The scavenging, in an internal combustion engine (IC Engine), is the process of removing the burnt gases from the combustion chamber of the engine cylinder. Though there are many types of scavenging, yet the following are important from the subject point of view:

1. Crossflow scavenging. In this method, the transfer port (or inlet port for the engine cylinder) and exhaust port are situated on the opposite sides of the engine cylinder (as in the case of two stroke cycle engines).

2. Back flow or loop scavenging. In this method, the inlet and outlet ports are situated on the same side of the engine cylinder.

3. Uniflow scavenging. In this method, the fresh charge, while entering from one side (or sometimes two sides) of the engine cylinder pushes out the gases through the exit valve situated on the top of the cylinder.

Note: The scavenging efficiency of a four stroke cycle diesel engine is between 95 and 100 percent.