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Old 10-10-2019, 10:08 AM
jcl777 jcl777 is offline
 
Join Date: May 2016
Location: Kingwood, TX
Posts: 20
Default RPM Rise Seems to be ... Normal

Found these two interesting tidbits from two different threads in the forums at rotax-owner.com. Interesting.

#1
The Fuel injected 912iS and 915iS engines use an ECM module that does NOT fire both plugs at the same time.

The Plugs fire alternately on every other cycle.

This allows the ECM to identify which plug in which cylinder might have a problem and remove it from the firing sequence with no power loss and the only indication being a warning light on the panel.

When performing an ignition check on these engines, the ECM fires the same plug on every cycle resulting in no rpm loss.

And because the ECM also enrichens the mixture slightly because it thinks there is an ignition failure, The engine RPM actually INCREASES during the ignition check.

#2
Sometimes during lane checks the RPM will actually rise then once both lanes are back on it will decrease back where it was. The mixture is just going full rich and thus more power.
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John Leon
Kingwood, TX
RV12-iS, N221TF, #121130, non-builder
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