Over lap period

It is the period where exhaust and inlet valve opened to gather it

will assist in final removal of the remain ant exhaust gas from the cylinder.

The effect of extension over lap period is-: 1 -Increase scavenge effects

2 -Provide pronounced cooling effects .

3-help to remove thermal stresses of engine parts

Over lap period more effective in 4 stroke than 2 stroke because the time which

A valiable for cleaning and charging air is much more than 2 stroke

In 2 stroke exhaust change process is carried in BDC while in 4 stroke carried

Out on TDC.