G3X Touch + EIS Owners - How is your tach wired?

[Ryan ORL]

Hey everyone!  I have a G3X Touch + 4 cylinder EIS in my J.  Before I had my panel installed, when I bought my airplane, it had a EI R1 Electric Tach in place of the factory tach.  I also had an old Insight G4.  When we installed the G3X, I elected to retain the old EI R1 tach as a backup, since in case of G3X PFD failure, I have no other source of tach info.  This setup seems to work fine.  I also happen to know, because of some other recent avionics debugging, that my G3X is configured to use P-lead inputs for tach sensing.  (In this case, my G3X RPM would read zero on the left mag only, and the problem was a bad connection at the resistor which is right at the P-lead)

Because of my recent (very costly) magneto/impulse coupling issues, I plan on switching my left (impulse) magneto to a SureFly EIS.  I would like to keep the same setup, however, with the G3X and the EI R1 continuing to work as before.  I've been doing some research on whether I can keep this setup and it seems that I should be able to (there a small capacitor needed for the R1 apparently)... but I am trying to figure out whether I will need the Tach2 box or not.

Based on the G3X Installation Manual, I believe it should be possible to have a magnetic pickup installed in only one magneto and that should not require any P-lead sensing.  I am not sure why mine wasn't setup this way.  In this case, I think I could just have this setup in the right (conventional) magneto, and I would not need any Tach2 box from SureFly.

Does anyone know if the G3X + EIS STC requires the dual P-lead setup, or did my avionics shop just choose that for convenience?  Only requiring a single tach input that is not dependent on the P-leads being ungrounded seems simpler to me.

[jetdriven]

We have the 275 EIS, but the JPI style Hall-effect magneto sensor works great with the system. It even reads Rpm with the key off.

[PT20J]

I used the the Hall effect sensor on my G3X also.

[Ryan ORL]

Thanks guys!  That seems to be the most straightforward solution then... switch to the hall effect sensor for the G3X and ditch the P-lead pickups entirely (except for the R1).  I think with that setup, there's no need for the Tach2.

[Advanced AeroTechnologies]

Ryan your tach hook up on the G3x has three methods shown per the installation manual.  One is to connect lines RPM1 and RPM2 to the P Leads either at the magnetos or the ignition switch.  The magnetos are the preferred location.  The other way is to use a Hall Effect pickup sensor on one of the magnetos.  The third method shows the Surefly connected via the Tach2 and then a P lead connection to the other magneto.  Hooking up to the P leads is the standard practice as it adds no additional cost to the customer typically when quoting the install.  If can be offered to the customer to add the Hall Effect sensor as an option.  This method adds additional cost to the install for the sensor and there is additional time to install it as the port is typically under the mag as it is installed so you have to pull it to install the sensor then reinstall and time the mags.  We do tons of these installs and 95% of the time we use the P lead connections.  There is a risk of failure with any probe install, you would lose the Hall Effect sensor and you would be left with zero RPM indication, if you lose one P lead you still have a reading in normal flight and get the broken lead fixed.  Hope this helps you may have already gotten this information, sorry if I restated what you already found out.  Thanks.