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P-mag installation

N941WR

N941WR

Legacy Member
Over the past few weeks I have spoken to a handful of builders/fliers regarding their installation.

Per the installation manual, please ground your P-mags to an engine case bolt, not a "Forrest of tabs" on the firewall!

This is your ignition we are talking about, please install it as described in the manual.
 
Bill: Is this a new recommendation? I don't recall seeing this in the manual three years ago when I installed mine.

What is the rationale?
 
Not new

It's not new, and besides what PMAG wants, you only want 1 ground path between your engine and airframe. This because if your ground strap becomes compromised the starter will begin using other paths with less resistance, perhaps even your PMAG ground wire, which of course will go up in smoke when you crank the engine if it's grounded to the firewall or battery instead of the engine case. Not to mention what may happen to the electronics in the PMAG
Tim
 
I think what Tim is saying is that you do not want any "small" ground wires between an engine and the firewall. Two heavy ground straps between the battery neg and the engine case is better than one (in case one develops a loose connection or is removed and forgotten during maintenance). But no small wires.

Bevan
 
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The idea is to keep your engine running, not your firewall.

Besides, why add additional failure points?
 
OK, I'm going to make that change.

But I'm curious now to check my original manual, cause I don't think it was in there.
 
But the current P-Mag Installation Manual specifically says, in the diagram on page 26, to also connect the ground "To ground on EFIS or tach instrument" which has to be connected to the airframe common ground or the EFIS won't work at all. I have each P-Mag with two ground wires. One to an engine bolt and one to the EFIS common ground.

:cool:
 
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GalinHdz said:
But the current P-Mag Installation Manual specifically says, in the diagram on page 26, to also connect the ground "To ground on EFIS or tach instrument" which has to be connected to the airframe common ground or the EFIS won't work at all. I have each P-Mag with two ground wires. One to an engine bolt and one to the EFIS common ground.

:cool:
Click to expand...

[email protected] said:
With 2 P-Mags, I use a different case bolt for each of the P-Mag grounds.
Click to expand...

Both are good practices.
 
what?

N941WR said:
But the current P-Mag Installation Manual specifically says, in the diagram on page 26, to also connect the ground "To ground on EFIS or tach instrument" which has to be connected to the airframe common ground or the EFIS won't work at all. I have each P-Mag with two ground wires. One to an engine bolt and one to the EFIS common ground.

With 2 P-Mags, I use a different case bolt for each of the P-Mag grounds.

Both are good practices.
Click to expand...

N941WR said:
Over the past few weeks I have spoken to a handful of builders/fliers regarding their installation.

Per the installation manual, please ground your P-mags to an engine case bolt, not a "Forrest of tabs" on the firewall!

This is your ignition we are talking about, please install it as described in the manual.
Click to expand...

Ok, this does not make sense to me.

Simple question - how many ground wires does the Pmag want?

Your response seems to imply 2 is better than one. One goes to a "case bolt" on the engine - and the other to... the forest of tabs on the firewall (connected to the EFIS)? That contradicts your first post.

It doesn't help that the manual, as quoted by GalinHdz says to ground to the EFIS. Maybe someone can enlighten me as I'm apparently pretty dense on this subject. Any help is much appreciated!

Can you tell the wiring is getting to me ?;)
 
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If you look at page 26 of Emag Ignition's P-mag installation manual, you will see a diagram that indicates the P-mag should be grounded to the "engine case" using 18 gauge wire.

That same diagram also depicts a dashed line labed "To ground on EFIS or tach instrument".

E-mag%2520P%2520Model%2520wiring.JPG


The ground to the engine case is there to help assure a good ground between the ignition and your engine. The secondary ground is to make sure there is a good ground for your tach signal.

Based on that, I would say the ground to your EFIS is optional but the ground to your engine case is manditory. If your EFIS and other electronics are grounded to your "forest of tabs", then grounding your P-mags there will be the same as grounding your P-mag directly to your EFIS.

(In my installation, I have a case ground and a ground wire leading to my EICommander. I have never had a secondary ground to my "forest of tabs" or to my EFIS but I can understand why they mention this. The additional ground will not hurt but you must make sure you have a primary ground going to your engine case.)
 
N941WR said:
If you look at page 26 of Emag Ignition's P-mag installation manual, you will see a diagram that indicates the P-mag should be grounded to the "engine case" using 18 gauge wire.

That same diagram also depicts a dashed line labed "To ground on EFIS or tach instrument".

E-mag%2520P%2520Model%2520wiring.JPG


The ground to the engine case is there to help assure a good ground between the ignition and your engine. The secondary ground is to make sure there is a good ground for your tach signal.

Based on that, I would say the ground to your EFIS is optional but the ground to your engine case is manditory. If your EFIS and other electronics are grounded to your "forest of tabs", then grounding your P-mags there will be the same as grounding your P-mag directly to your EFIS.

(In my installation, I have a case ground and a ground wire leading to my EICommander. I have never had a secondary ground to my "forest of tabs" or to my EFIS but I can understand why they mention this. The additional ground will not hurt but you must make sure you have a primary ground going to your engine case.)
Click to expand...

Thanks for the response Bill. I'll plan on an 18 awg wire to an engine bolt, and a 20 awg to the EFIS ground location (which happens to be the faston tabs).
 
In planning my wiring for a dual P Mag installation, I am thinking of using a single three position switch for each P MAG with
the top position for ON (12 V),
middle position for TEST (turns off power but does not ground),
and the bottom position for OFF (grounded for engine shut down).

Is this configuration what others have done?

Is there any reason to separate the switch functions?

Randall
 
Very good point, Bill. Thanks for raising this point. I have a reliable, robust firewall forward ground network, but maybe not as good as it can be.
 
Randy said:
In planning my wiring for a dual P Mag installation, I am thinking of using a single three position switch for each P MAG with
the top position for ON (12 V),
middle position for TEST (turns off power but does not ground),
and the bottom position for OFF (grounded for engine shut down).

Is this configuration what others have done?

Is there any reason to separate the switch functions?

Randall
Click to expand...
Here is my wiring diagram. It is a modified version of an old AeroElectric's diagram, one that Emag DOES NOT recommend. However, it has worked fine for over 500 hours. Rather than a switch, which could be bumped in flight, I used a stereo plug to put the P-mags in ground setup mode.

Pmag%20wiring%203.jpg


This allows me to perform my pre-flight like this. One item of note, I came up with this when I was running 113 P-mags. With 114's, the P-mags will run off of internal power as soon as your RPM is above around 800. This pre-flight procedure will catch a bad internal generator, as it did for mine a few months back. However, it may not catch a broken power line unless you throttle back below 800 RPM.

pmag%20preflight.jpg
 
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Here's another idea. Pulled from G-IKON's RV4 install. Basically it's a three position like you describe, but setup as

p-lead off - p-lead on - (momentary power off)

So you use position 1 & 2 like a normal mag then momentary push up to kill the power to a p-mag. Seems like a nice simple setup.

p-mag+bmp.bmp
 
akarmy said:
Here's another idea. Pulled from G-IKON's RV4 install. Basically it's a three position like you describe, but setup as

p-lead off - p-lead on - (momentary power off)

So you use position 1 & 2 like a normal mag then momentary push up to kill the power to a p-mag. Seems like a nice simple setup.

...
Click to expand...
Simple? Yes and no. You now have two switches in series to power it and two switches that can fail. (I looked at a similar setup back when I wired mine and went for simple. That's why I used the stereo plug in place of a switch.)

Also, how do you put it in ground setup mode so you can time the P-mags?
 
Bill and Andy,

Thank you for the detailed replies. I had to go study the install manual again to see how the stereo plug idea makes sense. Having the stereo plug in the system allows entering ground setup mode with only two switches in place, and protects from accidental activation of setup mode.

I think all this will make alot more sense once I work with the P mags some, but for now I need to get the wiring in place and the information provided sure helps.

Randall
 
Bill,

You mentioned discovery of an internal alternator failure on one of your P Mags. Can you provide some details? Did you have to send it in for repair? What caused the failure?

Thanks!

Randall
 
Randy said:
Bill,

You mentioned discovery of an internal alternator failure on one of your P Mags. Can you provide some details? Did you have to send it in for repair? What caused the failure?

Thanks!

Randall
Click to expand...
First a little history lesson.
My Mags started life as 113's on the back of my first engine, which was an O-290-d2b. I had a serious prop strike which destroyed the engine. While replacing that engine with the O-360 I currently have I sent both P-mags in for inspection. E-Mag disassembled them, found nothing wrong and sent them back. Some time later I convinced them to sell me the 114 boards, which I installed myself. With 225 hours on the new engine one of my P-mags internal generators stopped working. When I pulled the P-mag out and spun the shaft it felt "crunchy", as if the magnet had crumbled. This could very well be a result of my prop strike.

The good thing was that it still worked on ship's power so I was able to fly it home. Essentially I had the equivalent of one P-mag and one E-mag.

That is why it is so important to test your P-mags on both ship's power and internal power. Also, due to the type of failure, the EICommander didn't pick it up because the ignition was still working.
 
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N941WR said:
Simple? Yes and no. You now have two switches in series to power it and two switches that can fail. (I looked at a similar setup back when I wired mine and went for simple. That's why I used the stereo plug in place of a switch.)

Also, how do you put it in ground setup mode so you can time the P-mags?
Click to expand...

Hi Bill,

I'm trying to understand the P-MAG wiring a bit better. I just reviewed the install guide and both diagrams.

It seems to me that both of these switch setups have the same level of risk. I don't see any series power switches in that setup. In fact it's just the same as your setup. Half of the switch is controlling the p-lead and half is controlling the power.

Isn't ground power mode just p-lead shorted, with power applied? So in that case the G-IKON setup has that whenever the master is on and the switch is off. The 2-50 switch vs the 2-10 that you use only differ in that the top position is momentary on the 2-50. So you would use it to test dropping the power and going internal generation only, but you would not run in that position.

Now a separate question is, would you ever need to run with power off but run on the internal generator while still having the master on? Not sure what situation would require that offhand.

Thanks for the help understanding this. I know you've looked at many systems and solutions to wiring p-mags!
 
Andy, I just saw your question. Sorry about the delay.

Yes, the diagrams are very similar. However, they do not ground the P lead until the switch is all the way down. (I'm writing this from my phone, so I'm a bit handicapped.)

To set my timing, I install the plug, turn the master on, and leave the P-mag switches in the full down (grounded) position. This provides power with both ignitions being grounded.

As for why the plug and not a switch, I read some place about switch failures and elected to go with the plug. That and I don't have to worry about bumping the switch in flight.

My three-way switches differ from the spring loaded variety in operation and wiring but they serve the same purpose and either setup will work.
 
Andy,

Now that you have had considerable time to use and evaluate your Pmag switch configuration, could you give an update on how you like the setup?

Would you use the same switches again?

Any down side that you experience with use of those particular switches?

Randall
 
Sooooo, if I'm reading and understanding all of this correctly, the 3 position switch just won't due by itself. There is no way to supply ship's power to the P-Mag while the P Lead is in the ground/kill position.

For installation purposes only you gotta have a separate power connection so that the P Lead can remain in the "ground/kill" position and at the same time allow a supply of power to the P-Mag.

Other than for installation, is there any other reason for that separate power connection?
 
Robert M said:
Sooooo, if I'm reading and understanding all of this correctly, the 3 position switch just won't due by itself. There is no way to supply ship's power to the P-Mag while the P Lead is in the ground/kill position.

For installation purposes only you gotta have a separate power connection so that the P Lead can remain in the "ground/kill" position and at the same time allow a supply of power to the P-Mag.

Other than for installation, is there any other reason for that separate power connection?
Click to expand...

Robert, give me a call, when you get a second.

If you wire the P-mags per the manual, the P lead simply provides a ground signal to the ignitions so they don't fire, just like a standard magneto. However, you still must provide a power and independent ground wire to provide power for the electronics. Typically, when you turn on the master, the P-mags are powered up but will not fire because the P lead is "grounded". This design allows the use of a standard key switch. So, they really need two grounds, one being the P lead and the other for the electronics.

It is this second ground, the one coming from Pin 1 that should go to an engine case bolt. The main power lead should go to a power feed via a breaker.
 
Blast Tube Cooling

hi there,
I am considering to install 2 P-Mags on my Lycoming IO360 M1B and have a question regarding the " Blast Tube Cooling ". Can anyone post here some pictures ( or send to me by email ) here showing the installation of these blast tubes ? Would like to get some ideas about how to best make / place these blast tubes.

Another question I have regarding the studs which are now holding the slick magneto with the impulse coupling in place. According to the installation manual the studs for this magneto have to be replaced by shorter ones. Does anyone have a specification for shorter studs which would fulfill the requirement ?

Thanks in advance.

Josef

RV-8A / OE-AJL
 
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P-Mag / problem with ignition swtich

fired up my P-Mags today and now I have this question:

I have the ignition switch from Van's Aircraft installed ( OFF - R - L - BOTH - START ) used that for the Slick magnetos. Now when I fired up the P-Mags strangely enough I can switch to right or left P-Mag, but when I turn the key to "both" the engine goes dead. Anything I overlooked in the installation manual ? Obviously I do have to change the wiring of the ignition switch ? Any advise ? Thanks a lot in advance !

best regards,

Josef
 
Assuming they are wired per E-mag's recommendation, each is grounded to a separate case bolt, each power lead has its own breaker and are wired to your main power bus, and the P-lead (pin #4) is all that runs to the key switch. I would check the switch to make sure it is not grounding them both when in the Both position.

Also, if this is a 180hp engine, make sure to put the jumper in between pins 2 and 3.
 
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proper wiring key switch for P-Mag

done as per manual, the P-lead is the only wire running to the key switch. Obviously on "BOTH" the P-Mags are grounded, will check that tmrw. Obviously I can not use the same wiring on the key switch as I have used for the slick magnetos.

best regards,

Josef
 
Josef said:
done as per manual, the P-lead is the only wire running to the key switch. Obviously on "BOTH" the P-Mags are grounded, will check that tmrw. Obviously I can not use the same wiring on the key switch as I have used for the slick magnetos.

best regards,

Josef
Click to expand...

The P-lead (pin #4) wiring should be the same for mags and P-mags, both are disabled when grounded. The only difference will be is if you disabled one mag when starting, due you only having one impulse coupled magneto. You can start on both P-mags.
 
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yes, the left magnet had impulse coupling, hence I disabled the right magnet during starting with a jumper on terminal 1 on the key switch. I have removed this jumper to be able to start on both P-mags. Do I have to change any other wiring in the key switch in order to prevent groudning both mags if I turn the key to "BOTH" ?

best regards,

Josef
 
Josef said:
yes, the left magnet had impulse coupling, hence I disabled the right magnet during starting with a jumper on terminal 1 on the key switch. I have removed this jumper to be able to start on both P-mags. Do I have to change any other wiring in the key switch in order to prevent groudning both mags if I turn the key to "BOTH" ?

best regards,

Josef
Click to expand...

You should NOT put an impulse coupler on a P-Mag, even in a dual P-Mag installation. The wiring for the P-Mag is exactly the same as for Slick or Bendix magnetos, but without the jumper. See pages 3 and 5 of the P-Mag Installation Manual for details. I think you have something wired incorrectly.

ACS Keyed Switch Installation Diagram

:cool:
 
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I did not put an impulse coupler on the P-Mag, I had one installed on the slick magneto which I had before. And I did remove the jumper....thanks for the wiring diagram

best regards,

Josef
 
problem solved

hi Bill,

problem solved - faulty wiring at the ignition switch. The right magnet was connected to the GND terminal next to terminal 1. With the use of a jumper between terminal 1 and the Gnd terminal when using the slick magnetos, it was not a problem. But when I removed the jumper for the P-Mag operation it was of course not working. Realized that when I studied the wiring diagram of the ignition switch this morning, thanks again for your support.

best regards,

Josef
 
Josef said:
hi Bill,

problem solved - faulty wiring at the ignition switch. The right magnet was connected to the GND terminal next to terminal 1. With the use of a jumper between terminal 1 and the Gnd terminal when using the slick magnetos, it was not a problem. But when I removed the jumper for the P-Mag operation it was of course not working. Realized that when I studied the wiring diagram of the ignition switch this morning, thanks again for your support.

best regards,

Josef
Click to expand...

Great news and congrats on getting it running.

Make sure to put the jumper in between pins 2 & 3. Also, check to make sure you have version 40, it will be written on the sticker on the side of the P-mags.
 
version is P-114-L4 - guess that is the latest version. And I put a jumper between 2 & 3. I did some ground runs, everything so far is as it is supposed to be. Will have to wait now for the clearance from the Austrian CAD to start with the flight testing.

best regards,

Josef
 
Josef said:
version is P-114-L4 - guess that is the latest version. And I put a jumper between 2 & 3. I did some ground runs, everything so far is as it is supposed to be. Will have to wait now for the clearance from the Austrian CAD to start with the flight testing.

best regards,

Josef
Click to expand...
The "P-114-L4" is the model number. There should be a hand written version number on it. Version 40 came out this time last fall. It has two major changes that you need to be aware of; however, one will not impact you because you are using a key switch, the other may.

Version 40 solved an issue with them losing their timing mark if one is powered up and grounded (off) while starting on the other ignition. Since you are using a key switch, that can't happen.

The other change included in this version is that it fires the plugs at four (4) degrees PAST Top Dead Center (TDC) when starting. This eliminated the kickback problem some people had and means you should set the timing to TDC, not after it, as some people have done.

Should your CHT's run a little hot, you can connect to both P-mags with the free EICAD program from Emag and put in a negative offset of 1.4 degrees (-1.4), which will help but won't make a noticeable change to your performance.

That program will also tell you what version of the P-mag's firmware you are running, if you really want to know.
 
hi Bill,
have the version 40 ( the no. on the P-MAGs is VL184012 where the second 2 numbers represent the firmware no. ).

With the slick magnetos I never had a temperature problem, not even at very hot days during summer. But in order to avoid any trouble I have installed a AntisplatAero cowlflap which I will use during take off at full power. In cruising mode there should not be any temperature problem.

best regards,

Josef
 
My Interpretation

My planned wiring paths for a dual PMag installation are shown below. I think this is a version of the setup Bill has shown. I haven't decided how to arrange the +12v, P-Lead grounded condition for initial timing of the mags. If I go with the phone jack connection he shows I'm sure I'll lose the plug in a pocket some time in the future. Perhaps a long jumper wire is best?

Ignition Switches.jpg
 
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That should work. For the purpose of documentation, you should show the Ground to an engine case and to your tach signal.
 
N941WR said:
Also, if this is a 180hp engine, make sure to put the jumper in between pins 2 and 3.
Click to expand...

Hi Bill,

I appreciate, as I'm sure many on this forum do, all the time you put into helping those with PMags. At your recommendation, I just changed my grounding circuit from the "forest of tabs" to an engine case bolt.

In another one of your recent posts, you recommend using the jumper between pins 2 and 3. I have been running my PMags (180 HP RV-4) for a couple of years without the jumper with no (apparent) issues. Should I put the jumper in now? What is the benefit? (Or risk of not using it?)

Thanks again for all the help.

Dean
 
Dean Pichon said:
Hi Bill,

I appreciate, as I'm sure many on this forum do, all the time you put into helping those with PMags. At your recommendation, I just changed my grounding circuit from the "forest of tabs" to an engine case bolt.

In another one of your recent posts, you recommend using the jumper between pins 2 and 3. I have been running my PMags (180 HP RV-4) for a couple of years without the jumper with no (apparent) issues. Should I put the jumper in now? What is the benefit? (Or risk of not using it?)

Thanks again for all the help.

Dean
Click to expand...
Dean,

The 180 hp, 8.5:1 engine is designed for 25? BTDC timing. With the jumper in, the P-mags start at 26? and advance up to 31? as the MAP falls off. This is the "A curve".

Leaving the jumper out (the "B curve") shifts those values five degrees, starting at 31? and moving to 36?. As near as I can tell, this is perfect for an A65 Continental engine.

If your CHT's are OK, it is your choice to put the jumper in. If you add the jumper, your CHT's will come down and you will probably not see any performance change.
 
Hi Bill,

Thanks. My -4, like so many, always has very low CHTs. Mine run between 290 and 320. Since you mention no other issues, I will leave well enough alone. Thanks again for the help.

Regards,
 
Dean,

With your low CHT's, I am really curious as to what your CHT's would be with the jumper installed.

Two questions, 1) Are your P-mags set to 0? TDC and 2) Are they both running firmware version?
 
Hi Bill,

Two years ago, I sent both (PMags) back to Brad for his Flat Fee Check Up service. At that time, he loaded VL 173501 R6. I reinstalled the mags and timed to 0 degrees TDC (at least to the best of my ability).

My IO-360 (A1A) has about 750 hrs on it (TTSN). For the first ~400 hrs, I ran it with the LASAR ignition it came with when I purchased it from Vans. Since the 400 hour mark, I have been using PMags. The CHTs have always been around 300F.

Regards,
 
Dean,

The version 40 upgrade came out in the fall of 2014 and solved the last known lost timing issue. It also improved starting by firing at 4? after TDC when below 200 RPM. Older versions fired at TDC, which caused kick back problems with light props or slightly miss timed ignitions.

The lost timing issue most commonly raised it's head when toggle switches are used.
 
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