Question about wiring Variable Reluctor (VR)...

[EWflyer]

My "it's go time!" moment has finally arrived. After several months of preparation I'm about to begin the installation and tuning work on my Kawasaki EX-250 Microsquirt fuel-only project.

Here's my current question: As many times as I've read over it, the description of wiring up the Variable Reluctor signal line to the Microsquirt still leaves me confused. On the Microsquirt.info website under the "wiring" heading there's a breakdown of the wiring for the Ampseal connector.

When it gets to pins #32 and #33 which it calls "VRIN1+" and "VRIN-" the description makes it sound like you only connect 1 (one) wire to 1 (one) of the four pins (#s 30,31,32,33) because they're all connected to the same processor. The description next to each of these pins contains this note:

Note that you can use only one of OPTIN+/- or VRIN+/-, because they connect to the same processor pin.

But just a couple of paragraphs later, in the section called "Grounds" it talks about the "VR(-)" input on the Ampseal that needs to be connected so the energy from the VR sensor is returned to the bike's VR circuit. I think I get that logic, but the pin description already mentioned above makes me wonder.

Could anyone describe the VR wiring in non-electrician speak?

[Martin Wagner]

Both the VRIN1+/- pair of wires and the OPTOIN+/- pair of wires feed preamp circuits. The outputs of the 2 separate preamp circuits go to a single CPU processor pin so you want to use only one pair of inputs. Since you are using a VR sensor you should use the VRIN1+/- pair and leave the OPTOIN+/- disconnected. You need to use both wires in the pair because the preamp is only looking at the voltage difference between the VRIN1+ wire and the VRIN1- wire, not between VRIN1+ and ground.