rising vs falling edge on "motronic" wheels + vr

[JoseMiguel]

When using motronic wheels (60-2 for instance) with a VR sensor, I have always followed the same pattern as per recommended in the manual. I go to the tooth logger, see if I get the two long teeth and adjust accordingly. As we all know, if also depends on the wiring of the VR sensor as one can also fix this by interchanging the + and - wires from the VR sensor. This has worked for many years now, but I have been working a lot with other ECU's and, although all of them permit selection of rising and falling edges, most of them recommend using falling edge for toothed wheels with a reluctor.

Haltech says in its manual that falling is preferred for VR and toothed wheel because "the edge that does not move with respect to the crank at all engine speeds" which is not a very clear argument.

I understand perfectly (I think) what the capture edge means, and my reasoning tells me that as long as the reluctor is not "double triggered" on the missing teeth, you are good to go. But that is my reasoning.

The question is: Is there any recommendation by the MS Designers on what edge to use on multitooth wheels? I can wire my reluctors so that I can always use rising or falling depending on if something is really better.

[JoseMiguel]

Any comments?

[grom_e30]

im using a motronic 1.3 setup from a bmw with rising edge and its been flaw less, i seem to recall reading some where that a vr sensor should be set to use rising edge and a hall sensor should use falling edge but i may be wrong on that one.

[billr]

And I use "falling edge" with a 60-2 and VR, also works flawless. Pots both full CCW and no series resistor added. Spark retard is about 1/2 to 1 deg. at 6400 rpm, so I don't bother fussing with spark latency. It seems like it can work with either rising or falling, if the sensor polarity is correct.

[Peter Florance]

As reported, it depends on the polarity. There will only be on correct edge.