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dabney

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Contemplating the install of a dual screen G3X system. My avionics "advisor" said it could be a problem getting prop rpm displayed on the G3X due to having dual Lightspeed Plasma elctronic ignitions. Anybody dealt with this situation yet?
 
IIRC, The G3X has only one RPM input so you'd have to install an external switch to select which CDI was providing the RPM pulse.
 
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We just started building our EIS harness for the G3X the other day, and yup - just one RPM input. I THINK I remember reading that the P-Mag puts out RPM with the ignition "OFF" however (because it is still powered - not sure I remember that right, someone can correct me.

On my GRT (and mag) - equipped -8, I only have the RPM signal coming from one mag, and it has never been an issue - yes, the RPM goes to zero on the right mag, but it has been my experience with mags of the decades that a real problem (with the mag or a fouled plug) is painfully obvious by ear.

Paul
 
Ironflight said:
We just started building our EIS harness for the G3X the other day, and yup - just one RPM input. I THINK I remember reading that the P-Mag puts out RPM with the ignition "OFF" however (because it is still powered - not sure I remember that right, someone can correct me...
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Paul,

You are correct. The P-mags have to be powered but grounded for this to work.

With my Dynon EMS I wired both P-mags to it. This way I don't lose the tach reading when turn them off, one at a time, of course.
 
Dual lightspeed inputs to G3X

Hey all. Long time reader, first time poster and I just happen to have some familiarity with the G3X system so I thought I'd chime in :).

I know we have been able to make a dual lightspeed interface work on a G900X system and I recall it required a switch and some external circuitry to make things play nice. I think a similar setup would work on G3X but I need to do some checking. I'll let you know what I find out.
 
AFS has an RPM sensor box that will take inputs from both LightSpeeds and then supply a single signal to their EFIS/EMS system. It knows how to automatically handle fail-overs of either EI. Maybe this box would work with the G3X?
 
dabney said:
Contemplating the install of a dual screen G3X system. My avionics "advisor" said it could be a problem getting prop rpm displayed on the G3X due to having dual Lightspeed Plasma elctronic ignitions. Anybody dealt with this situation yet?
Click to expand...

Support for a secondary RPM input for aircraft with dual electronic ignition is something that's planned for a future software update later this spring. If you're in a position where you need to prewire the second RPM input right away, you can use pin 36 on the GSU 73 for the tach signal from the #2 ignition. (in conjunction with the software update, the install manual will be revised to identify this pin as "CAP FUEL 1 / RPM 2").

mcb
 
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The PMag tach signal is good even while the "mag switch" input is grounded, but it does have to be powered. At least it is on mine.

Could you use a tach sensor installed on the old tach drive, which is independent of the mag switch? Of course, that's one more thing...
 
an option

I have the GRT HX EFIS/EIS setup that has the same problem. There is only one tach lead to the EIS 4000 that feeds the engine monitoring functionality for GRT.

I did not change any wiring or connectivity in the instrument setup. What I did is placed one of these on the dash. It works flawlessly to measure the prop RPM. So when I turn the ignition switch to the Right side I get the RPM's showing up on the GRT EIS because the tach is wired to that side. The Prop Tach shows the drop in line with the EIS tach reading. When I turn the switch to the Left side the EIS drops to 0 but the Prop Tach still shows the RPM reading at the prop. I can clearly see the RPM drop every time.

Of course there is the issue of having a small 1.5x2x3.5 inch box sitting on the dash but I have found it works out for me very well.
 
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