John Collier
Active Member
I have been running P-Mags since my aircraft was completed about 1.5 years ago. I have an Electronic Ignition Commander (EIC) that monitors timing divergence and I've always received a timing divergence warning on Takeoff...around 7-8 degrees. The timing almost always went to less than 6 degrees post takeoff as the power was reduced (either by me or by altitude)...thereby eliminating the warning.
At cruise everything was fine...CHTs, EGTs, engine always ran great all the way around. I've sent the EIC back...I've sent a P-mag back. I quadruple checked the P-Mag timing index. All was normal...very frustrating!
Finally, thanks to VAF I narrowed the problem down to this: No filter/orifice in my Manifold Pressure line. The P-Mags were seeing a surge in Manifold Pressure from the engine and varying timing between the two P-Mags. My Skyview MP was always solid...maybe the skyview software smooths out the varying MP...not sure. My filter is a small foam earplug inserted into the T-fitting going to the P-Mags.
So for all you guys running P-Mags without a monitor...make sure you have installed a filter or orifice in the Manifold Pressure line. I can tell a difference in smoothness on takeoff.
Hope this helps someone out there running P-Mags.
At cruise everything was fine...CHTs, EGTs, engine always ran great all the way around. I've sent the EIC back...I've sent a P-mag back. I quadruple checked the P-Mag timing index. All was normal...very frustrating!
Finally, thanks to VAF I narrowed the problem down to this: No filter/orifice in my Manifold Pressure line. The P-Mags were seeing a surge in Manifold Pressure from the engine and varying timing between the two P-Mags. My Skyview MP was always solid...maybe the skyview software smooths out the varying MP...not sure. My filter is a small foam earplug inserted into the T-fitting going to the P-Mags.
So for all you guys running P-Mags without a monitor...make sure you have installed a filter or orifice in the Manifold Pressure line. I can tell a difference in smoothness on takeoff.
Hope this helps someone out there running P-Mags.