Intake Air Systems: Overview
The intake air system provides clean air to the engine, optimizes air flow, and reduces unwanted induction noise. The intake air system consists of an air cleaner assembly, resonator assemblies, and hoses. Some vehicles use a hydrocarbon filter trap to help reduce emissions by preventing fuel vapor from escaping into the atmosphere from the intake when the engine is off. It is typically located inside the air intake system. The mass air flow (MAF) sensor is attached to the air cleaner assembly and measures the volume of air delivered to the engine. The hydrocarbon trap is part of the EVAP system. For more information on the EVAP System, refer to EVAPORATIVE EMISSION (EVAP) SYSTEMS . The MAF sensor can be repaired or replaced as an individual component. The intake air system also contains a sensor that measures the intake air temperature (IAT), and which may also be integrated with the MAF sensor. (Refer to POWERTRAIN CONTROL MODULE (PCM) INPUTS for additional information on the MAF and IAT sensors.) Air induction resonators can be separate components or part of the intake air housing. The function of a resonator is to reduce induction noise. The air induction components are connected to each other and to the throttle body assembly with hoses.
There are 3 basic types of intake air sub-systems:
- Intake Manifold Runner Control (IMRC) electric actuated system
- Intake Manifold Runner Control (IMRC) vacuum actuated system
- Tuning Valve (IMTV)
There are several different styles of hardware used to control airflow within the engine air intake system. In general, the devices are defined based on whether they control in-cylinder motion (charge motion) or manifold dynamics (tuning).
Systems designed to control charge motion are defined to be intake manifold runner controls. Intake manifold runner control systems generally have to modify spark when the systems are active because altering the charge motion affects the burn rate within the cylinder.
Systems designed to control intake manifold dynamics or tuning are defined to be intake manifold tuning valves. Intake manifold tuning systems generally do not require any changes to spark or air/fuel ratio because these systems only alter the amount of airflow entering the engine.
These subsystems are used to provide increased intake airflow to improve torque, emissions and performance. The overall volume of air metered to the engine is controlled by the throttle body. Vehicles equipped with electronic throttle control (ETC) will not use an idle air control (IAC).