The Vaned AFS

 

The two Air Flow Sensors (AFS) sit between the air filter and the throttle body. As the air flows through the sensor it deflects the vane and moves a potentiometer. The greater the air volume the more the vane moves. As the potentiometer moves, the resistance is varied and allows a varied voltage to be returned to the EEC.

The quantity of fuel injected is greatly influenced by two AFS units

Three wires are used in the sensor circuitry, 5v is applied to the resitance track with an earth applied to the other side.

From the returned voltage the EEC is able to calculate the volume of air entering the engine and this is used to calculate the length of the fuel injected pulse.

To help smooth inlet pulses, a damper is connected to the AFS vane.

AFS Voltages

AFS
EEC
Item
Volts
Ignition on : Engine Running
9
26
Supply Voltage
5.0 +/- 0.1
6
46
Sensor Return
200mV Max
7
43
Signal Voltage
See AFS Table

AFS Resitance Measurements

AFS
EEC
Item
Res. (Ohms)
9 and 6
26 and 46
Fixed
250 to 600
7 and 6
43 and 46
Variable
See AFS Table
7 and 6
43 and 46

AFS Voltage Table (Signal Output at Terminal 7)

Flap Position
Volts
Ignition On
0.20 - 0.30
Idle
0.50 - 0.60
2000 rpm
1.00 - 1.50
3000 rpm
1.20 - 2.50
Snap Accelerate
3.00 - 4.50
Fully Open
4.50+

AFS Resistance Table

AFS
EEC
Item
Res. (Ohms)
7 and 6
43 and 46
Closed
25 - 120
7 and 6
43 and 46
Fully Open
Below 2100*
7 and 9
43 and 26
Closed
250 - 600
7 and 9
43 and 26
Fully Open
Below 2100*

* All resistance values are approximate. More important than the actual value is the ability of the AFS to open and close smoothly with a smooth increase and decrease of the resitance values.

AFS Circuitry

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