* since the trigger mod for deviating missing tooth wasn't requested in order comment, had to disassemble ECU to modify R181 to greater (>=270k) value

* luckily with active COP-s there is barely any heat on TO220, so the ECU can be carefully tested first without clamping/assembling

Sick in multiple ways:

* Amplitude of tooth56 is appr 1/6 of tooth0 (missing tooth) amplitude

* NOT always going below GND (will NOT trigger!). Maybe some serious metal-mud in the gap right after the missing tooth ? - NO, the wheel looks clean (but also looks exactly like a wheel originally designed for HALL)

** EC36/27 (R30 pullup already removed). Add 27k pulldown to -8V (LCD header) as a bandaid to mask the real problem. This (some capacitor trick, or much weaker pulldown = higher resistance if directly to LM1815/pin3, but avoid that for now)

* Turned out the VR sensor was not fastened. It was lose, could easily be moved by hand, significantly. Some washer helped a lot.

** this alone does NOT explain the "signal not going below 0mV" symptom (metal mud is more likely) => but at least the first improvement since experimenting with all kind of mods :-)

** fastening the sensor helped (upto 6000 RPM), but did NOT solve it. Changing to another VR sensor completely fixed the problem. Interestingly, the signal is quite different with the new sensor. hmm...

* Originally show up at 5000 RPM

** 2k7 pulldown made it much worse (1500 RPM)

** R181=270k (instead of 150k) appr 4000 RPM (

** given that greater R181 did NOT help, only C30 remains that might prevent the compination of signal with such sicknesses and >5000 RPM. (C30*R56 = 18usec which should be perfect for period >= 100usec == 10000 RPM, but any cheat can help if so close to the edge and the real problem cannot be fixed at the moment)

Do we wonder that removing pullup does NOT help ?

Trigger types from best to worst:

* HALL type (less prone to noise). For any home-made wheel we can only recommend HALL type

* proper VR type, with tooth amplitudes almost same ("Bosch wheel")

** adaptive hysteresis is a GOOD thing: it allows proper sensing even with greater (amplitude) high RPM noise than the full signal at low RPM (cold cranking)

* worst: VR with stupid wheel (or HALL wheel used with VR sensor)

** the amplitude at the missing tooth deviates (greater).

** supported with greater R181 (at primtrig LM1815pin7). Or R182 (at sectrig LM1815pin7). 270k or greater (~180k factory)

** Done, ECU trigger inputs GOOD up to 11k RPM