LVDell

Who said he's "pulling air"?

wdonovan

About time someone didn't reduce this to "not pushing it to limits", "good leakdown numbers", etc. He said his oil pressure drops. That IS a problem. Yes, you need to address that. Some combination of baffles, extra oil, increased head drainbacks, etc. If drainback is sluggish, I would overfill to compensate while at the track. Then with a warm and running engine, you never have an overfill condition except at startup. This is less likely to do damage then dry main bearings. I'd experiment with a half then maybe a quart extra and monitor the gauge. Try to keep yopur eyes on the track too, as to not induce a diferent type of problem.

wdonovan

Big6 said it. "On several turns the oil preassure drops dramatically". I'm thinking he ain't running through these turns at idle. Only other thing to drop pressure is from gulping air.

LVDell

That's quite a bit to infer from his statement. It is imperative to know EXACTLY what the pressure reading was at, tire and suspension setup, as well as engine telemetry. But to turn this into panic mode saying that he needs "this and that" to address this "problem" is ludicrous.

JimB

Bad advice. Overfilling will result in your 996 becoming a mosquito fogger after the first long sweeper.

Mike Murphy

Look, it's really simple, actually. If you've got good oil pressure, and it drops suddenly for any reason, you either have a failing oil pump, a failing bearing, or you're pulling air (cavitation) from the intake side of the pump. If you're pulling air, then you're pushing that air through the bearings, and the bearings will collide with the rod or crank journal. Over time, you'll ruin the bearings. Air compresses about 1000 times easier than a liquid (oil), so you cannot have any air in the oil that is supplied to the main or rod bearings.

This might not produce a problem immediately, but over time, you will have to replace the bearings in the engine or else throw a rod ultimately.

insite

mantis sport has a replacement baffle and spacer setup with a sump extension that adds 1.5qt and solves the oiling issues. they run it on their PCA racer. i think it's around $600 canadian. not sure what that is in 'real' dollars. i think it's like $515 US.

LVDell

last thing we need here is another smart ***. I understand the concept of oil pressure, as do most that have posted to this thread. As I have already stated, we have ZERO telemetry data for his problem. His situation has been addressed with possbile "upgrades" to ease his mind for the track and the associated lateral g's. Beyond that, there is really nothing else to comment on.

wdonovan

LVDell, with all due respect, can you explain the possible causes of oil pressure plummeting on executing high g-force turns? I, like the other poster, can reason only a few possibilities. A bad oil pump, large bearing clearance or huge leak in a main pressure gallery are most but not all. The other clue given us is that this phenomenon occurs only during high lateral g's. By far, the most common reason for loss of pressure during cornering is the oil moving away from the oil pickup. Much less common (but still possible) is so much oil moving into the rotating assembly that it is churned and aerated, giving the same result of air in the oil pump pickup. This possibility is pretty much impossible on a 996 engine because of the crankcase design and pickup position. I don't understand why you won't acknowledge any diagnosis that does not rely on telemetry. If you can suggest some other remote possibilities that do not include air being ingested, some of like would like to consider them. BTW Porsche put baffles around the oil pickup in these engines to combat exactly this type of situation. I speculate they are just not 100% effective on a racetrack.

LVDell

At this point in the thread there is absolutely no reason to continue to SPECULATE as to what the OP experienced without proper data. For example, what EXACTLY is "drastic drop"? We could debate what-ifs until this dead horse is beat, but why?

Mike Murphy

Sorry, I felt the need to elaborate because if a prior post, you said "need not worry." Truth is, it's an issue.

On a slightly different note, something that might be of interest to everyone reading this thread relates to two problems I have seen on a 1965-1990 smallblock Chevy engine with a 4-quart oil pan.

When turning tight corners, the oil pressure would drop dramatically, suddenly and then rise again, indicating oil starvation. This is why one of the major upgrades on these types of engines was a larger and deeper 6,7 or 8 quart oil pan. The oil pickup was deeper and the pan held more oil. Solved that problem, but then there was another, separate problem potentially going on.

When running higher RPMs, the oil pressure would drop slowly and gradually as the crank and rods created windage in the oil pan. The problem was worse the higher the RPM and higher the temperature. Basically, oil was being whipped around and aerated, so the solution here was to install a windage tray below the crank.

Basically, any time you have a drop in oil pressure, it has to do with windage, starvation, excessive heat or improper viscosity.

LVDell

No need to apologize. If anybody does it is me for calling you a smart ***. Apparently we are approaching this from 2 different sides.

However, the truth is, that it is NOT an issue. However, the caveat to that is, unless you are running slicks and have the suspension to take full advantage of that. Not sure why you feel this is an issue. Are you talking in general or specific to the OP?

Mike Murphy

Why? Because I have direct experience with non-Porsche engines having oil starvation issues and I've had to replace bearings because of it. Replacing bearings on a non-Porsche engine can sometimes be quick and easy to do, but on a flat-6, it usually means a total engine rebuild.

insite

from what i understand, it's not an issue on the 3.6L, but IS an issue on the 3.4L and on the 987 boxsters. any truth to this?

on my track car (boxster), sustained high G cornering (>1.0G) will cause some valve chatter that goes away after a few seconds. it's almost like the lifters sag from either starvation or from oil saturated with air. i always attributed this to the pickup point in the car's sump & the sump design; i've seen other boxsters and 996's do this. no logged data to verify pressure drops, just a noticable symptom.

JimB

Dell beat me to it but my question would be, what evidence is there that oil starvation is a problem? I don't think you can take a few examples where the oil pressure gauge dips in corners and use it to come to that conclusion. Not when we've seen hundreds of thousands of 996 track miles without oiling kits with relatively few engine problems.
Jim