SureFly SIM4P Installation with P-Mag
A few working notes for installing a SureFly SIM4P along side an existing P-Mag.
Background - original configuration was a P-Mag on the RH side and a Slick 4371 on the LH side. Tach signal is wired per Dynon SV install manual figure 62.
There has been several discussions about kick back with the SureFly SIM4P and a lightweight prop like a Catto and the loss of the RPM signal from the SureFly SIM4P to the Dynon SV-EMS-220. I have both applications, so I had a few concerns during installation.
I installed the SureFly SIM4P per the instructions, the DIP switches were set for 28 deg with vacuum advance (the P-mag was already set up of for vacuum advance).
I timed the SureFly SIM4P to the engine at 3 deg After TCD so it will fire after TCD and with the goal of preventing kick backs. The initial 28 deg - 3 = 25 Before TDC. The P-mag was also timed at 3 deg After TDC.
Both the SureFly SIM4P and P-Mag vacuum lines are plumbed off the #2 cylinder with a splitter and separate lines to each one.
I connected the original Dynon SV configured P-lead from the Slick 4371 to the SureFly SIM4P with no changes to the resistor or adding the "tach signal box" I bought from SureFly.
The original Slick harness and REM 38 plugs (installed on the top of the cylinders) were left in place and connected to the SureFly SIM4P.
The P-Mag is running NGK plugs / adapters installed on the bottom of the cylinders.
Time to test it - normal cold start prime and turn of the key to start......it started like a car engine, the tach signal from the SureFly SIM4P to the Dynon was perfect. Once warm, the engine runs very smooth at idle down to 500 RPM with the Catto prop. On multiple hot and cold starts, no kick back (yet).
First test flight shows no abnormal CHT or EGT indications. Running on each mag inflight shows a normal response. I run a mix of 93 E10 with 100LL, during max power climbs and cruise, there have been no abnormal CHT or EGT indications.
In summary, the SureFly SIM4P works fine (on my configuration) with a P-Mag in the vacuum advance mode. If timed at 3 deg after TDC, this seems to alleviate the kick back issue with lightweight props. The SureFly SIM4P tach signal appears to work fine with the Dynon SV-EMS-220 and the 30 kΩ resistor.
The only slightly negative comment I have, which has been previously reported, that when switch between the SureFly SIM4P and the P-Mag is the "blip" in the engine...which sounds like power is momentarily cut from the SureFly SIM4P.
As far as redundancy of ignition - the P-Mag gets tested each flight for its ability to run at 800 rpm on its own internal alternator. The SureFly SIM4P is connected hot to the battery, which has at least 30 mins of power. With engine running and the Master switch OFF, both ignitions still work.