david fracolli

The turbo is a TO4B. One of the reasons I asked is that it takes about 10 minutes of driving before the car starts to smoke on boost. the syptoms are that the after the 10 minutes if you build any type of boost the car spews oil smoke out of the exhaust. As soon as you let off the throttle though the smoke stops. Then if you give it any gas at all it bellows out a huge cloud of oil smoke for about 5 seconds.

fast951

It appears that the oil smoke is NOT under vacuum (also NOT under low exhaust pressure). If the spark plugs are not oily, your turbo is the prime suspect. Now, is it a bad turbo or something else is causing this?
A high crankcase pressure (or incorrectly vented crankcase) will cause bad oil drainage out of the turbo, and it'll flood. You will see the il on the front of the turbo..
Based on your description, the turbo is on its way out. Make sure you eliminate all other possibilities before removing the turbo.

Some one in an earlier post stated that Vitesse uses a restrictor in the oil feed line. This is not true, we do lots of work internally to the center section so it lives in the 951.

kasturbo

When you say incorrectly vented crankcase, are you reffering to one that is vented and not redirected back into the intake track?

fast951

That's one way not to have a properly vented 951 crankcase.

kasturbo

Any other ways that you would like to explain?

Laust Pedersen

John, it apparently can be difficult to fully wake up on a Sunday morning

huh?


and one more huh?


Bingo, that sounds more like it.

Let me try again to explain, this time with a picture of a TO4 turbocharger form Hugh MacInnes book (1984). This is a fairly common and still used design of a center section with journal bearings, but again I do not know the details of SFR’s stage 1 turbo.

The oil enters under pressure from the top and is directed in parallel (same entry pressure) to each of the three bearings (two radial and one thrust bearing). The thrust bearing has a few small through holes that ensures lubrication on both sides. The floating radial bearings are rotating at about half the shaft speed and have radial holes in the center feeding the inner oil film. The oil pressure has to overcome the centrifugal forces in these holes. The oil flow is restricted by the (parallel connection of) all the oil films in these three bearings.

The dynamic (shaft) seals are typically small piston rings (two on the turbine and one on compressor side for the KKK) which are not in the direct path of the oil and is on the inside exposed to the same pressure as the drainage hole, which in turn has the same pressure as the crankcase.

If the crankcase pressure exceeds the boost or exhaust back-pressure, there will be a net flow from the inside of the center section through the dynamic seals to either or both the intake or/and exhaust. Since there is a lot of oil on the inner walls of the center section, oil will be pushed out as well.
If the crankcase pressure exceeds the inlet oil pressure, it will simply prevent the turbo and any other internal bearing from being oiled (except very slightly from the oil mist in the crankcase), an unlikely, but not impossible scenario.

For this and many other reasons, low leak-down numbers are worth fighting for.

Laust

fast951

Laust, I'm glad someone is awake (not me LOL). I typed the opposite of what I was thinking, added the "NOT" and now it should make sense...

david fracolli

Well guys, thanks for all the cooments but I am pretty sure that the seals in the turbo are now shot! I took the car to work today and while cruising down the freeway at about 60mph all of a sudden a cloud of blue smoke came out of the exhaust. About 15 seconds later the car started smoking like crazy! Now the car bellows oil smoke even at idle and is actually blowing oil out of the exhaust pipe. Also there is oil smoke pouring out of the cold side of the turbo.
To say I am not happy would be an understatement as I bought the turbo brand new and it did not even last 500 miles! Went through over a 1/2 quart of oil in just the 15 miles to get home!

david fracolli

By the the way, the car runs fine and the plugs look great!

kasturbo

Do you have the AOS routed to the stock location or to a catch can?

david fracolli

Right now it is plumbed to the stock location because when I ran a catch can it really made no difference.

Mike Murcia

What do you mean by this? Is there oil smoke being blown into the IC pipe out of the compressor housing, or is there just smoke just coming from the compressor housing area?

david fracolli

The smoke is coming out of the compressor housing near where it mounts to the hot side.

david fracolli

Anyone want a slightly used turbo? Less than 700 miles and if you are lucky you might get 50 miles to the quart.

Crazy Eddie

David
Isn't there a warranty on this turbo ??
Regards
Ed