUNKIE28

you sure it's a td06?

rppngears

That's what Greddy has it listed as. Any particular reason why you seem uncertain?

kenn_chan

maybe because a TD06 has a decent sized compressor wheel, which could be too large for a high comp motor? if the turbine is costantly creating boost in the surge region of its compressor map it can quickly lead to bearing failure, and off of what you said about the wastegate signal and the throttle only being partially open at full boost, you may be running under the surge line (far left of any compressor map)

this will quickly chew up bearings if its the case.

kenn

GUITARJUNKIE28

i got 306 whp from a td06 @6psi once. but i thought i remembered the rx8 kit being listed as something else.

i think the rx8 kit runs out of juice somewhere in the low 300 range, where the td06 (20g iirc?) is barely getting going.

i could be mistaken though.

RETed

You're right.
This will cause an initial boost spike.
Most turbo's plumb the wastegate vacuum line closer to the turbo (compressor) itself.
Why not try and move it closer to the turbo to see if this helps the problem?
Just be warned that the boost might not hit as hard as before.


-Ted