EI Tach Installation Question

[Dean Pichon]

I just purchased and received an EI tachometer (P/N R-1-4L2). The unit came with 2 pairs of "RPM isolators" to be installed on the back of the mag switch.

According the to instructions, one pair or both pairs may be required to provide a steady tach reading, depending upon the type of mags in use.

In my -4, I am running a pair of PMags, can anyone who has installed this system in their aircraft (with PMags) tell me whether one or both sets of isolators was required?

Thanks in advance,

[chrisbryanolsen]

Dean,
I have 1 slick mag and 1 pmag and that EI tach.
I have tried many different combos and have not yet been able to get the EI to read the tach signal from the pmag. The slick reads fine with out the isolators.
So let me know if you have better luck.

Thanks!

[grubbat]

Dean, I may be wrong but I think the isolators are there if you run standard mags ignition, not Pmag. The Pmag will give 2ppm but not enough voltage for the EI tach. I think the EI tach will need to be modified by EI for a cost of 125.00 to be used with electronic ignitions.
Good luck.

[Dean Pichon]

Originally Posted by grubbat

Dean, I may be wrong but I think the isolators are there if you run standard mags ignition, not Pmag. The Pmag will give 2ppm but not enough voltage for the EI tach. I think the EI tach will need to be modified by EI for a cost of 125.00 to be used with electronic ignitions.
Good luck.

Thanks for the reply. I just contacted EI with this concern. EI confirmed the isolators are only for conventional mags. However, they confirmed by part number, my tach is configured for electronic ignition. According to the PMag manual, pin 6 on the PMag connectors is available to drive a tach. The output is 12 VDC, 2 pulses per revolution. According to EI, this output is compatible with my tach. Now, I am more optimistic this unit will work...

Thanks again