321.7 tach hours - Oil change

321.7 Tach hours

Auto plug testing in the Pmag

I have been testing plugs along with long reach adapters. I started with an RPM drop of 120 with the standard NGK plugs... switching to Iridium Denso brought that down to 60 or so... the same Denso plugs in long reach form have the drop down to 40. All of the plugs seemed to work well with the exception of a single NGK installed in the bottom of #4 that accumulated quite a bit of debris.

The long reach adapters that I found are from http://www.sparkplugadapters.com/services.html (they focus on farm tractor performance). The adaptors were cheap (6 each including shipping). They are machined anticipating a taper seat but will accommodate a gasket seat which is how it works out to be longer...

long reach auto plug compared with the long reach massive aviation plug

these adapters are not ideal since they are cut to accommodate a tapered seal or a gasket seal... I added some high temp RTV on the threads to fill the void from the tapper cut

after several hours plug color is looking very nice

Pmag wrap up and testing

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.

Pmag wiring to the top of #1 and #3

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.

manifold pressure tap for the Pmag

Pmag engine wiring complete

Pmag electronic ignition

I have been looking to move to an electronic ignition for a long time... even before ordering the engine.  Initially, the credit offered to delete magnetos with the engine order were pretty modest so I decided to simply take them and get flying then evaluate options later.  After 320 hours on the tach and much research I decided to replace the standard magneto on the right side with a Pmag unit using auto plugs.

The Pmag uses the existing drive gear on the magneto to gain crank position information and is mostly a drop in replacement with some minor wiring changes.

One outstanding issue in using auto plugs is the reach into the heads.  My engine uses long reach heads that are about 1/4" deeper.  Pmag reports good success with standard length plug adapters and plugs but other systems specifically call for long reach adapters and plugs so I am looking to find longer adapters and test for myself.

Pmag installed on the right side

standard auto plug and insert compared with a long reach aviation plug

long reach auto plug with a standard reach insert... looking for long reach adapters

removed magneto ignition harness

removed standard magneto Model 4370

removed magneto drive gear to be used with the Pmag

I used a 3" gear puller to remove the gear from the shaft

looking into the case and the idler gear from the main crankshaft to the magneto

imprints from closing up Adel clamps in tight spaces... ouch!

new hat!