AND LITTLE RECOGNISED, COMMON PHENOMENON
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, Pages 40~41); 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 owner, of a non-standard VW Beetle, with 1641 cc engine, has observed exceedingly low oil pressure (illumination of the oil-pressure warning light, served by the standard 0•30 ± 0•15 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.
Oil windage tray, for VW 12/13/15/1600 Type 1, 2 & 3 engines:
http://www.scatvw.com/OilPumps.htm
An oil windage tray, with neoprene rubber, edge-sealing strips, is a standard fitment in the VW 411LE & 412LE, plus the VW-Porsche 914 engine crankcases. These windage trays can be retro-fitted to the 1972~83 VW 17/18/2000 Type 2 engine, as I have done (illustrated in the photographs) with my 1911 cm³ displacement, VW 17/1800 Type 2 & 4 hybrid engine.
Modified camshaft drive-gear and original factory-fitted windage tray (edge-sealing strips not shown), in a WO-Series VW Type 4 engine, originating from a British specification, 1971 VW 411LE
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 which lubricates 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 seen no mention of it, in any other books!
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 12/13/15/1600 Type 1, 2 & 3 engines, with ¾ 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$ 39•99 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) were, and might still be, 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 by Bill Fisher. 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 1•5, 3•5 & 4•0 US quart capacities (i.e. 1•4, 3•3 & 3•8 litres respectively; noting that 1 US quart = 0•9464 litres) are available for VW 12/13/15/1600 Type 1, 2 & 3 engines, from Gene Berg (reputedly pioneered by him) Kustom 1 Warehouse, Performance Express, SCAT, So. Cal. Imports, Unique Supply and other suppliers; including some in Great Britain. There is also a SCAT branded, 1•5 US quart (i.e. 1•4 litres) capacity, supplementary oil-sump available direct from SCAT, for the VW 17/18/2000 Type 2 & 4 engines, but from what other sources if any, I don't know!
Supplementary oil sump, for VW 12/13/15/1600 Type 1, 2 & 3 engines:
http://www.scatvw.com/OilPumps.htm
Supplementary oil sump, for VW 17/18/2000 Type 2 & 4 engines:
http://www.scatvw.com/TypeIV.htm
A way of virtually eliminating oil surge, is to use a dry-sump lubrication system, which is a standard fitting on the air-cooled, flat-six, Porsche 911 engines. The absence of oil surge, helps increase engine life and reduces the risk of bearing failure. Only a shallow oil reservoir is needed, so the vehicle's ground clearance can safely be reduced for on-road driving or alternatively reduces the likelyhood of grounding when traversing rough terrain.
Dry-sump lubrication systems (see Heinz Heissler, 1999, Pages 498~499), are generally used for engines, running at continuously high speeds (e.g. rally or racing cars), supercharged or turbocharged engines, engines used on earth-moving equipment which experience repeated bursts of heavy loading and engines installed in vehicles which are designed to travel over rough ground and are subjected to large longitudinal or transverse tilt angles.
Other advantages of dry-sump lubrication, are reduced oil leakage because the scavenge pump reduces pressure inside the crankcase, resulting from piston blow-by of combustion gases and a power increase of 3~4%. However, dry-sump lubrication systems, require a pressure pump and a scavenge pump, the first of which pumps oil from an oil tank, through an oil cooler and then the engine. The scavenge pump collects hot, aerated oil from the engine and returns it to the oil tank, where it is de-aerated by a series of vents and baffles.
To efficiently de-aerate the oil, requires an oil tank with a volume, almost twice that of the system's total oil capacity and must also prevent any oil loss, as a result of oil-mist escaping into the atmosphere. A more sophisticated system, incorporates a centrifuge between the scavenge pump and the oil tank, which minimises the required oil tank size and reduces the oil's final air content from about 7% to circa 2~3%
B. A. S. dry-sump lubrication systems, for retro-fitment to the VW 12/13/16/1600 Type 1, 2 & 3 or VW 17/18/2000 Type 2 & 4 engines, are available in Great Britain, from B. R. Motorsport or from Bernd Ahnendorp (the principal source), in Germany. However, these are far from cheap; the approximate prices in 1995, for just the two-stage pumps (i.e. combined pressure & scavenge pumps) and 5 litre dry-sump oil tank, being circa £530 and £570, for the two engine types respectively. Remote-mounted oil coolers, fittings and pipework, would incur additional cost.
REFERENCES
Peter Noad, "Pace Notes", VW Motoring, November 1997, Pages 40~41
Bill Fisher, "How To Hot Rod Volkswagen Engines", HP Books, 1970, ISBN 0-912656-03-4, Pages 96~98.
Tom Wilson, "How to Rebuild Your Volkswagen Air-Cooled Engine", HP Books, 1987, ISBN 0-89586-225-5, Pages 72, 74 & 123.
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 - Four Strokes", Haynes Publishing Group, 1981, ISBN 0-85428-275-6, Pages 191~192.
J. H. Haynes & K. F. Kinchin, "VW 411 & 412, Owners' Workshop Manual; 1679cc & 1795cc; 1968 to 1975", Haynes Publishing, 1988.
Peter G. Strasman & Peter Ward, "Porsche 911 Owners' Workshop Manual - 2•0, 2•2, 2•4, 2•7, 3•0 & 3•2 litre; 1965 to 1985; Coupé & Targa", Haynes Publishing, 1986.
Heinz Heisler, "Vehicle and Engine Technology", Arnold, 2nd Edition, 1999, ISBN0-340-69186-7; Chapter 19 - Engine Lubrication System, Section 19.7 - Dry sump lubrication system with liquid-to-liquid oil cooler, Pages 498~499.
USEFUL ADDRESSES
Bernd Ahnendorp, Ahnendorp GmbH, Industrie Straße 2, 46419 Isselburg, Germany.
Tel. (Germany) 02874 - 4047 Tel. (International) +49 2874 4047
Fax. (Germany) 02874 - 1816 Fax. (International) +49 2874 1616
Internet website: http://www.ahnendorp.com
E-mail:
B. R. Motorsport, 8a Berrington Road, Sydenham Industrial Estate, Leamington Spa, Warwickshire, CV31 1NB, Great Britain.
Tel. (UK) 01 926 - 451 545 Tel. (International) +44 1926 451 545
Fax. (UK) 01 926 - 885535 Fax. (International) +44 1926 885 535
Car Custom, 915 West Foothill Boulevard, Azusa, California, CA 91702, USA.
Tel. (USA) 626 334 4951 or 626 969 7967 Tel. (International) +1 626 334 4951 or +1 626 969 7967
Fax. (USA) 626 334 4729 Fax. (International) +1 626 334 4729
Internet website: http://www.carcustom.com
Gene Berg, 1725 North Lime Street, Orange, California, CA 92665, USA.
Tel. (USA) 714 998 7500 Tel. (International) +1 714 998 7500
Fax. (USA) 714 998 7528 Fax. (International) +1 714 998 7528
Internet website: http://www.geneberg.com
Kustom 1 Warehouse, 1314 West Collins Avenue, Orange, California, CA 92867, USA.
Tel. (USA) 714 997 9893 Fax. (USA) 714 289 0893
Performance Express, P. O. Box 84075, Phoenix, Arizona, AZ 85071, USA
Tel. (USA) 602 375 0075 Fax. (USA) 602 942 9790
SCAT Enterprises Inc., 1400 Kingsdale Avenue, Redondo Beach, Califorinia, CA 90278, USA.
Tel. (USA) 310 370 5501 Fax. (USA) 310 214 2285
Internet website: http://www.scatenterprises.com/
Internet website: http://www.scatvw.com/
E-mail:
So. Cal. Imports Inc., 6851 North Paramount Boulevard, Long Beach, California, CA 90805, USA.
Tel. (USA) 562 633 9731 Walk-in Only Tel. (USA) 562 633 4979 Phone Orders Only
Unique Supply Inc., 610 Tennessee Street, Redlands, California, CA 92374, USA.
Tel. (USA) 909 793 0212 Information Tel. (USA) 800 576 2882 Orders only
Fax. (USA) 909 798 5025
Unique Supply Inc., 18768 Highway 18, #110 Apple Valley, California, CA 92307, USA.
Tel. (USA) 760 242 0986 Information Tel. (USA) 800 576 2882 Orders only
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Heinz Heisler, "Vehicle and Engine Technology", Arnold, 2nd Edition, 1999, ISBN0-340-69186-7.
Chapter 13 - Cylinder Block & Head Construction, Section 13.10 - Crankcase sump & baffle plates, Page 367.
« Baffle plates are sometimes installed inside the sump to prevent oil surge due to bouncing, rolling, and pitching of the vehicle, or to guide and prevent splashing of the stray jets of oil escaping from the journals and bearings of both the crankshaft and the camshaft. For special applications a horizontal gauze sheet supported in a steel frame may be positioned just below the sump flange joint, the object being to strain out draining contaminants created by combustion-gas blow-by and to minimise oil splashing. »
Heinz Heisler, "Vehicle and Engine Technology", Arnold, 2nd Edition, 1999, ISBN0-340-69186-7.
Chapter 19 - Engine Lubrication System, Section 19.7 - Dry sump lubrication system with liquid-to-liquid oil cooler, Pages 498~499.
19.7 - Dry sump lubrication system with liquid-to-liquid oil cooler (Fig. 19.35)
« Engines can be subjected to abnormal operating conditions, such as racing-car engines running continuously at high engine speeds, large diesel stationary engines working continuously at high brake loads, supercharged engines, engines used on earth-moving equipment which experience repeated bursts of heavy loading, and engines installed in vehicles which are designed to travel over rough ground and are subjected to large amounts of longitudinal and transverse tilt. Dry sump lubrication systems generally incorporate a pair of oil pumps:
1) a large low-pressure scavenging pump
2) a smaller high-pressure circulating pump »
19.7.1 - Scavenging pump (Fig. 19.35)
« This pump collects the hot aerated and expanded oil which drips into the sump from the deliberate spillage of oil from the crankshaft and camshaft journal bearings, oil spray that is directed onto the cylinder bore walls, the undersides of the pistons, the faces of the camshaft lobes and the timing gears, and dumps it into the storage tank by way of the liquid-to-liquid oil cooler. »
19.7.2 - High-pressure pump (Fig. 19.35)
« The pump draws cooled oil from the storage tank and delivers it under pressure via the full-flow oil filter to the main oil gallery. It is then fed to the individual main bearings, through diogonal crankshaft drillings and to the big end and small end bearings of the connecting rod. Oil is also supplied to the camshaft where it is distributed through a central drilling to each support bearing. »
19.7.3 - Oil cooler (liquid-to-liquid heat exchanger) (Fig. 19.35)
« This is a heat exchanger which extracts heat from the hot lubricating oil and conveys it through the circulating coolant to the radiator where it is dispersed into the surrounding atmosphere. This liquid-to-liquid heat exchanger consists of a stack of copper tubes supported by sealed end-plates and enclosed in an aluminium alloy casing. The engine coolant flows through the tubes whereas the lubrication oil is guided by baffle plates to pass several times over and across the tubes from one to the other, working its way from the entrance to the exit in the opposite direction to the flow of the coolant. Thus, as the oil passes one way and then the other over the tubes, heat will be transferred by conduction through the walls of the tubes. It is then absorbed by the coolant which then delivers it to the engine's cooling system radiator. »
19.7.4 - Oil storage tank (Fig. 19.35)
« After leaving the oil cooler, the de-aerated cooler oil lubricant enters the steep (Nigel's note: this word should probably be deep, rather than steep) storage tank to provide a ready supply of of cool oil at gravity head pressure to the inlet side of the high-pressure feed pump. Excess tilting or pitching of the engine wil not prevent this oil supply being delivered to the high-pressure feed pump. Thus at all times high-pressure lubricating oil will be circulated to the main oil gallery and to the various parts that require lubricating. »
Nigel's note: Figure 19.35 shows the large, low-pressure scavenge pump extracting aerated oil from the sump, via a strainer on the suction side and feeding oil to oil cooler and thence the oil storage tank. The cooled, de-aerated oil is then gravity-fed from the oil-storage tank to the small high-pressure feed pump. Both the large, low-pressure scavenge pump anf the small high-pressure feed pump, appear to be of the "external-spur-gear" (i.e. “positive-displacement, rotary, gear”) oil pump type (i.e. two intermeshing gears; one driven and the other an idler, as normally factory-fitted to air-cooled VWs)
A few pictures would be useful, to illustrate (a) the baffle shape itself; (b) how the baffle is welded to the oil-pump pick-up tube & strainer shroud; and (c) how the baffle, pick-up tube & strainer-shroud assembly, is fitted and secured in one side of the crankcase, along the parting line. 