How an Air Intake Works

Here's how the air intake system works on your car.

The air intake system has been designed by the car manufacturer to provide a balance of airflow, sound tuning and packaging capabilities. It is responsible for supplying the engine with sufficient air to ensure optimal combustion.

Key components of the air intake system include:

Air inlet tube
Air intake resonator
Air filter housing
Air filter
Mass airflow sensor
Evaporative emissions purge valve
Accelerator pedal
Throttle body
Intake plenum
Various vacuum hoses

This video demonstrates where these parts are positioned as part of the larger assembly in the car. It will then break down each individual component and explain how it works.

The air intake tube sucks air from the front of the engine bay near the radiator cradle. The air then proceeds down into the air resonator box, mounted behind the bumper, below the headlights. The resonator will reduce any unwanted sounds and tunes the intake to match the vehicle's characteristics.

The air then travels to the air box, where it is past through an air filter. The filter is designed to maximize filtration area, with a corrugated felt pattern. The mass air flow sensor and EVAP purge valve are also mounted to the air filter box.

The EVAP purge valve is a simple check valve that allows air to be vented to the intake system from the gas tank. It is activated by a solenoid which is controlled by the ECU. Enough ventilation will enrich the air with gasoline vapours before it enters the intake manifold and the engine.

The Mass air flow sensor, or MAF sensor, is responsible for detecting how much air is flowing through the intake. There are two resistors inside upon which the air flow and cool down when a current is applied. When more air flows past, it cools further, decreasing resistance and increasing the current. The ECU will detect the change in current and correlate it to density (and hence mass) of air flowing through the sensor.

According to the ideal gas law, the pressure can go up or the temperature can drop accordingly, but the MAF sensor can still determine the mass of air flowing through. This is ideal for automotive applications, where atmospheric conditions can vary drastically. The MAF sensor is also fitted with an intake air temperature sensor or IAT sensor to tell the ECU how warm or cold the incoming air is.

The throttle body controls how much air enters the air intake manifold through a butterfly valve. The accelerator pedal opens the throttle body with a cable linkage. Many newer vehicles use a drive - by - wire setup, where the gas pedal has an electronic linkage via an electric motor to open the throttle plate.

The throttle body also has various connections to vacuum lines, as well as the idle air control valve below, two coolant lines to prevent freezing, and the throttle position sensor.

The air intake manifold distributes the air from the throttle body across all the pistons. It is made up of a casted section where the throttle body mounts, and aluminum tubing that is bent to shape. Newer vehicles use plastic intake plenums to save weight and reduce cost.