Rotax 185 CDI Conversion...easy!

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Postby rayjb60 » Mon Feb 07, 2005 11:40 am

Here is the final update:

RPM's for CDI converted Rotax 185 engines.

Left Engine 5770 rpm
Right Engine 5860 rpm

I noticed the Left was a little slower so I advanced the ignition slightly but there was no significant difference.

Since its only 90rpm, I'm not going to bother equalizing them for now.

These are new engines with only 4 hrs TT on them so perhaps they are not quite broken in yet.

CDI conversion is complete and working beautifully......1 pull restarts every time....so I can shut them down in flight to thermal, with confidence of getting an easy restart.

:D
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Postby Guest » Mon Feb 07, 2005 5:48 pm

What is the exact procedure you used for setting the carbs ? Did you adjust the high side on each engine while at full throttle. What is your idle rpms.
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Postby lazair » Mon Feb 07, 2005 8:16 pm

Nice Movie there Ray,

I Looked at it and will put it up here for you in case your "FREE SITE"
shuts you down.


CDI movie
Lazair :)


btw I found quicktime did not like it so i used DIVX player
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Postby rayjb60 » Tue Feb 08, 2005 3:56 am

Thanks for storing the movie on this site...it should help since Im maxed out on the other one.


The Carbs are easy to tune, set them for max rpms and then make them 1/4 turn to the rich side and you are done.

Im not sure if the idle rpms are correct but it seems like they want to idle at 2200 rpm, which seems kind of high, so Im thinking that perhaps the CDI unit is firing the plugs twice per cycle at the low rpm speeds.

They are just slowly ticking over and I find it hard to believe that they are actally doing 2200 rpm, so Im thinking its half that, makes more sense.

The thrust at idle is next to nothing in any case, which is all that really matters.
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Postby lazair » Tue Feb 08, 2005 7:49 pm

Ray, Space not a problem at all.

If you have any large videos or pictures let me know web@lazair.com and we will put them up for you. Free sites are basically useless nowadays as bandwidth is dirt cheap.

And Wonderful job on the CDI units. Your work I am sure is cherished by many here. ( I see the traffic and you got a lot of pages views 1700 in 3 weeks on this topic.)

Hard to believe it but Lazair.com has a pretty good traffic flow and search engine ranking. I would venture to guess it one of the higher volume ultralight sites. And the traffic is still climbing. Not bad for almost no promotion. :-)


:)
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Postby Guest » Tue Feb 08, 2005 8:09 pm

Ray you may want to play with carb tuning now that the CDI is on. Carb tuning is best done with engine running. Bring idle down to 1900-2000 with the L. Adjust the H counterclockwise from best rpm setting and find the point just before engine looses speed. Carbs are tuned right when engine will go from idle to full power quickly with no hesitation or bogging.
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Postby JPXman » Wed Feb 09, 2005 1:50 am

Hi Ray

Good theory on the double-RPM thing at idle - an interesting thing to consider with the tiny tach's - I wonder why the problem would apparently disappear at higher RPM's? I have two tiny tach's on each of my lazairs and every now and then they get a mind of their own - play with the number of wraps on the plug wire, spacing of the wraps etc etc, i found that there is an optimum position of that red wire.

Wow, an 1100 rpm idle on a 185... i wonder what that will do to the flare! probably reduce landing roll by another 100' dropping it to, oh, about 27.6'... :)

Tyler
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Postby rayjb60 » Wed Feb 09, 2005 11:45 am

Ive noticed that you can get the idle down really low with the CDI ignition.....you can actually hear that the engine is only firing every second or third revolution due to the low amount of fuel, but it shakes a lot that low, so I would not keep it set like that...cant be good for the engine or the mounts.

My Tiny Tachs are actually a different brand(Tach $35 ), on mine you can set the pulses per stroke and I have mine set for the 2 sparks every revolution, for it to read properly, so I presume it sparks on the TDC and BDC part of the stroke.
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Postby Guest » Thu Feb 10, 2005 10:16 am

The tach reads 2200 and you think the engine idles at 1100 ? Why is this ? Does anyone else care to share the idle they are getting. Book says idle around is set around 2000-2200 on the fire pump ??
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Postby rayjb60 » Thu Feb 10, 2005 11:02 am

Maybe the idle speed is that high....

I'd love to hear what others are getting just to confirm it.....perhaps 4 cycles idle slower as in car engines, so maybe my tach is correct.

The most import thing that I know for certain, is that the thrust produced at that speed is very minimal, which is important to keep landing runs shorter.
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