"Engine Speed" Warning

[kritsher]

With about 14 hours on my -12, I was up a couple of days ago and after pulling back the throttle from climb to cruise, the Dynon starting yelling "Engine Speed" at me. Looking at the tach, it was jumping around between about 4500 and 6500, and when it jumped high, the Dynon lady got upset.

Now, the engine was running fine, judging by its sound, and it wasn't overspeeding. When I adjusted the throttle a bit, the tach stabilized at a normal value and it didn't happen again.

I assume this is some loose connection perhaps triggered at a particular resonant frequency. Any thoughts on how to go about trouble-shooting something like this?

[cfiidon]

May not be the same issue, but I kept getting RPM warning. Looked at the data and saw values over 31000 rpm. Impossible of course! Dynon recommends a 30k resistor on the p leads, but I had to go to 100k. Take a look at your data download.

Don

[pjsquare]

I had similar false alarms on my Dynon, in the EGT (had to disable the function entirely), on the Amp meter, wild swings from +96 amps to -50 amps, took a new Dynon to correct tat problem, occasional false alarms on fuel quantity (had a mechanical gage revealed no problem), but no false RPM alarms. Apparently false alarms are not all that uncommon.
Paul Johnson

[ryanflys]

Originally Posted by kritsher

With about 14 hours on my -12, I was up a couple of days ago and after pulling back the throttle from climb to cruise, the Dynon starting yelling "Engine Speed" at me. Looking at the tach, it was jumping around between about 4500 and 6500, and when it jumped high, the Dynon lady got upset.

Now, the engine was running fine, judging by its sound, and it wasn't overspeeding. When I adjusted the throttle a bit, the tach stabilized at a normal value and it didn't happen again.

I assume this is some loose connection perhaps triggered at a particular resonant frequency. Any thoughts on how to go about trouble-shooting something like this?

So this is kind of funny Ken, I bought your beautiful 1769K and have started having this same issue but on climb out right after takeoff. When I just googled it the first thing that came up was your post

Do you ever come up with any troubleshooting to adjust the sensor? I'm also confident it's the sensor and not the engine.

[rvbuilder2002]

The sensor used for engine RPM on the RV 12 is the tach sensor that comes mounted to the engine from the factory. It is basically just another one of the trigger coils that is also on the back of the engine for triggering the ignition system, only it is dedicated to a signal output for the tachometer.
The first thing I would look for is an intermittent connection anywhere along the length of that circuit from the harness connector forward of the firewall.