Question about coils

[BASS-TREBLE]

Does anyone know how much amperage is drawn by the negative signal wire going from the Ignitor to the coils? Not the constant positive supply but the one providing the 'pulses'.

Asking as I am playing with a quickshifter idea and want some diodes just to cover my ass.

I'm hoping I can get at least a ball part figure since I think a multimeter probably wont get a good reading.

Cheers

[NinjaNanna]

what are the diodes meant to do? Induced Voltage Protection?

Without seeing the specifics, the ignitor doesn't "supply" the pulses, it is switching the 12V supply to ground via the coil, this in turn creates the pulses. Minor differentiation but important to understand.

[BASS-TREBLE]

I have made a circuit to ground out the 'signal' wires from the ignitor to the coils during a shift.

It will be wired like this
http://www.mpsracing.com/instructions/MPS/Electronic_Kill.pdf

I know that this will work as it is a common way of going about it but my only worry is if the ignitor will be happy that this wire is grounded as it is still trying to switch (pulse) it?

So my thought was to use some diodes to stop the earthing out reaching the ignitor.

Cheers for your help mate

[NinjaNanna]

Grounding out the coil is going to create an "extra" spark this will result in either pre-ignition or be of no effect at all if the shift is after the properly timed "true" spark.

Are you sure the professional kit is not actually supplying 12V to the switched side of the coil thereby inhibiting any spark?

[bogan]

Won't the MPS thingumy have all the required protection internally? Or are you making one from scratch?

Also the negative signal wire will see the same current as the positive (unless they are shorted internally) as per Kirchoff's 1st Law. Not that I can help with what exactly that current might be, but would expect in the single digit amps range.

[BASS-TREBLE]

Bogan, I'm making one from scratch, but it is most probably very similar to the MPS one.
I don't think the current will be very high either but wondering if a 5amp relay will be enough.

So NinjaNanna, no matter if I relay the +12V supply or earth the trigger form the ignitor I will have the extra spark? I knew this extra spark can be an issue but I thought it wouldn't happen when earthing it out, why I thought that, I don't know.

My original plan was to relay the +12V supply to the coils but wanted to avoid this due to the extra spark so went onto the trigger wire hoping I could avoid it.

Just to give a bit of extra info, the circuit uses a little 555 chip and has a a variable pulse time from 14 to 140ms and this 'pulse' is a +12V so am planing to run a relay of that.

[bogan]

I think connecting it to +12 will give the best operation, you won't get an extra spark as the the coil is already pulling that wire to +12, you just need to make sure the CDI can handle discharge straight through +12 rather than the slower through coil then +12 it is expecting. Something to investigate also, I think the CDI will pull that line well below (a few hundred volts) earth on discharge, so it might change the setup of your protection diodes/circuitry. For this reason it is unlikely that you would get an extra spark on earthing it as well.

[BASS-TREBLE]

I will look into that idea bogan.

Approaching it from another angle, what about using a normally closed double throw relay inline to the crank pickup sensor (2 wires) and opening this during the shift, effectively making the Ignitor engine is doing 0rpm?