The release of exhaust gases from the cylinder starts from the moment the exhaust valves are opened, i.e. when the piston position is 48 ° BC. in the stroke of the working stroke.
The cylinder is cleaned of combustion products:
- when the piston moves to N.m.t. in the stroke of the working stroke due to the pressure difference in the cylinder and the surrounding atmosphere (the pressure in the cylinder at the moment of opening the exhaust valves is 2.5-3 times higher than atmospheric);
- as a result of the expulsion of the exhaust gases by the piston moving towards the engine compartment. in the cycle of release;
- due to the inertia of the flow and its displacement by fresh air when the intake valves are opened in the intake stroke, when the piston moves from top dead center to bottom.
The duration of the release of the exhaust gases is 248 ° in the angle of rotation of the crankshaft (in the stroke - 48 °, forced exhaust - 180 °, in the intake stroke - 20 °).
From the beginning of the intake (20 ° before TDM) to the end of the exhaust (20 ° after TDM), i.e., within 40 ° along the angle of rotation of the crankshaft, the intake and exhaust valves are simultaneously open. In this range, which is called valve overlap, the cylinder is purged, which contributes to better cleaning of residual gases and better filling with fresh air charge.