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Date:         Wed, 27 Jun 2001 22:36:26 EDT
Reply-To:     FrankGRUN@AOL.COM
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Frank Grunthaner <FrankGRUN@AOL.COM>
Subject:      Oil Level Issue and Comment
Content-Type: text/plain; charset="US-ASCII"

Several posters are correct in referring to the problem of aeration by the crank and aeration of the oil. The impact (as others have mentioned and examples cited by Smokey Yurnick) is severe in a great loss in cooling ability and a viscosity reduction. In addition, the gear type oil pump can lose pump pressure because of the breakup of the side wall seal (gear-to-gear and gear-to-pump body) with the excess gas included in the aerated oil. This effect is universal for overfilled pans and is exaggerated with immersed cam gears.

The windage tray and a well controlled oil level (or a dry sump) can eliminate the problem and return lost horsepower/torque which had been expended in whipping up the oil. This effect is also much more significant with classical paraffin-based oils and worst for single viscosity grades.

I raise all of this again because I have literally seen the effect and am trying to generate a video. In my I-4 conversion, laying over at 55 degrees, the oil level in the oil pan is closer to the crank than in the normal mount angle (with the regular oil pan). When using a I-4 engine from a previous transverse installation, there is the problem of the oil dipstick tube. In my case, I cut it off and sealed it with PCV tubing. Later, when I added the windage tray to my RV engine, I was concerned as to the proper fill level.

To wit, I took an Olympus Borescope (about 1/8 inch diameter, including light and image conduit) and put it through the dipstick port (details in the archives). This let me image the oil level statically and let me watch all hell break loose when the engine was running. Interestingly, at the point about halfway between the full and add marks on the vanagon diesel dipstick, the oil level just came up to the base of the windage tray, statically.

When the engine was running at idle speeds, clear oil was spraying/pouring from the windage tray slots. As the engine revved up, the oil seemed to bias up on the side in the direction of crankshaft rotation. By 2,000, it was just sheeting and the oil level had dropped by about 1 cm or so. When I added the rest of the oil (about 0.5 quart) the oil became cloudy but dark. Lots of froth, and oil everywhere with strong jets of oil coming out of the windage tray baffles. the Oil level was now burping - oscillating up and down - maybe rapid sloshing is the best term (rapid waves going front to back and side to side). When I overfilled by 0.5 quarts, all hell broke loose. The oil now foamed, it came from everywhere as if in a hurricane. No well defined streamers from the windage tray, and the color was now gray or nearly white. The level in the sump was now very difficult to judge, but seemed several cm. higher than before. I had been using the edge of the Al oil pan for a reference, but I could no longer see it. In addition, the pressure in the pan increased and began to squirt oil out of the dipstick hole and everywhere.

Here the experiment was truncated by a few terse and well chosen words and stock phrases from SWMBO. I had not setup to tape the event, so I have no images to show. My son and I intend to duplicate the event as we work out the oil return issue on the Audi turbo project. This time we will tape, and cover the rear of the Westfalia with plastic. (What a mess!)

Anyway, the actual oil level is a big deal. Although I would never suggest the engineers got something like this wrong, I will note that crankcase pressure is a major part of this problem. Older engines with excessive blowby will show the aeration onset earlier. Again this effect is exaggerated by the boxer configuration. So wrong oil, high blowby (bad rings), high temperatures (high working load, high ambient) and a clogged ventilation system will all conspire to enhance the effect.

Oh well, I'm quiet, hope this helps clarify the problem slightly,

Frank Grunthaner


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