Diesel Engine Model 2 Stroke Vertical flask type demonstration model, on metal base. This type of engine is mostly used in motor boats. A two stroke diesel engine takes in air and discharges exhaust a system called crank - case scavenging. Scavenging begins with piston at bottom dead centre. At this point , the intake port inside the cylinder are uncovered and the exhaust valve is open. The air is forced into the cylinder, and as the air is forced in , the burned gases from the previous operting cycle are forced out . The two stroke involved are compression stroke and power stroke.