[ischmitz]

The 3.2 DME simply compares the O2 input signal against an internal reference voltage. For the time the sensor voltage is below the reference voltage (indicates lean mixture) the mixture trim value increases with a given rate (rate depends on RPM) and for the time the value is above the reference voltage (rich mixture) the mixture trim value decreases with the same rate.

The rate of change is about 5% per second at 3000 RPM. The trim value can modify the mixture by plus or minus 20% in part-throttle. If the O2 input voltage is zero all the time (sensor damaged or not connected) the mixture trim will simply walk all the way towards richening the mixture by 20%.

So the bottom line is without the sensor connected you run rich in your part-throttle range. Newer DME's from the 964 onwards detect a damaged or missing sensor and keep the mixture trim a zero.

Ingo