Rotax 185 CDI Conversion...easy!

[artman12us]

[lazair3ca]

[JPXman]

i just want to revive this thread a bit and ask a couple of questions:

1) the link to the ducati module, P200, is that different than the one supplied in the wildfire kit?

2) the coil, what makes a coil 6V or 12V? to my understanding its just wire with a known ohmage/foot and you wrap until you get the desired impedance, both DC and AC (because the diameter, wire thickness, core material, all play important parts in determining AC impedance which is the important number)

Tyler

[JPXman]

I'm just trying to figure out why you would ever need a new flywheel to do this modification. if its purely to adjust the timing, just move the stator plate, it does the same thing.

are the magnets in the flywheel different? probably not, magnets are magnets.

so like ray was saying (even though he's out of the lazair game now ) you really only need the box and the new stator coil. If the box is the one on the net for $60 and a coil can't cost more than $20, sounds pretty cheap.

Tyler

[JPXman]

OK so not many opinions on this eh? well its winter and this is the time I like to figure stuff out. Been thinking on this a lot lately.

The regular 185 ignition has the coil on the inside of the flywheel - and this is the only coil correct? it doesn't go to a coil on the outside right?

but with the CDI modification, the "new" coil on the inside that gets installed feeds a larger coil outside the engine that is part of the Ducati module?

I have a feeling that this "new" coil on the inside is just an "impedance match" to the coil on the outside as I guess the old coil wasn't quite what was needed. The coil on the inside is there I'll bet purely to "feel" the field levels so that the module knows when to fire the spark, and it uses the two coils together to get the hotter spark that everyone is noticing. If you have two coils, of course your spark is going to be stronger right?

all i need to do is measure the properties of this "new" internal coil and find or make copies then all I need is the Ducati module.... i think ray already figured this out but now it makes sense to me (takes me a year or two to chew on something before i get the "eureka")

Tyler

[crazyneosimpson]

Tyler,
Google the ducati part no. and you will find these are not compatable with the P200 which is a three wire instead of the two wire. The inner coil is a lower voltage than the old coil, the CDI's use a step up coil system, by doing this you mount the high voltage coil outside the flywheel so you have more space so you can wind a larger coil that won't overheat and fail so much.
Hand winding coils is a very satisfying job, two beers to unwind and measure the coil, + three to work out how many turns of what guage wire I need, + three to wind them on and laquer, verry satisfied.
There are other converter kits around, you need one for the 90mm Boch system.
And points converter coils are wound backwards so you dont have to rotate the stator plate so far, or the timing will be out by about 45degrees. eg check which end the earth tag is on.

[JPXman]

looks like someone in europe has already CDI'd a JPX 425... found this picture, now to find this module. Also the JPX is really easy to change the timing, as the flywheel is basically press fit onto the crank - so i can rotate it around 360 degrees and then tighten it down...

[crazyneosimpson]

Here's a compatable CDI coil unit, if you want to replicate the ducati system.
Ebay CDI

[rayjb60]

Wow, great find on that CDI Module.

All one needs to do now is determine the number of windings and gauge wire of the Wildfire coil under the flywheel and unwind your original, and rewind to copy the Wildfire unit.

Then change the Armature plate advance (Drill new holes) and voila....cheap CDI for under $100 per engine.

The "external coil" is simply a part inside the CDI module.

There are really just 4 peices to the complete CDI ignition system.

1) Flywheel with magents
2) Armature plate
3) flywheel coil
4) CDI module

The Flywheel is identical to the stock Lazair unit except for the advance, but if you modify the armature plate, no change is required.

The armature plate is advanced differently in relation to the magnets so since you are leaving the flywheel alone, the armature advance needs to be repositioned by drilling extra holes in the plate.

Flywheel coil is the same physically, except for the number of windings, so it needs to be rewound....easy boring work once you know the wire gauge and the number of turns (or length of wire or resistance of winding) You do not have to be very exact for it to still work properly.

CDI module just needs mounting....I found that you should mount it on the non-vibrating part of the nacelle as mine vibrated loose once already.

On the 185's there is also a lighting coil that you can use as the form for your flywheel coil windings so you only really need to buy the enameled wire for the windings.

You could probably do the conversion for only the cost of the CDI module and the wire about $55 + $10 if you are on a tight budget.

I still have my Lazair and now that I bought my own place and can store it with my other projects at home I just might hang on to it and fly it some more.


I hope someone goes ahead with this and shows all the Lazairheads how to do it for $150 for both engines. Then the points woes and engine failures will be a thing of the past, with a lot of happy flyers...instead of engine tweakers on the ground.


Ray

[JPXman]

yes, but this red module in the last link (not my picture) is not aducati module is it?

I just re-read the whole thread - crazyneo, whats the model number of the CDI unit you are using? and you say P200 is no good? why not? different coil inside maybe?

Tyler