Lynn E. Hanover

As you can see the spec leans to the piston engine use. The rotary uses top oil or (Premix) to keep the apex seal from over heating and changing shape. The lubrication of corner and side seals is less of a challenge. Why is that Mr. Wizard?



There are places (between the spark plugs) where the rotor housing is always very hot and that means the surface is not as dead flat as we would like. Those points need a very good lubricant. So you notice that old damaged housings have grooves in this area, where compression is lost on every revolution.



It is a unit pressure problem. The reason that a needle has a pointed end, or a knife blade is sharp. So as to concentrate any force applied over the very smallest surface area. You know this but never think about it.



So look at how much of the apex seal surface is in contact with the housing chrome at any rotational position.

Oops. Not much is there?

So, the little spring behind the seal is able to produce a very high unit pressure across the face of the seal. The premix oil must support that seal at very high speed and high temperature, and very high pressure so as to prevent metal to metal (or carbon or ceramic) contact. Actual contact produces wear

in both materials, so contact is not permitted.



So, to get any wear at all were must exceed the lubrication capabilities of the oil (break down the film strength) or just let the car sit for a long time so that the oil runs off of the surfaces, and get a bit of wear on start-up.



The corner seal button and the side seals have a very large footprint area wise compared to the apex seal, (microscopic) so keeping them alive is just not very difficult. They have low unit pressure. Like pushing on the needle sideways, or using the wrong side of the knife blade. So, there will be a large quantity of oil supporting those seals per unit of area.



The top oil needs to be as close to ash free as is possible, so the pieces of burned oil are so small that they cannot start a combustion process should a fragment be reinserted during overlap. Very bad Mojo.



So ash free, detergent, high film strength, and remain in suspension for long periods. And not form varnish deposits over time. That is all you need for a top oil. The one thing about the spec that may be lacking is the unit pressure of the apex seal, but most modern 2 cycle engines use needle bearing rods and wrist pins, so there may be similar unit pressures there.



For the crank case, (when the OMP is not used) there are few demands. The plain bearings are huge for the loads involved. Just about any name brand oil is fine. This will be accurate up to about 9,000 RPM where antis scuff and film strength in the rotor bearings starts to become a concern. Then a name brand racing oil should be used. Unless your oil temps are out of control, synthetics will give a few HP but not much help otherwise. The racing oils have added Zinc antiscuff compounds. There will be more antifoaming agents, very important for the rotary with the foamed oil falling out of the rotors.



Multigrade oils are made of base stocks of the lower number. So, a 20W-50 is a 20 weight oil with a bunch of polymer strings that will link up when heated to produce a slower pouring oil. So, when hot the oil act like 50 weight oil but it is not 50 weight oil. It just acts like it. If there is no need for a multi grade oil, use a straight weight. Where the night time, and daytime temps are far apart, then a multigrade may be of value. In winter operation a 5W-20 or 30 might be good. Easy cranking is helpful because the rotary is sensitive to cranking RPM.



In Pheonix you might use a straight 40 or 50 weight synthetic when the temps are above 100 midnight to noon.



The farther apart those two numbers, the less oil in the can. Oil is made up of clumps of different size molecules (nonpolar) and the pour rate (actual leak rate out of little funnel) determins the weight.

Synthetics tend to be all the same size molecules, and the weight does not tell the whole story.



The most important function of crank case oil is to cool the plain bearings. You need cool oil to do that.

The grey stuff on the bearing surface has a low melting point. If it melts you are screwed. So, move oil across that bearing quickly so as to keep the temp down (high oil pressure for high performance use).

And the lowest reccomended oil weight (resistance to flow).



I use Redline 40 weight synthetic racing oil in the case (dry sump) and Redline racing 2 cycle oil in the premix. One ounce per galon of 93 octane fuel. For NA engines.



I have used Valvolene racing oil as well, with no lubrication related failures in rotary racing since 1980.



Lynn E. Hanover

Maxt

Idemitsu is a major Japanese oil company.. Eneos, HKS, Gulf, RE, and Revolution have their own rotary specific oils. Something neat about the rotary specific oils, is that in engines I have taken apart that have used it, they are spotless on the inside, and you basically just rinse the film off the parts..

I took apart an FD engine that used generic Greddy synthetic, and I could not get the staining off the inside of that motor, its like it had been painted with brown deck stain.

The rotary has alot more blow by than other engines, dilution with fuel does different things to different oils. I think that and the oil breakdown temp are the details which are different with the rotary specific stuff..

It was ungodly expensive over there , like 80 canuck bucks for 5 liters.

Here's a link to Gulfs oil

http://translate.google.com/translate?lang...m/oil_sf_re.htm