912 uls soft start
in 912 / 914 Technical Questions
11 years ago
Does anyone know when Rotax went to the retarded timing on start up?
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by Roger Lee » 11 years ago
Hi Wayne,
Rob will probably have a more exact answer, but I think it was around 6 years ago. Don't quote me on that.
Rob wasn't it in 2008?
Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell
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by Mike Goodrich » 11 years ago
I thought that the 9XX engines always had the ignition retarded during start-up by switching the ignition trigger coils from the leading edge of the flywheel cam to the trailing edge.
My understanding is that the problem was that it tended to switch back to the leading edge (advancing the ignition) too early and that this was sometimes problematic on some 912S engines causing starting difficulty and problems with the starters themselves probably due to kickback. Apparently some engine suffered and some didn't and the only explanation I heard that makes sense is that the components in the ignition module were not specified with a tight enough tolerance so some worked well and other didn't. I have no experience of these problems, this is what I've heard.
About 2006 a company called ConAir in UK asked SmartAvionics to develop a device to delay this return to advanced ignition and they have since sold about 1400 "soft start" units around the world, there is a US agent but I don't know who it is. Rotax finally got off their butts and included a soft start in their ignition modules, I'm told, about 2 to 3 years ago.
I hope this helps.
Mike G
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