Date: Tue, 17 Dec 2002 21:56:55 -0600
Reply-To: Stan Wilder <wilden1@JUNO.COM>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Stan Wilder <wilden1@JUNO.COM>
Subject: Of Interest to Air Coolers
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From: Nigel A. Skeet
To: Type 2 Listees
Date: Friday, 13th December 2002 !
Reply to: naskeet@hotmail.com OR naskeet@yahoo.co.uk
INHIBITING OIL SURGE IN VW FLAT-FOUR ENGINES (AN
UNDESIRABLE AND LITTLE RECOGNISED, COMMON PHENOMENON),
BY MEANS OF A WINDAGE TRAY, 'WINDAGE-STYLE' PUSHROD
TUBES AND/OR OIL-SUMP EXTENSION
Compiled & Written by Nigel A. Skeet
Although unfamiliar to most VW owners, oil surge is a relatively common
phenomenon, to which the VW flat-four engine is particularly prone (see
Peter Noad, "Pace Notes", VW Motoring, November 1997, pp40~41); resulting
from centrifugal effects, which cause the oil to surge out of the
crankcase, through the pushrod tubes and into the valve rocker box
covers, under conditions of 'high-speed' cornering.
This leads to there being inadequate oil in the crankcase, such that the
oil pump pick-up tube is not fully immersed and so sucks up a mixture of
oil and air, which does not provide adequate lubrication; yet another
reason to ensure that the oil level is always at the maximum mark.
'High speed', is a relative term and in the case of the flat-four engine,
oil surge can occur, even under normal driving conditions with a VW 1200
Beetle, as Peter Noad personally discovered. One British owner, of a
non-standard VW Beetle, with 1641cc engine, has observed exceedingly low
oil pressure (illumination of the oil-pressure warning light, served by
the standard 0730 1 0715 BAR oil-pressure switch), as a result of oil
surge, when accelerating and/or cornering.
Although not in the same class as a Porsche 911, the 1968~79 VW Type 2,
is a remarkably agile vehicle (even without after-market, front & rear
anti-roll bars!), when skillfully driven, so it is probably equally prone
to oil surge, as the VW Beetles. With the aid of an oil-pressure gauge or
high-pressure, oil-pressure switch, one has the option of changing one's
driving style in order to avoid oil surge or alternatively, to combat it,
by implementing one or more of the recognised engine modifications. These
modifications are a supplementary deep sump, a set of 'windage style'
pushrod tubes and an oil windage tray.
As the name suggests, the principal purpose of the windage tray, is to
prevent windage. Windage is the process whereby air is entrained into the
oil, owing to the rotation of the crankshaft and connecting rods, plus to
a lesser extent the camshaft; the air being dragged around by the moving
surfaces owing to viscous friction. If by chance the oil-sump has been
over-filled, then in extreme cases, the oil is whipped-up into a frothy
foam. This not only radically reduces the lubricating properties of the
oil, but
also increases oil temperature and wastes power, hence increasing fuel
consumption.
Being a horizontal baffle, which is positioned below the camshaft and
just above the surface of the oil, when filled to the maximum, a windage
tray also serves the secondary purpose, of limiting the extent to which
the oil level can rise at one end of the crankcase (i.e. sump) and fall
at the other, so reducing the effects of surge. The windage tray should
cover the entire area of the oil reservoir and its edges be a tight fit,
to the internal contours of the crankcase.
To allow previously circulated oil, to drain back into the crankcase, it
should have a limited area of slots or holes, close to the longitudinal,
central axis.
Where practical, these slots or holes should ideally have down-turned
flanges or spigots In conventional engines with a separate bolt-on oil
sump, oil would be further inhibited from sloshing to and fro, by
incorporating vertical baffles, arranged longitudinally and transversely.
Ideally, the baffles should incorporate one-way valves, to facilitate a
rapid return of the oil to the pre-surge level. For a VW flat-four
engine, any such vertical baffles, would have to form part of the windage
tray. Home-made and proprietory aftermarket windage trays are discussed
by Peter Noad, Bill Fisher and A. Graham Bell. Bill Fisher observed that
all but the home-made windage trays he had seen (i.e. prior to his book
being published in 1970), interfered with the camshaft.
An oil windage tray, with neoprene rubber, edge-sealing strips, is a
standard fitment in the VW 411LE & 412LE, plus the VW-Porsche 914-4
engine crankcases. These windage trays can be retro-fitted to the 1972~83
VW 17/18/2000 Type 2 engine, as I have done with my 1911cc, VW 17/1800
Type 2 & 4 hybrid engine; which I photographed for inclusion in my
technical book & magazine articles.
If a windage tray is being fitted to a VW Type 4 engine, equipped with
carburettors and associated mechanical fuel pump, provision must be made,
for oil lubricating the fuel-pump pushrod, to escape back into the
crankcase. Tom Wilson's book (see pages 72, 74 & 123), both documents and
illustrates the windage tray, but no mention is made of it, in the Haynes
manual for the VW 411 & 412 and so far, I have not seen it mentioned in
any other books!
A few years ago, whilst on a desk-top publishing course, I prepared an
illustrated sheet, showing my VW 411LE windage tray, positioned in one
half of the crankcase, together with the camshaft gear, which had been
modified, by cutting two 0.090 inch wide grooves, to the depth of the
gear teeth. Regretably, I neither possess an Internet website (my local
public library, is my only access to Internet & e-mail facilities!) nor
have any present means of scanning, my illustrated sheet or photographs,
to send as e-mail attachments.
However, I can send photocopies by snail mail, if desired.
According to Bill Fisher's book (see pages 99 & 107), this grooving
modification, is attributable to Gene Berg (that icon of Southern
Californian, VW air-cooled engine tuning!), which is said to reduce the
internal pressure and excessive oil mist (hence reducing crankcase
breather emissions!) inside the crankcase, plus recovering a little of
the power, used to squeeze the oil between the gear teeth.
Keith Seume advocates substituting windage style pushrod tubes, which
also inhibit oil surge. These are characterised by a longer section of
tube, which extends further into the crankcase. Bill Fisher suggests
supplementing the standard pushrod tubes, of the VW 12/13/15/16000 Type
1, 2 & 3 engines, with inch (i.e 19 mm) long sections of pushrod tube, to
obtain the advantages of the windage style pushrod tubes. One end of the
short tube section, is peened over to form a lip, so that it is held in
position by the pushrod tube seal. He states that this simple
modification, is commonly used in Formula Vees
Priced at US$ 39799 in October 1997, windage style pushrod tubes (stock
No. 46-8531), for the VW 12/13/15/16000 Type 1, 2 & 3 engines, made from
stainless steel (a useful bonus, as the original factory fitted
components are prone to rusting) are available by mail-order from Car
Custom Inc., in California, USA. I am not aware of any off-the-shelf,
windage style pushrod tubes, for the VW Type 4 engines and owing to the
form of the pushrod tube seals and crankcase design, it would not be
practical to supplement the standard pushrod tubes, as suggested in Bill
Fisher's book (see page 98). However, it might be possible to extend the
standard VW Type 4 pushrod tubes, by welding or brazing on, an extra
length of tube.
Fitting a supplementary oil-sump beneath the engine crankcase, in
conjunction with an extended oil pick-up tube, overcomes the problem of
inadequate oil supply, associated with oil surge. Although oil surge can
still occur within the crankcase, the oil does not surge out of the
supplementary sump and hence the extended oil pick-up tube remains fully
immersed in the oil.
Supplementary oil-sumps, of 175, 375 & 470 US quart capacities (note 1 US
quart = 079464 litres) are available for VW 12/13/15/1600 Type 1, 2 & 3
engines, from Gene Berg (reputedly pioneered by him) Unique Supply, So.
Cal. Imports, Kustom 1 Warehouse, Performance Express and other
suppliers; including some in Great Britain. I believe there is also a
SCAT branded, 175 US quart capacity, supplementary oil-sump available,
for the VW 17/18/2000 Type 2 & 4 engines, but from what sources, I don't
know! If anyone knows, please tell me?
REFERENCES
Peter Noad, "Pace Notes", VW Motoring, November 1997, pp40~41
Tom Wilson, "How to Rebuild Your Volkswagen Air-cooled Engine", HP Books,
1987, pp72, 74 & 123.
Bill Fisher, "How to Hot Rod Volkswagen Engines", HP Books, 1970, pp96~99
& 107.
Keith Seume, "Aircooled VW Engine Interchange Manual the Users' Guide to
Original & Aftermarket Parts for
Tuning", Bay View Books, 1996.
A. Graham Bell, "Performance Tuning in Theory & Practice", Haynes
Publishing, 1981, pp191~192.
J. H. Haynes & K. F. Kinchin, "VW 411 & 412, Owners' Workshop Manual;
1679cc & 1795cc; 1968 to 1975",
Haynes Publishing, 1988.
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