S-class W202 Mercedes

1993-2000 of release

Repair and car operation



W202 Mercedes
+ 1.2. General information
+ 2. Maintenance
+ 3. Engines
+ 4. Greasing system
+ 5. Cooling system
+ 6. Heating, ventilation
+ 7. Ignition system
- 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 fuel injection
      8.2.3. Air flowmeter
      8.2.4. A temperature-sensitive element of cooling liquid
      8.2.5. The sensor of soaked-up air
      8.2.6. System of vacuum pipelines
      8.2.7. The fuel distributor with klapanny nozzles
      8.2.8. Klapannye of a nozzle
      8.2.9. Oxygen sensor (lambda probe)
      8.2.10. Diagnostics of malfunctions of system of injection of gasoline
      8.2.11. That it is necessary to know to the owner of the car with the injector engine
      8.2.12. Turbo doctor
   + 8.3. System of injection and food 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. Electroschemes








b47c026d b47c026d


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 a film heater (HFM) instead of the sensor of pressure of air.

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 up by means of an electricity is cooled with let-in air proceeding by.

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

Klapannye nozzles cope in turn according to an operating procedure of cylinders, thanks to it it is possible to coordinate fuel dispensing 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.

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

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