INTAKE AND EXHAUST SYSTEMS

Combustion requires air, fuel, and heat; certain ratios of all three are necessary if an engine is to operate. This chapter deals with AIR as it is required to support combustion in the cylinder of an engine. The processes of scavenging and supercharging are considered as well as the group of parts involved in supplying the cylinders of an engine with air and in removing the waste gases after combustion and the power event are finished. The engine parts that accomplish these functions are commonly referred to as the IN-TAKE and EXHAUST systems.

After reading the information in this chapter, you should be able to describe the purposes, principles of operation, and functions associated with the components of air intake and exhaust systems. You should also be able to trace the path of the intake air and exhaust gases through these systems, and you should understand the significance of scavenging and supercharging and how these processes differ in the operating cycles of 2- and 4-stroke engines.

INTAKE SYSTEMS

This section deals with intake systems of diesel engines only; nevertheless, much of the information dealing with the parts of diesel engine air systems is also applicable to most of the parts in similar systems of gasoline engines.

Although the primary function of a diesel engine intake system is to supply the air required for combustion, the system also cleans the air and reduces the noise created by the air as it enters the engine. An intake system may include an air silencer, an air cleaner and screen, an air box or header, intake valves or ports, a blower, an air heater, and an air cooler. Not all of these parts are common to every intake system. The differences will be explained as these systems are discussed.