Interesting idea that top oil injection. The ideal method of delivery is to premix the oil with the fuel. That way the apex seals, corner seals, side seals and oil scrapers get uniform and continuous lubrication. In the periphery exhaust ported engine this is most important for the center of the apex seal when the seal opens the port and exhaust gasses remove the oil film and then super heat the center of the apex seal.

The oil film on the rotor housing face cools the seal as it continues it's circuit.

 

In the later Renesis engines (with side exhaust ports) the side seals are at risk in a similar manor. One method to assure thorough mixing of oil and fuel is to mix all of the oil for one fuel tank in a gallon jug with just under a gallon of fuel and dump that in just before that tank is full. The oil and fuel mixture will disperse very well. Works just fine.

 

The one ounce per gallon mixture is for racing engines working above 9,000 RPM. And since the aircraft engine duty cycle is actually more severe than that of a racing engine, it would seem as though a similar mixture would be required. Probably close to accurate. However, some racers use only 1/2 ounce per gallon and they go as fast or faster than my racer. If you have new oil scrapers then use more top oil. If you rebuilt with old oil scrapers or didn't rebuild at all you can use less top oil, as the old oil scrapers will let some crank case oil out onto the irons

and lubrication is achieved. On old smoky engines it is the warn out scrapers providing the excessive crank case oil for the smoke.

 

Item of interest. It takes a long time to abuse the apex seals to death

(In non turbo installations) If you notice that you have no oil in your fire wall mounted bottle some morning, just fill it up and go. Make a note for a hot compression check soon.  

 

Some Mazdas have run for years with no OMP operating and still have good compression. (Mr Hanover could you look at my car?) It has been smoking).  (OMP minus plastic lines peeing oil on my shop floor)

 

 Yes I will. Might I ask who was President the last time this hood was opened? 

 

If you use the OMP, feed it 2 cycle oil from a bottle on the fire wall. Crank case oil is designed not to burn. So, most of it does not burn as expected. This cokes up the rotor and sticks seals in their grooves from the remains of unburned crank case oil. Use the synthetic crank case oil in the crank case, and an ash free 2 cycle oil in the OMP. Mazda had a rule against using synthetics in their engines because they do not burn at all, and when the OMP puts it into the rotor housings, it just gums up the rotor housings and sticks the apex seals. So it's not just a good idea, it's the LAW.

 

Note 2. Racing synthetics have the highest film strengths and more antis-scuff and anti foaming additives. (The rotor cooling oil gets full of foam in normal operation and produces slightly lower oil pressure and slightly higher oil temperatures, as air in the foam is an insulator and defeats the oil coolers to some degree).  

 

When I open one of my engines, I see the side seals and corner seals and their springs sitting on the iron after I lift off the rotors. This is what you will see when you premix and, or, feed the OMP an ashless 2 cycle oil.  I do not have to dig the seals out of the rotors with various little tools, as is the case with a used street engine that is fed crank case oil.

 

Lynn E. Hanover

 

 

In a message dated 4/10/2012 8:30:40 A.M. Eastern Daylight Time, msteitle@gmail.com writes:

Bill, 

It is just a SWAG on the cause of the damage to the apex seals.  They didn't break, but they had deep scratches across the wear face.  Tracy thinks it could have been foreign matter, but couldn't say for sure.  I can't recall any time the engine was run without an air filter.  So, I don't know how/when debris could have gotten into the engine.

You may be correct in that I could be trying to solve a non-problem with the oil-fuel mix.  But, logic tells me that the ribs in the Lancair fuel tanks don't help to mix up the oil, especially if you pour the oil in first, then add fuel.  All of the oil will end up inboard due to the dihedral of the wings.  I wish I had thought to run the fuel return line to the outer most fuel bay.  That would have helped to mix the oil/fuel.  Too late for that now.

Also, it seems that we're wasting most of the 2-stroke by having it mixed in with the fuel.  Not that it doesn't help, but by injecting the oil through the rotor housing, you're putting the oil right on the apex seal where it is most needed.  Mazda engineers knew what they were doing here.

(I'll respond to the TB question in a separate post.)  

Mark