Date: Wed, 27 Mar 2002 13:29:02 -0600
Reply-To: Chris Mills <scmills@TNTECH.EDU>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Chris Mills <scmills@TNTECH.EDU>
Subject: Re: Windage Trays and Lubrication Issues (Air and Water Cooled)
In-Reply-To: <5b.253a57c5.29d2d1f7@aol.com>
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Frank, what about the splash lube of the cylinder walls?
Wouldn't the windage tray reduce the lube of items like this?
Learning lots. Good day.
At 02:42 AM 3/27/02 -0500, you wrote:
>Stan and Matthew,
>
>It is really quite frustrating that modifications such as K&N air cleaner
>substitutions are pitched to the masses and quick and cheap power increases
>(actual power increase is around 0.05 to 0.12% in an otherwise unmodified car
>- difficult to measure!) while addition of a windage tray can return 5 to 10
>"free" hp. I say free because no aspect of the engine combustion dynamics or
>output stresses are increased. In fact internal stresses are actually
>decreased. Your comments (quoted below) are essentially correct, but there is
>even more to the story.
>
>The oil in the sump and where it goes are critical issues for power output,
>fuel economy and engine longevity. As Matthew points out, the crankshaft acts
>as a gigantic egg beater. At very low rpm, the crankshaft is just agitating
>the oil as it throws it around. But as early as 1500 rpm (depends on the
>viscosity and film shear strength - which are in turn functions of
>temperature and parent oil stocks) the oil wraps around the crankshaft much
>like cotton candy on a spool. The crank can become a liquid encapsulated
>object with slots cut out for the connecting rods and the main journal webs.
>With higher rpm the oil is so strongly aerated that it becomes a milky foam.
>This oil foam now becomes hard to pump with the typical gear pump, oil
>pressure drops and crankcase pressure soars. Oil is thrashing on the cylinder
>barrels, undersides of pistons - you name it .... and the reserve level
>accessible to your oil pump pickup falls. Add moderate braking or 0.5G turns
>and there is no oil under the pickup. Prescription for disaster or at least
>short lifetime between bearing replacements.
>
>There are several solutions (all mostly developed in racing, since these
>effects get worse with higher rpm and temperature).
>
>1. The best solution is a dry sump oil system. Here an external pump with
>high capacity (actually organized into several pumping stages and externally
>driven) is used to evacuate all the oil from the oil pan as it falls down
>from feeding the galley, pistons and mains. The oil is removed from several
>areas in a very small volume pan and pumped into a holding reservoir. The oil
>is then degassed and pumped back into the engine. Dry sump engines also run a
>higher quantity of oil (often 10 quarts or more). Solution good but
>expensive. A Dry sump system for the VW I4 engines runs about $1400, and
>costs about 10 hp (because of the work required to drive the multiple high
>capacity pumps).
>
>2. Carefully adjust the oil level. Cheap, can work, could be dangerous. If
>you keep the mean oil level below the crankshaft arc, and above the oil
>pickup tube inlet, and refrain from adventure, you can minimize the whipping
>whirlpool. It will still be there, but less oil will be captured. Careful
>measurement of oil temperature as a function of the static oil dipstick level
>will show the onset of this problem. Unfortunately, that onset is far below
>the factory recommended level (often 1 to 1.5 quarts below). The corollary
>here is that if you overfill (by as little as 0.5 quarts), you can seriously
>drop oil pressure, increase oil temperature (the aerated oil acts as a
>thermal insulator and minimizes the thermal exchange in the oil cooler) and
>blow out the crankcase seal with excess pressure.
>
>3. Add a windage tray. A good windage tray provides a barrier between the oil
>in the sump and the crankshaft lobes minimizing the amount of oil that can be
>whipped up by that flying crank. This eliminates the work done by the engine
>in overcoming the frictional mass and drag represented by the sheeting oil
>(worth about 5 hp in the VW crankcase. In addition, oil pressure will be
>higher, temperature lower and lubricity higher because of the lower level of
>dissolved gas. However, there are still sheets of oil clinging to the crank.
>In a good windage tray, like the VW one for the water-cooled inline 4
>cylinder engines, a set of cutters (or scrapers) are formed into the tray and
>run at a gap of about 1 mm from the crank lobes. The opening of these
>scrapers is oriented so crank rotation is towards the scraper mouth. These
>scrapers literally scrape the excess oil sheets from the crank lobes just
>like a clay potter shapes his work on the rotating table.
>
>3A. Many professional engine builders find that the functions of windage tray
>and oil scraper should be separated and they use thick strong steel scrapers
>to run with a 0.010 inch clearance to the crank. These are followed by a
>windage tray with the extensive use of screen over open return paths. This
>screen deaerates the oil before it drops back to the holding sump.
>
>But this still doesn't treat the oil sloshing caused by starts, stops and
>turns. With a boxer engine, these issues can become critical as large amounts
>of oil can go to the pushrod tubes and the cylinder barrels.
>
>4. This is handled by the use of baffles in the oil pan and, in some designs,
>by trap doors which protect the area around the oil pickup tube entrance.
>
>So, the best solution for the I4 crowd (Vanagons) with the engine mounted at
>the Golf angle is to buy the windage tray (I've posted part numbers and
>prices in the archives - VW dealer is around $90, but internet prices go as
>low as $29). It includes a reusable rubber gasket. You will need longer
>bolts. 1 hour operation including cleanup. I would also add a baffled oil pan
>by Shrick. Aluminum and around $250+.
>
>For the I4 crowd at the diesel mounting angle, buy the windage tray (note
>there are benefits here for gas, diesel or turbo). Your diesel pan has two
>small baffles to stop front to back or back to front oil movement. I find
>this inadequate. As part of my turbo Audi 3A I am building a modified oil pan
>with an internal hexagonal core. The core has 1 cm open zones and is 2 cm
>thick. I am mounting it 1 cm above the pan floor with openings for a revised
>oil pump pickup. On top of the hex core, I have mounted a 1 mm. open mesh. In
>laboratory tests, the oil moves freely under the core to replenish the oil
>pickup, but it doesn't slosh since its constrained within the hex cores
>vertically. I have also prepared oil level sensors for the pan and will
>calibrate the optimal oil level, probably reducing capacity in the pan by one
>quart. I'm also adding the dual oil filter system with external
>thermostatically controlled oil cooler from the Audi 5000T. Also keeping the
>VW coolant to oil heat exchanger. I will make plans and drawings available
>when I'm done for anyone who wants to fabricate their own.
>
>For the air cooled crowd, the installation of the windage tray is harder
>since it involves a case split. But I would add the 914 part at the first
>opportunity. But there is another nice trick. (probably wont work with the
>2.0 Air Cooleds but a clever man with time (is there anything else on the
>Texan landscape???) One could add a 2.5 quart sump extension from the type 1
>engine placing the oil pickup down in that extended sump. This will do two
>things at least. First, it will reduce the engine case clearance by 3 inches.
>I think this is now the lowest engine point, but only about a 1 inch
>reduction in ground clearance. Second, If you keep the same amount of oil in
>the crankcase, this will drastically drop the oil level (helps the windage
>tray) and the small central fill will eliminate sloshing issues.
>
>Just one more point. You can see it all! As I reported some time ago, I have
>placed a borescope in the crankcase and watched all hell break loose in the
>RV engine I'm currently using. It is my intention to video tape the results
>as I calibrate optimal oil levels on the Turbo 3A, and "field test" the
>baffled diesel pan.
>
>Sorry for the length, got carried away again.
>
>Frank Grunthaner
>
>
>On Tue, 26 Mar 2002 06:57:28 -0500 "G. Matthew Bulley"
><gmbulley@BULLEY-HEWLETT.COM> writes:
> > I've wondered the same thing. Having ripped apart and re-built a
> > bunch of 914/912e motor, I was a little shocked to see no windage tray in
> > the vanagon.
> > My understanding of the function of the tray though went beyond just
> > oil "sloshing" around, but was more to prevent the upper surface of the
> > oil from forming "fans" of oil that followed the crank throws.
> > These fans not only slowed the crank (if ever so slightly) but also
> > created tiny foam bubbles in the oil, which essentially dropped the
> > oil pressure/viscosity at the bearings. Why VW would eliminate it, one
> > may never know. >>
>
>In a message dated 3/26/02 6:35:37 AM, wilden1@JUNO.COM writes:
>
><< I would go along with your "fans" theory.
>There is a hell of a lot of things going on in the internal engine
>chamber that we don't even conceive of and will never be privileged to
>see.
>
>Stan Wilder
Chris M. <Busbodger - "TEAM SLOWPOKE">
Cookeville, Tennessee
ICQ# 5944649
scm9985@tntech.edu
'78 VW Westfalia (67 HP -> that is...67 Hamster Power)
'65 Beetle - Type IV powered
'99 CR-V AWD station wagon
'81 CB900 Custom moto-chickle
2.5 Corvair engines for my Trans-vair Conversion
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