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

Hey guys,

I'm having a real tough time with a V3 MS2 trying to run direct coil control. This is for a formula SAE team running a Honda CRF450X single cylinder engine. Right now we have a VR sensor and 24 tooth trigger wheel that puts out a nice signal via oscilliscope. Were trying to drive a Honda CBRf4i coil, and are having no luck whatsoever obtaining a spark. RPM signal looks great, as do the rest of the sensors (for what thats worth).

The MS2 box we have was set up to run the Hall effect circuit. Im not sure how that circuit works with a VR, but common sence told me that we needed to use the VR input circuit with a VR sensor. With that said, we made the appropriate jumpers for direct coil control and the VR circuit
VRIN to TACHSELECT
TSEL to VROUT

and for direct coil control:
IGBTIN to JS10
IGBTOUT to IGN

The negative terminal is hooked up to Pin 36, and the positive to a 12 volt signal.

but to no avail. Still no spark. The Board had some jumpers in place of D1 and D2. Seeing how the Instillation procedure for VR circuit doesn't mention those Diodes at all, I cut the jumpers. But still no change.

The MS works great on the V2.1 Stimulator. The "IG" LED on the Stim flickers pretty consistently. But I dont see a signal on pin 36 at all. Just battery voltage and noise. The lack of signal on Pin 36 leads me to believe that our problem is internal to MS. So I really dont think this is a setting thats causing my problems. But im really not sure.
Any help would be appreciated guys. We leave for competition in 2 weeks, and our chief engineer is threatening to toss the Carb on the car if I cant get this figured out soon!

I have one thing to add, Apparently I dont know how to use an oscilloscope very well..

After a buddy helped me out with the scope, We DO see a clean 5V square wave signal coming out of Pin 36.

What still confuses me is, after connecting all the jumpers for Direct coil control, why an I getting 5V instead of 12?? And for what its worth I do have the VB921 Ignition Module installed on the MS2. And even with that 5V signal we cant get our coil to fire (obviously). So we hooked up to a driven LS1 coil, and gave that a shot. But still no luck with spark.

postman,
After moving over to the Vr tach input circuit, was there still a solid tach signal coming in (megatune shows solid RPM when cranking the engine)?
You are correct - D1 / D2 are not used by Vr circuit so cutting a jumper around them would have not changed anything.
The VB921 just grounds the coil; it does not provide an voltage, but rather just a path to ground when activiated. When it is not turned on, its output should float (be ~open), which when connected to a powered coil => ~12V.

Where did you see the 5V wave form? on the STIM or on the engine? If it was on the STIM, it might make some sense - the LED on the stim is connected to Vref (5v) and then goes through R13 to the ign pin 36 of DB37. The VB921 provides a ground path when activiated to light up the LED. When not activiated, pin 36 of DB37 could be close to the 5V Vref value.

It sounds like it is working on the STIM, any chance there is an engine wiring harness problem? I'd check for continuity between the center pin (2) of the VB921 to the negative terminal of the coil. The power should be off when doing this. I would also check the voltage (~12v) on the positive (+) side of the coil when you are cranking.

- Charles.

Postman,

I had a similar issue with the ignition signal. I finally traced problem down to a short with the shielding on the ignition trigger wire. My set up worked fine on the Stim (w/o the wiring harness).

Check your harness for shorts and pay close attention to the shield on the ignition trigger wire. I used shrink tubing to protect the shielding but inadvertently created a short when the strands were compressed by the shrink.

Cheers