The cycle of operation of the four-stoke engine begins with the piston at TDC and the intakevalveopen.
四冲程发动机的工作循环是以活塞在上止点、进气门打开为开始的。
2
The intake stroke starts with the pistonat the top of the cylinder (intakevalveopen and exhaust valve closed) and stops with the pistonat the bottom of its travel.