REFLECTOR: Ignition Noise

[Brian Michalk]

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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