912 CDI (SMD) Failures

Mike, from your description it sounds like you have some experience of delving inside these modules too. When I fly now, I always start on the left ignition when departing my home base and the right ignition when returning to my home base. That way I can always detect a module that doesn't fire at cranking RPM.

I have heard of a number of owners report that they were unable to start their engine and were surprised to find that both of their modules had failed. What they didn't realise is that one of them probably failed some time ago.

Kevin, I also alternate between the A & B modules for starting. 

I  found the documentation you posted for the pre soft start version helpful, thank you. Here’s the soft start version. I redrew the schematic in a more logical arrangement, it’s a little easier to understand the sequence.  I also duplicated your component numbering and I didn’t verify SMT cap values, I used your values.

Thanks Mike for the schematic, I've never had the opportunity to disassemble a module with the soft-start circuit. The whole circuit is intriguing. A few relatively minor tweaks would improve the circuit reliability, it is a shame that Rotax or Ducati haven’t improved it over the years.

Hi Kevin/Mike,

I believe I am a pretty handy ("bush") mechanic, unfortunately completely lost in the electronics world - So:

1. Can I do anything to minimise the chances of module failure?

2. I had a brief look at the Ignitec web site - Would I be correct in saying that their module is a "drop in replacement" to the Rotax/Ducati? With no claims of improved performance, other than the possibility of extended durability? The durability, likely due to the extended cables, that facilitate remote location of the modules, in a less hostile environment?

3. You referred to Mark Kyle manufacturing an  "upgraded version of the module" please expand on this statement.

Hi Sean,

I think that there is little that you can do to improve the failure rate if you cannot change the module installation. Starting on a single module will improve your chances of detecting a dormant starting failure.

Assuming that an electronic circuit is manufactured correctly then most failures will be linked to the stress put upon the circuit. In the Rotax application the main stresses will be heat (internal or external) and voltage. In theory if the circuit has been designed correctly, then it should be able to cope with all temperatures and voltages that it will experience.

Although the Ignitech modules are programmable, they are configured to give the same performance as the Rotax units. The reasons that these units have become popular in the UK are:

1. They are much cheaper than the Rotax units.

2, They are more available.

3. They are plug and play.

4. The longer harness allows mounting away from the heat of the engine.

5. They include a DC-DC converter to provide improved sparking during cranking.

6. They are approved for use by the BMAA and LAA which covers most Rotax engined aircraft in the UK.

Mark Kyle used to post on this forum but I haven't seen him for some time now. You can contact him through his company website: https://www.kyle.com.au/ or on one of the forums on which he is still active https://www.recreationalflying.com/profile/827-kyle-communications/

I have not seen him advertising his upgraded modules but I know that he did a load of development work and started producing new units a few years ago.