What is an apex seal?
The “piston” in a rotary is a triangular cast iron assembly. Each tip of the triangle is an apex, so the seal placed there is called an apex seal. It is the only moving part that actually comes in contact with the rotor housing. It’s rather unique feature is that its position in the engine doesn’t allow for lubrication from the main oil system, so some other method of lubricating them is normally provided. Mazda uses an oil injection pump, similar to those used on many two-stroke boingers, to inject oil into the intake stream, thus reaching the apex seals. The consequences of this are that the injected oil is burned along with the fuel, and adding oil between oil changes is normally required. Along the sides of the rotor, in between the ends of the apex seals, there are side seals. There are also corner seals at the ends of each apex on the side, whose job it is to pickup the function of sealing where the apex seals and side seals end. The apex, side & corners seals combine to serve a
