1FastRedSC

I have a crank trigger wheel with a 60-2 setup on the front pulley from SFR that was used on an old tec2 setup. I want to try and use the factory sensors on the flywheel to pick up signal. I already had a machine shop install 62 evenly spaced set screws as teeth in the flywheel with 2 of the screws recessing into the flywheel. My question is what type of sensor are those stock bosch pick up sensors? The factory manual talks about supplying them with 5 volts in order to get signal, does this mean that they are hall effect sensors? Or are they some strange type of VR sensors?

pete95zhn

VR sensors.

jlturpin

No voltage required for VR sensors.

pete95zhn

Yes, VR-sensors generate a signal ( output ) by themselves, no voltage input required. As you might already know, 951's original system is a 132+1, ie. the other VR-sensor reads the one lonely pin on the flywheel and the other 132 teeth on starter's gear ring.

So, after reading your post again, you have converted the flywheel to 60-2. Very interesting. Actually quite handy...I could have used that one myself...

Olli Snellman

Actually seems to me the front pulley has been modified

1FastRedSC

Actually both. There's an extra tooth wheel that bolts to the front pulley for my old tec2 setup. However that setup is a real hassle with the sensor mounting on the power steering pumps belt adjuster. So that's why i wanted to move it to the back where the original setup was. So i had a machine shop (less then 100 bucks btw) machine in 60 set screws into the flywheel along the same plane as that "lonely" single set screw used to be. Therefore with 2 fully recessed screws and the rest sticking out the same distance as the factory you end up with something similar to that toothed wheel on the front but relatively factory looking. Or well at least that is the plan. Anyhow, so why does it have three three pins on the connector if it's a vr sensor? The GM vr sensor i have laying around is single wired connector with a ground shield.

jlturpin

VR +/- and shield. It is an analog signal and needs to be shielded from EMI.

1FastRedSC

I don't understand this part, i thought vr sensors generated there own potential. Why would there be two vr signal wires and a ground? Why not a signal wire and ground? I think i need to read through the factory manual some more.....

jlturpin

Yes, they do generate a AC voltage signal with no input. There are three wires coming from the Bosch VR sensor, Positive (+), Ground (-) and shield.

pete95zhn

Here's a scoped image of pulse generated by an original VR-signal, inverted though... When + and - are connected as they should be, rising positive ( and also arming ) peak comes first, and then the decending negative ( and triggering ) peak follows.



Also the voltage we're talking about is around 50-200mV, arming positive voltage slightly more than triggering negative.
You can test this by yourself with standard voltmeter. Put some tape ( slightly less than 1mm ) on top of the VR-sensor, attach voltmeters wires to the sensor's pins #1&2 ( 3's the shield ) and move the sensor across non-stainless steel. From voltmeter you can see positive voltage when approaching that steel, and negative when leaving it. If other way around, switch wires.

1FastRedSC

Thank you that is some really good information there (is that labview that you're using?). I'm not sure but i think my dad has a fluke with a scope so i'll borrow it to test it. I also have been going through the wiring diagrams for the MSII and it seems that there are ground wires, a sensor ground, and a shield ground all separate from each other. So i "think" that VR- pin will ground to sensor ground, the shield is well shield, and the VR+ will go to the shielded tach input wire which goes to the VR pick up circuit. Maybe it's a good idea to try and hook up power to the MSII and connect the VR as described above, then run it across a ferrous material to see if i get an rpm signal in megatune. Anyhow thank you again.

jlturpin

There should be a VR+ and a VR- input. The sensor ground is for the MAP, tps, coolant, and IAT sensors.

1FastRedSC

I got my hands on a scope this weekend. I was able to identify the positive and negative pins using the advise above. What impressed me is just how clean the signal is, i mean it seems like it's a really good sensor. Kind of strange i guess as to why other mod shops haven't thought of using the factory VR sensor setup yet.