Technical Information

Engine Lubrication | Permanent grease lubrication of main bearings| Engine torque data

Engine Lubrication

 The following are a few opinions on the issue of commercial oil “additives” contained in a document, which was received by the club committee (the marketing of some of these products makes use of strong psychological effects in order to influence prospective buyers to spend money on them):

 “AVCO LYCOMING, a major manufacturer of aircraft engines, states, ‘We have tried every additive we could find on the market, and they are all worthless’.

Briggs and Stratton, renowned builder of durable engines, says in their report on engine oil additives, ‘They do not appear to offer any benefits.’

North Dakota State University conducted tests on oil additives and said in their report, ’The theory sounds good - the only problem is that the products simply don’t work.’

Ed Hackett, chemist at the University of Nevada Desert Research Centre, says, ‘Oil additives should not be used. The oil companies have gone to great lengths to develop an additive package that meets the vehicle’s requirements. If you add anything to this oil you may upset the balance and prevent the oil from performing to specification.’ “

It is interesting to note that Du Pont, the manufacturers of PTFE, states that this product is not suitable as an engine lubricant, and would not sell it to marketers of engine oil additives.

 It would be safe for our members to stick to well known brands of  two-stroke oils. Semi-synthetic oils like Total Chain Saw Engine oil is a very good, and economical oil for our vehicles if bought in 20 l containers, directly from the local Total oil depot. The more demanding applications like racing,  requires  full synthetic oils. Whatever your choice, make sure to get a good corrosion inhibiting oil in order to protect your crankshaft bearings against moisture. Also use an oil with very low residual ash content, which should ensure the minimum of deposits on your spark plugs and combustion chambers. Deposits may cause pre-ignition or knocking which may lead to piston/ring seizures.

PERMANENT GREASE LUBRICATION OF MAIN BEARINGS: A SUCCESS?

 This is a topic frequently discussed with many opinions from the various “specialists” as we all see ourselves.

 AUTO UNION experimented with a great variety of bearing and sealing designs in order to find the ultimate solution. If one talks to the old hands in the service departments, one comes to the conclusion that this was a headache for the designers. Two-stroke oils were not as advanced as presently, and this complicated the situation even more for the Auto Union engineers.

 SAAB for instance produced a pressure type lubricating system where the lubricant was pumped to the various bearings and cylinders via small oil passages in the block. The lubricant emerging from the bearings was splashed around the crankcase and it lubricated the pistons/rings before it left the engine after combustion took place. Possible pitfalls: uneven distribution of the oil through the engine, and possible pumping problems at sub-zero temperatures. Due to the cost of this system, only the Saab Sport was fitted with this device.

 The “petroil” mixture was widely preferred for racing purposes.

 The DKW Lubrimat, was experimented with even before the Second World War. The design was not matured and the public demand was not there yet. From old literature it becomes clear that the mixing of the oil in the fuel tank was a very critical issue at low temperatures, because of the unwillingness of the oil to mix with the fuel. The “Shell-Mixer” inside the fuel tank was introduced during the early fifties, and it averted the premixing of the oil with some petrol in a can before the tank was filled. As we know it is a slow process, and time consuming and depended on the memory of the driver.

 The Lubrimat, as it appeared on the market at the end of 1961, metered the oil from a separate oil tank, according  to engine speed and engine loading (throttle position). The fuel and oil is mixed in the carburetor. From my own experience, this device provides an average oil to petrol ratio of about 1:40. This was measured over a few thousand kilometers on a DKW F12.

 Under very cold conditions, the oil in the oil tank is so viscous that the pump would not suck it into the suction side of the pump. Unfortunately for Auto Union, the European winter 1961/1962 was a very cold winter with plenty lubrication problems for their new lubrication system. This led to numerous engine failures, which really hurt the company at a time when public opinion started to turn against the use of two-stroke engines in motor cars.

  During 1964/5 Auto Union changed the system to include an oil heater underneath the oil tank, and a mixing chamber before the carburettor in order to improve the distribution of the oil in the engine, especially during cold weather conditions.

 The early 3=6 crankshafts with the narrow main bearings were lubricated by the splash lubrication of the fuel/oil mixture, while the bearings were open on the one side and covered by a mechanical seal on the other side. To my knowledge, this system worked very well. Though, corrosion problems occurred due to condensation of moisture inside the engines, which affected the bearing surfaces. The big-end roller bearings were also lubricated this way.

 Around 1958/9 Auto Union changed the design of the main bearings to a sealed for life main ball bearing system, lubricated by grease. I assume this design was adopted due to corrosion problems, which may have caused the open rollers to fail due to water vapour which condensed inside the engine under very cold European conditions. Unfortunately, these seals were not very tight and some of the grease leaked out due to the relatively high temperatures inside the engine, and was also washed out by the “petroil” mixture passing through the crankcase. The grease was also lost due to centrifugal action past the sealing surfaces. These bearings were modified by about 1961/2 by using the “small sealing rings” which prevented this centrifugal action. Notwithstanding all these “improvements” to the main bearings, the big-end bearings were still subject to splash lubrication, and not sealed against corrosion.

 My personal opinion regarding the lubrication is: if splash lubrication is good enough for the big-end bearings, it should also be good enough for the main bearings. The steel these two types of bearings are made of are similar and should have the same corrosion resistance. Splash lubrication ensures a constant supply of fresh lubricant to them. In order to curb the possible corrosion problems, a high quality two-stroke oil containing anti corrosion additives should be used. My recommendation is to convert your crankshaft to “petroil” splash lubrication when the crankshaft needs attention at some stage in its life. It is also interesting to note that the published load carrying capacity and allowable speed ratings of  bearings are higher with oil lubrication than with grease.

 By 1959 the first crankshafts were produced with the needle roller bearings replacing the bronze bushes as gudgeon pin bearings. The bushes were not capable of accepting the heavier loadings of the 1000S and Sp engines. If you are using bushes it is recommended to stick to the bushes with the “oil pockets” milled into the bush in order to assist with lubricant distribution throughout the bush. Bush failures may lead to seized up gudgeon pins which will cause the gudgeon pins to wear out the pistons - a costly exercise.

 I have seen many ruined crankshafts, while the owners neglected to protect them properly during storage. A recent tragedy was a F12 block  in apparently good shape which showed corrosion marks of about 2 mm deep in the cylinder wall due to the fact that the pistons started to corrode the cast iron in the presence of some water. You are urged to make certain that water do not enter the working parts of the engine. Pour some oil through the ports and the spark plug holes in order to cover all surfaces. The best recipe is to seal off the intake and exhaust ports with masking tape as well.

 If the crank is in the engine and you plan to mothball the engine, fit the engine with some old spark plugs and let it idle at about 1000-2000 r/min. Pour some 100 ml oil slowly through the carburettor. Stop the engine and leave it in this condition until you would like to use it again. Fit new spark plugs before attempting to start it.

 If the crankshaft is stored outside the engine, pour some oil over the whole crankshaft and put it in a strong plastic bag, which must me closed properly in order to prevent air and moisture to enter.

 The protective plates underneath the engine prevent cold air to cool the sump. If the sump is hot, the separation of the oil and petrol in the crank case is improved and the completely evaporated petrol would pass on to the combustion chambers, which leaves more oil in the crank case for lubrication purposes. Blue smoke is a common scene with a cold engine: incomplete combustion of the cold petroil mixture and also some of the oil trapped in the sump which is worked through to the combustion chambers (This is normally the condition when the spark plugs are easily fouled up with oil: the flash point of  your oil should be as low as possible in order to reduce this tendency).

ENGINE TORQUE DATA FOR DKW 1000/1000S/1000Sp and 3=6