OPERATION

INTAKE STROKE

The first part of the combustion cycle starts with the intake, which is when the engine draws in the mixture of air and fuel. When the apex of the rotor passes the intake port and the port is exposed to the chamber, the chamber is at its smallest size, but then when the rotor moves past the intake port, the chamber size grows as it draws in the mixture. Finally, as the rotor apex passes the intake port, the chamber is fully sealed off, and the compression stroke begins.

COMPRESSION STROKE

As the rotor continues its path around the housing, the chamber size gets smaller and the air/fuel mixture gets compressed, as that’s all it can do — it has nowhere else to go. By the time the face of the rotor has made it around to the spark plugs, the chamber is again close to its minimum volume, and this is when the combustion stage of the fourstroke cycle starts.

COMBUSTION STROKE

Because the combustion chamber is long, Mazda uses two spark plugs for each rotor, as the flame would spread too slowly if there was only one. As the spark plugs ignite the well-compressed mixture, there is combustion, which expands the gases and forces the rotor to move (the same combustion in a piston engine forces the piston downwards). This then provides the motive force until the rotor tip passes the exhaust port.

EXHAUST STROKE

Once the apex of the rotor passes the exhaust port, those combustion gases start to flow out of said port, and are fed into the exhaust manifold and exhaust system. As the rotor continues to move, the chamber volume decreases in size, again forcing the remaining exhaust out of the port. By this time, the apex of the rotor is once again passing the intake port, and the whole cycle starts again.