A.at TDC B.before TDC C.after TDC D.during air starting
A.Spark plug B.Heat of compression C.Carburetor D.Glow ping
A.seal the space between the piston and the liner B.reduce the amount of lube oil burned in the combustion chamber C.transmit heat from the piston to the cylinder liner D.damp out fluctuations of the piston side thrust