Noisy Magneto

Use this area for aviation related general discussions, newsworthy items, and non model specific topics.

Noisy Magneto

Postby saddler » Tue Dec 09, 2014 6:01 pm

I've got an issue that I just can't seem to solve. Looking for any insight...

Setup:
Hummel 2400cc VW conversion with 1 slick mag and 1 electronic secondary ignition
MGL EFIS Xtreme linked to an MGL RDAC XF
Sonex CHT Probes
MGL EGT thermocouples


Problem:
When the engine is running, the engine instruments are very unreliable, meaning they jump all over the place. It is most noticeable in the CHT/EGT however the oil pressure and oil temp jump all over as well. This problem only occurs when the magneto is firing. In other words, with the engine running and mag grounded(off), running only on the secondary ignition the problem completely goes away. Flip the mag switch back on and the problem comes back immediately.

Trouble shooting so far:
Disconnected p-lead from mag isolating the wiring. Disconnected all items from RDAC and connected one at a time. The problem seems to be noise from the mag coming in from the thermocouples. I have tried 1 thermocouple at a time and the problem doesn't happen with just 1. I can plug up to 3 of them (any 3) at a time and the problem doesn't exist. As soon as I plug in the 4th thermocouple (any of the remaining 3) the problem comes back. MGL sent me a replacement RDAC to see if that would fix the problem...no luck. Rerouted CAN Bus and power supply wiring between EFIS and RDAC.

The engine has automotive type plug wires on both ignitions as well as automotive type resistor spark plugs on both ignitions. My next step is to try a new set of plugs. I am also having a set of shielded aviation type plug wires sent to try. I am at a complete loss as to where to go next. I have tried everything I can possibly think of and nothing seems to fix the problem.

Any suggestions?
Sean Saddler
Troy, OH
Waiex #165
First Flight 10/16/2015
https://www.facebook.com/Waiex165?ref=hl
saddler
 
Posts: 55
Joined: Tue Mar 25, 2014 9:14 am

Re: Noisy Magneto

Postby grevaly » Tue Dec 09, 2014 8:01 pm

I would first call MGL
Mark Conner
Sonex Std Gear Aerovee #1242
Mostly Plans Built
grevaly
 
Posts: 35
Joined: Sat Nov 16, 2013 7:05 pm

Re: Noisy Magneto

Postby saddler » Tue Dec 09, 2014 10:24 pm

I have talked to MGL multiple times. They are pretty much out of ideas as well
Sean Saddler
Troy, OH
Waiex #165
First Flight 10/16/2015
https://www.facebook.com/Waiex165?ref=hl
saddler
 
Posts: 55
Joined: Tue Mar 25, 2014 9:14 am

Re: Noisy Magneto

Postby Rick524 » Wed Dec 10, 2014 1:16 am

Hi Sean, Just some things I would check. Don't know if the Extreme has a backup battery, but if it does, does the Extreme act up while powered up from backup alone? Have you tried powering the Extreme from an independent from the aircraft source? Do you have a ground connection from the RDAC XF to the engine block? Do you have a 20,000Mfd capacitor across your 12V supply?

Good luck!

Rick
Sonex 524
Rick524
 
Posts: 159
Joined: Fri Jun 03, 2011 11:40 am

Re: Noisy Magneto

Postby kmacht » Wed Dec 10, 2014 12:16 pm

Without seeing a wiring diagram it is hard to give advice but it sounds like a grounding issue to me. Are all grounds run to a common point (don't use the airframe as a ground). Do you have a heavy gage dedicated ground wire running from the engine block to your common ground point? Does the RDAC ground to that same point? Does each mag have a dedicated ground wire running from it (not just the p-lead)? The red annodize on the accessory case will actually act as an insulator and can cause things that you think are grounded to act funny because of a weak or intermittant ground.

Keith
#554
kmacht
 
Posts: 772
Joined: Tue Jun 21, 2011 11:30 am

Re: Noisy Magneto

Postby saddler » Wed Dec 10, 2014 4:13 pm

The system works perfect without the engine running and with it running only on the secondary electronic ignition. The RDAC is powered from the avionics bus and so is the EFIS. I do have a common ground bus where the battery, and the engine are grounded to with 4awg wire. This is the same grounding location as the RDAC and the magneto. I have tried changing the grounding location of each of the items with no success. I even powered the RDAC from a completely separate power source but keeping a common ground. Nothing I have done seems to make any difference. It almost acts like the noise is jumping from the magneto case itself to the thermocouple wires. When I get the shielded plug wires I should be able to confirm whether that is true or not. I also ran a separate ground wire from the heads to the ground bus just to make sure that the heads weren't floating due to the cylinders being painted, etc.
Sean Saddler
Troy, OH
Waiex #165
First Flight 10/16/2015
https://www.facebook.com/Waiex165?ref=hl
saddler
 
Posts: 55
Joined: Tue Mar 25, 2014 9:14 am

Re: Noisy Magneto

Postby tonyr » Wed Dec 10, 2014 5:51 pm

Hi Sean,

Have you had a look at your magneto?
I assume its new but I"d be checking the points for burning and arcing. The internal capacitor is serviceable and connected. Making sure nothing is loose inside.
Magnetos produce a lot of energy, if there is something not quite right, it could be producing extra electrical "noise" or arcing over inside the cap.

Edit:You don't mention P leads are shielded. P lead grounding... from Aeroelectric http://www.aeroelectric.com/articles/MagnetoSwitchOptions.pdf

magnetos and the magneto switches. Spark plug wires and magneto p-lead wires are the ONLY wires in the airplane which are ALWAYS shielded. Further, p-lead shields should be grounded to the airframe/engine only at the engine end. The shield is used to provide a ground for the "GRD" terminals at the switch but no other connection to the shields should be made at the instrument panel end (I assume Bob is referring to a standard aircraft key switch)

Cheers
Tony
Last edited by tonyr on Wed Dec 10, 2014 6:43 pm, edited 1 time in total.
Sonex #813
First Flight... 4 Oct 14
298 hours having fun!
http://sonexaus.wikispaces.com/Tony+%28Richo%29+Richardson+Sonex+813
User avatar
tonyr
 
Posts: 200
Joined: Thu Jun 27, 2013 12:50 am

Re: Noisy Magneto

Postby tonyr » Wed Dec 10, 2014 6:38 pm

This is how I'd wire in the magneto with a toggle switch, but not knowing whats hanging off your magneto.. its a guess :)
A good quality switch is probably a good idea as well.

Image
Sonex #813
First Flight... 4 Oct 14
298 hours having fun!
http://sonexaus.wikispaces.com/Tony+%28Richo%29+Richardson+Sonex+813
User avatar
tonyr
 
Posts: 200
Joined: Thu Jun 27, 2013 12:50 am

Re: Noisy Magneto

Postby saddler » Wed Dec 10, 2014 7:30 pm

That's exactly how mine is wired. I bought, read, and followed the advice written in the Aerolectric Connection. The first thing I did when trouble shooting was unhook the p-lead and mag ground from he mag completely leaving the mag "hot" the whole time. Problem didn't go away. I have not checked the magneto. I am starting to wonder. It is new. I spoke to Scott Casler (he built the engine) and he said that if the capacitor was bad, the engine would have a miss and wouldn't run correctly. I know nothing about overhauling a mag but I guess I need to learn.
Sean Saddler
Troy, OH
Waiex #165
First Flight 10/16/2015
https://www.facebook.com/Waiex165?ref=hl
saddler
 
Posts: 55
Joined: Tue Mar 25, 2014 9:14 am

Re: Noisy Magneto

Postby Bryan Cotton » Wed Dec 10, 2014 7:43 pm

On the hummelbird group there was some magneto discussion. Not sure which mag you have - but if it an old military surplus slick mag from a GPU the condensers are known to go bad with age. Might go along with what Tony is saying. Scott Casler would know.
Bryan Cotton
Poplar Grove, IL C77
Waiex 191 N191YX
Taildragger, Aerovee, acro ailerons
dual sticks with sport trainer controls
Prebuilt spars and machined angle kit
Year 2 flying and approaching 200 hours December 23
User avatar
Bryan Cotton
 
Posts: 5496
Joined: Mon Jul 01, 2013 9:54 pm
Location: C77

Next

Return to General Discussion

Who is online

Users browsing this forum: No registered users and 73 guests