Function

Although the air volume measurement did function, it had however, the disadvantages of the additional flap in the inlet manifold (loss of power) and the not always reliable mechanics of the rotary potentiometer. Apart from that, also an additional barometer was mostly necessary in the equipment for the altitude correction. All this was replaced by the air-mass meter. This was also the first time that a digital control device with a micro-processor was used.

How it works

In the LH-Jetronic a platinum hot-wire forms a resistance of a bridge connection, to which a temperature compensator in the slipstream, a precision resistance outside and an adjustable resistance also belong. This circuit is thus calibrated, that the temperature of the hot-wire always lies 100°C higher than the outside air temperature. The air which is suctioned in, cools down the wire. Thus the applied current forms a measure for air-mass through-flow.

By the way, there were still, for a long time, vehicles which had to keep the volume air flow sensor. This could cope better with the pulsating air-mass. Only now can the repeatedly measured air-mass be deducted out again.In addition, the stupid auxillary air valve was finally replaced by a clocked, idling-filling regulator. It was switched on electronically within 1/100 of a second, in percentage, for as long as the bypass line should be opened. The sluggish armature or starter solenoid could not follow the commands that quickly and adjusted itself exactly to the percentage value. The line could be arbitrarily widely opened- or closed by the control device. Indeed, the times when the idling setting was done with a screwdriver were finally over. 09/09

Sensors

Hot wire, Lambda sensor, temperature sensor (coolant), throttle switch, ignition signal (terminal 1)

Actuators

Injection valve, relay (fuel pump), idling filling-regulator

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