Hi,

Got the reading from my new air flow sensor. This is for Bosch Part number 0438121 072. My car is a German 1989 190 Sport Evolution 1. However this part as far as I know was fitted to all 16V's including the stock 2.5 and the Evolution II. I have a Bosch specification for the unit kindly supplied by Cor de jong in Holland. For a start I'll list those values, but bear in mind this was in German and I've done my best to translate it.

Supply Voltage: Pin 1 & 3 of Airflow meter Potentiometer - 4.35-5.35V
Tension Signal: Pins 1 & 2 of Airflow meter Potentiometer:

This is a graph which I unfortunately can't scan in. I'll give the ranges. With a supply of 4.35v volts on 1 & 2 should be _approximately 0.435V to 0.78V. With a supply of 5.35V volts on 1 & 2 should be _approximately 0.54v to 0.92v. These numbers have been derived from simply looking at values on a graph. I'd say they should be accurate to around 0.20v.

Now to the airflow meter plate. The Zero position of the air flow meter plate should be 4.2-4.4mm from the rest position.

There should be 0.1-2.0mm free travel. More on this later.

Right, thats it for the Bosch details, now for my testing on my new airflow meter.

I have used a vernier caliper to take these readings. They are taken from the centre of the rubber rest on the very top of the meter, down to the washer under the nut securing the airflow meter plate.

The distance to the washer from the top of the rubber stop in the centre is 30mm. Be aware this isn't science as it's very difficult to measure this accurately, but I'd say the numbers are good for maybe 10-15% variation - ie 15 ohmns.

Here are the values.

30mm 1.022K (2K scale)

This area the readings fluctuate slightly but pretty much fall to the 30mm position.

34.2mm 1.000k (2K scale - according to Bosch the Zero position)

I'm a little concerned as to what Bosch consider the "Free Travel" as plainly there is 4.2mm of free travel in mine, but at 4.2mm that is exactly where Zero position is supposed to be according to the literature. I may have to adjust the pin to lower the height of mine by at least 2mm to take up some of the free travel. But if I do, it will no longer contact the rubber stop. Bit of a mystery... Anyone? I think I will leave it for now.

35mm 1.070k (First place I see a change)
35.80mm 2.00k (Very rapid ramp up to 2.0K from 1K in the space of less than a single mm)

36mm 2.35k
37mm 3.35k
38mm 4.25k
39mm 4.95k
40mm 5.55k
41mm 5.95k
42mm 6.35k
43mm 6.80k
44mm 7.10k
45mm 7.30k
46mm 7.60k
47mm 7.80k
48mm 7.90k
49mm 8.15k
50mm 8.20k
51mm 8.20k
52mm 8.28k
53mm 8.28k
54mm 8.32k
55mm 8.50k
60mm 9.40k

65mm 9.50k (peaks here, then begins to fall)

68mm 9.40k
70mm 9.20k
71mm 9.10k
72mm 8.90k
73mm 8.80k
74mm 8.60k
75mm 8.45k
76mm 8.25k
77mm 8.10k
78mm 7.85k
79mm 7.60k

80mm 7.50k (Plate bottoms out - no more travel).

Well, I hope this helps somebody!

Cheers,
Neil