Throttle body

The combustion inside the engine requires constant supply of air. Do you know? Where does this air comes from ? Or, what controls the amount of air supply to the engine. What mechanism is lying behind allow these? What effect does the air supply has on the engine performance. Let us answer all these questions one by one.

Effect of air on engine performance

The air is needed for combustion of fuel inside the engine. The air and fuel are needed in a particular ratio for proper combustion to take place. For greater power requirements we need greater amount of air and for that we need a grater amount of air too. Many vehicles are being equipment with technologies like Four Valves, or Variable valve actuation so as to meet the greater air supply demands at higher speeds. 

Air Supply Control Mechanism

The air in engines is supplied from the atmosphere. Yes, the atmospheric air is sucked inside through the air filters . The air reaches the engine cylinder passing either through carburator or through the throttle body. The fuel injected engines contain throttle body in place of carburator. in case of fuel injected engines. The amount of air flow is controlled using throttle valves. These valves are either fitted in carburator or the throttle body. The driver can control the actuation of the throttle valve using the accelerator.  In this post we will discuss about the throttle bodies. 

Throttle Body

Throttle body is a small unit fitted between the intake manifold and the air filter, This small unit whose work appears to control air supply houses mannuly other components which are essential for better engine performance. It houses the throttle valve, TPS sensor, MAP sensor, air intake temperature sensor and intake air control valve. All these components have a key role to play in proper functioning of the engine. Let's discuss all these parts in detail. 

Throttle valve

Throttle valve is a butterfly valve which controls the air supply to the engine. It is actuates using accelerator pedal through cable connection. This cable connected between accelerator pedal and spring loaded actuators. When we press the accelerator pedal this cable is stretched. This cable cause the actuator tk open the throttle accordingly.

Also read : Engine Management System

Throttle Position Sensor (TPS)

Throttle position sensor or TPS is a potentiometer based sensor located in throttle body. It senses the amount of valve opening and send the data to Engine control unit. ECU uses this data to calculate the amount of fuel required for that throttle condition. 

TPS contains a printed resistance circuit as shown in the picture. The needle shown rotates along with the shaft of the butterfly valve. This needle and the circuit works as angular potentiometer circuit. The point X and You are connected to the ECU and the point Z is grounded.  As the needle rotates, the amount of resistance across the circuit increases. This causes voltage drop across it. This voltage drop is measured by the ECU to determine the level of throttle opening.

Idle Air Control Valve

In idle conditions the accelerator is completely released. This causes the throttle valve to close completely. The closing of the valve completely blocks the air supply through it. Now in this condition, the air needed for the combustion is provided through a bypass circuit. This is a small orifice in the throttle body. The flow through this bypass circuit is regulated using Idle air control valve. This is a solenoid valve and can be actuated by ECU whenever required. The ECU get to know about the idling from the data of the TPS, Speed sensor and O2 sensor.