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How to replace points with Solid State 277cc Rotax?

2 August 2006 7:04 AM Comox BC

I have a 277cc 2 cycle Rotax engine with point ignition and a built in charging sytem on the flywheel. We are using this engine on a homebuilt air cushion vehicle (hovercraft) primarily on salt water. The salt spray is everywhere. The points become encrusted within a short time and the engine will not take high rpm's or simply quit. Fresh water spray around the points produces the same results. Is there a replacement module that will eliminate the points altogether or as a last resort a circuit that uses the points as a low current trigger for a transistor or the like to initiate ignition? I am assuming if the points are used in a low current configuration the degraded current carrying capacity would not be as big an issue. Covering the points and venting them would be my last choice as it makes it very difficult ( impossible) to adjust through an already small inspection hole. Any ideas will be most welcomed. Cheers...Gerry

PS. I have thought of replacement Solid State ignition modules for lawnmowers etc. but apparently the built in charging coil on the flywheel will not allow this setup.

Reply to
Gerryo
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Saran Wrap?

Good Luck! Rich

Reply to
Rich Grise

OOH! I love it when someone asks a question that I can answer intelligently. Sort of. Anyway, you can google for breakerless ignition kit or solid state ignition kit and find many products. There are also plans on the web for building one from scratch. Here is a link to a company who makes conversion kits to eliminate points:

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. Here are some links for building from scratch:
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---->This web site belongs to a fellow named Gary. He is nice and answers any questions related to his site quickly.
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----> This link is from the above web site ( Chemelec) that belongs to Gary. Good Luck! Eric

Reply to
Eric R Snow

Yes, view this in a fixed font:

switched +12 v | | to coil ,---------+ ^ | | | | | | | 2k2 | | | | | | _|C 10K | | automotive | +--------|| coil driver | | |_ IGBT | | |E | /c | +--1k---| gnd | \\e | | | gnd V to points The transistor connected to the IGBT gate can be any small general purpose NPN transistor, for example PN2222. I've used a couple of different coil driver IGBT's. Here's a link to a digikey search page showing some IGBT's that you can look at. Check the data sheets to see which ones are actual automotive coil drivers, then go to mouser to order because it looks like digikey doesn't sell onesies.

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Reply to
kell

It just occurred to me, it sounds like you have a magneto, in which case this will not work.

Reply to
kell
4 August 2006 7:23 AM

Thanks to every one for their replies! Kell, I have a magneto for ignition but there is a battery charger circuit on board that I use for auxiliary lighting . Could your circuit be used if this is the case? I can't follow the ascii diagram, if you have time could you point me to a schematic?

Cheers..Gerry

kell wrote:

Reply to
Gerryo

Change your google setting to "fixed font" - there shouls be a link somewhere near the upper-right-hand corner.

And please bottom-post.

Good Luck! Rich

Reply to
Rich Grise

Like Rich said, all you have to do is click the fixed font option and you will be able to view the schematic. All I really know is that the circuit will work on a conventional (battery driven, dwell based) ignition. Although I said it wouldn't work on a magneto, I actually don't know; I've never installed this circuit on a magneto. Might actually work. From what I know about magnetos, the points break the coil current to create a spark, which is what this circuit does: when the points open, the IGBT breaks the coil circuit. As for the charging circuit, that is certainly separate from your magneto and will not have any effect. On vehicles with magnetos, the magneto is not even connected to the rest of the electrical system (lights, charging etc.). I have built a few ignition modules with the circuit in the diagram, used them on my own vehicles, and even sold a few to friends. As long as you use a good device such as a coil driver IGBT or a high voltage avalanche-rated mosfet, it won't fail. I've put thousands of miles on my old vehicles using this circuit, and other circuits that are related but have a heavier current going through the points. You don't want heavy points current though, so I didn't post those other circuits. If you go with a mosfet, pay attention to Rds and coil current. You could take a look at the IRFP460.

Reply to
kell

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