Mercedes of the S-class W202

1993-2000 of release

Repair and operation of the car



Mercedes W202
+ 1.2. General information
+ 2. Maintenance
+ 3. Engines
+ 4. Lubrication system
+ 5. Cooling system
+ 6. Heating, ventilation
+ 7. System of ignition
- 8. Fuel system
   + 8.1.1. Introduction
   - 8.2. System of injection of petrol engines
      8.2.1.1. Principle of work of PMS
      8.2.1.2. Principle of work of HFM
      8.2.2. Self-diagnosing of a condition of system of ignition and injection of fuel
      8.2.3. Air flowmeter
      8.2.4. Thermal sensor of cooling liquid
      8.2.5. The sensor of the soaked-up air
      8.2.6. System of vacuum pipelines
      8.2.7. The fuel distributor with valvate nozzles
      8.2.8. Valvate nozzles
      8.2.9. Oxygen sensor (lambda probe)
      8.2.10. Diagnostics of malfunctions of system of injection of gasoline
      8.2.11. What should be known to the owner of the car with the injector engine
      8.2.12. Turbo doctor
   + 8.3. System of injection and power supply of diesel engines
   + 8.4. System of production of exhaust gases
+ 9. Transmission
+ 10. Running gear
+ 11. Steering
+ 12. Brake system
+ 13. Body
+ 14. Electric equipment
+ 14.2. Electrical circuitries






8.2.1.2. Principle of work of HFM

GENERAL INFORMATION

Considerable difference in comparison with a PMS control system of the engine is application of a flowmeter of air with the film heater (HFM) instead of the air pressure sensor.

The flowmeter of air (B2/5) promotes even more exact dispensing of fuel. Principle of functioning of measurement of a consumption of air: the plate of the sensor (70/1) heated by means of electricity is cooled with the let-in air proceeding by.

To maintain a constant sensor plate temperature, current of heating changes according to density and temperature of the let-in air. On the basis of fluctuations of current of heating the actuation device determines the mass of the let-in air and according to it regulates amount of injectable fuel. (70/4 - protective lattice.)

Valvate nozzles are controlled in turn according to an operating procedure of cylinders, thanks to it it is possible to coordinate dispensing of fuel with the corresponding power setting even more precisely. Professional term of process: consecutive injection.

The system of anti-detonation regulation serves for definition and establishment of the optimum moment of ignition of fuel, even at its more poor quality. In case of malfunction of system of ignition supply of fuel to the corresponding cylinder stops.

Through electrohydraulic executive body there is a shift of the inlet camshaft in relation to an asterisk of the actuation device. By means of shift in the direction of late ignition the smooth course of the engine in the idling mode improves, or with high frequencies of rotation increases power. In the lower and average range of valves filling of cylinders and by that torque improves.

6-cylinder engine: the resonant switching inlet gas pipeline which depending on the frequency of rotation of a shaft of the engine changes an air route to cylinders is used to improvement of nature of torque with low frequencies of rotation. For this purpose the air collector behind a butterfly valve is divided into two half by the shutter pneumatic put in action: one air stream moves respectively on 3 cylinders. Extent of an inlet path with low frequencies of rotation thanks to resonant effect provides good filling of the cylinder and, therefore, high torque. With high frequencies of rotation the shutter opens in order that is able to use engine capacity potential completely.