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Metering Pump Adapter for Wankel Engine.




Wankel engines such as the one used in the MAZDA RX7 sports car need oil in the combustion area for lubricating the metal seals.

Most stock engines use a metering pump pumping a small amount of engine oil  from the oil pan into the intake manifold and/or directly into the  combustion chamber. Engine oil is designed to lubricate sleeve bearings and carry heat from the engine interior to some cooling areas. In the RX7 the heat is removed from the oil in an oil cooler. When engine oil is getting into the combustion chamber, it only is burning partially, leaving some unburned deposits behind. These deposits can build up and  reduce engine performance.

One obvious method of preventing this is to disconnect the metering pump altogether and mix two-stroke oil to the gasoline like some older  two-stroke engines require. With this method it has been demonstrated that two-stroke oil is an effective lubricant and there is no build up of combustion residues.

The Metering Pump Adapter, as offered by Richard Sohn takes the solution one step further in allowing to still using the stock  metering pump but supply it with two-stroke oil. With the Adapter  installed, all that is needed is a small oil tank with two-stroke oil,  connected to the Metering Pump Adapter. The oil level in the tank should never be less then 6� above metering pump.Oil consumption is approximately 1/100 of fuel used.





The RENESIS engine is becoming increasingly popular for conversion for use  in experimental airplanes. Using the Oil Metering Pump for top  lubrication is an open question, because most after market EMSs do not provide an output for OMP control.

In the RX8 automobile the OMP oil flow is controlled by engine RPM and pump-rate. The pump-rate control is activated by the engine computer.  This pump-rate control is used to increase oil flow when there is an increased power demand at low engine RPM. This condition does generally  not occur in an airplane.

When the engine is used with an EMS with no output for the OMP, the only option is to mix some oil in the fuel for top lubrication. The preferred oil used for this method is two-stroke oil for its ability to readily  mix with gasoline and lower combustion residues than regular motor oil.


To overcome this draw back in aircraft use, the OMP pump-rate control can  be fixed to a certain position, and the oil flow will only change with  engine RPM.




The RX8 OMP is equipped with a position sensor, (pic 1.), which monitors the position of the control shaft on the pump. This position sensor may  be replaced with an adjuster (pic.2.) to set the control shaft to a fixed position. In this way, the OMP is fully functional, giving an oil  amount comparable to oil mixed in the fuel.


Picture 1.

  Picture 3

Picture 2.

Picture 4.

If the use of two-stroke oil is desired, the ADJUSTER with the ADAPTER

represents a complete conversion (pic 4.).

All adapter versions are available through RWS at