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.
  • Live Display of RPM and Timing via Wifi.
  • 2 inputs for an inductive pickup (VR).
  • VR conditioner to extract pickup signal in noisy environment.
  • 1 input for Digital sensors (Hall, Optical sensors).
  • 1 output for a Capacitive coil type.
  • Stator can be half or full rectified. (For more power and ground isolation)
  • Non volatile configuration.
  • Optional 12v Tachometer signal.
  • Kill switch input.
  • Power supply voltage DC 6 to 18 volts (For Setup AND to operate).
  • Current drain: 30mA – 100mA.
  • 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 code 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


Click here for more info

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.

ACCDIv11 has:
– 1 input for inductive pickup (VR/pickup coil) with 1 signal per crank revolution. (Pickup must puts out 3 to 100Vac)
– 1 input for Digital sensor (Hall Effect Sensor, Optical sensors even breakerpoints).

– 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 going then Positive/(I call it NP) or the opposite PN: Positive going then Negative) 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?

Temporary Legal Rev Limiter:

Click here for more info
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.

Live Display of RPM vs Timing via Wifi:

For diagnostic or tuning purpose, it’s possible to live view RPM and Timing in degrees BTDC on a remote PC connected through Wifi: Video
Because of the impact on CDI performance, please disable this function when you are done!

Ignition timing

Draw the ignition timing curve into this XLS sheet.

Rev Limiter:

The last RPM value that has been entered is the “rev limit” that stop all sparks.

How to Wire

12 pins Connector
For Half-Rectification and Common ground.
For Full-Rectification and Isolated ground. (More power)
HowTo wire ACCDIv11 on XT550-600

HowTo setup

Please Print and follow this procedure: Setup Ignition box.pdf

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 named “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.


Translation of the video above

The connection to the mobile phone can be established
Various parameters must be memorized beforehand
I recommend to roughly determine the position of the sensor with a graduated disc
The stator must be labeled for a pre-adjustment with 10,20,30° marks
First try with a car battery
The positive pulse from the pickup must come first, otherwise swap the cables, otherwise the timing will be clearly wrong
So not this way !
The engine runs under 6v under its own power supply
5 degrees offset
Offset corrected
Will it go with the Vape too?

Safe settings: pickup position:70/pickup type:0/adv 0-500:0/5@1000/5@2000/10@3000/20@4000/30@6000


Click here for more info
  • Version v11r0c0:
    • POC.
  • Version v11r4c0:
    • First commercial version.
  • Version v11r5c0:
    • [soft] Firmware improvement.
  • Version v11r5c1:
    • [soft] Wifi Console mode added.
    • [soft] Legal Rev Limiter can be disabled.
    • [soft] Max pickup position is now 180°.
    • [soft] Add Hall Effect Sensor compatibility.
    • [hard] Add Input for a Hall Effect Sensor.
    • [hard] Add Input for a 2nd analog pickup.
  • Version v11r5c3:
    • [soft] Pickup diagnostic feature added.

14 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)

  2. Thanks for the Answer! I want the V11 so bad but from the text I took it that it sadly won’t work with 2 pick-ups, right?

    After reading the text more thoroughly, I think that two pickups should work, but I’m not sure where I can connect the second one, just to the same port as the first? (That can’t be right, can it? )
    Or do I not need two pickups at all with the programmable ignition curve and one is enough? (sorry for the spam)

    1. You took it right. ACCDIv11 DID NOT used 2 pickups.
      In fact it didn’t need the LOW pickup that sends a pulse at 12°btdc
      The cdi uses the HIGH rpm pickup at 36° to make 12° from it.

      I’m currently testing a new version of ACCDIv11r5c1 with added features (See )

      This version now uses the two pickups on XT550-600 but I haven’t got the time to write the documentation…

      1. Thank you so much!

        I think I’m slowly getting there.
        now I ask myself only the question with the wiring. I have the circuit diagram from am motorcycle, sind from the pickups come 3 cables: 12°, 36° and the pickup ground. Is said ground important or is it simply ignored?
        and what exactly is the HV cable in your wiring scheme? a brown and a red cable come out of my alternator, where do i connect them? 🙂

  3. I have purchased this excellent product for older 4-stroke motorcycles, programmable curve between 0 degrees and 38 degrees. Thank you for your help and knowledge on these products.

        1. I think that the most reliable assembly is a TCI with a Hall sensor so there is no use of the alternator neither the pickup coil, but it needs a battery and it’s a big mod !

  4. Hello,
    Looking for a cdi for Artic Cat spirit 500 2cyl 2 stroke. Have your accdi 2.7+ and have had the motor running but not well. nipponddenso 070000-0680 is factory unit cdi. Can you help out..

    1. Hello,
      You mean the Artic Cat snowmobile with the “Spirit” engine from Suzuki?
      It seems to be a 360° parallel twin (both pistons up and down simultanously)
      Beside it runs with the ACCDIv27+ so I bet there is only ONE pickup and a twin ignition coil to fire both cyl. at the same time.

      Sure the ACCDIv27 is a crude ignition created as an affordable solution.
      If you want to fine tune the advance timing, the ACCDIv11 is better (or a TCIv11 but the ignition coil MUST be replaced)
      To set the v11 you MUST know the pickup position BTDC, don’t ask me 🙂
      I described same ways to do it on both web pages.

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