Rotax 185 CDI Conversion...easy!

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Postby rayjb60 » Tue Jan 25, 2005 7:23 pm

I ordered a Tiny Tach, should get it in a week, so I'll post the RPMs im getting then.....

Even when my timing was incorrect it felt that I was getting full power as with the points, so now that Ive corrected that, it should be even better.

The tach will tell the real story when I get it in place.

I opted for a Tiny Tach clone which has more features for the same price.

Tach/hour/maintenance meter (TLPT14) on this page
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Postby lazairiii » Tue Jan 25, 2005 7:52 pm

Ray,

Excellent! I'm very curious what the tach will tell. I'm hoping for improved performance, even if it's by a small degree. Too bad you didn't have a tach to see what you were getting prior to conversion.

George
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Postby Guest » Tue Jan 25, 2005 10:52 pm

Report to Lazair flyers,

Bill has been talking about George and his CDI conversion - I'm George.

One engine is done and in minus 20 degree Celsius (which is damn cold in Farenheit) the engine started first time everytime. The start was easy, the idle was smooth and at full power it wanted to put the test stand into orbit. I am delighted. Also, there was no vibration to speak of at high speed.

In order to keep my friend Bill happy, we'll do some proper tuning later but I suspect that it will be minor.

The second engine will not stay running. It seems that the fuel pump does not pump the fuel at all well and I think this leads to fuel starvation. The average run time is 3 to 5 seconds. Tomorrow my fuel pump part of the carburetor will be attacked and defeated.

g e o r g e C-IFYB CYRP
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Postby ozzie » Wed Jan 26, 2005 4:53 am

george, when you know the rpm work out the tip speed of the prop. it will be interesting to know how close it is to the speed of sound. with the tip speed right up there you may be loosing thrust rather than gaining it plus upsetting the neighbours with excess noise. also a test of static thrust is a truer measurement of performance gain. either way from what you have already commented on this cdi unit will be a win win result. so endeth this scribe on Australia Day celebrated in 32deg c and lamb chops on the barby
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Postby rayjb60 » Wed Jan 26, 2005 4:31 pm

I had an idea that I could put together a CDI conversion kit/service for the Rotax 185, that includes everything you need to convert; CDI/coil, armature coil and instructions.

I figure if we wanted to do it really cheap, I could have people mail me their existing armature plate, so I can drill new holes for the advance, and they could send me their lighting coil, and I will rewind it to the new spec for the armature ignition coil.

I could probably do this for $300 USD for a pair of conversions and have it be worth my time.

Of course I would test the exact combination on my engines first to perfect the setup, and ensure its performance.

The only brand new part is the CDI/coil unit....everything else is modified existing parts.

If I supplied instructions and sources only, you could do it your self for about $80 USD each engine, but, some one would have to test the combination first to make sure that it all works properly together...and I dont really feel like taking my engines apart again, and spending more money to try this particular combination.....is anyone willing to possibly sacrafice $80 and some time to be the first to try it out?.

You would need to buy a $60 US CDI/Coil, rewind your existing lighting coil with some new wire, and drill some new holes in your existing armature plate.

If it doesnt work you will still be able to convert back to your points....and be up and running in a couple hours.

In the end we would have free instructions on how to convert your Rotax to CDI fairly painlessly and really cheap.....only a drill required, and the ability to wind wire evenly on a form :P

Any comments, ideas, or interest?
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Postby Guest » Thu Jan 27, 2005 8:16 am

Ray,

Your last statement ranks along with finding marijuana plots in the corn fields. Some things are better left to the authorities.
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Postby rayjb60 » Thu Jan 27, 2005 11:31 am

Yaa....but the authorities don't fly Lazairs....so wheres the fun in that.... B)

I guess the Monteray, CA police used to fly Lazairs.....but now they are rich and can afford choppers!
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Postby Guest » Thu Jan 27, 2005 10:33 pm

Guest @ Jan 25 2005, 10:52 PM wrote: Report to Lazair flyers,

Bill has been talking about George and his CDI conversion - I'm George.

One engine is done and in minus 20 degree Celsius (which is damn cold in Farenheit) the engine started first time everytime. The start was easy, the idle was smooth and at full power it wanted to put the test stand into orbit. I am delighted. Also, there was no vibration to speak of at high speed.

In order to keep my friend Bill happy, we'll do some proper tuning later but I suspect that it will be minor.

The second engine will not stay running. It seems that the fuel pump does not pump the fuel at all well and I think this leads to fuel starvation. The average run time is 3 to 5 seconds. Tomorrow my fuel pump part of the carburetor will be attacked and defeated.

g e o r g e C-IFYB CYRP


Thanks for the report George. Sounds like a Winner ! Now to get some RPM figures !!
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Postby lazair3ca » Fri Jan 28, 2005 7:49 am

Hi I'm Bill part of the George & Bill tag team.

Debugging balky engines is slow in this weather. But the carb is now pumping but we have determined that we are losing a lot of compression out the decompression valve. So George will try to locate a decompression valve. I know some people have replaced the valve with a screw but on an engine with reasonable compression the pull is more than we want to exert on the nacelle/Lord mounts.

Does anyone have a source for the Lord mounts? Some of the engines I have worked on have groves in the lord mounts from the pull cord.

Don't expect comparative results or a great rpm increase. We are doing the conversions to reduce the downtime and increase the reliability both for starting and running. We do not have before RPM readings for these engines. The atmospheric conditions are different now vs when George will be flying the Lazair. Humidity is less and temperature is a lot lower.

If you have a lot of black (Carbon) coming out of the engine suspect a leaky decompression valve.
Bill
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Postby Guest » Fri Jan 28, 2005 8:25 am

Before we tested the CDI unit we were concerned that turning over the prop would cause the engine to fire. So George added the safety wire shown in the photo. Whenever the engine is remove from the kill switch the CDI unit can be grounded by connecting the ground wire to the case.

After doing some pull, flip, and turning tests we found that the engine still needs a good pull on the starter cord or a strong flip before the CDI unit will fire. Do not be overly concerned that the CDI unit will fire prematurely. It reacts much the same as the points ignition.
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