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Discussion Starter #1
Fresh off a complete head job and head gasket replacement, my '91 Turbo Supra has suddenly developed a bad smoking problem. It's weird, the car was running GREAT with no signs of smoke for about 2 days after my nephew and I got it running. Driving home from work on the 3rd day, I noticed significant blue smoke during deceleration, when accelerating hard (boost) and also when negotiating sharp bends. Oil consumption was always high prior to the engine work, but now I am going through a quart every 100 miles and I can see it in the rearview mirror!

During the HG replacement (now a MHG with ARP studs), we replaced my turbo with another stock CT26 which had been rebuilt within the past few years. Considering the fresh turbo was just put in, my first thought was a broken ring, improperly sealing MHG, or bad valve seal (even though they were all just replaced with the head job). So...I picked up a compression tester and ran dry and wet tests. IMO, the results are fine:

Cylinder #1: 162 Dry, 176 Wet
Cylinder #2: 170 Dry, 182 Wet
Cylinder #3: 168 Dry, 180 Wet
Cylinder #4: 166 Dry, 177 Wet
Cylinder #5: 177 Dry, 191 Wet
Cylinder #6: 162 Dry, 180 Wet

When I pulled the spark plugs, they were black with soot, but dry. Also pulled the O2 sensor, same thing. Can't quite tell if it is oil residue or the result of running overly rich. Could be a little of both. But the smoke is definitely oil - it's blue and has the distinctive smell of burnt oil.

After passing the compression test, I pulled the accordian off the turbo inlet to inspect the compressor wheel. There was some oil in the intake hoses and near the compressor inlet, but nothing more than usual. I took hold of the nut on the compressor wheel and gave it a spin...no binding. Then I moved it axially and radially...there was no axial movement, but it definitely moves a good 0.010" radially. I know the spec for max radial movement is 0.007", but could this be the source of my oil smoke?

My nephew thinks the turbo is probably OK, it certainly spools nicely and produces nearly 10psi thanks to the actuator arm washers. He is afraid it might be a busted oil control ring, something that wouldn't show up on a compression test. I can't imagine it would suddenly break an oil control ring, but you never know.

I'm looking for other potential sources of the problem from you guys. Could a PCV system with plenty of sludge in the chrome pipe cause a problem like this? Are there other items I can eliminate as the source of the problem before paying big $$$ to have the turbo rebuilt (read "upgraded")?

As a diagnostic measure, I was planning to put a catch can on the car and see if that reduces the smoke. I was also thinking of bumping up my viscosity from 5W-30 since the car has 146,000 miles on it. Maybe a thicker oil (10W-40) will reduce oil consumption. But I really don't want a "band-aid", I'd rather find the culprit than mask it with a heavier weight oil.

Thanks in advance for any insight...

- Frank

1991 Supra Turbo Targa 5spd
Fresh Cylinder Head and Valve Job
Greddy 1.5mm MHG (ARP Studs @ 80 ft-lb)
Custom "Sammydafish" Downpipe/Elbow
Exhaust Wrapped Turbine
K&N FIPK
MSD Ignition Wires
NGK BCPR7ES Copper Plugs
10psi (Wastegate washers)
 

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This makes x4.

You mentioned this was a rebuilt turbo that replaced an earlier one - do you still have the earlier one? Does it work at all? If so, throw it back on there and run it for a day!
 
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You mentioned this was a rebuilt turbo that replaced an earlier one - do you still have the earlier one? Does it work at all? If so, throw it back on there and run it for a day!
Wish I could, but the original turbo is in worse shape than this one...seems a foreign object passed over the compressor blades.:rolleyes:

I will probably have the original sent out for a rebuild, or for an upgrade which apparently doesn't cost much more than the rebuild. Any recommendations on good quality rebuilders? I'm new to this, but I've heard of places like Majestic, Performance Techniques, Turbonetics, and Precision Turbo (to name a few).

- Frank
 
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