Understanding Car Engine Components & Operation
Pressure Regulator
The pressure regulator is a mechanical system within the fuel injection ramp. It features two chambers:
- One filled with gasoline, including a pressure valve that allows gasoline return if pressure exceeds a set limit.
- A second chamber, isolated from the first, connected by a tube to the intake manifold.
A membrane separates these chambers. This membrane is affected by the depression in the intake, and its movement adjusts the pressure valve setting. This varies the fuel pressure based on engine load.
Relay Pump
The relay pump receives positive ignition and negative signals from the control unit. This relay operates for a few seconds when the ignition is turned on to prime the circuit. After this, it cuts the negative signal and activates the safety relay.
Flow Meter
The flow meter measures the volume of air drawn into the engine and converts this data into an electrical signal for the Engine Control Unit (ECU). It’s located after the air filter, before the throttle body. It consists of:
- A mobile trap operated by the airflow.
- A cap that cushions the trap’s return.
- A damping flap.
- A potentiometer (possibly with one or two tracks) with a cursor, providing a variable electrical signal based on the trap’s position.
This potentiometer changes the input voltage (nominally 5 volts). Its signal, crucial for engine operation, is essential for calculating injection time.
Additional Valve
The additional valve is an element that aids engine operation when cold, up to an operating temperature of 70°C. It provides the necessary amount of air during cold starts. It’s mounted in parallel with the idle air circuit, bypassing the throttle, and connected by two rubber tubes to the air circuit. It’s fixed to the engine for accurate temperature reference. A rotating trap, operated by a bimetal, regulates the air passage. When the engine is cold, a return spring keeps the air passage fully open. As the temperature rises, the bimetal deforms, acting on the trapdoor. At 60°C, the passage is completely closed.
Stepper Motor
Stepper motors typically consist of a rotor with permanent magnets and a stator with exciting coils. There are two main types:
- Bipolar: These generally have four output wires.
- Unipolar: These usually have five or six output wires, depending on their internal wiring.
These motors require sequential current reversal in the coils. Each polarity reversal causes a single-step movement of the shaft. The rotation direction is determined by the sequence followed.
Hot-Wire Flow Meter
If airflow increases, the wire cools, decreasing its resistance. This causes a voltage imbalance (nominally maintained at 5V). This variation is sent to the ECU, informing it of the incoming air volume.