Effects of supercharging on engine operation
Application of supercharging to engines

In addition to the transfer phenomena linked to piston movement, which are predominant in the 4-stroke cycle, scavenging phenomena can occur, similar to those found in 2-stroke engines. These are caused by pressure differences between intake and exhaust, which can generate a flow during the period of simultaneous opening of intake and exhaust valves (valve "crossover" period).

• If p _a > p _e , flow will be established in the intake-to-exhaust direction, causing the engine to overbalance. The flow delivered by the compressor will be greater than the cylinder's filling capacity, hence λ > η _v ...