mag ground wire 0470 R engine

Henning said:
If you had ever done a 'mags cold' check by briefly turning the switch to off before shutting down,
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I do it at every shutdown, only takes a half second before pulling the mixture. Nice to know the mags are not hot.
 
Bill Jennings said:
I do it at every shutdown, only takes a half second before pulling the mixture. Nice to know the mags are not hot.
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I like to do it at full power on a zoom takeoff, feels like afterburner when i turn the switch back to "both". :rofl:
 
bnt83 said:
I like to do it at full power on a zoom takeoff, feels like afterburner when i turn the switch back to "both". :rofl:
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sounds like a typical day of flight instructing.
 
bnt83 said:
I like to do it at full power on a zoom takeoff, feels like afterburner when i turn the switch back to "both". :rofl:
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Honey, did we just go supersonic or did we just blow out the muffler can? :D
 
gismo said:
The capacitor is electrically connected in parallel with the breaker points. It's purpose is NOT to reduce ignition noise but rather to store energy from the coil when the points open. This not only reduces the arcing at the points but also increases the energy delivered to the spark plugs.

It's size (capacitance) needs to be matched to the coil and I don't think it's a good idea to be adding one externally to the magneto, at least not without some analysis. Too much capacitance and the points will suffer.

It is possible that the capacitor in your magneto has failed (open or high impedance) but that's fairly unusual in "modern" capacitors (old ones tended to "dry up" and lose much of their capacitance over time). If the capacitor (aka condenser) was defunct you might see increased ignition noise but more importantly your points would quickly deteriorate.

First thing I'd do is confirm that the plugs have internal resistors. Without some series resistance in the high voltage path considerably more RF noise is generated and radiated. Next I'd confirm that the shields on the spark plug wires are well grounded on both ends and make certain that the P-lead shields are continuous from the magneto back to the switch. There shouldn't be any more than an inch or so of unshielded wire on either end of those leads.

One way to determine if your ignition noise is from the primary side (P-lead) or secondary (spark plug wires) is to temporarily disconnect both P-leads from the magnetos and see if the noise abates.

BTW it might just be that your antenna isn't well grounded at it's mounting. On a fabric covered airplane you may have to fabricate a ground plane under the antenna.
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The spark plugs are Champion C26S. They do not have the internal resistor.

The noise is the exact same with the p-leads completely disconnected.

It looks like I can just switch to the REM40E plug.
 
jesse said:
I looks like I can just switch to the REM40E plug.
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I haven't seen anything that says otherwise. Still just seems odd that you could change from a non-resistor type plug to a resistor plug with the same SF4 mags. Or the C26S really is a resistor plug :dunno:

The REM37BY or URHM37BY might be a better option, being virtually impossible to short out due to lead fouling. Hopefully someone has experience here.

That yellow 172 was running the 37BY's FWIW
 
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gismo said:
The capacitor is electrically connected in parallel with the breaker points. It's purpose is NOT to reduce ignition noise but rather to store energy from the coil when the points open. This not only reduces the arcing at the points but also increases the energy delivered to the spark plugs.

It's size (capacitance) needs to be matched to the coil and I don't think it's a good idea to be adding one externally to the magneto, at least not without some analysis. Too much capacitance and the points will suffer.

It is possible that the capacitor in your magneto has failed (open or high impedance) but that's fairly unusual in "modern" capacitors (old ones tended to "dry up" and lose much of their capacitance over time). If the capacitor (aka condenser) was defunct you might see increased ignition noise but more importantly your points would quickly deteriorate.
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When the mag's condenser fails open, the mag fails. That condenser prevents arcing at the points, and arcing represents continued primary current flow. We want that flow interrupted as abruptly as possible so that the field collapses rapidly to create the spark voltage in the secondary. A slow collapse caused by arcing at the points decreases the secondary's voltage enough to kill the spark. Just try running a mag without a condenser in it.

The condenser absorbs a bit of electron flow just until the points are far enough open that the primary current can't jump the gap. And as you say, the stored current then helps boost the flow in the opposite direction just before the points close again.

Dan
 
jesse said:
It seems to mag along quite nicely. My only issue is that I have a ton of ignition noise in my radio that overpowers the squelch. I've yet to figure out how to fix it since all the wires going to the plugs are shielded...Drives me crazy though (I just turn the radio off when I leave the pattern).
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Sometimes that noise isn't cured with filters on mags. It comes through your audio wiring. See if the mic and headphone jacks are grounded to the airframe; if they are, get some isolation insulators for them. Various interfering currents (including P-lead signals) can travel through the airframe and thereby find a path through the audio shielding (yours IS shielded, right?) and get transferred into the audio wires and picked up by the intercom or radio.

I have cured some of that noise by isolating the intercom case itself from the ground.

Dan
 
bnt83 said:
I haven't seen anything that says otherwise. Still just seems odd that you could change from a non-resistor type plug to a resistor plug with the same SF4 mags. Or the C26S really is a resistor plug :dunno:

The REM37BY or URHM37BY might be a better option, being virtually impossible to short out due to lead fouling. Hopefully someone has experience here.

That yellow 172 was running the 37BY's FWIW
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I really can't determine if the C26S has resistors or not, other than one random post on an old mailing list where some guy says they do not. Kinda hard for me to pull the trigger without more concrete info.
 
For reference....................

My hangar mate has a RV-6 with a 0-320... One Mag with a regular aircraft harness feeding one set of aircraft plugs.. Electronic ignition using auto wires leading to auto 18MM sparkplugs.....

His system is VERY quiet and noise free..:yes:
 
jesse said:
I really can't determine if the C26S has resistors or not, other than one random post on an old mailing list where some guy says they do not. Kinda hard for me to pull the trigger without more concrete info.
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Tom-D has to be the vintage guru here on this one.
 
jesse said:
...The noise is the exact same with the p-leads completely disconnected...
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Just a point: when the mag switch is ON the p-leads are disconnected.

The first question I would ask - does the noise you hear vary with engine rpm?
 
Silvaire said:
Just a point: when the mag switch is ON the p-leads are disconnected.
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correct but I believe the test is to see if noise is coming through them.

silvaire said:
The first question I would ask - does the noise you hear vary with engine rpm?
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Yes you can practically hear the cylinders firing at low rpms. When I turn the fuel off you can hear the last of the firing as the prop comes to a stop.

It's definitely ignition noise as I have no electrical system and nothing else that could be making the noise.
 
Dan Thomas said:
Sometimes that noise isn't cured with filters on mags. It comes through your audio wiring. See if the mic and headphone jacks are grounded to the airframe; if they are, get some isolation insulators for them. Various interfering currents (including P-lead signals) can travel through the airframe and thereby find a path through the audio shielding (yours IS shielded, right?) and get transferred into the audio wires and picked up by the intercom or radio.

I have cured some of that noise by isolating the intercom case itself from the ground.

Dan
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Radio is handheld, even with the headset unplugged the noise comes out the internal speaker the same way.
 
Is the handheld connected to a mounted antenna? Do you get the noise using the handheld's antenna?
 
Silvaire said:
Is the handheld connected to a mounted antenna? Do you get the noise using the handheld's antenna?
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Yes and Yes although I believe with less intensity. Also it happens on either mag.
 
I think you're on the right track with the spark plugs.
 
Is there a grounding (bonding) strap from the engine to the airframe? Think cheap braided uninsulated battery cable, very low resistance connection.
 
You can determine if your present plugs are resistor or not. Use an ohm meter to measure resistance between the plug terminaol and the plug electrode. Look for something like 2K to 10 Kohms or so. If they are dead short (less than say 500 ohms) you don't have resistor plugs.

You might buy or borrow ($?$) four plugs and install them on one mag's harness. See if there is a big difference.

Do both mags individually make roughly the same amount of noise?
 
jesse said:
I really can't determine if the C26S has resistors or not, other than one random post on an old mailing list where some guy says they do not. Kinda hard for me to pull the trigger without more concrete info.
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The Champion Catalog AV-14 shows what all the letters and numbers mean on page 2. The number 26 is the heat range and the letter 'S' means single iridium electrode. If it had a resistor the first letter should be 'R' but I don't know what 'C' means - not listed in the chart. Also the lack of an 'E' or 'H' prefix would mean unshielded.

What's your engine, A65?
 
Silvaire said:
The Champion Catalog AV-14 shows what all the letters and numbers mean on page 2. The number 26 is the heat range and the letter 'S' means single iridium electrode. If it had a resistor the first letter should be 'R' but I don't know what 'C' means - not listed in the chart. Also the lack of an 'E' or 'H' prefix would mean unshielded.

What's your engine, A65?
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A75 - I suspect the champion codes in their specs were not the codes when the C26S was made.
 
I see what you mean. Out of curiosity I Googled "Champion C26S" and the first link to Texas Air Parts Inc starts off "In the early 1900's..." :D

I guess you could use REM40E's but it's a big outlay not being absolutely sure it's the problem. Plus you probably don't use the radio much anyway.
 
I noticed on a different vintage site the guy had REM40E's in the bottom holes and unshielded pugs in the tops due to cowling fit/interference issues. When using the radio he turned off the mag/harness/plugs that were unshielded.
 
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Yea my Champ has little bumps over the #3 and #4 cylinders to accommodate the shielded harness.
 
I called Champion Aerospace - they weren't sure, tried to check part diagrams, and finally conferenced in the oldest guy in the company that said they are in fact shielded but do not have an internal resistor. (Appreciate your help Champion :))
 
jesse said:
I called Champion Aerospace - they weren't sure, tried to check part diagrams, and finally conferenced in the oldest guy in the company that said they are in fact shielded but do not have an internal resistor. (Appreciate your help Champion :))
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Well, in the spirit of experimental aviation, I might try ignition leads made from good old RG-59 (the 75 ohm stuff) with the SOLID POLYETHYLENE insulation (not the foam stuff) with the braid pigtailed to ground at both ends.

Or, if you aren't willing to gamble on voltage breakdown, get some copper braid material and cloak each regular ignition lead inside of braid, with the aforementioned SHORT pigtail to ground at both ends.

I'd only do one mag at a time, then test to see whether or not THAT mag is now quiet.

(Please, no comments on rated voltage breakdown of coax. In the first place, coax isn't hipot tested at all, and in the second place, the rated breakdown is for RF at a specific frequency. Besides, remember the word "experimental" I used above. Thanks, jw)
 
jesse said:
I called Champion Aerospace - they weren't sure, tried to check part diagrams, and finally conferenced in the oldest guy in the company that said they are in fact shielded but do not have an internal resistor. (Appreciate your help Champion :))
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That's why they don't have an "R" in the designation.
 
weirdjim said:
Well, in the spirit of experimental aviation, I might try ignition leads made from good old RG-59 (the 75 ohm stuff) with the SOLID POLYETHYLENE insulation (not the foam stuff) with the braid pigtailed to ground at both ends.

Or, if you aren't willing to gamble on voltage breakdown, get some copper braid material and cloak each regular ignition lead inside of braid, with the aforementioned SHORT pigtail to ground at both ends.

I'd only do one mag at a time, then test to see whether or not THAT mag is now quiet.

(Please, no comments on rated voltage breakdown of coax. In the first place, coax isn't hipot tested at all, and in the second place, the rated breakdown is for RF at a specific frequency. Besides, remember the word "experimental" I used above. Thanks, jw)
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Look at the pictures of his mags, that is what he has.
 
Silvaire said:
Just a point: when the mag switch is ON the p-leads are disconnected.
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Who disconnected them?

My ignition switch simply opens the circuit to ground, leaving the primary circuit subject to the points opening and closing.
 
bnt83 said:
Tom-D has to be the vintage guru here on this one.
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guilty,, I ran 26S in my Warner, no noise from them either.

They are shielded but not a resisted plug. That old mag probably is too weak to run a resisted plug, so I wouldn't try it, but that is just me.
 
jesse said:
A75 - I suspect the champion codes in their specs were not the codes when the C26S was made.
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Believe it or not,,,, the model designation for plugs hasn't changed since they wrote my Warner M/M in 193?
 
Tom-D said:
Who disconnected them?

My ignition switch simply opens the circuit to ground, leaving the primary circuit subject to the points opening and closing.
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That's not a primary circuit Tom, that's just a means to short the magneto to ground. doesn't matter which end you break it's open/disconnected, no longer a circuit. A path to nowhere.
 
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The primary circuit is inside the magneto. The p-lead is simply a means to disable it by shorting the points to the case. I guess you could call it an anti-prime circuit. Regardless, if you break it at one end or the other - no difference, The mag is hot.
 
Silvaire said:
The primary circuit is inside the magneto.
YEP,, except the "P" Lead.
The p-lead is simply a means to disable it by shorting the points to the case.
No not really, only in a round about way. the outer shielding is grounded to the case, it does nothing to the mag or ignition circuit, the outer shielding is only that, radio shielding. The inner core wire is the actual "P" lead, that is grounded to a known good ground in the Ignition switch, in SOME cases that is the outer shielding, ( the round about way)

I guess you could call it an anti-prime circuit. Regardless, if you break it at one end or the other - no difference, The mag is hot.
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I wonder why they named it the "P" lead if it is not a part of the Primary circuit?
 
Call it what you like Tom but I can't see how it can possibly be the primary circuit when the only way the magneto will work is if it isn't there. Primary circuit is the current that flows through the primary coil windings and the points. When the points open the field collapses and that's how it all works. The p-lead ain't got nothing to do with it.

Furthermore, I don't know how you have your mags hooked up but the shielding is supposed to be the ground path for the p-lead to the magneto case. The ignition switch is supposed to connect the p-lead to the shield, not a ground point in the cabin.

There are two reasons for that: Number one, you have positive grounding to the magneto case (not through the engine) and number two, if your engine bonding strap were to fail there is a good possibility you could fry the shields as they tried to take it's place. They aren't supposed to be grounded in the cabin.
 
Silvaire said:
Call it what you like Tom
I didn't name the wire? I simply know what the all the folks in aviation call it on ever skit, i've seen.


but I can't see how it can possibly be the primary circuit when the only way the magneto will work is if it isn't there. Primary circuit is the current that flows through the primary coil windings and the points. When the points open the field collapses and that's how it all works. The p-lead ain't got nothing to do with it.

Furthermore, I don't know how you have your mags hooked up but the shielding is supposed to be the ground path for the p-lead to the magneto case. The ignition switch is supposed to connect the p-lead to the shield, not a ground point in the cabin.

There are two reasons for that: Number one, you have positive grounding to the magneto case (not through the engine) and number two, if your engine bonding strap were to fail there is a good possibility you could fry the shields as they tried to take it's place. They aren't supposed to be grounded in the cabin.
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I guess you didn't read the link above.

How many Ignition switched have you had apart, cleaned and returned to service. ?

All the BAS and Bendix have an internal ground to the case.

I'll take some pictures of the back of the key start type and you can see the post marked "G"
 
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