REFLECTOR: Ignition Noise
Brian Michalk
michalk at awpi.com
Tue Jun 12 21:12:42 CDT 2007
Noise at twice RPM would be right for a four cylinder two stroke wasted
spark configuration.
Your extra battery test wasn't clear. I meant that you should get a
test battery, and connect it right to the EI, bypassing all of the duct
wiring, etc. I assume you are not running the engine, and are testing
with a drill or something.
20 gauge sounds quite small. I had to troubleshoot my EFI system
because I had low voltage at the ignition modules. It is always quite
interesting to map out where all of the voltage drops are. My ignition
modules are Bosch modules with internal dwell. When the voltage is low,
they extend dwell which puts an even heavier load on the system.
Anyway, I assume you have a handy voltmeter, and about 20feet of wire of
any gauge. It's not going to carry any current. Turn on your EI and
have it sparking, or putting a load on your power system.
Connect one end of your wire to battery ground, the other end to the
negative lead on your voltmeter. Probe your ground right at the EI to
see what your effective ground is. It won't be 0 volts. It will most
likely be 1 to 1.5 volts. For each connector along the way, probe your
ground potential. This will show you which connectors need some extra
attention.
Next, connect your wire to the positive post, and to the positive lead
on the meter. Probe at the EI, and the power feed to the ignition
modules. Take care of any connectors which show a large voltage drop.
The EI probably doesn't require much current; however those ignition
modules do. I checked the ElectroAir site for schematics, and they
don't offer any. I don't know if the modules are powered off the EI, or
on a separate wire. Pay attention to the EI ground path. For
troubleshooting, maybe clamp a ground wire from the copper tube to the
EI ground.
If all this poking around fails, I would consider a diode across the
ignition modules. Maybe there is some flyback going on there ... but
first I would ask someone who knows something about that system.
If your separate battery test was done completely separate, then the
noise would most likely be spark plug wires, but you've already ruled
that out.
Oh yeah. Wasted spark sends a voltage down one spark plug wire, through
the engine, across the "wasted" spark plug, and then back to the EI via
spark plug wire. Non-wasted spark needs to return via a ground wire
attached from the engine to the ignition module. If you suspect low
continuity, you can clip some leads to the bases of your spark plugs.
I guess it's too much to ask if you have an oscilloscope? This would be
childs play then.
Ron Brown wrote:
>The Electro Air is at http://www.electroair.net/ - mine is similar except
>the controller module is mounted to the left of the coils (instead of
>separately).
>
>Power is supplied via a shielded 20 ga wire through a toggle switch on the
>panel. The power feed is directly from the battery or from the main power
>bus - selectable.
>
>The ignition power goes down the right duct with the other noisy wires such
>as the 4 ga main feed to the starter and alternator and the copper ground
>tubing vacuum line . My headphone connections are in the keel behind the
>seats. My antenna wires run down either side of the fuselage just above the
>floor ducts.
>
>All of my instrument panel grounds are to a single point - ground bus bar
>which is connected to the negative side of the battery. The avionics are
>fed off an avionics bus which can be fed off of the main power bus or
>directly from the battery (an implementation of Nuckolls essential bus).
>There is a diode between the main bus and the essential bus which prevents
>the main bus from dragging down the essential bus.
>
>Oh and if I didn't mention it before - the sparking noise is twice the
>frequency of the RPM's. I recorded the audio from the 430, then examined
>the peaks using some audio software that I have and measured the peaks per
>second.
>
>Thanks for your help, Brian!!!
>
>Ronnie
>
>----- Original Message -----
>From: "Brian Michalk" <michalk at awpi.com>
>To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>Sent: Tuesday, June 12, 2007 8:57 PM
>Subject: Re: REFLECTOR: Ignition Noise
>
>
>
>
>>Is there a schematic online?
>>Do the ignition modules have their own power line?
>>
>>Ron Brown wrote:
>>
>>
>>
>>>Sorry, Brian, No Beer tonight!!!
>>>
>>>I have worked all day chasing the noise problem on my Garmin 430:
>>>
>>>Disconnected the shield for the power to the EI at the instrument panel
>>>(it
>>>was indeed grounded on both ends), found a loose ground wire on the single
>>>point grounding terminal block on the panel; ran the Jeff Rose EI off an
>>>independent battery, using a separate twisted wire, grounded only at the
>>>Electronic Ignition end; installed a big capacitor at the EI end of the
>>>power wire, installed the Radio Shack inductive noise filter kit swapped
>>>out the direct fire coils (NAPA IC39SB); replaced one plug wire at a time,
>>>removed the EI timing head so that I could spin it and make sparks while
>>>the
>>>engine was not running looking for spark jumping anywhere, none found.
>>>
>>>I'm tired - I think I'll drink the beer that I was going to send you - and
>>>go to bed and sleep on it!!! (and copy the Aeroelectric list and see if
>>>anyone else has any suggestions short of replacing the EI with a Slick -
>>>ain't going there!!!!)
>>>
>>>ARRGGHHHHH!!!
>>>
>>>Ronnie Brown
>>>Velocity 173 Elite RG - IO360 Lycoming
>>>
>>>----- Original Message -----
>>>From: "michalk" <michalk at awpi.com>
>>>To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>>>Sent: Monday, June 11, 2007 3:21 PM
>>>Subject: Re: REFLECTOR: Ignition Noise
>>>
>>>
>>>"power for the EI is in a shielded wire"
>>>"the EI is grounded on the firewall"
>>>
>>>Do you mean that your power path to the EI is battery->panel switch->EI?
>>> And that this wire is a single conductor shielded wire?
>>>
>>>How does your firewall ground return to the battery? If you patch in a
>>>battery to your EI and do not send this power down the duct, does that
>>>solve the problem?
>>>
>>>You have two problems. First, your 430 is a receiver of this noise, and
>>>second, your EI is generating this noise.
>>>
>>>Fixing the noise generator usually makes other things work better, so
>>>start there. The EI may have a large dV/dT, meaning a large voltage
>>>spike in a short time causes magnetic flux lines and electrical fields
>>>to be coupled into other things.
>>>
>>>If your shield is connected in two places, remove the one closest to
>>>your instrument panel. If the noise goes away, good, but you still have
>>>a problem. The EI sent current down that shield because its a least
>>>path of resistance back to your battery. Impedance goes up as frequency
>>>goes up ... not just resistance. Your EI will be much happier giving
>>>you a stronger spark if you fix the root cause of your problem. Look at
>>>your ground path. No need really for shielded wires. The real need is
>>>to have your power and ground wires twisted. Shielding is for
>>>capacitive noise. If your power is balanced (no common mode noise) then
>>>there is no energy to capacitively couple. Most likely you are
>>>magnetically coupling the noise.
>>>
>>>Don't fix the symptom, fix the problem. Use twisted wire, and if you
>>>still want shielded, shield it at the EI(the radiator), not at the
>>>instrument panel. Try to not ground your EI power to the firewall.
>>>Even if the ground is attached to the firewall, the electricity will
>>>like that path better, resulting in lower noise.
>>>
>>>I'll bet you a beer that will fix it.
>>>
>>>
>>>Ronnie Brown wrote:
>>>
>>>
>>>
>>>
>>>>The headsets are grounded at the PS4000 intercom and no where else (but I
>>>>will verify) The head set wiring is through the keel, EI is powered and
>>>>grounded through the right side duct. Power for the EI is in a shielded
>>>>wire and the shielded wire is grounded at the mag - by way of the panel.
>>>>Now that I think of it, the EI shield is grounded twice! Might need to
>>>>lift
>>>>one end. Hmmm - thanks for the suggestions, Brian!
>>>>
>>>>The EI is grounded on the SS firewall as well as to the engine (but not
>>>>using a braided wire - wonder if that would help?)
>>>>
>>>>Ron
>>>>
>>>>----- Original Message -----
>>>>From: "michalk" <michalk at awpi.com>
>>>>To: "Velocity Aircraft Owners and Builders list" <reflector at tvbf.org>
>>>>Sent: Monday, June 11, 2007 2:12 PM
>>>>Subject: Re: REFLECTOR: Ignition Noise
>>>>
>>>>
>>>>It's not a high frequency coupling.
>>>>
>>>>I would guess that your antenna shield is a ground path for your EI.
>>>>Are your headset jacks insulated from the instrument panel? Or, do your
>>>>headset wires share a common ground with your EI?
>>>>
>>>>Ron Brown wrote:
>>>>
>>>>
>>>>
>>>>
>>>>>Actually, I have been chasing a spark noise in my Garmin 430 for a
>>>>>several weeks. It is only coming in the 430, it goes away when I turn
>>>>>off the Jeff Rose Electroair electronic ignition, it changes frequency
>>>>>with engine RPM, it does not come in to the #2 com which is a lowly
>>>>>Microair 760, it does not make noise if the antenna is disconnected from
>>>>>the 430. Arrrggghhh!
>>>>>
>>>>>I have changed antennas from right to left, used a portable antenna,
>>>>>bought new plugs and plug wires, connected the 430 to a separate
>>>>>battery, swapped 430's with a friend, removed ground wires, cleaned and
>>>>>retightened them, installed noise filters on the 430 and Electroair,
>>>>>removed and inspected new plugs and new wires. Next I am going to
>>>>>remove the timing unit from the distributor hole, spin the unit and see
>>>>>if I can hear sparks, then try replace one high energy coil at a time.
>>>>>
>>>>>We are planning to fly to Colorado next week and I sure would like to
>>>>>NOT hear sparking noises when I am receiving a far away aircraft or ATC.
>>>>>
>>>>>Any other suggestions from the collective???
>>>>>Ronnie
>>>>>
>>>>>
>>>>>
>>>>>
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>
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