FORANE
Well Known Member
Wrong.
magneto harness auto plugs
www.g3ignition.com
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Why don't we use 18mm spark plugs instead of fooling with spark plug adapters?
- Thread starter FORANE
- Start date
Pilot135pd
Well Known Member
That's why I asked the question, thanks. So for around $600 a kit you can then save 1/2 price on NGK Iridium Plugs 2743 plugs ($20).
So price wise I supposed for someone starting new it would be cheaper than buying all new $50 plugs, but for us who already have everything working fine, what would be the advantage to change to the newer harness system?
Can the $4/plug Autolite 386 be used with this harness kit?
FORANE
Well Known Member
I have been using the NGK 3961 plugs which are currently running around $3 a plug. When I converted to the g3i system with dual slick mags I noticed it started easier and ran better immediately. At annual there is no checking or cleaning plugs; simply replace plugs with new. It's less than $600 I think; closer to half that.
Certainly if you sell your traditional harnesses here it would be.
Pilot135pd
Well Known Member
I just added up the price in that list you posted. Kit is around $375 but then you have to buy the end caps at $41 each so I rounded it up to $600. I might give them a call to find out exactly what I would need. Thanks.
FORANE
Well Known Member
Ah, inflation...
Pilot135pd
Well Known Member
I don't think politics have anything to do with it. Things just get more expensive as the years go by, it happens with everything.
PilotjohnS
Well Known Member
So my slick harness is shielded, but auto plug wires are not. Any trouble with electrical noise or does the resistor plugs take care of that?
Inflation is a thing. It is printing money from thin air. Just a fact and represented by officially calculated and published value. That’s all. It is one of the main thing the Fed tries to throttle by changing the bank rate. The Fed isn’t government. Why do you consider inflation political? It affects everyone both domestic and abroad. Must be a trigger term or something.
FORANE
Well Known Member
Don't know about shielding but I didn't have noise trouble when I converted to the g3i and ngk plugs from slick harness.
Actually, no. You can convert the harness from a Slick Magneto. I do not know if the vendor where I got the kit is an advertiser so I am not sure I can mention them by name but PM me for it. The only part re-used is the cap on the mag so you have a completely new (and much improved) harness which fits automotive plugs. Since you make the harness, the leads can each be custom length and lead on the path you choose. Makes for a much cleaner installation. The new 8MM wire is what is used in high performance car ignition. No radio noise.
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This was okay in bold, but you really should have gone with ALL CAPS to communicate an authentic “curmudgeon who argues with the Post Office” vibe.
How about NGK 7909 (https://www.ngk.com/ngk-7909-ab-8-nickel-spark-plug) + resistor caps?
Tandem46
Well Known Member
I just bought the kit for one mag…$168. You use the cap off your old mag.
Toobuilder
Well Known Member
I've thought about adding caps to solve the 18mm non-resistor plug issue but have no experience with them. Might be worth an experiment on one set of plugs to find out if that's a practical solution. Appreciate the kick start to the brain!
Those are not resistor plugs. Assuming it was, and if it's specs match the heat range appropriate for Pmags, the tips are not solid tips. They are threaded tips. Always use solid tips or else the tips unscrew under aircraft engine vibration.
Toobuilder
Well Known Member
Right, and that’s why he specified use of the resistor caps.
Aha. Missed that. Got it now. Thanks for that clarification. As a rule the closer the resistor is to the spark gap the more effective it is for RFI control. Which is the main reason for adding a resistor in the first place. So a resistor plug is more ideal than a resistor cap because it is right at the spark plug air gap. An old rule of thumb about the order of effectiveness for RFI control in the ignition systems is 1. Resistor plugs, 2. Resistor wires (the wires are the noise transmission antennas) and then 3. Resistor caps. Resistor caps came about as a fix for traditional non-shielded ignition systems using solid wire leads. That's why you will find modern resistor caps as an upgrade band aid for lawn equipment and other small engines that can create nuisance noise for neighboring homes and automobiles. But hard to find for larger type modern engines that come from the factory with RFI resistant ignitions. Granted a resistor plug also raises the voltage necessary to jump the spark air gap, thus raising the amount of energy imparted into the spark itself. Very common attribute in modern ignition systems. A resistor cap will also do same just less efficiently. But the main point of added resistance is for RFI noise suppression. On a side note when using legacy magnetos for ignition resistance needs to be watched carefully because that same increase in voltage needed to fire the plug can also cause a spark to jump through the coils and short the secondary wiring. Especially with a very old mag that uses shellac on the coils. One of the reasons that piston aircraft magnetos traditionally come with the shielded high tension leads with screw on caps vs. modern automotive style ignition wire and cap boots.
SDS spark plug adapters are $12 each. . Go the link below. Lots of good items on that page, so use the find function, insert "spark plug"
I wanted to move away from the 386’s due to the heat range. Too chep to shell out hundreds for adapters. Found a good 18mm ngk plug with a heat range i licked, so bought the resistor plugs and tried them. All sorts of noise on the intercom and they were pulled on landing. Unsure why they didn’t work. Finally settled on ngk lr4U or something like that. Better heat range and didn’t rust like the 386s. They are listed as non resistor plugs. However,they are totally noise free and have been using them for 800 trouble free hours. No resistor caps being used. I wonder if they are resistor plugs and the specs are wrong. They do have an r in them. These are fired by an auto coil. Still using aviation plugs on the mag.
PilotjohnS
Well Known Member
When you have plug adapters in, does the standard compression tester still work?
You have to either remove the spark plug adapters, or buy a 14mm extension for the compression tester. https://www.aircraftspruce.com/catalog/topages/compExt14.php
I saw a few members stating spark plug use upward of 500 hours. Please be careful. Emag recommends changing the 3961’s every 100 hours and the iridium variant every 125 hours. They’re so cheap there is really no reason not to change them.
One issue I have experienced. I have had 4 spark plug lead terminals fail on my aircraft. There is a small black steel retainer clip inside the boot that holds tension on the terminal cuff and the spark plug post. This black clip is prone to fatigue and even breaking. I re-terminated 3 leads, ohm checked, etc, all good.
After my condition inspection this year, I had a less than optimal run-up on my left mag. Felt like plug fouling so I ran the plug clearing procedure and things felt fine after that. Shortly after lifting off, I noticed a vibration from the engine I was not used to feeling. After landing I ran another mag check. Left mag dropped 350 rpm, ran quite rough, and I noticed cylinder 4 EGT dropped very quickly to 650F. Pulled the top cowl and immediately noticed bottom lead on cylinder 4 dangling and not at all connected. The black clip on this lead failed and due to it being on a bottom cylinder, the boot was not sufficient to hold the lead on the plug.
A buddy of mine uses zip ties as an extra fail safe to secure the boot to the plug. Changes them every year and inspects the terminals. I will be adopting this zip tie practice!
One issue I have experienced. I have had 4 spark plug lead terminals fail on my aircraft. There is a small black steel retainer clip inside the boot that holds tension on the terminal cuff and the spark plug post. This black clip is prone to fatigue and even breaking. I re-terminated 3 leads, ohm checked, etc, all good.
After my condition inspection this year, I had a less than optimal run-up on my left mag. Felt like plug fouling so I ran the plug clearing procedure and things felt fine after that. Shortly after lifting off, I noticed a vibration from the engine I was not used to feeling. After landing I ran another mag check. Left mag dropped 350 rpm, ran quite rough, and I noticed cylinder 4 EGT dropped very quickly to 650F. Pulled the top cowl and immediately noticed bottom lead on cylinder 4 dangling and not at all connected. The black clip on this lead failed and due to it being on a bottom cylinder, the boot was not sufficient to hold the lead on the plug.
A buddy of mine uses zip ties as an extra fail safe to secure the boot to the plug. Changes them every year and inspects the terminals. I will be adopting this zip tie practice!
Attachments
Pmag ships pretty crappy plug wires I believe. Their poor performance does not necessarily require excessively short plug replacement intervals. I use msd plug wires and have had no issues in 1800 hours across two aircraft with them. They don’t fall off the spark plugs and the internal pieces do not break off. I also run plugs (std coppers, not iridium’s) well over 500 hours and never had an issue, though I don’t use pmags. Maybe the pmags have some deficiencies that require brand new plugs every 100 hours. I replace them when i see enough wear to warrant a replacement or they don’t pass a resistance test. Never had one fail yet.
You may be shocked to here this, but i go 100,000 miles (roughly 3000 hours) on a set of iridium plugs in my cars. Replacing them at 125 hours just doesn’t make any sense.
Also, your experience with the plug was more likely to have been caused by lead fouling vs a bad plug.
Not suggesting folks don’t follow the mfg guidance, but wanted to clarify that a spark plug can last well over 100 hours.
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I would tend to agree as far as lifespan, but when the recommendation was given to me by Emag over the phone, I just kind of went with it. It costs me about $36 to replace all 8 plugs. If it cost hundreds or thousands of dollars I’m sure I’d be asking more questions.
Interesting experience with your MSD leads I may need to try a set. It’s an uneasy feeling when I hesitate to trust connections in my ignition system!
Definitely suspected lead fowling which is why I attempted to clear that first. The second time after my brief flight, it felt so bad my gut was telling me to pull the cowling and have a look around. After addressing the terminal she was back to normal checks and operation.
Side question. I’m told the iridium plugs burn hotter and cleaner than the standard 3961s. I’ve heard this from multiple people, but I have had just as many say there’s no real difference. I suppose that means no one really has any solid data to support this.
I don't have data, but I have tested almost every plug that will work and could not feel a difference or see any in my engine monitor data, so I settled on the NGK 3961 with the solid terminals. Currently about $1 each from Rock Auto, normal price less than $2 each.
FORANE
Well Known Member
I have a couple Pmag wire harnesses and a couple msd harnesses. I concur with your assessment. The msd connects at the plug with a palpable pop when compared to the Pmag boot which lacks any feedback to confirm it is in proper position. The msd harnesses just appear to be better quality all around.
Now I need to learn how to make msd harnesses. What msd parts are needed to make wires that fit a Pmag?
That is not correct.
The sparking action of a plug produces no meaningfull heat and the metalurgic composition of the electrodes has little to do with how hot they run. All sprkplugs need an appropriate heat shedding capability though and plugs are offered in a wide variety of heat ranges. They need to run hot enough to burn off deposits, but not so hot that they destroy themselves over time. The electrode composition has nothing to do with this. It is all about the design of the metallic shell and ceramic insulator. Differing designs move the heat absorbed to the head (via the threads) at different rates. The key difference with iridium is that the electrodes wear down at a significantly slower rate and therefore last significantly longer.
You can buy a generic 8 cyl kit which includes everything, but the crimper. Reccomed the 8.8's. You can get a crimper tool from amazon for around $15. Don't try using the little plastic crimper dies. They can work, but are difficult to get good results with. These kits are sold with two different connection types at the coil. Be sure to figure out what the pmag uses. I think it uses the old ford style which is not that common.
I would also love to know part numbers to build MSD harnesses if anyone has them. While zip tying the boots to the plugs may help to keep them from coming completely off, it’s really just a bandaid for an issue I’d rather not have at all. As with anything electrical, a solid connection is going to be the safest.
I figured it was mostly an assumption. The additional research I did late last night falls in line with your statements. Thanks for confirming my suspicion!
Not disputing your experience, yet I have been roughing 8 P-Mags (two each on four aircraft) for over fifteen years, and have yet to have a plug wire pop off or a plug wire fail. Wait - I did have one incident where I was getting a very small misfire, and discovered corrosion on the connector at the P-Mag end on two wires…but it was easily cleaned and we went on our way. So…. Some folks have good luck with them. Are there better options? Almost assuredly (as you have found), but I don’t think everyone needs to ditch the P-Mag harnesses out of the box.
I also run the cheap 3961 NGK’s in everything, and replace them at 100-150 hours (rather than cleaning) simply because they are so cheap that the cleaning process takes more time than the plugs cost. I totally agree with you that they would last far longer than that - I just worry about the number of times the “built on” crush gaskets will seal after being torqued. I think that in automotive use, they know that no one will ever re-use them because (as you say) they go 100,000 miles!
One of these days I need to clean up the couple dozen nearly-new aviation plugs I have on hand (removed from nearly new engines to go with P-Mags) and put them up for sale!
Dandlac58
Well Known Member
Hi RMarshall, what is the model number of the Autolites you are using? Have you completed the installation with the copper gasket? By opening the gap some, what do you mean in actual gap width change in mm?
Thanks,
Dan
I don’t have enough experience to throw stones at the pmag products. My only experience is with pmag is what i read here. But i have heard several posts with connectors falling off the coil posts and posts similar to the one above. I don’t advocate people throw out what the have. However, if they do have issues, I believe msd is a quality product. It is the leading supplier in the hot rod world.
Larry
I plan on calling Emag and MSD tomorrow to see if I can figure out what components I’d need to order. I find that I really enjoy having all 8 plugs firing!
If I can get part numbers I’ll post them here.
I purchased an E-MAG auto lead kit from Emag years ago. Unfortunately they have discontinued the kits. However, they still maintain the documentation and have a very nice write up in their manual on how to trim, crimp and test new leads. Good DIY video from Holly
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FORANE
Well Known Member
Really? I bought a set from them 11 months ago and they are still listed on their website.
Discontinued years ago. You can buy a completed harness, but not the kit. The kit consisted of ignition wire, terminals, boots and a crimping tool. You measured to desired length, cut, terminated, installed the boots before installing.
NGK & Denso have non resistor 18mm plugs of the correct heat range. Under $5 each. You you will need to use either a resistor end cap or resistor plug wires.
NGK AB6 [aka 2910]
Denso M17 [crossed over from NGK AB6] & L14-U
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Mike,
Thanks for posting the instructions. Your link for the MSD wire video shows only the parts available and a link to a PDF for installation of the terminals. Maybe they moved the video???
Thanks for the heads up. Link updated. You can view it here:
The SDS CPI-2 installation manual (available for download on their site) lists recommended MSD part numbers, but they are for bulk quantities (100 connectors, 100 boots, etc.). Easier & cheaper to buy the complete wire set intended for a V8.
Here's the manufacturers page - https://www.holley.com/products/ign...ug_wires/universal_super_conductor_wire_sets/
Look at part numbers 31229 or 31239, depending on which type of connector you need on the coil end.
MSD 35051 is the gold-standard crimper, and is priced accordingly. There are more reasonable alternatives such as this -
I ordered the MSD wire set from the aviation department on Amazon & it was shipped directly from MSD/Holley.
Here's the manufacturers page - https://www.holley.com/products/ign...ug_wires/universal_super_conductor_wire_sets/
Look at part numbers 31229 or 31239, depending on which type of connector you need on the coil end.
MSD 35051 is the gold-standard crimper, and is priced accordingly. There are more reasonable alternatives such as this -
I ordered the MSD wire set from the aviation department on Amazon & it was shipped directly from MSD/Holley.
I use the l14-u on my 320. Am happy with the heat range. The specs say non resistor, but completely noise free in my installation. I do not use resistor caps. I speculate that they do have some resistance in them, though maybe not the std 5k, and the spec is wrong.
The msds use the preferred double crimp terminals..the core likes to ride up, so push it into the area between tabs before crimping
Are you using the Denso L14-Us on an electronic ignition, a magneto or both? What do you gap them to?
Using them with megasquirt based EI. I gap them to .035", but could go larger. My coils are strong enough to handle probably .050" - .060" but don't think I need a stronger spark. If using with mags, it is critical to keep the gaps not much bigger than .018" The coils are small and larger gaps will put a lot of stress on them and prematurely wear them out.
I use the aviation plugs for the one mag in the 6. It is not worth the hassle of making harnesses. I have been getting 6-700 hours out of them with regular gapping. At a point, the footballing becomes to excessive to get a good gap.
rocketbob
Well Known Member
Years ago I had a lot of problems running Autolite 386 plugs on a O-360. One of the RV-7s I do a yearly CI on has been running 386 plugs with Taylor blue wires and the EFII system with no problem. I change the plugs every year but find no signs of distress. 150+ hours per year so not a hangar queen.
i also ran the 386's for quite a while. they also worked fine, but they would rust badly. the 14-u's have a better heat range than the 386's and have a nickel coating, so no rust. all around a better plug for the lyc's imho. i also run taylor blue on the 320 that use these plugs. i believe they are the spiro-wrap variety cores. maybe that is what makes it all work. have never tried it with any other wires. on the 540, i splurged and got adapters to run 14mm plugs. it is definately the better way to go.
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rocketbob
Well Known Member
Depends on type. Looking at their catalog, bulk resistor wire that's available in blue:
Taylor 8mm Spiro Pro 35672 -> 350 ohms per foot
Taylor 8mm 409 Pro Race Spiral-Wound 36672 -> 3500 ohms per foot
Taylor 8mm High Energy 35652 -> 5000 ohms per foot
