P-Mag installation - Help

I am trying to finish up my dual P-Mag installation and have run into a problem, it's the weekend, and the office is closed! I hope someone can help.
The installation has gone well, and right by the book. However, when I get to the "set the timing" stage, I set the timing by blowing into the tube per instructions. Beginning with the right mag, everything is normal. Moving to the left mag, I get the blinking red light and then a blinking green light. When I turn the power off and then back on to take it out of the set-up mode, the light on the left Mag turns kind of an orange color (looks like it is cycling very fast between red and green and appears orange in color). What am I doing wrong? I have checked and double checked all connections.
Ideas anyone?

Check your PM's.

Did you try turning the prop after cycling power? It may be that your right on the edge of the timing point.

Jim,

I just experienced pretty much the same symptoms and was perplexed by the faded orange like LED. My problem was that I had an intermittent ground connection at the terminal on my left PMAG. We removed 1/4 inch of insulation from the end of the ground wire, reattached the wire to the terminal, swung the prop a few times after cycling power and timed the engine. End result was sold green LEDs at TDC.

We then removed plugs and placed them on top of the cylinders with the leads connected and performed a pull through test to confirm plugs were firing.

Prepped and started the engine without any issues.

Good luck.
Mike

Got it fixed!

OK, after some good telephone advise from Bill R., I got it going today. Turns out I had to loosen my left P-mag and rotate it just slightly, then repeat the timing process. Worked like a charm! Thanks Bill! I ran the engine for the first time today with the P-Mags on it. It runs great, started right up, and idles smoothly. Thanks for the replies guys!

Bill is a real help with these. Hope Brad appreciates him....

When I get a second P-Mag I'll certainly buy his controller!

MississippiJim said:

OK, after some good telephone advise from Bill R., I got it going today. Turns out I had to loosen my left P-mag and rotate it just slightly, then repeat the timing process. Worked like a charm! Thanks Bill! I ran the engine for the first time today with the P-Mags on it. It runs great, started right up, and idles smoothly. Thanks for the replies guys!

Click to expand...

Why did this fix the problem? I thought P-Mags could be mounted in any orientation and you can correctly time them.

Hi Jim,
As explained to me by Bill R., sometimes the mag just needs to be rotated "just a hair" to put it in that magic spot where it is not at a point where it is sitting on a halfway point of a tooth, or something like that. I guess you get lucky most of the time and this is not required. Mine happened to fall in the spot where it was an issue. Probably couldn't make it happen again if I tried. Anyway, it sure worked, and I was a happy boy once again. I only moved it a little bit, barely detectable. The green light then came on bold and beautiful! Really an easy fix.

I have 250 hours on my P-Mags. From talking to the factory and looking at the software I am aware that the "resolution" on the sensor is reasonably coarse. Also there is backlash in the accessories case gears. All of this means that it is very difficult to get both units absolutely syncronised.

It is common to have one P-Mag turn green a fraction sooner than the other. I am happy as long as I can rotate the prop to a position where both P-Mags show a green light at the same time even if it looks like one is very slightly ahead. The engine runs just fine.

Pmags do not have a harness to syncronise the firing between units. Whereas some other units I have always observed that they are very similar to the Mag in that I get 125-150RPM drop during runup, increased EGT with only one operating in flight. Of course fuel flow is reduced and the starting is much easier.

I have been told that the amount of RPM drop is dependant on plugs, RPM, mixture, firing advance and any number of other things, so whilst I was hoping the engine would run just as well on one unit as on both, I am not too concerned.

Richard

RV-7A flying

Thanks for the explanation guys. Makes sense.

rwtalbot said:

I am happy as long as I can rotate the prop to a position where both P-Mags show a green light at the same time even if it looks like one is very slightly ahead.

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I don't understand what this means. How would it "look like one is very slightly ahead"?

Erich

Erich,
I think he means that while slowly rotating the prop by hand to TDC, one mag lights up green very slightly ahead of the other one. I'm sure this could be caused by lash in the gears in the mag drive train, or some magnetic jump as the armature in the built in generator turns, or maybe the sensor resolution? I'm not an expert on this by any means, but it is starting to make sense to me.
I cranked mine again today and ground-ran it. I set the idle speed (very smooth, I might add) down to about 625 rpm. While testing the system with the P-mag power shut off and running on one P-mag only at a time, my engine quit at exactly 800 RPM on each one........good thing to know. This way I know that on my particular airplane, it will self-support right down to 800 RPM.
I hope this helps.
Jim

Got it. Thanks

Erich

What we have discovered during the development of the EICommander is that the gear lash allows the ignition to swing a good bit. This also applies to standard mags, not just P-mags. Because of this, we do not report on any timing discrepancy below two degrees. That coupled with the P-mags timing resolution is probably what caused Jim to display the yellow LED.

Truth is, he probably could have flown that way and not seen a difference and his engine wouldn?t have known the P-mag was off just a bit. However, by bumping the mag just a 1/2 a degree or so allowed both P-mags to display a green LED when at TDC.

I seriously doubt there is any dual magneto setup running as close tolerance as a pair of P-mags. Remember, the P-mags are independent, same as a standard magneto and they will fire at slightly different times, same as a traditional mag.

(Jim, good to hear all is working with your installation!)

The timing resolution on the P-mag is 1.40625 degrees between steps. This is due to the fact that the hardware/firmware does not truly support floating point and the timing is constrained to 1 byte of data. In practical terms, this is no problem at all. Most other ignitions have no idea what the crank angle is except once or twice per rev. The P-mag knows 256 times per rev where it is.

Brantel said:

The timing resolution on the P-mag is 1.40625 degrees between steps. This is due to the fact that the hardware/firmware does not truly support floating point and the timing is constrained to 1 byte of data. In practical terms, this is no problem at all. Most other ignitions have no idea what the crank angle is except once or twice per rev. The P-mag knows 256 times per rev where it is.

Click to expand...

This is correct and is another reason why there is some minor timing differences. Still it is less than with regular mags.

Set Both PMags Together

You mentioned that you set one Pmag and than the other.

Both of my Pmags are attached to the same MAP tube, so I blow into the tube, and watch both led's to set the timing for both PMags at the same time. Ignition timing for both mags takes less than one minute. Occasionally one led looks orange, but less than a 1 degree prop rotation will turn it green. Next time this happens, I will rotate one PMag to get 2 greens, and see if this improves the timing.