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

I'm sure this question comes up often, but I searched I could find what I'm looking for.
I'm thinking of converting a single cylinder 4 stroke MC engine to EFI and use stock ignition. What sensors would I need? TPS, MAP, IAT, and a tach input? Can I piggyback the hall sensor being used for the CDI currently?

Thanks,
CR

You'll want CLT for cold start / warm up as well - sort of a choke function. Depending on the thread size of the stock thermoswitch for the fan, you may be able to find a CLT sensor that will thread right in. Of course, at that point you'll want to provide a fan switch function through the MicroSquirt.

You could certainly use the Hall sensor; the question then becomes, what is the trigger wheel pattern? Is it a single short or long tooth (Hall sensors don't have the problems with long teeth that plague VR sensors), a pattern of teeth, ?

Is the ignition CDI or TCI? This may have some input on driving your tach input. (A LOT of people refer to bike electronic ignitions simply as "the CDI"; this is very often completely wrong)

Thanks for the reply, yes I did leave out a temp sender, and do understand the system needs it. You probably right, it's most likely a TCI circuit, not really sure if that matters, I just need to tap the hall sensor. Unless you're saying I can tap the coil for a tach signal?
Yes it does have a single large "bump" on the stator to trigger the spark.

CR

If that's a Hall sensor (3 wires), go with that. If it's a VR sensor (2 wires), you'll need to use the TCI coil negative. VR and CDI with a long tooth would need rather more thought ...

I think you're right, it's a 2 wire, must be a variable reluctor? Then would that make it def a TCI? It's funny I had a electronics background, I never dove too deep into engine electronics other to understand how to repair the factory stuff. Thanks for the education!!!!

The ignition could be TCI or CDI, the pickup type doesn't enter into it. Inspect your coil wiring, noting how the power flows. Do you have +12v on one wire, with the other wire going to the black box? Or does the wiring run from the ignitor to the coil to ground? If one side of the coil is hot,it's a TCI system. If one side is wired straight to ground, it's CDI.

dontz125 wrote:The ignition could be TCI or CDI, the pickup type doesn't enter into it. Inspect your coil wiring, noting how the power flows. Do you have +12v on one wire, with the other wire going to the black box? Or does the wiring run from the ignitor to the coil to ground? If one side of the coil is hot,it's a TCI system. If one side is wired straight to ground, it's CDI.

One side is straight to ground, the other side comes directly from the "CDI" box. There isn't any 12 volts on the system at all, everything is tested with a peak meter when trouble shooting.... I would have to check the manual, but I remember something like a 100 volts peak at the coil.

CR

Yuk - CDI and a VR reading a single long tooth is pretty much the worst combination. There is just nothing for the uS to read! You could add an edge detector circuit reading the VR signal, and fed to the OPTO+ pin; ground the OPTO- pin. I'm on my phone right now ; I'll try to post a circuit example tomorrow.

One question - if you have no 12v, how will you power the uS, the pump, injectors ...? Running total loss on a battery is possible for a race bike, but won't last all that long on the street or trails!

Ok, as promised - a circuit to turn a long-tooth into a sharp edge. As mentioned, ground the OPTOIN- pin.

And here's what the output looks like - since you'll be running it through the OPTOIN+ pin, the Vin (labelled +12v) can be +5 or +12.

I knew you were going to ask about the lack of 12volt!!!! This will be for a racing kart, 30 minute races max, so either total loss, or they build a charging coil to add to it...
The flywheel is oil bath, and I have to see if there's room, but I guess the best way would be some sort of trigger wheel, and a hall sensor?

CR