Com noise need Input...

Maybe someone has a good idea!
I have a new Funkwerk 8.33 comm installed.
During reception with a lower level (stations more far away) I hear the ignition in the background.
When the station is near like a tower 10nm away it is clear and almost perfect.

First I thought it is coming from a bad gnd connection of the power supply or the alternator, but I routed a separate gnd wire from the battery to the com and switched the alternator of, no change...

Next was a ferrit filter around the wires of the com, nothing...

I have a electronic ignition with auto plugs and auto sparkplug wires. (EFII dual)
Maybe the antenna is picking up some EMP from the ignition?

What could it be, ideas?
Solutions?

Thanks for help!

Christoph

30h on the -8 now and still smiling!

Based on what you stated I'd guess it is some sort of radiated EMI form the ignition. Are all your audio leads shielded and grounded at a common point?

lowering ignition noise

Hi Christoph,
Ignition noise radiates from the spark plug wires.
There are two simple steps you can take to reduce ignition noise.
1. Reduce the spark plug gap. The voltage that is present in the spark plug wires is controlled by the spark plug gap. Reducing the size of the gap reduces the secondary voltage and reduces the radiated electrical noise. The spark plugs we use are gapped from the factory at .032". You can reduce the gap to .025" without having any effect on engine operation. This is the simplest first step.

2. You can completely knock out ignition noise by using carbon core spark plug wires. Carbon core wires have 10 times the noise suppression of the spiral core wires supplied in our kits. We supply spiral core wires in our kits because they have good noise limiting for most installations and they are durable. Carbon core wires will mechanically break down over time with engine vibration. If you run carbon core spark plug wires, they should be changed out every two years.

I would start with step 1 and then go to step 2 if necessary,
Robert

A few ideas....

Make sure your mic and headphone jacks are isolated from the airframe. They have little plastic grommets the help out, but its still possible for the mic to make contact.

Make sure your aux audio jack is isolated from the airframe.

Good luck, I spent a month chasing down radio problems. Not fun!

Thanks for the Ideas,

I have changed the spark plugs to .025 no change...
The intercom and all other audio is crisp and clear as it should be!
So I think the best way will be to change the ign. wires.

Thanks

Christoph

I had noise on my com that came from the unshielded 32 & 33 wires from the ignition switch pleads to the EMS. Replaced with shielded wire an most of the noise went away. I have Slick mags, don't know what kind of signal the EFII uses.

Almost all good quality radios suffer from this, as the signal is further amplified with weaker signals, and ignition noise can get picked up. Some radios do not amplify weak signals as well and so you don't hear them because they typically won't break squelch for weaker transmissions.

Its mildly annoying but really not worth spending a bunch of time and effort to knock out. I certainly would't trade ignition wires just to be able to listen to a unicom freq. 100 miles away.

Agree

Good point Bob,
Also, there are many sources of noise that can enter a radio.
Strobes, alternator noise, ignition noise, EL lighting transformers and more.
A good test is to turn off individual systems (except the ignition of course).
Questions to ask yourself:
Does the noise follow the engine rpm. If it does, you will hear the frequency of the noise change with a change in engine rpm. If it does follow the engine rpm, it is likely from the alternator or ignition. Then turn off the alternator field. This will kill the alternator output - does the noise go away - if so it is from the alternator - if not, it is probably from the ignition.
These tests can usually be done on a ground run.

Robert

I had similar noise from my electronic ignition on my comm radio recently. It followed RPM so was clearly related directly to the ignition system.

Easy way to tell if it is coming into the antenna: disconnect the comm coax plug at the antenna and run the engine with comm radio powered on. Is the noise still there? In my case it disappeared completely, so we knew it was radiating straight into the antenna from the engine.

Then we tested whether it was present on L or R ignition. In my case it was only on the R electronic ignition (so associated with the rear bank of spark plugs). Tested plugs, leads and grounding - all OK - so must be between the ignition units and the leads.

After further troubleshooting we found that an electronic ignition coil was faulty. The coil can develop an internal fault on the ground side, which turns it into a "Marconi transmitter". The plug can still usually fire with this fault, so there was no noticeable difference in the parameters on that cylinder.

We replaced the coil. All fixed, and no "tick tick tick" anymore.

I'm also running the Dual EFii and have developed a pretty severe ignition noise in the com.

Edited and updated 03/08/2020- ignition noise totally disappeared once I changed to a solid tip spark plug. I've been using NGK BR8ES 3961 with good results. I just couldn't get rid of arching at the aluminum screw on terminal tips.

plug wire arcing?

Hi David,
Check your plug wire resistances. They should ohm out at about 300 ohms per foot. If the center conductor was nicked during stripping, this might cause a high resistance spot. You shouldn't ever have arcing from a plug wire.

Robert

Thanks for the reply Robert. I'll do that. I can't say for sure what I'm seeing. For all I know it's normal, but it was the only place that I saw anything suspicious at all on the high tension leads.

Christoph, I'm curious what ever came of your findings with new plug wires. I'm looking at a trouble shooting procedure to check noise coming from my wires as well and was wondering if you ever got any resolution?

EFii ignition noise solution

UPDATED 03/08/2020 - My apologies for this really really late update. WAY over due. You can disregard the original post but I will leave it intact (to my embarrassment) in case there is any value in it for other readers. This faraday cage set up out lined below that I so painstakingly constructed and installed was unnecessary as Robert Paisley pointed out. My issue was that I was not able to get rid of the arching I was getting at the spark plug terminals with the screw on aluminum terminals. Once I went to a steel solid spark terminal spark plug, everything went quiet and stayed quiet. I've been using NGK BR8ES 3961 plugs with good results. Nothing fancy and inexpensive. Thanks again to Robert Paisley for being so patient with me through all of this. Great great customer support.

It would seem that I have resolved my ignition noise issue with my EFii dual ignition installation. My installation consists of the dual ignition but not the electronic fuel injection. My coil packs are mounted on the firewall and the engine is a Lycoming IO360A3B6D. My apologies in advance for the tardiness of this post since the fix was installed back in July of this year (2015), but it has given me the opportunity to put some hours on this fix and prove it's worth and to make note of an issue that popped up shortly (5-10 hours) after the initial flights that might have gone unaddressed had I posted too soon. Also, please try to excuse my ignorance if so noted. I'm a learning creature. A work in progress so to speak.

What has worked for me involves a bit of work, but the results were really worth it for me.I had times that on my takeoff roll on rwy 20, where the the ATC control tower signal is probably the weakest for me. I couldn't hear the towers transmissions due to the volume of the immense ignition noise in my headset. With brand new (note that I say "brand new" spark plugs. I'll get to this later) spark plugs, it's now whisper quiet. Also, I'm no Einstein and couldn't have done this on my own without the help from several of my Los Alamos brain-iack friends.

In a nut shell, here's what seems to be happening. The harness going to the coils and the coil packs themselves are radiating RF like a Banshee. The fix was to fit a large 3/4" copper braid shielding on the entire length of the harness going to the coil packs and to fabricate a faraday cage for each of the coil packs. See photos. There's a ink at the bottom for the photos if I did it right.

With the harness shielding, I only shielded the harness firewall forward with very good results. If I were doing it again with a fresh installation, I might shield the harness all the way back to the ECU(s), although it has proven itself not to be necessary. Firewall forward is working great for me. The 3/4" copper braid is the minimum size needed to slip over those large connectors. If you have a way of removing and then re-installing the pins in the connectors, you could definitely use a smaller size braid and save some weight. The stuff is pretty heavy. I made pigtails and quick disconnects to continue the shielding on the short harness runs for the coil packs. You see a little of this at the top of one of the photos. A pigtail was also used to ground the shielding to my firewall.

The faraday cage was fabricated from a very fine 80 or 100 copper screen. I'm not sure what the numbers (80 or 100) really mean other than it's really fine stuff. Although the screen seems to allow air to circulate easy enough through it, I placed a blast tube on each of the coil packs to aide in the cooling. The packs are mounted on my firewall (see photos). At the corner of each of the cages I soldered leads with quick disconnects that of course go to ground. The copper screen cages are delicate and very light and were made with a flange at the base used for mounting. I just used aluminum tape and made sure that the firewall surface and the flange were really clean. It's holding up very well. The copper screen solders very easily, but you might want to practice a little before attempting the finished product if you're not experienced with working with solder. I used a lot of soldering paste to help keep the solder flowing.

A note in regard to my approach to fabricating the cages. I made a cardboard (thin cardboard like cereal boxes or poster board) template and found that I could make it in one piece, and by keeping one of the corners unfastened, I could slip it over the coil pack if I held my mouth just so. I fabricated a crude hinge from very small copper tubbing for the open corner of the cage which allows me to close it up once I have it fit in place. The cages had to be fit after the coils were mounted on the firewall so had to be designed to be removable, which is good for the inevitable unexpected maintenance issues that always seem to pop up.

I tested this all with brand new spark plugs and was in awe of just how quiet my radio had become. It was really impressive. Weak signals still got the static that you get from those situations, but there was very little if any ignition noise. Then my bubble burst after about 5 or 10 hours or so. The ignition noise returned little by little. It was in no way as obnoxious as it was before I did all of the shielding, but it was very noticeable and irritating after all of that work. I figured that it had to be the spark plugs. Maybe the resistors breaking down??? I really don't know. The only thing that I knew to try was to reduce the spark plug gap down to .025" as recommended by Robert (Robert Paisley from EFii). That seems to do the trick. It may not be quite as quiet as the brand new plugs, but it really does quiet things down. I think that it's the last little detail needed to keep the noise at bay, at least on my installation.

I hope that this helpful to anyone who is suffering the same issues. It sure worked for me.

photos here http://imgur.com/a/ro3MB

ignition noise

Wow, that was a lot of work!
It's important to realize where ignition noise comes from.
It comes from the high secondary voltage in an ignition system.
This voltage is present in the secondary winding of the ignition coil, the spark plug wires and the spark plugs. No where else. Not in the ECU, not in the control wires from the ECU to the coil.

The firing voltage of a spark plug is a function of the gap of the spark plug.
Smaller gap = lower firing voltage = less ignition noise. In a properly working system, ignition noise is mitigated through the use of resistive spark plug wires and resistor spark plugs. These are both standard issue in any modern car as well in EFII systems. The resistance of these elements slows the rise time of the secondary voltage and reduces ignition noise.

Electrical noise in radios from electronic ignition systems is not big problem, but it does occur in a small number of installations. This can be caused by a radio that does not have good noise rejection or is not well grounded. It can also be caused by a problem with the spark plug wires or a spark plug that causes an extra high firing voltage and hence extra high levels of emitted noise.

Our spark plug wires measure approx 300ohms per ft resistance. if the center conductor is nicked when the wires lengths are terminated, this can cause an unwanted spark gap that will make lots of extra noise.

The focus on fixing this issue should be to find out what the source of the noise is and work on that. In a dual ignition, it is easy to isolate ignition noise sources since you can turn off one half of the ignition at a time. Also, turn off the alternator field power and see if that helps. Alternators are another noise source in vehicles. Spark plug wires can be disconnected from plugs, one at a time to isolate a problem wire (make sure to ground the end of the disconnected wire or coil damage could occur). Engines need to be grounded well. Ground cables should go directly to an engine case bolt, not to a motor mount bolt. Poor ground systems in home built aircraft are a common cause of all kinds of problems with electronic systems.

Robert

David, that's a lot of work? Looks nice!
I have installed new spark plugs and reduced the gap to 0.020" I have flown the plane only for some minutes and I'm not sure if that helped...
As soon as the weather gets better I will fly and check!

Robert, do you have a suggestion on different spark plugs other than the iridium ones with maybe a higher internal resistance?

I'm building a Glasair Super IIS RG now and if I get the com noise to a level that is acceptable I want to put your EFII system in it too.

By the way, David what type of com radio do you have that is affected?

Spark plugs

The plugs we use are resistor plugs. There isn't a selection of resistances with spark plugs.

However, there are spark plug wires with greater resistance.
We use spiral core plug wires which have less noise reduction than the plug wires in your car. For most aircraft installations, these work well.
The next step that can be taken with the plug wires is to go to a carbon core wire, also known as graphite or RFI suppression wires.
ACCEL# 4041 wires available from Summit Racing is a good universal carbon core wire kit that will work with our system.

For anyone getting ignition noise into their radios, these are some good steps to take:
1. Measure the resistance of your spark plug wires, make sure you don't have a damaged wire. Look for a consistent ohms per ft measurement on all your wires. Spiral core wires about 300ohms per ft, carbon core wires about 1000ohms per ft.
2. Improve your systems grounding - this is a big issue with many home built aircraft.
3. Change to carbon core spark plug wires.
4. Reduce the spark plug gap to .020"

Robert


Robert

SparkPlug Screw on cap

My experience and my opinion (not worth 1 cent)... one possible source is the screw on spark plug caps. Take a look at the cap and if you are starting to see what appears to be 'etching' or pits in the cap there is your spark jumping. Change the spark plug caps. A friend and I were discussing this the other day and it seems the spark plug cap and different vendor spark plug wires attach better to the spark plug cap and thus the possible reason for why the movement between spark plug wire clip and plug cap is occurring. If you have the spark plug wires strain relief to hold them fixed you can get good results but once you remove the plug wire and reconnect you might start hearing the noise because you disturbed the contact point. To help the cap from spinning squeeze the cap a little and make it be more like a lock nut.

Second location can be the coil towers. There is nothing you can do about this location as the towers are fixed so make sure the wires are secure in that location from vibration etc.

Hi Robert

Thanks for the input. As I first noted, please excuse my ignorance. I think that EFii is a great product. It was a lot of work, but it's what ended up working for me, probably in spite of myself. It's what took a good 90% of the noise away for me. I'm still a fan of EFii.

As I recall, I went through everything that you touched on. Knowing the havoc that a poor ground can create, I spent a lot of care in making sure that proper grounding procedures were followed during the build of the plane as well as the installation of my EFii, though that's not to say that there isn't something that I missed. I do feel confident in the grounding of the airplane though. An engine case bolt is used and I made sure to have metal to metal contact with no paint and such at the attach lug and I have a central grounding bus. I soldered my ground connections and lugs.

I'm not a huge fan of my radios. They're early generation Microair radios and took me a while to sort out some poor quality transmission problems. A good quality high noise environment Sigtronics mic solved that one. I wouldn't be surprised if my radios were a contributing culprit.

I remember measuring the resistance of the plug wires when I was first trying to approach this issue. It's been long enough that I don't remember the exact numbers that I got, but I'm pretty sure that the numbers were in line with the 300ohm plf. I think that I saw more like 350ohms. I wouldn't think that would be enough to raise suspicions, or am I wrong on that account?

I did the alternator tests as well with no effect. I have a back up alternator as my backup electrical source and I even totally removed it from the airplane to verify that it was or wasn't the cause. There was no change.

I do see some of the arching (if that's the right word) on the plug screw-on caps that Gaylon mentioned. I've tried making sure that they were secure and such but I can always do better. I could see that as a problem.

It was the dual ignition that aided with the trouble shooting for me. I could use one side as my base line and render the other side with testing for comparison at a flip of a switch. It served me well on that aha moment in testing.

I understand and believe what you say about the source of the noise. Once again it's my ignorance since I thought that I was seeing the source of the noise at the coils (secondary winding). I'm a little puzzled with my findings with my testing. The system didn't really quiet down until I did both the faraday cage around the coil packs AND the shielding around the control wire harness?? Either/or of the two may have helped a little, but when I did both, everything got really quiet. Makes no sense to me in light of the information you gave. Does that say anything to you that might help?

Thanks again.