Throttle operation

The throttle valve is one of the most important parts of the intake system of an internal combustion engine. In a car, it is located between the intake manifold and the air filter. On diesel engines, a throttle is not needed, but on modern engines it is still installed in case of emergency operation. The situation is similar with gasoline engines if they have a valve lift control system. The main function of the throttle valve is to supply and regulate the air flow necessary for the formation of an air-fuel mixture. Thus, the stability of the engine operating modes, the level of fuel consumption and the characteristics of the car as a whole depend on the correct operation of the shock absorber.

Choke device

From a practical point of view, the throttle valve is a bypass valve. In the open position, the pressure in the intake system is equal to atmospheric. As it closes, it decreases, approaching the vacuum value (this is because the motor is actually working as a pump). It is for this reason that the vacuum brake booster is connected to the intake manifold. Structurally, the damper itself is a round plate that can rotate 90 degrees. One such revolution represents one cycle from full opening to closing of the valve.

Acceleration device

Butterfly valve block (module) includes the following elements:

• The case is equipped with various nozzles. They are connected to ventilation systems that trap fuel and coolant vapors (to heat the damper).
• Activation that moves the valve when the driver presses the accelerator pedal.
• Position sensors or potentiometers. They measure the throttle opening angle and send a signal to the engine control unit. In modern systems, two throttle position control sensors are installed, which can be sliding contact (potentiometers) or magnetoresistive (non-contact).
• Idling regulator. It is necessary to maintain the set speed of the crankshaft in closed mode. That is, the minimum opening angle of the shock absorber is ensured when the accelerator pedal is not depressed.

Types and modes of operation of the throttle valve

The type of throttle actuator determines its design, mode of operation and control. It can be mechanical or electrical (electronic).

Mechanical drive device

Older and cheaper models of cars have a mechanical valve actuator in which the accelerator pedal is directly connected to the wastegate using a special cable. The mechanical actuator of the butterfly valve consists of the following elements:

• accelerator (gas pedal);
• pull and twist the levers;
• steel rope.

Depressing the accelerator pedal activates the mechanical system of levers, rods and cable, causing the damper to rotate (open). As a result, air begins to enter the system, and an air-fuel mixture is formed. The more air is supplied, the more fuel will flow and therefore the speed will increase. When the throttle is in the idle position, the throttle returns to the closed position. In addition to the main mode, mechanical systems may also include manual control of the throttle position using a special knob.

The principle of operation of the electronic drive

The second and more modern type of shock absorbers is an electronic throttle (with electric drive and electronic control). Its main characteristics:

• There is no direct mechanical interaction between pedal and damper. Instead, electronic control is used, which also allows you to change the engine torque without having to press the pedal.
• Engine idling is controlled automatically by moving the throttle.

The electronic system includes:

• throttle position and gas sensors;
• electronic engine control unit (ECU);
• electric traction

The electronic throttle control system also takes into account signals from the transmission, climate control system, brake pedal position sensor and cruise control.

When you press the accelerator pedal, the accelerator pedal position sensor, consisting of two independent potentiometers, changes the resistance in the circuit, which is a signal to the electronic control unit. The latter transmits the appropriate command to the electric drive (motor) and turns the throttle. Its position, in turn, is controlled by appropriate sensors. They send information about the new valve position to the ECU.

The current throttle position sensor is a potentiometer with multidirectional signals and a total resistance of 8 kOhm. It is located in its body and reacts to the rotation of the shaft, converting the opening angle of the valve into a DC voltage.

In the closed position of the valve, the voltage will be about 0,7 V, and in the fully open position, about 4 V. This signal is received by the controller, thus learning about the percentage of throttle opening. Based on this, the amount of fuel supplied is calculated.

The damper position sensor output curves are multidirectional. The control signal is the difference between two values. This approach helps to cope with potential interference.

Throttle service and repair

If the throttle valve fails, your module changes completely, but in some cases it is enough to make an adjustment (adaptation) or cleaning. Therefore, for more accurate operation of electrically driven systems, it is necessary to adapt or learn the throttle. This procedure consists in entering data on the extreme positions of the valve (opening and closing) into the memory of the controller).

Throttle adaptation is mandatory in the following cases:

• When replacing or reconfiguring the electronic engine control unit of the car.
• When replacing a shock absorber.
• When the engine is unstable at idle.

The throttle valve unit is trained at the service station using special equipment (scanners). Unprofessional intervention can lead to incorrect adaptation and deterioration of vehicle performance.

If there is a problem with the sensors, a warning light will come on in the instrument panel to notify you of the problem. This may indicate both an incorrect setting and a break in contacts. Another common malfunction is air leakage, which can be diagnosed by a sharp increase in engine speed.

Despite the simplicity of the design, it is better to entrust the diagnosis and repair of the throttle valve to an experienced specialist. This will ensure economical, comfortable and, most importantly, safe operation of the car and increase the engine life.