79 930 turbo boost trouble
 

I just got back from my first DE at Watkins Glen in my 79 930 turbo....first DE in the turbo as I have driven many times before in my 911SC.
I had a question on several items that bothered me with the car that occurred at the track.
1) The car went thru several quarts of oil at the track yet it does not burn a drop in over 800 miles street driving. Every time I started the car at the beginning of a session it would smoke heavily from the exhaust for about 3 minutes before it would clear up. It would puff at every upshift on the track as well.
My question was is it possible that the oil was getting pulled thru the tank breather into the inlet side of the compressor causing the loss of oil and heavy smoking? I was told to keep the oil level slightly below the minimum mark on the stick to prevent this from happeneing, but I was skeptical to run the oil level below the min mark......OPINIONS on this?
2) I noticed after 3-4 laps once the car was hot, it would hesitate or stumble on acceleration at around 4500-5000rpm. It would then pick up and run again if I eased off a little, but it almost felt like a miss or momentary shut down. What could this be?
3) At the same time as all this was going on I noticed that the oil gage pressure would bounce occasionally, is it possible that I was experiencing the oil foaming issues that plagued early 911SC before they changed the venturi pick-up on the oil pump, DOES THE 79 930 TURBO HAVE THIS ISSUE? IS THERE AN UPGRADE KIT TO SOLVE THIS?

Here are a couple opinions based on my ownership of a 79 930.

Oil consuption at the track is always more than the street. Mine used a quart every 250 or 300 miles of track use. On the street, it was close to 800 miles.

I've never heard to put the oil level just below min mark. Since this is an air and oil cooled motor, this makes no sense. I keep mine half-way between min and max.

The smoking sounds like either valve guides or rings. You need to perform a leakdown to find out where it is leaking. Puffs of smoke just after start is fairly normal, but not after each shift.

The hesitation sounds like a lean spot.

Some oil gauges bounce - this is more a rough estimate of oil level and should never be used to measure the level. Use it as a guide, but always verify with the dipstick.

It's true that some 911s and 930s are sensitive to overly full oil. Just last week I saw an 84 Carrera that smoked through the exhaust pipe like a mosquito fogger. The owner had just added oil, and the level was near the top mark. He dropped it by 2 quarts, which brought the level closer to the bottom mark, and the smoke disappeared. He was obviously getting oil from the breather into the intake. I've never heard of running the oil level below the bottom mark (though for street use you may get away with it), but I like to see it on the minus side of the middle for all driving.

Just wanted to clarify that the oil pressure gage bounced, not the oil level gage. I do not use the oil level gage for anything other than an ruff estimate....I always use the stick to measure.
-----The real question I had was if anyone ever heard of the turbo engine having the same oil starvation trouble the 79 911SC had before the redesign of the oil pump pick up strainer?
IS IT POSSIBLE THAT I AM NOT GETTING THE CASE EMPTY AND AM FOAMING THE OIL INSIDE THE CASE VIA THE CRANKSHAFT BEATING IT UP. THIS WOULD CAUSE THE POWER LOSS AND OIL BLOWBY INTO THE INTAKE MANIFOLD.
----ANY THOUGHTS OR EXPERIENCE?

I'm not aware of any oil pickup or foaming issues with the 930 engine, as long as the oil level is correct, but others may have a different take. From my experience, the 930 oiling system is very robust. My sense is that the "bouncing" of the oil pressure gauge, if it was rapid and during relatively steady-state operation, was due to an electrical anomaly and is not reflective of your actual oil pressure. If you saw a rapid drop in oil pressure during some repeatable maneuver, such as in hard corners or when the throttle closes during a shift, then you may have a real issue to look into. If you're concerned about the internals of your engine, you might drain and inspect or test your oil. Cutting the filter open can reveal any damage to bearings.

I know this isn't really an issue here, but since you brought it up: Remember that the oil level gauge is only accurate at idle with the engine warm (and shouldn't be trusted even then). It should be treated like a remotely viewable dipstick, though not as accurate.

I'm not sure about your power loss problem. I think it's very unlikely that it has anything to do with the oiling system. It could be a lot of things, but is most likely in the fuel, ignition, or vacuum/boost category. Sounds like it could be figured out if you put it on a dyno and monitored the right things, including ignition output and air fuel ratio. If you're driving your car on the track, it's always good to run it up on the dyno anyway, especially to make sure your air/fuel ratio is within bounds.

Regarding the oil consumption and smoking: you may well need to have your turbocharger rebuilt. the symptoms you describe (smoking at startup and during shifts) are common for a turbo with worn out shaft seals. I'd discuss your symptoms with a Porsche turbocharger specialist, such as Kevin at ultimatemotorwerks.com

I ran my 87 930 for many. many track days and never had any type of oil foaming issues. The only time it smoked is when the piston rings broke on cyl 1-3 because of clogged fuel injectors.

A compression and leakdown test would tell you if there are engine problems. If the tests are good then look at the turbocharger.