Unshielded ignition ends

[PA1195]

Re: Unshielded ignition ends

I've used a hand held radio to sniff out ignition static. Sometimes it's easier to connect a portable antenna with a long piece of coax to make the sensing flexible in tight spots. Remove the antenna to lower the sensitivity if needed. On one engine it was due to a poor engine-frame ground that allowed the control cables and tach to carry the noise into the cockpit. If common mode current on cables or wires are suspect static can sometimes be suppressed with ferrite beads or cores placed on the wires. There's also firewall mounted feed-through filter capacitors available. The cowling should be electrically bonded to the frame.

But sparks are sparks and I wonder if resistor plugs or wires are available? (Edit: for the older non-shielded spark plugs only...shielded plugs typically contain resistors)

[Guest]

Re: Unshielded ignition ends

I've used a hand held radio to sniff out ignition static. Sometimes it's easier to connect a portable antenna with a long piece of coax to make the sensing flexible in tight spots. Remove the antenna to lower the sensitivity if needed. On one engine it was due to a poor engine-frame ground that allowed the control cables and tach to carry the noise into the cockpit. If common mode current on cables or wires are suspect static can sometimes be suppressed with ferrite beads or cores placed on the wires. There's also firewall mounted feed-through filter capacitors available. The cowling should be electrically bonded to the frame.

But sparks are sparks and I wonder if resistor plugs or wires are available? (Edit: for the older non-shielded spark plugs only...shielded plugs typically contain resistors)

Gary,

Funny you should mention that. I think that I had the same issue with mine.

Started out with shielded pugs & wires still had noise.
Went to shield with grounds on the P-leads.
Then added filters on P-leads.
Realized that the only thing that grounded my P-leads with switch off were the controls you mentioned and added a nice engine to frame ground strap. Did it as means of positively being able to ground the mags from the cockpit and wondered about the effective impedance that the controls provided to airframe ground.

Troubles and noise gone.

I thought I was just imagining things or missing something.

Dave

[PA1195]

Re: Unshielded ignition ends

Here's an interesting discussion regarding static. I'm sure there's many more out there: http://forum.shortwingpiperclub.org/...php/t-152.html

Note the dual grounding suggestion for the P-leads both at the engine and in the cockpit...not all suggest that but I've done it to some success if they get noisy over the radio. They also note looking for and dealing with RF ingress into the radio system if it's hardwired into the plane's DC source. A portable radio can get the same if it's connected to a headset jack or intercom.

I fuss with the amateur radio hobby and over the years have had CB and HF radios in aircraft and ground vehicles. Seems like there's always some source of noise that needs suppression. A good transceiver will hear the slightest pop which is why some offer both analog and digital noise blanking and limiting/reducing circuits. With charging systems and P-static it just gets worse. Aircraft radios that operate in the AM mode are the worst for noise pickup it seems.

Edit: forgot to mention the engine ground strap. Best to use a short as possible low impedance flat piece of braided strap from the engine to engine mount and mount to frame bolt it it's a long reach. Same for the buss ground and battery to frame in addition to any starting or charging wiring. If non-electric then still bonding the engine-frame-metal cowl-boot cowl can help with various electrical issues. Stripped and flattened coaxial cable shield can be used for light current duty bonding or shielding.

Gary

[astjp2]

Re: Unshielded ignition ends

Mags that need service can also cause noise, usually a bad condenser but brushes and coils can cause it. If you ground on both ends, it doesn't work too well acts like a wave guide....for the noise to go right into the cockpit. Tim

[PA1195]

Re: Unshielded ignition ends

Probably why Piper installed the firewall P-lead filters...to stop the cockpit ingress. External/common mode flow can be decreased with ferrite beads or wrapping around ferrite cores. Differential mode is more of a challenge. See below:

http://www.murata.com/~/media/webrenewal/products/emc/emifil/knowhow/26to30.ashx

Gary

[8708]

Re: Unshielded ignition ends

Hi folks,
I am trying to figure out how the unshielded spark plug connectors connect to the spark plug wire?
In the attached photos you can see the connectors. They are hollow heavy plastic with a copper collar to capture the spark plug.
Do I solder the sparkplug wire into the hole on the end of the connector and then does the connector just float around the spark plug wire.
I do not see any other means to connect the two. Any advice would be appreciated!
Thanks!
Jay

[Robert Lees]

Re: Unshielded ignition ends

"Never the twain shall meet" (Rudyard Kipling)

You are trying to attach two different ignition leads. In your photos, the upper connector is for an unshielded sparking plug such as a Champion C26 or M41E. Below it is a shielded connection.

You cannot connect the two.

Rob

[astjp2]

Re: Unshielded ignition ends

Go to Napa and buy the length of spark plug wire you need, its 7mm unshielded copper core. Then you get the ends for the mags from Fresno and you solder the ends you have on one end, the other you install the nut, insulator then solder the brass tang if you have SF4 mags.

[Hank Jarrett]

Re: Unshielded ignition ends

You can also buy braided shielding to put over the 7mm plug wire to provide a little more shielding of the wire itself. I did mine that way but don't know if it made much difference. I wouldn't bother unless you are also using some kind of shield around the mag and plug.
I reduced the radio noise a LOT more by making sure the shielded ant. leads were run AFT as soon as possible and placing the ant. as far back as was practical (mine is just behind the aileron cable cross overs). Also DO NOT run the ant cable parallel to other conductive cables, especially the Mag P leads!!!!

Hank

[astjp2]

Re: Unshielded ignition ends

Tried that, got an intermittent misfire, even through sealed heat shrink on the end of the shielding.

[Hank Jarrett]

Re: Unshielded ignition ends

You have to be VERY careful how close you let the shielding get to the conductor! If you are doing it to reduce radio noise you will get a LOT more return on investment by routing the antenna than shielding the leads.

Hank

[astjp2]

Re: Unshielded ignition ends

The shielding stopped about 3/4" before the AN661 ends. I put the heat shrink with adhesive on it to keep the shielding from fraying, but I was still getting some bleed through.

[8708]

Re: Unshielded ignition ends

Hi folks,
I now have some of the AN661 Unshielded ignition clips for my top spark plugs.
Can anyone tell me how they are soldered onto the spark plug wire?
The clips have a hole where the spark plug wire comes through but what would be the best way to solder it?
Thanks!
Jay

[Robert Lees]

Re: Unshielded ignition ends

Silver solder

[Hank Jarrett]

Re: Unshielded ignition ends

There are several types of "Silver Solder" in the US. I think what the Brits call Silver Solder is high temp solder, not true high silver solder and has much less actual silver than "real" silver solder like jewelers here use. If someone here has soldered these and knows for sure (I DO NOT know for sure, just what I was told when I first posted here at the start of this thread) please let all know. I have a feeling that true jewelers silver solder might need to be so hot it will destroy the clips. As far as I remember what I used was a "high Temperature solder" that WAS NOT what is used to make and repair jewelry. The Jewelry stuff was WICKED EXPENSIVE!

Who knows for sure before someone starts soldering?

Hank