BstdPrelude

So a few months ago I was getting alot of white smoke out of the exhaust on my turbo prelude while on the dyno. Compression test came out okay (all cylinders were within 5% of each other). So we rebuilt the turbo and found out it had a bad journal bearing. So after the rebuild, no smoke. Now, 3 months later, im getting this white smoke again under 10-15 psi pulls. No smoke at idle or normal driving under vacuum. No blowby in the catch can but im losing oil somewhere (2 qt in 3 weeks, no puddles under car). Im using 10w40 synthetic oil. Block was rebuilt w low comp pistons, sleeved and bored. My questions are: would a thicker oil, 20w-50 help with the smoke? can it still be a bad ring land if comp test was okay? and ive heard rumors that when shops bore out blocks, they leave a small gap between the ring lands and the sleeves so when the car starts to heat up the ring lands expand and seal. anyone else hear anything like this? Im trying to cover all the bases before I fork out $3k to get new ringlands installed. Thanks in advance

Artifex

You should do a leakdown test, that will tell you if you have engine issues.

Your turbo also might be bad again. Some rebuilders are really terrible; It's possible the seals are gone again. Especially with all the Chinese turbos going around; those things won't last very long.

I'm just throwing out some ideas.

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jimnissan

when you say you did a comp test what is the numbers. if there all within 5% of each other but that 5% is a low number to start then that could be your problem. only a leak down as stated before can tell you whats going on inside.

rayslude

bad turbo is very likely, instead of having it rebuilt again, save up and get a turbo from a reputable source, like Precision.

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jimnissan

I will agree with rayslude on the absoludte need for a good turbo not only will effect the oil consuption but overall engine performance.
Do a leak down test could be a valve issue
if the motor checks out ensure you get a good turbo like Precision.
your post refers to a "bad journal bearing" that you replaced.
What caused this? would be my first question there have been some question about oil presure with some turbos.
also you are using old tech journal bearings are the way of the past.
Im not flaming you dont worry I have journal bearing tourbo on my lude and also have an oil consomption problem, but i know its coming from scratches in the cylinder walls not the turbo. I have had my head off resently for a complete race head and found scratches n the cylinder walls, that conf. my low but not abnormaly low comp test.
this is something i can live with especial since it made 397WHP at 17lbs

BstdPrelude

What size turbo are you running and what rpms do you spool well in? I had the head taken off and rebuilt and im still losing about a qt of 15w50 a week, if i dont run it hard. I just about saved enough for a p28 w neptune to fix my fuel issues and will be possibly investing in an SPA turbo. Also if you dont mind, what size injectors are on your build? Im on 15 psi now and only made 240ish whp depending on dyno.