fluctuating rpm / map

[mmcelrea]

The rpm is sensed by the g3x from the digital tach signal output on the pmag. you can hear that the rpm is fluctuating and garmin pilot shows the fluctuations. I will probably change the restrictor or add a smaller one to try and damp out the fluctuations.
Could a resonance be caused in the vacuum tube to the mags causing the timing to go out at both 1150 and 2300rpm?
Are pmags more sensitive to vacuum?

[bjdecker]

Originally Posted by mmcelrea

The rpm is sensed by the g3x from the digital tach signal output on the pmag. you can hear that the rpm is fluctuating and garmin pilot shows the fluctuations. I will probably change the restrictor or add a smaller one to try and damp out the fluctuations.
Could a resonance be caused in the vacuum tube to the mags causing the timing to go out at both 1150 and 2300rpm?
Are pmags more sensitive to vacuum?

The quick way to check that theory is to disconnect the vacuum line from the pMag.

[RV7A Flyer]

Originally Posted by bjdecker

On MAP irregularities: I know Van's provides "restricted" AN fittings for the Oil Pressure and Fuel Pressure -- didn't know about the MAP.

If you are using the parts that came in the IE VMP install kit, those are not sufficient to damp out the pulses seen in the MAP when connected to the #3 intake port.

You will need OMEGA Engineering Snubber or similar damping between the #3 intake port and the MAP sender (https://www.omega.com/en-us/sensors-.../p/PS-SNUBBERS). Or, drill/tap another hole in the intake manifold and use that for the MAP source.

I installed the Van's-supplied restrictor for MAP on #3 cylinder per the plans, connected to a Dynon-provided MAP XDCR, and it's been rock-solid for 700+ hours on a stock IO-360-M1B. (ETA BTW, that part you reference is steel, which tends to gall when used in aluminum parts).