sportflyer-RCU

My Feedback: (35)

Can the Bosch metal spark plug cap be used with a spark plug cable with stranded wire core ? If use a copper sleeve over the spark plug wire and connect the sleeve to the metal spark plug cap , is it then still necessary to ground the sleeve at the ignition unit end ? Tks

Antique

My Feedback: (4)

Yes...That's the way it's done at C&H....[8D]

sportflyer-RCU

My Feedback: (35)

Do you know whether the Bosch Metal plug cap can fit RCJ6Y plug ? TKs

Antique

My Feedback: (4)

Yes

sportflyer-RCU

My Feedback: (35)

Any idea were I can buy short length of copper braid sleeving to shield the spark plug wire? Unfortunately I cannot replace the whole length of spark plug wire with a shielded one because the Fuji ignition unit is completely potted and I have no access to the plug wire that is connected to the ignition module . This means that I have to use the same plug wire that comes out of the ignition unit but insert a sleeving for shield once I remove the rubber boot from the spark plug end . Tks

Big_Bird

My Feedback: (1)

Go to Radio Shack and buy a piece of RG-8 or RG-11 coaxial cable. Cut a piece about 10" long. Strip the outer covering off. You will find a nice shiny copper braid. Slip it off of the inner core. All you lack at this point is finishing.

Check around and find someone who is into ham radio or CB. They usually have a spare piece of coax that can be used. Even the smaller RG-58 or RG-59 can be used.

Before you solder the braid onto the Bosch cap, you will have to remove the plating on the cap or it will not accept solder.

I assume that you are having ignition noise or you wouldn't be going to all of this trouble. I can't remember whether it was Bill or Terry at CH Ignitions that told me about this trick but it certainly worked. I was having some ignition noise with a G-62 which does not have a shielded spark plug wire and cap. I was told that most of the noise radiation was from the area of the spark plug porcelain and that I needed to shield that area only. I wrapped aluminum foil around the spark plug and secured it with nylon ties. That was about 3 years ago and I never had any more radio noise. I'm sure the plane has over 100 flights since then. This is so simple to try that I would do it first and range check to see if it fixed the problem before I would go to all the other trouble.

Ken

sportflyer-RCU

My Feedback: (35)

I am having a lot of ignition noise and its driving me crazy . My spark plug has stranded wire core so Al foiaround the plug might not work but worth a try. Saves a lot of effort if it does. I do have RG 8 lying around, I didnt think I could remove the braid that easily. . Thanks

Antique

My Feedback: (4)

All Zenoah ignition coils have solid wire cores...And rubber caps...And most have no problem..
Foil around the plug does the same thing as a Bosch cap, without the resistor...Try a new plug, maybe yours has a small crack in the procelain...
Make sure the ignition unit screws are tight, on of them is a ground....

sportflyer-RCU

My Feedback: (35)

Tried 2 different plugs , no difference. I will try the foil or metal spark cap next. Shielding the spark plug wire with copper braid should be last thing to do because it does add more capacitance and so will reduce spark energy.

Big_Bird

My Feedback: (1)

I have a college degree in electronics and retired in the same field after 33 years. Your statement about the shield capacitance reducing the spark energy is pure poppy cock. The amount of capacitance between the shield, the dielectric and the inner conductor is extremely small, probably in the low picofarads. Just my humble opinion.

Ken

Antique

My Feedback: (4)

There's way more than enough spark energy present anyway...That's part of the problem, too much energy, causing interference....Every DA, 3W, and almost all foreign engines use CM6 non resistor spark plugs and completely shielded systems, from the plug cap to the ignition box....The plug wires are carbon center...They have way less spark energy coming from the ignition and still work fine...Those little CM6 spark plugs are gapped at about .015..Doesn't take a lot of energy to jump that gap...I have gapped the RCJ7Y plugs in my conversions to .050, they still work fine..I took the side electrode clean off one of the plugs, the engine would start and run but started to miss about 3000 rpm...That's with a circuit drawing about 180 ma..I suspect a C&H twin circuit that draws 450 or so ma would work with that spark plug pretty well, maybe some day I'll try it..

sportflyer-RCU

My Feedback: (35)

I was told by CH ignitions that shielding spark plug wire reduces spark energy so to try it last. I was also told by Fuji Engine people not to add shielding to the spark wire for their engines. I also have practical experience because adding shielding foil does make the engine more difficult to start . I tend to agree with Big_ Bird that the incremental shield capacity added would be small and should not affect starting ..but it does with my experience on this engine . Looks like the added capacitance is not so insignificant .

Big_Bird

My Feedback: (1)

If you have already been talking to Fuji about this problem and they told you not to add shielding then why are we having this exchange of ideas? If you had said this in the beginning then I would have not wasted my time. Let Fuji handle the problem.

Ken

sportflyer-RCU

My Feedback: (35)

I doubted Fuji's advise for same reasoning as yours. But I had same inputs from CH ignitions yesterday .

tkg

My Feedback: (1)

Capacitance, inductance, black magic mumbo jumbo... what ever, shielding the plug wire reduces the spark quality. It is easily adjusted for with a battery powered system, less so with a mag not designed for a shielded lead. Even bumping up the power to get the needed spark the radiated RFI is reduced. About 80% of the radiated noise is rom the spark plug itsself and shielding the plug is often all that is needed.

BillS

Big Bird is correct. If you shield the plug wire and get less spark then the plug wire was leaking to start with. The leak was generating RF noise, which is often dangerous (read crash prone) to the operation of the radio. There is no black magic and this is not rocket science. However it is your airplane.

Bill

Jim Branaum

My Feedback: (3)

Since this seems to be going the wrong way it might be good to double check your set up. You don't just happen to have a cable or cable driving your throttle? That will act as an antenna and bring the RFI back to the servo and down line to your RX. The other thing to watch out for is keeping your switch harness, battery pack, and all radio system stuff at least 8 inches from the engine.

I am sure that what C&H told you is applicable to electronic ignitions where capacitances are critical in the design of the circuitry needed to generate a spark and the antenna capacitance represented by the spark line probably should not be tampered with by the uneducated <G>. However, I don't think they are that critical in a magneto system, which is what Ken indicates. As for the Fuji, the only experiences I have had with their systems were bad. Their "ATM" modules seem to have a very short life from what I have seen. Something measured in minutes rather than hours...

rideon67

My Feedback: (1)

Same thing is driving me crazy too. See the glitch stuff in giants forum. My ignition guy said not to shield the plug wire because after 20 or 30 flights the carbon core will get fractures and if a leak path (ie plug wire shield) is available it can cause more problems than it will solve.

If you turn off the lights and hold the plug wire by the insulation you can see a glow around it next to your fingers when it fires. spooky.

sportflyer-RCU

My Feedback: (35)

My Fuji engine has electronic ignition ( not magneto ) . The spark plug cable core is stranded wire , not carbon filament. Throttle cable is Nyrod. All radio components more than 16 inches away from engine .

alpinestar

Question for the ignition gurus out there...
I have a 3W ignition with a bit of wear on the braided shielding surrounding the spark plug wire.. there is one small spot worn to the silicone (about 1/8" high and about 1/4" long) but the silicone itself is totally intact. The ignition functions fine & no hits to date, but I am concerned about the overall "health" of this shielding as I'm moving the engine to a new plane and don't need any extra worries!! Should I be concerned with this small worn area? Should I slip an additional layer of braid from some RG-8 cable over the existing braided sleeve?? Can't replace the wire as it's potted in.
thanks for the help!

altavillan

My Feedback: (1)

You should be able to scrunch the shielding to close the hole and tape it to stay together. Should be good to go as long as it isn't completly severed. At the very least tape the abraided section to stop unraveling.

Big_Bird

My Feedback: (1)

A small piece of aluminum foil taped tightly over the shielding with vinyl tape will fix it. Make sure the foil contacts the shielding.

alpinestar

cool thanks guys! much cheaper than a new ignition!

bcchi

Wrap a piece of solder wick around plug wire until it covers the bare spot,can be spot soldered if you want .Then wrap with tape.
BCCHI