Microsquirt request 3 cylinder two stroke

[Malkus]

Thanks lav1000! Great help

[dontz125]

On the phone, maybe circuit later.

3x VR circuits (2x jbperf's Dual VR boards?), each one triggering OPTO pin. 3rd circuit activates a 0.1ms one-shot (555 or equivalent, falling edge trigger); the output drives a second falling-edge trigger connected to VR2. This gives you a 3-0/1 Dual wheel arrangement with no physical modifications (besides rewiring the VR sensors).

[Malkus]

Dontz125, that really sounds like a solution I want to try out! If you do have the possibility please do post more info on this

[dontz125]

Hi, Malkus.

Here's the circuit:

3-cyl 2 Stroke.jpg

I gave some thought to using the VR1 input for one of the sensors, and feeding the other two to the OPTO inputs as shown; this would allow the use of only one Dual VR board. My concern is that the additional components of the OPTO circuit would cause a phase shift, causing cyl 2 & 3 to be advanced or retarded vs cyl 1.

Edit - values of C1 and C4 changed to 0.001uF, to give a sharper rising edge signal to the uS.

Edit - D4 deleted; revised schematic attached

Edit - OPTO pins changed to VRIN1- , second trigger input changed to VRIN2-.

[Malkus]

Thanks a million! I would never have managed this by myself. From here I can get it done. Cheers

Malkus

[dontz125]

Schematic revised; D4 deleted.

[Malkus]

Ok!!

[racingmini_mtl]

Why do you want to use the Opto input on a uS V3? That circuit has all sorts of issues and has only one use: a coil '-' input.

Jean

[dontz125]

Good point. That thought was probably a left-over from the initial plan of having one sensor feed the VR1 input on the uS, and the other two coming into the OPTO via one of your boards. Since the plan now has all three sensors feeding into your boards, feeding the outputs to the uS VR1 input makes sense.

Ok - schematic is revised again. OPTO is gone, replaced by VR_IN1-. Note also that the 'cam' signal pin has been corrected to VR_IN2-; it was on VR_IN2+.

[Wrigh06]

I'm also trying to set Microsquirt up on a 3 cylinder 4 stroke with wasted spark (so same as a 3 cylinder 2 stroke). How did you get Tuner Studio set up to give 3 120 degree spark intervals?

[dontz125]

There's two ways to do it. If you have a cam sensor you can just set it as 3 cylinders. If you don't, you can lie to the box, and set it for 6 cyls.