MicroSquirt.com read only forum (Jan.15,2018)

For the tachRef i showed at the begining of this post:

stock VR1 sensor+ to MS VR1+
stock VR1 sensor- to MS VR1-

stock VR2 sensor+ to MS VR2+
stock VR2 sensor- to MS VR2-

**note :stock VR connector was unplugged from the TCI unit.


For the latest tachRef :

VR1+ from MS and VR2+ from MS are left floating

stock VR1 sensor- to MS VR1-

stock VR2 sensor- to MS VR2-

** note : i had no rpm reading on tunerstudio unless i connected back the stock VR connector to the TCI unit.


I did a couple of test today but didnt make any progress

Ok, I did mention an edge detection circuit, not just wiring the sensors directly to the uS ...

Try this:
Sensor 1+ to diode (band towards uS) to VR1-
Sensor 1- to diode (band away from uS) to power GND

Sensor 2+ to diode (band towards uS) to VR2-
Sensor 2- to diode (band away from uS) to power GND

Any rectifier diode with a rating over 100v will do; I might suggest Schottky as a high Vf might absorb the signal at cranking.

i ll try that tomorrow but what do you mean by "power GND"?

Some of the pins are labelled "Power GND"; there is also "Sensor GND" and "Serial GND." Just rechecking the schematic, all the ground pins are tied together at the circuit board, so it doesn't particularly matter.

ok thanks !!

heres a pic of my VR1 wiring: I used 1N4004 diodes which are rated for 400V i believe.

SO in the morning i wired up like this , only using VR1 and check the tachRef which gave me a nice reading , i tried it twice and worked great.

I was very happy and felt excited but...

then i wired VR2 the same way and checked the tachRef but it didnt gave me any reading at all not even for VR1.

So i disconnected VR2 to check back at VR1 signal on tachRef, nothing came out, no readings at all.

i know sometimes i forget the boothloader connected to ground after loading code and tachRef wont work but in this case boothloader cable was floating when i tried VR1.

Checked my wiring and diodes with a multimeter and everything looks OK.

Checked MS VR1 and MS VR2 circuit and they work.

So i dont know why it worked twice this morning and got nothing after that, didnt have time to print screen the tachRef to show you the new signal

i dont know if tachRef is playing me some tricks but i ll run some more test tomorrow , battery had a long day and needs charging.

i ll keep you updated thanks for your help!!

Update :

ok so now i got a signal like this on tachRef

Why cant tachRef see the 180 deg offset that seperates both signal like i see in my oscilloscope?
I mean in the picture they dont look like they are separate equally like an even-fire would be...

Looking at your pic, the wiring is incorrect. The uS pin VR1+ is not used. The +ve side of the VR sensor goes to uS pin VR1- (diode band towards the uS); the -ve side of the VR sensor goes to uS GND (diode band AWAY from the uS).

i tried different variation including what you told me to which is exemple #2 on this picture.

on exemple #2 , vr2 was connected too but signal didnt show up on tachRef thats why it only shows one signal.

Still no offset showing in tachRef , but i guess that its how tachRef works...

ok im starting to get good results here but there is so much confusion about my understanding of the manual and how MS handles spark calculations for my setup.

1- Since in dual tach input mode M = 0 :

-how does MS knows the engine position and fire at an accurate position if there is only one teeth? Does it calculate it based on "Time since last teeth"?

- how can trigger offset be applied if M = 0 ?

- What about cranking trigger mode "Calculated" or auto-trigger ? How does MS handles that if M = 0?

- how does MS knows when to start charging the coils?