AC-CDI v11

WITHOUT Tachometer output

WITH Tachometer output


  • Programmable AC-CDI
  • Suitable for ONE or TWO* cylinders
  • For [2 strokes engines] and for [4 strokes engines with wasted spark*]

    * On 4stk engines with 1 pickup on the crankshaft, one spark occur at compression stroke and one at exhaust stroke.
    Firing in the exhaust stroke is a wasted spark. Hence the name…

  • Easy programming via WiFi connection.
  • You need a simple web browser on any smartphone or laptop.
  • One programmable ignition timing curve.
  • 80MHz MicroController control unit.
  • Rev from 10 to 30,000 RPM.
  • 0 deg advance from 1 to 500 RPM. (To avoid kickback)
  • Adjustable timing in 13 steps from 500 to 20,000RPM.
  • Hard rev limiter.
  • Legal Temporary rev limiter.
  • Stator can be half or full rectified. (For more power and ground isolation)
  • 1 input for an inductive pickup (VR).
  • VR conditioner to extract pickup signal in noisy environment.
  • Does NOT work with Digital sensors (Hall, Optical or Points).
  • 1 output for a Capacitive coil type.
  • Non volatile configuration.
  • Optional 12v Tachometer signal.
  • Kill switch input.
  • Power supply voltage DC 10 to 16 volts.
  • Current drain: 100mA – 200mA.
  • Protected against reverse supply voltage.

  • Dimensions: 100 x 60 x 25mm (3.9 x 2.4 x 1inch)
  • Plastic box potted for Electrical insulation, Protecting components from mechanical shock and vibration, thermal shock or Moisture.
  • Source not available.
  • Made in France.


* Twin-cylinders at 360° crankshaft angle:
The engine works with WASTED spark.
If there is ONE twin coil:
=> This AC-CDI works.

See: CDI compatibility


A pickup (aka: VR, Variable Reluctor, Reluctor) is a sensor that have a signal wires and a ground wire.
It’s made of a coil of wire wrapped around a magnet.
When a ferrous part passes by the magnet, the magnetic field is modified and a voltage pulse is created in the coil generating a sine wave.

– 1 input for inductive pickup with 1 signal per crank revolution.
– Pickup must puts out 3 to 100Vac
– Points, Hall sensors and optical sensors CANNOT be used.

– This CDI works with 1 reluctor (The metal stripe on the flywheel).
– This CDI DOES NOT work with multi-pulse pickup (ie 2 reluctors on flywheel).
– This CDI DOES NOT work with a missing tooth flywheel.

Pickup Polarity

Pickup Polarity MUST be Positive then Negative.

Check the polarity of the pickup (Negative then Positive/NP or the opposite PN) with a Needle galvanometer (in milliAmp position) while kicking.

If the polarity is Negative then Positive(NP) then swap the wires to change the pickup polarity !

Pickup Position
Even if it seems instantaneous, the flame front take some time to expand and ignite all the air+fuel mixture in the combustion chamber.
It become crucial at high rpm. That’s why the ignition box should fire the spark a few degrees before the piston reaches Top Dead Center so the mixture explode just when the piston begin to back up. Generally engines need to be ignited around 30 to 40° BTDC (Before Top Dead Center)

It’s the ignition box job to calculate the timing according to the RPM. It makes the calculation as soon as it detect a pickup signal.
Therefore if the box needs to ignite the engine at 40° BTDC, the pickup signal MUST trigger the box BEFORE 40° BTDC.
So the pickup position can be 42° BTDC but also anywhere above!
Due to mechanical constraint, manufacturers put the pickup at different position, Yam XT600 was 36° btdc, Honda often uses 72° and so on.

As the ignition box has been triggered way before it needs to fire the engine, the box just wait until it’s time to fire.

How to calculate the Pickup Position?

Rev Limiter:

The last RPM value you enter is the “rev limit” that stop all sparks.

Temporary Legal Rev Limiter:

If the Kill switch is switched ON then OFF once during the first 30 seconds after the engine started, a Temporary Rev Limiter will allow 3500RPM maximum for the current run.
After 30 seconds, Kill switch will acts normally and stop the CDI.
After the bike has been stopped and restarted by the Master Ignition Key, the CDI runs without restriction.
In countries where 50cc are strictly restricted, the bike seems legal in case of control…
It can also be handy if a beginner rider tries the bike.

Ignition timing

Draw the ignition timing curve into this XLS sheet.

HowTo setup

Setup Ignition box v11r0.pdf


Ready-to-use unit:
For Half-Rectification and Common ground.
For Full-Rectification and Isolated ground. (More power)

Test the Setup Mode

The 12pins connector has a marker trace on pin4 which is Ground.
1) Connect a Black wire from pin4 to black plug of a 12v battery.
2) Wire a bridge between ground-pin4 and kill-pin6.
3) Connect a Red wire to +12v pin5 only.
Don’t mix them up !
4) Connect the Red wire to the red plug of the battery.
5) Led blinks 3times while a WiFi Access Point “Transmic_ign” show up on you laptop/smartphone.

Diagnose with LED.

Click here for more info
– If the box starts in RUN Mode: The Led turns ON until a pickup is detected.
As soon as a pickup signal is detected, led blinks in rhythm.
If the Maximum RPM is reached, the led turns off. If minimum RPM is reached, led turns off.

– If the box starts in SETUP Mode : Led blinks 3 times before flashing once every 5 seconds.
When data arrives via WIFI, led briefly flashes.


Click here for more videos


Click here for more info

  • Version v11r0c0:

    • POC.

  • Version v11r4c1:

    • First commercial version.

3 thoughts on “AC-CDI v11”

  1. great job congratulations! I wanted to ask you, in your opinion is it possible that it works on a vespa 50 (pk 50 s) with electronic ignition? In this case I’m talking about the original Ducati 4-pole ignition with pick-up on the stator. In case I can send you some photos or you can find them on the internet! Thanks and Merry Christmas!

    1. Thanks!
      Is it this one ?

      If it has one external pickup, only one bar on the flywheel and a +12v battery: Yes it works.
      You just have to be sure that the pickup puts out a positive pulse first otherwise you’ll have to invert the 2 wires that go the pkp.
      (Read Pickup polarity section in this page)

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