The M50 series of engines (m50 / m52 / s50 / s52) seem to have used a number of different sensor configurations over the years. This can make it somewhat complicated when configuring VEMS.
I got alittle ahead of myself, and ordered VEMS configured differently then the sensors on my car.
I was under the impression that my car had two vr sensors, one for crank and one for cam. This may in fact be the case in older m50 style engines. My engine however had a hall sensor (i think) for the crank mounted at the rear of the engine near the flywheel and another style sensor for the cam.
i was under the impression the cam sensor was hall after examining it.. but found a reference to it on a MoTec sight where they think it might be some sort of current sensor. Basically the solution is to swap it out, but I don't want to go with VR. I'd rather have hall - but my VEMS is configured for VR as the second trigger.
Here is a note from the MoTec site on the cam sensor
Cam Sensor we know wont work DANGER DANGER : BMW 1 703 221 Siemens 5WK9 6011
- very special (requires supply, perhaps electromagnet instead of permanent magnet?), but otherwise VR-style (it won't work with Motec either).
- Gunnar provided scopeshot (with factory ECU) on MembersPage/GunnarReynisson/BigMotronicPin
(otherwise, if no factory ECU, than with +12V supply applied through a 47 Ohm resistor: max 15V/59 Ohm = 237mA current)
Sensor resistance, 12.2 Ohms between Term 1 and 2
.5 ohms between Term 2 and 3
12.7 ohms between Term 1 and 3
Any sensor which matches this resistance scheme cannot be used by MoTeC (or VEMS).
We know for sure this sensor when used as a mag, requires Magnets to
produce any voltage a/c between 1 and 2 with 1 being the falling edge.
The answer is to pick a different sensor.
Cam Sensor which we know works (is this a simple bolt-on replacement ?)
BMW 12 14 1 438 081 - Hall Effect Falling Edge
To solve the crank issue, i installed a VR sensor in the mounting location at the front of the engine. I'm getting a nice signal out of it, but VEMS does not seem to be picking it up. Gotta check into this more.
Questions:
I have a nice signal from my VR sensor, which has been verified with a scope.
- No noise
- appr 7 volt signal at cranking
- a good time to verify VR polarity: watching zero-crossing falling edges, there must be 1 missing tooth (2 long for N-1 or 3 long for N-2 wheel), not 2 missing tooth (each 1.5 long for N-1 or 2 long for N-2).
But no trigger events were being seen in VEMS. So i traced the signal across the board.
output of U11 LM1815 problem.
- output signal at pin12 is only 0.6 volts and is a square pulse down to 0.3 volts (while cranking).
- If i place the primary VR sensor onto U12 LM1815 (secondary trigger chip), I get a nice 5 volt square wave and get trigger events into the AVR (i jumpered the output to the primary input of the AVR)
Let's check the 10k pullup resistor. One end connected to pin 12 of U11 LM1815.
- The other end should be appr 5V, actually LM1815 U11pin7, check the solder joint and trace (only 2 layer board)
- What potential do you measure on this ?
- what is the voltage between LM1815 U11pin7 and GND ?
- maybe there is a short to GND ?
I can't seem to trace this back to where the issue might be?
Any help would be great. I'm banging my head here. Thanks!