Spark Plug electrical noise
in 912 / 914 Technical Questions
12 years ago
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Re: Spark Plug electrical noise
by BERNARD BERGER » 12 years ago
I have just installed a 76000uf cap without positive results. I have replaced the bnc connectors on my radios, put ,01 caps across my starter switch. The electrical noise is being transmitted by the engine picked up by the antennas, 3 1/2 meters away. I suspect either a couple of spark plugs are bad or my plug wires are bad. Can I use a resistive spark plugs, resistive spark plug wires, or install restive plug caps?
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Re: Spark Plug electrical noise
by bill martin » 12 years ago
bernard,
If you are using an ngk plug I think the number is DPR9EA-9. whichever plug you are using, it should have an R in the part number, This indicates a resistance type plug. The rubber Rotax plug cap is also has a resistor built into it. I believe it is 5000 ohms. You can unscrew the plug cap off the wire and check it with an ohmmeter to see if it is a resistance type.
Bill.
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Re: Spark Plug electrical noise
by Peter Craig » 5 years ago
Hey Bernard,
Wondering if you ever found a solution. I'm going through the same.
Have new 33,000uF cap, new antenna and coax, grounded both ends of ignition wires (as specifically instructed by Rotax), have done extensive trouble-shooting and checked plugs are resistor, checked plug caps (and even covered plug caps with foil tape), etc, etc, etc.
Turning ignition to one set of plugs or the other doesn't seem to vary radio noise.
Still tons of radio noise, varying with RPM, and interferring tremendously with even separate handheld, run on batteries with rubber-ducky antenna.
Holy cow this is hard to diagnose and fix.
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Re: Spark Plug electrical noise
by Roger Lee » 5 years ago
Do you have a noise suppressor in the radio line?
Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell
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Re: Spark Plug electrical noise
by Gary Hunter » 4 years ago
I am experiencing the same issues. I have found it is highly directional. Flying towards a fixed base station like ASOS/ATIS or TWR is the worst. You can barely understand the transmission. Flying directly away from same station is perfectly clear. Flying angles between varies the Intensity. There is no doubt it is ignition noise. I would think ROTAX would have a handle on this type issue by now. Definitely not safe. Not certifiable.
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