Gas exchange process in four stroke engine

The purpose of the exhaust and inlet processes (or scavenging process in the two stroke engine) is to remove the burned gasses at the end of the power stroke and admit the fresh charge for the next cycle. The indicated power of an internal combustion engine at a given speed is proportional to the mass flow rate of air.
Engine gas exchange process is characterized by overall parameter such as volumetric efficiency (for four stroke engine) and scavenging efficiency and trapping efficiency (for two stroke cycle) these overall parameters depend on the design of engine subsystems such as manifolds, valves, and ports as well as engine operation conditions. Turbochargers or superchargers are used to increase air flow to engine and hence power.
Inlet and exhaust processes in the four stroke cycle:
In a spark ignition engine, the intake system typically consist of an air filter, a carburetor and throttle and intake manifold. During the induction process pressure loss occur as the mixture pass through each of these components.
The exhaust system typically consists of an exhaust manifold, exhaust pipe, and silencer.