P-mag Timing Explained

[KatanaPilot]

For this post...

Just reinstalled my Pmags today and am struggling somewhat with EICAD to set the advance shift to -1.4 degrees. It seems to take when I send the configuration to the Pmag, but when I power down and power back up, restart EICAD and read the configuration - the advance shift shows positive 12 point something degrees.

Called Emag but the tech that answered could not answer my question - but did duplicate the settings and readings I am seeing on the bench there.

Anyone know if this is just a bug/limitation of EICAD? I really would like to confirm the advance shift. I would prefer not to set the base timing advance mechanically.

[revenson]

Yes, there is a bug in the display indication. But it's just in the display. If you go one 'click' negative from '0', it will set the advance correctly at -1.4, even though on a subsequent check, it displays incorrectly.

I had this explained from Brad some time ago. I would think they'd want to clean up the code, but apparently, not done yet.

[KatanaPilot]

Originally Posted by revenson

Yes, there is a bug in the display indication. But it's just in the display. If you go one 'click' negative from '0', it will set the advance correctly at -1.4, even though on a subsequent check, it displays incorrectly.

I had this explained from Brad some time ago. I would think they'd want to clean up the code, but apparently, not done yet.

Thanks. Bug in EICAD makes it impossible to verify that advance shift was set to what you uploaded.

[N941WR]

Originally Posted by KatanaPilot

Thanks. Bug in EICAD makes it impossible to verify that advance shift was set to what you uploaded.

I recommend you use Version 3 of the EICAD program. Once you make and save your change, exit the program completely, start it up again, and query the P-mags to verify your configuration.

Here is a screen shot I took after configuring a friend's 114 series P-mags with the EICAD V3 program



If you are going to use this program to change the settings on your P-mags, DO NOT change the "LED MODE" setting. As stated above, this controls the LED and if you turn off the LED, it will be very difficult to set the timing as the LED will not light up.

[KatanaPilot]

I appreciate the suggestion. The Technician at Emag thought you would know the answer. Now to obtain V3 of EICAD.

[WingnutWick]

I had the same issue. Changed with V4 and verified with V3. Took a while of frustration to figure that out.

[Scott Hersha]

I just reset the timing to 1.5 degrees after TDC, as recommended by Brad at EmagAir when I questioned him about making my ignition a little less aggressive. This results in a corresponding retard of all position references - start up firing position as well as the bottom and top of the variable range - and this is with the jumper in, so ?A? curve. My advance shift should now be 25.1 and the max advance should be about 33.5. This is a less aggressive curve for my IO-360 with 9:1 compression, but what is recommended by Superior for my engine (25 degrees for high power settings). Resetting the timing was much easier than wiring up a harness to enable EICAD or EIC. I don?t have the wider range of choices for spark advance, but is a more simple way to accomplish what I was after. If any of this is wrong, or I am mis-interpreting how this works, please sound off (Bill R.?).

My Pmags are new and running V40 software so there is a built in 4 degree retard for starting when the mag is timed to TDC. Mine will now fire at 5.5 after TDC on start, and that is fine according to Brad. I have a light weight Whirlwind 200RV prop, so this will help prevent kickbacks during engine start if I have a low battery.

[Nova RV]

Originally Posted by Scott Hersha

I just reset the timing to 1.5 degrees after TDC, as recommended by Brad at EmagAir when I questioned him about making my ignition a little less aggressive. This results in a corresponding retard of all position references - start up firing position as well as the bottom and top of the variable range - and this is with the jumper in, so ‘A’ curve. My advance shift should now be 25.1 and the max advance should be about 33.5. This is a less aggressive curve for my IO-360 with 9:1 compression, but what is recommended by Superior for my engine (25 degrees for high power settings). Resetting the timing was much easier than wiring up a harness to enable EICAD or EIC. I don’t have the wider range of choices for spark advance, but is a more simple way to accomplish what I was after. If any of this is wrong, or I am mis-interpreting how this works, please sound off (Bill R.?).

My Pmags are new and running V40 software so there is a built in 4 degree retard for starting when the mag is timed to TDC. Mine will now fire at 5.5 after TDC on start, and that is fine according to Brad. I have a light weight Whirlwind 200RV prop, so this will help prevent kickbacks during engine start if I have a low battery.

My understanding is the "A" curve is fixed and cannot be changed at all, the only way for any changes to be made is via the "B" curve with jumper out.

[drill_and_buck]

Originally Posted by Nova RV

My understanding is the "A" curve is fixed and cannot be changed at all, the only way for any changes to be made is via the "B" curve with jumper out.

That is correct. The "A" curve can not be changed. I believe Scott positioned the timing marks not at TDC but 1.5 degrees after TDC before using the standard procedure for timing the Emags. Scott, can you elaborate?

[N941WR]

Scott,

You should be good to go.

With you indexing the P-mags 1.4 degrees, not starter teeth, you should be fine.

Let us know if you see a drop in CHT's. The couple of knots increase in speed is difficult to measure. (I did it by changing the P-mag configuration in flight; same air, same temp, etc.)

For starting, when version 40 came out, they started firing the plugs at 4.2° after TDC when below 200 RPM, based on our request to eliminate kickback issues associated with lightweight props. With you clocking the P-mags, firing at 5.6 for starting won't hurt anything.

Please document what you did in your engine logbook and how you did it.

My only concern with using the clocking method is that if someone else works on the engine, they may just download the manual and reset the timing mark to TDC.

I had a conversation with an RV-14A builder earlier this week about this. Their engine builder clocked their P-mag and test ran the engine. After installing the engine, the builder reset the P-mag to TDC, not knowing/understanding what it should be.

Regarding the EIC, it does much more than just allowing you to set the configuration of your P-mags, think of it as an engine monitor for your ignition.