I have heard this right left rationale mentioned before... What is the >foundation for that effect. The pan and pickup are absolutely symmetrical. What difference would it make whether it was a right or left hander. Is it that the crank rotation makes the oil climb higher on one wall or the other? Curious...

It's left turns. I know some of you have heard about Louie Ott's "holy valve cover". He took a valve cover, cut a hole in it, and fitted a Plexiglas window over it. He made a bracket to mount a video camera and spot light, to be able top look through the Plexiglas window. He then had an instructor drive the car on the track while he observed and filmed the oil flow in the cam area of the head. The oil flow was nice and smooth during acceleration, braking, and right turns. As soon as the car would go into a left turn, the oil flow would turn to foam. This was with a GTS baffle and a street version of the Accusump on his GT. The 2/6 rod bearings have since been destroyed, and he's currently doing an engine rebuild.

The pump pickup and pan are symmetrical, but left turns cause more of a problem due to the direction of engine rotation and those ribs on the floor of that flat rear section of the oil pan. Those raised ribs on that section of the pan are there to help direct oil forwards, back into the sump. The crank and rods throw the oil in the same direction as they're moving, and the angled ribs help to turn that sideways movement of the oil forwards. Those ribs also do a surprisingly good job of moving that oil to the right side of the pan. During a left hand turn with high G forces, the oil in the sump is pushed against the right side of the pan, the ribs are moving oil to that side, and the windage from the rotating assembly is also helping to hold the oil on that side.

With the oil piled up on that one side, it doesn't take much before it runs out of the sump onto that rear flat portion of the pan. In some experimenting I did with my oil pan when I had it off, fluid in the sump would run up onto that rear flat portion of the pan before the pump pickup was in any danger of being uncovered and sucking air. The GTS baffle made no real measurable difference in the amount the pan could be tilted before the fluid ran out of the sump. After looking at it, and giving it some thought, I'm convinced that the baffle was put in the GTS due to increased windage problems from the longer stroke compared to the 5 liter engines. The crankcase breather was also changed on the GTS to help keep as much oil from being sucked out along with the blowby gasses, which would also indicate a change due to increased windage.

The rotating assembly comes surprisingly close to that flat rear floor of the oil pan. It's so close that those two bumps in that section of the pan are actually clearance for bolts holding on the lower engine cradle. Once the oil runs up onto that flat rear portion of the pan, it wouldn't take much before the rotating assembly whips it into foam, the same way a blender makes a milkshake. This effect would occur the most when there was the most oil on that rear portion of the pan, and the rotating assembly was spinning at the fastest speed. High RPM left hand turns. On my pan I made a full baffle for the sump. Testing compared to either no baffle or the GTS baffle showed that the pan could be tilted a significant amount more before the oil would come out of the sump area with the full baffle.

Mike Schmidt
'88 928S4 Auto Black/Black "PORSCHE" cloth


Interesting. Then the oil (in whatever state it's in) comes into the main galley across from the second main bearing...the one feeding #2/#6. Foamed oil is thinner, and that's the "path of least resistance." Which concentrates the foamed oil on those. Then the oiling passages in the crank accentuate the problem by having the oil fight centrifugal forces (especially in the 4.7L, 5.0L and 5.4L) engines...as the engine revs up, the five bar oil pressure is "offsetting" less and less. The low revs of street driving provide no challenge in this, so no problem...in that usage. Just a warning for you. There have been drysumped "stock-crank" engines (so there could be very little foamed oil, as you describe) that still have failed, with what I call "944 disease." So while your sump modifications may have improved things...I doubt you're 100% Out of the Woods yet on this problem (for track use.) All my experience tells me that the crank has to be dealt with too. Thought everybody needed to know that, and thanks for sharing! Vroommm.... Kim



Good discussion.

Very true... but, the 4.5L isn't safe either if revs and Gs take the game to the point where air is entrained in the pumped oil and the oil in the crank drilling hydrolocks. Crank drilling from all that have had failures imply is mandatory for higher shift points. And feeding good oil is necessary to counteract Gs. That's why the dry sump is so safe. Because the oil is pumped from a deep reservoir where the fed oil has had a chance to settle and the pickup is near impossible to uncover. The Accusump buys you 17 seconds or something like that of the same effect.

In my Kawasaki days engines that reved to 14,000 rpm were not uncommon.
Custom design of windage trays that stripped the oil from the crank assembly and sheeted it out before letting it get to the sump were common. Motorcycles were never dry sumped in those days. Same approach could be applied to the guts of the 928 engine.

And yes, the modified main bearing is where you said. My bad. Very cool to see that stuff when it is all apart on the bench. The guts of the Hallet Handgrenade were a very graphic example of what not to do (sorry Dave). So why couldn't an industrious person just plain cut or stuff a pan to  eliminate the sump and then use the cooler lines to run a tall narrow external tank with a clunk pickup? The cooler could be kept or deleted depending on how much cooling the tank provided. Poor mans dry sump. That and drill the crank and install the modified bearings on the rebuild and you got it. Peace of mind. Couldn't be much more than an Accusump setup.



Interesting technical experiment you're suggesting. There was this Group H racing 928S4 that was driven by Roland Kussmaul (Porsche factory test driver) a decade ago. Called it DAS BULLE! I figured with his factory connection that any "inside dope" would get applied. They junked the intake manifold, of course! I sent the German story (translated by Andial for us 928 folks in Minnesota) about it to Michael, a week ago. Just what he needs...more work... fun to have it up on a website? They refer to a lot of fiddling with the oil pan, and having it almost as good as a dry sump. Knowing the details more would matter. They also referred to a video where this, and more, could be seen! Maybe somebody with good German could inquire about trying to get this video? Michael has their business & private phone numbers. We are back to Doing the Work. The I-Net isn't going to be just a place to come and "get" something, as in any community, somebody has to put it "in." Who will do this work, this time? Your community is calling.... Kim


The question of oil pump volume .... " mounted on the left front corner of the engine had a capacity ..... sixty five liters per minute at the Porsche peak power of 5250 rpm" page 840 , Porsche Excellence Was Expected by Karl Ludvigsen . So just for grins lets say 1 liter per second anyone care to guess how long the pressurized two or three quarts of oil in an accusump maintains oil pressure ? It is also worth noting that only the first drops of oil out of an accusump are at "full pressure" ; half empty and the pressure should be way down , the last few drops are literally drops , little pressure at all . If using a stock crankshaft which many believe needs high pressure at high RPM to overcome " centrifugal force " to feed oil to #2 and #6 rod bearings , only the first bit of high pressure oil from the accusump would seem to have the requisite pressure . Somehow to me it almost seems that the oil inside the accusump must be Super Oil , smart enough to jump in at just the right moment and save the day !! The care and feeding of an accusump including something as simple as using the dipstick to determine how much oil is in the engine is not so easy . Since the accusump is an accumulator (similar to the fuel accumulator used on CIS cars) but uses pressurized air as a spring . The pressure of the oil in the accumulator and therefore volume of oil captured when you close the valve on the end varies greatly depending on what the oil pressure is in the engine . Hot engine after a race session engine at idle speed there is little oil in
the accumulator , shut it off ( accumulator valve closes ) . Wait a couple minutes and pull the dip stick and the oil is above the full line . So you think about draining some oil but happen to start the engine rev it to 3,000 shut it off check the dipstick and now it is just right !! , the next morning you start the engine for a minute and shut it off check the oil and now it is LOW . When the engine was cold it may have been making 9 bar of oil pressure and the accumulator is now full of oil ! If you happen to add oil at this point in time , when you do hit the track and heat up the oil , pressures drop and you are part of the mosquito abatement program as the oil level in the sump gets high , too high . I do not think using an accumulator can hurt anything and it may help but the real solution is to dry sump the engine ( just like every air cooled 911 engine has always been since 1965 ). And if spinning it much over 6,000 RPM the crank needs to be drilled like a Chevy or it is only a matter of time (Kim Crumb as I recall circulated a memorandum about 10-11 years ago indicating that after 10 hours of drivers education people were having rod bearing failure ). I was able to spin the bearings out in about 15 minutes several years ago .

Jim Bailey
928 International