Air flow meter (flow meter) with integrated temperature sensor Air HFM 6

3 Engine 1.3 16V Multijet 75 hp and 90

3.12 Air flow meter (flow meter) with integrated temperature sensor Air HFM 6

The advantages of the new flow meter are:

Greater protection of the sensitive element in the sensor against impurities the air (particles, water, oil vapor, etc..)

Greater accuracy of measurements.

The differences between the flow meter HFM6 and earlier are:

Digital signals of temperature and air flow Four-wire electrical connection.

Different channeling of the air flow which invests the sensitive element of measurement (new by- pass).

Turret heat-sealed to the duct flushing air.

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Protection grid to the outlet section of the duct flushing air (with the function of condensation of oil vapors).

The flow meter HFM6, has a new plastic grid (1) positioned on the outlet section of the duct sensor housing, which has the function of protecting the measuring sensor

(Sensing element) from the blow-by vapors that may riflussare during the off state of the motor.

In the digital flow meter the turret (2) is heat sealed to the duct housing the sensor, and therefore inseparable from it. In the analogue flow meter tower is attached to the conduit for means of two screws.

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Diagram digital meter mass air intake temperature

A = digital output temperature value B = 12v

C = mass

E = digital output value of air flow

1 = function generator 2 = data memory 3 = A / D converter

Flow meter DIGITAL OPERATION

Performance temperature signal

In debimetre the digital temperature value, sent to the engine control unit, is a signal of type PWM duty cycle (fixed frequency).

The working voltage is 5 volts and the measurement range is between -50 º C to +150 º C (with a consequent value of duty cycle of between 10% and 90%)

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1 2 3

The variation of the resistive values is converted from analogue to logic thanks to a

"Analog Digital Converter" (3). The data obtained is stored in a memory data

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(2). And thanks to a "Function Generator" (1) the data is sent to the control unit Engine.

Performance Signal AIR FLOW

In the digital flow meter, the signal sent to the engine control unit has an amplitude of 5 Volts and is variable in frequency from 1.4 kHz and 12 kHz.:

To an increase of incoming air capacity corresponds to an increase in the frequency of the output signal from the meter (and consequently a decrease of the value of

period).

Airflow

Frequency output

Flow meter digital signal AIR FLOW

To detect and verify the signal amplitude (voltage 5Volt), it is necessary the use of a voltmeter graph. To detect the frequency value and sufficient to use a multimeter with

selected the frequency measurement and the related caps connected one on the ground pin flow meter and a signal on the pin on the air flow.

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RDS fuel pressure sensor 4

E 'attached to the end of the single fuel manifold "rail" and has the task of providing to the injection unit a signal of "feedback" to:

adjust the injection pressure;

adjust the duration of injection.

The sensor is powered directly by the engine control unit with a voltage

5V. The output voltage varies linearly between 0.5V (0 bar) and 4.5 V (1500 bar).

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Pinout fuel pressure sensor

Name

Mass

Sensor Output

Supply

Type signal

Mass Exit Analog 5V Input

In case of failure of the sensor unit through the mapping of emergency commands the quantity control valve drv2 to erecting the minimum pressure of 100 bar (250

bar to 350 bar). N.B. the engine can 'start and run with the faulty sensor.

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Potentiometer accelerator pedal

The sensor is constituted by a casing fixed to the accelerator pedal, within which, in axial position, is placed a shaft connected to the two potentiometers: the main one and of safety.

On the shaft a helical spring ensures the correct pressure resistance, while a second spring assures the return of release.

The reading of the redundant signal allows to continuously monitor the plausibility of measured values, in order to ensure complete driving safety even in case of failure.

Operation

The position of the accelerator pedal is converted into an electric voltage signal and sent to the control unit from the potentiometer connected to its foot.

The accelerator pedal position signal is processed together with information relating the number of revolutions to derive the injection timing and the relative pressure.

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Ground Track 1

Track 1 Signal

Ground Track 2

Signal track 2

Type

Specifications Sensor Bosch

Supply voltage: 5V ± 0.3V

Resistance to terminal sliders knobs: 1 ± 0.4 Kohm Kohm Resistance Track 1: 1.2 ± 0.4 Kohm Kohm

Resistance Track 2: 1.7 ± 0.8 Kohm Kohm

Specifications Sensor hella

Supply voltage: 5V ± 0.3V

Resistance to terminal sliders knobs: 1 ± 0.4 Kohm Kohm Resistance Track 1: 0.9 Kohm 1.4 Kohm ± 35% ± 35% ....

Track 2 Resistance: 1.2 ohm ± 35% .... 35% ± 2.0 Kohm

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In document Fiat Grande Punto Service Manual_translated (Page 186-195)