I completed the Pmag installation and tested the system, put everything away and did a test run. The first start took a bit more effort to fire than expected but I attribute that to having plugs out, new plugs first fire, having turned the prop quite a bit during the install... after the first try it started with a couple of blades and ran very smooth. I did a run up and checked out the operation of the Pmag generator and observed operation on the single magneto and with the Pmag alone. The Pmag runs smooth at all RPMs and is notably smooth at low RPM.
The Pmag provides a tach signal continuously so only a single source is needed but I left the tach signal from the magneto installed and replaced the wiring from the switch from the old mag with the signal from the Pmag. On run-up it was obvious that the RPM reading on the SkyView was twice actual and I had to poke around the menus a bit to find the pulse counter and change it from 1 per revolution to 2.
Most of the time doing the installation was spent on routing and securing everything. One interesting item to note is that the wires are not shielded and must be separated from each other to prevent signal coupling... not a big deal but it does add a bit of extra time to keep everything tidy and functional while ensuring that good access is maintained for everything else.
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| Pmag wiring to the top of #1 and #3 |
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| Pmag routing from the bottom plugs on #2 and #4 |
One of the most challenging connection and routing issues turned out to be getting the manifold pressure to the Pmag. I have a standard Vans -4 braided hose from a restrictor fitting on the #3 primer port to a firewall fitting with a hose to the manifold pressure gauge in the cabin. So... I needed to come up with a way to tap the line where I can easily access the Pmag tap to initialize the timing mode. After a bit of puzzling out a plan I ended up using a 1/8" pipe thread T with a couple of -4 fittings and a quick connect 1/4" tube connection using left over static line. I have an extra quick connect T that I plan to use if/when I change the other magneto over. I decided to use the existing -4 braided hose and figure out a location where I could use some hard pipe from the T to the firewall. It worked out great. I might end up replacing the hard pipe with a braided line but there is no relative movement between T and the firewall fitting so it can stay.
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| manifold pressure tap for the Pmag |
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| Pmag engine wiring complete |
