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Ignition systems option and 14mm or 18mm spark plugs?

apkp777

apkp777

Well Known Member
Hey all,

Just getting ready to order my engine kit and would appreciate some input on the ignition systems options.

I am considering a P-mag/ E-mag option and traditional mags. The electronic ignition comes with 14mm plugs the traditional 18mm. Should I get the 14 or 18mm cylinders? I know I can get an adapter from 18 to 14 but not the other way around.

Your thoughts?
 
A vote for 14mm

You have the flexibility with 18mm option, but I would go for the 14mm. Running big-gapped cheap NGK plugs that are near-impossible to foul with powerful dual electronic ignitions makes for a easy-starting, economical-to-run engine. If that is what you want, then the adaptors are just a pain in the butt to deal with every time you pull a spark plug. This is where I live. :)

Hans
 
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Personally I have no problem with the adaptors, but given the option why mess with them? Can you still borescope with 14 mm plug holes?
 
frankh said:
Personally I have no problem with the adaptors, but given the option why mess with them? Can you still borescope with 14 mm plug holes?
Click to expand...

One other issue, most airport loaner tools are set up for doing compression checks on 18 mm holes.
 
I have ordered my engine with 18mm plugs. I am going to be using P-mags, I still have time to get my cylinders with 14mm plug holes. Anyone else have some input on this?
 
Reemphasizing the two prime reasons mentioned:

1. You can't go back to 18mm. Someday you may want to install a mag - say to clinch a sale. What then? No options except cobbling up a mag-to-auto interface.

2. You'll need the proper non-standard fitting for compression checks.

I've had no problem with bushings, and my buyer wanted a mag to replace a P-mag! Fortunately ASP couldn't get the 14mm heads so I had 18s.

Oh, BTW, I've a 65 hour P-mag with gear for sale.

John Siebold
 
Spark plug adapters 18mm - 14mm

nucleus said:
You have the flexibility with 18mm option, but I would go for the 14mm. Running big-gapped cheap NGK plugs that are near-impossible to foul with powerful dual electronic ignitions makes for a easy-starting, economical-to-run engine. If that is what you want, then the adaptors are just a pain in the butt to deal with every time you pull a spark plug. This is where I live. :)

Hans
Click to expand...

Hans, here's a link http://www.vansairforce.com/community/showthread.php?t=49350&highlight=g3i to an earlier post about those darn 14mm spark plug adapters.

Thomas Shpakow
www.g3ignition.com
 
Speak of the Devil...

Had a rough running engine on the "mag" check the other day, postponed the flight. Had lead shorting out the bottom plug on #4. Decided to put in all new plugs because I want to test the the EIX Iridium plugs anyway, and guess what? The adaptor tore rather than come off the plug. Not sure what kind of torque was involved, as my nine year old plane elf was doing that job.
RV6ASparkPlug2.jpg

RV6ASparkPlug2.jpg

Anyway, I am waiting on a set of (4) spark plug adapters, which, according to Aircraft Spruce, have a "new and improved corrosion resistant design" that "substantially extends the operational life". I hope so. Despite liberally applying anti-seize, mine only lasted about 120 hours. I did pull the spark plugs three or four times.

Thomas, that is an interesting approach you linked in here. How long have you been doing that? The documentation that came with my pmags specifically said to not install the adapters by themselves, but to thread them onto the spark plug first.

Hans
 
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Received the Adaptors

Interesting, the adaptors are Klaus's and the instructions say to torque them into the head at 25 ft-lbs and then put in the spark-plugs at 15 ft-lbs. Completely different from the emagair instructions! I'm going to follow Klaus's instructions and maybe build one of Thomas's tools for the next time I pull the plugs.

Hans
 
I made my own adapters out of 304 stainless hex stock. I recently bought a CNC turret lathe and will be going into production with these by the end of Jan. They will be significantly less expensive and better than the ones available from Spruce.
 
nucleus said:
Interesting, the adaptors are Klaus's and the instructions say to torque them into the head at 25 ft-lbs and then put in the spark-plugs at 15 ft-lbs. Completely different from the emagair instructions! I'm going to follow Klaus's instructions and maybe build one of Thomas's tools for the next time I pull the plugs.

Hans
Click to expand...

I think if you torque them to 25 ft-lbs they will snap. Make sure you put the plugs in them before tightening them, there is less chance of breaking them.

Nice to here that you are going to be making these adapters Bob.

Have a merry Christmas.

Norman
 
Never had any trouble..

I have LSE adapters with1000hrs on one set and 500 on the 2nd set with no problems. I have always torqued the adapters to 25lbs without the plugs in them and the plugs to 15lbs, have never had an adapter come out with the plug. I usually pull/change/clean plugs around 100hrs and have never had a problem with plugs or adapters (knock on wood).

I do like the idea of SS adapters though if they really are better?
 
One issue I have not seen mentioned yet. With 18mm spark plugs, you have a larger air gap between the center electrode and the steel side wall of the plug. This extra space becomes a benefit as altitude increases. The larger air gap prevents "mis-firing". I suppose it helps only if you tend to fly your RV at higher altitudes.
You can also purchase 18mm automotive spark plugs for use with an electronic ignition. I seem to remember a thread on here a few years back which mentioned specific numbers to use. I could not locate it with a quick search. 18mm spark plugs were common on cars in the first half of the 20th century. Just another data point to consider.
Charlie Kuss
 
a 14mm hole in the cylinder head leaves a lot more material in the head making it more robust against cracking.

Also, adaptors will make your 14mm plugs run hotter, due to the additional barrier to heat transfer. I would have thought stainless steel adaptors would be close to a disaster for reasons of heat transfer too!

An automotive compression tester can't be that expensive, or better yet, get a proper leakdown test kit - much more repeatable and can be used to determine where you problem area lies (if you have one)

I'm going to go 2x14mm when I get to choose.
 
Autolite 386 plugs are 18mm. I had nothing but problems with those plugs when I ran them almost ten years ago. I would not recommend them.

NGK BR8ES work well, last a long time, and are cheap.

Autolite aircraft plugs are stainless, and so are the helicoil threads. I haven't had any issues with heat transfer.

The stainless adapters should hold up better than silicon bronze, since 304 stainless is harder and has better corrosion resistance. Harder to machine though.
 
I've had customers run Autolite 386's without a problem. Champion also hand-makes plugs that are 18mm with auto ends (you can only get them a the Reno Air Races...:p)

I would never order an aero engine with 14mm plugs, BUT champion also makes 14mm aircraft plugs, so you aren't SOL if you do and want to run mags eventually, just have same rare plugs to track down.

It's also not that big a deal to put together a mag with Auto leads for the cap either.

So go with whatever makes you warm and fuzzy. I only run Aero plugs in my personal airplanes.
 
Autolite automotive plugs suck!

rocketbob said:
Autolite 386 plugs are 18mm. I had nothing but problems with those plugs when I ran them almost ten years ago. I would not recommend them.
snipped
Click to expand...

Bob,
I won't use any Autolite spark plugs in my customers cars and trucks. They don't hold up. A quick check shows that they cross over to the following:

Champion D14
NGK A7
ND M22
Bosch M5A

No experience with any of these, but I've always had good luck with NGK and ND [Nippon Denso] spark plugs. Just my opinion. It appears that you could find any of these spark plugs at your local small engine repair shop.

Charlie Kuss
 
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Automotive 18mm spark plugs available

A little Google searching led me to the following links. Autolite 386 below. I note that these are resistor style spark plugs. See

https://www.oreillyauto.com/detail/...13d7/autolite-copper-core-spark-plug/ato1/386

NGK offers 2 different spark plugs when I cross referenced Autolite 386. Both the A6 and A7 are listed. This means that you can play around with the heat range a bit when using an NGK plug.

It appears that the A6 and A7 NGK plugs are obsolete. They are replaced by the AB6 [aka 9610]

https://www.ngk.com/ngk-2910-ab-6-nickel-spark-plug

and the AB7 [aka 3010]

https://www.ngk.com/ngk-3010-ab-7-nickel-spark-plug

Later in this thread, the colder NGK AB-8 is mentioned.

https://www.ngk.com/search/all?q=AB-8

https://tinyurl.com/2p892v4w

All of these NGK spark plugs are non-resistor units.

Here is a link for the ND M22 spark plug. [aka 5003] See

https://www.densoproducts.com/search/all?q=M22

Charlie
 
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Charlie,

Autolite 386's were recommended by Jeff Rose (don't know if they still are) but I had issues with misfires and excessive electrode erosion after just a 20-30 hours. I remember talking to Klaus Savier and he recommended strongly against using those plugs...think he said they were too hot of a plug for a Lycoming. It makes sense to me as the electrode on the BR8ES's is recessed quite a bit further inside the plug.

FWIW I've had the last set BR8ES plugs for 400+ hours. I used to change them more often but quit changing them since they appeared to be perfectly well whenever I checked them.
 
Heat range issues

Bob,
Thanks for posting your experiences with the Autolite 386 spark plugs. The BR8ES [14mm] spark plugs would be 1 heat range colder than NGK's AB7 [18mm] spark plugs. [The number in NGK's part number shows the heat range] It seems that if someone wanted to try an automotive 18mm spark plug, the NGK AB8 spark plug would be a better choice. It's the same heat range as the BR8ES, which works well for you. See heat range chart below.

http://www.championsparkplugs.com/glossaryImage.asp?imgID=722

What compression ratio is your engine? Compression ratio affects spark plug temperature. I take it that you have no issues using the BE8ES spark plugs at higher altitudes. What is the maximum altitude you've used these spark plugs?
I'm not trying to say that 18mm plugs are better. I'm just trying to offer an alternative for those who may not wish to use 18mm to 14mm adapters.
Charlie
 
14.5K is the highest I've gone in the RV. No issues with the plugs whatsoever. Std. compression ratio O-360 8.5:1. In the rocket I put BR9ES plugs in since I have H2AD pistons in it (9:1).

Those plugs being non-resistor type might make a racket in the radios.
 
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Resistor wires needed with non resistor spark plugs

rocketbob said:
14.5K is the highest I've gone in the RV. No issues with the plugs whatsoever. Std. compression ratio O-360 8.5:1. In the rocket I put BR9ES plugs in since I have H2AD pistons in it (9:1).

Those plugs being non-resistor type might make a racket in the radios.
Click to expand...

Bob,
I agree. When using non resistor spark plugs you WILL need to use resistor spark plug wires. Non resistor spark plug wires use an actual copper wire as the conductor. Resistor wires, commonly referred to as "spiral wound" use powdered carbon on stranded fiberglass as the conductor.
An easy way to tell if you have resistor or non resistor plug wires is to check them with an ohmmeter. Typically, resistor wires will show 2,000 to 5,000 ohms per foot of length. Non resistor wires will have less than 1 ohm resistance.
I agree with you that the adapters should not significantly impede heat transfer. Lycoming cylinders [don't know about ECI or Superior] have HeliCoil inserts in the spark plug holes. The HeliCoil inserts are made of stainless steel.
Charlie
 
spark plug inserts 18mm / 14mm

Hans,
I believe the reason that P-Mag suggests threading the plug into the insert first is to remove the potential of breaking off when just the insert is installed in the cylinder head. Where the insert threads end near the 7/8-nut end, the insert material is real thin. With the spark plug in the insert, this beefs up the insert integrity when installing as a unit. Once the insert is in, removal and installation of just the spark plug is only needed if the torque of the insert is not disturbed. I have been using my adapter tool a few years now; I do a leak down every oil service, which is every ten hours of severe service. Just got tiered of those inserts coming out all the time.
Sincerely,
Thomas Shpakow
www.g3ignition.com
 
The current...

rocketbob said:
Charlie,

Autolite 386's were recommended by Jeff Rose (don't know if they still are) but I had issues with misfires and excessive electrode erosion after just a 20-30 hours. I remember talking to Klaus Savier and he recommended strongly against using those plugs...think he said they were too hot of a plug for a Lycoming. It makes sense to me as the electrode on the BR8ES's is recessed quite a bit further inside the plug.

FWIW I've had the last set BR8ES plugs for 400+ hours. I used to change them more often but quit changing them since they appeared to be perfectly well whenever I checked them.
Click to expand...

...Electroair (aka Jeff Rose) recommendation is here...

All aircraft spark plugs will work with the EIS. We have found that the REM37BY (or equivalent) plugs work the best because they are easier to gap to the range required and fit the broadest heat range recommended by the engine manufacturer. We strongly recommend that you verify the heat range for your engine and use the appropriate plug.

Automotive spark plugs vary widely in heat range applicability. The EIS system will work with properly adapted automotive spark plugs. You MUST verify that the automotive spark satisfies the heat range requirement of your engine. An improper plug heat range risks pre-detonation and severe damage to your engine. As a general rule, we do not recommend the use of automotive spark plugs in aircraft engines.

It seems that the aircraft REM37BY would be the easiest Lycoming solution in an 18 mm hole...

http://www.electroair.net/technical.html
 
Dont waste your time with Autolite 386 plugs

There are some posts that highly recommend the Autolite 386 and others that don't. So I thought I would give it a shot in my Lyc O-235 with 2 P-Mags. I liked the idea of using an 18mm plug without having to deal with removing the brass adapters each time I changed the 14 mm plugs. Fortunately I experimented with only 4 386s and 4 standard NGK BR8ESs. Good mag check, and then took off with full power. When I reached 2000 ft AGL the engine suddenly started to loose power and misfire. Tried all the stuff we are taught to troubleshoot these types of engine problems and nothing worked except to keep the engine speed under 1500 rpm. Called the tower and said I had a poor running engine and requested a straight in approach back to the runway. They asked how many souls on board, I answered 2. Landed without a problem, and a fire truck followed me back to my hanger. I was a little embarrassed about the stir that I caused and mentioned to the firemen that my plugs were misfiring, and thanked them for their assistance, they said, glad to be of service and left. I replaced the 386s with the NGKs, and took off again and flew for an hour without any more problems. On the way back I thanked the folks in the tower for their assistance and for the professional manor that they handled this incident.

This experiment using the Autolite 386 plugs didn't work for me. 386s are used mainly for tractor engines. I think that the heat range for these plugs is too hot for my engine. So don't waste your time or engine using Autolite 386 plugs when the NGK BR8ES or equivalent works fine.
 
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14mm Thread holes

Hi I have 14mm thread holes , using Denso Iridium plugs with LSE Plasma III using a 24 heat range (NGK 8 range)
works great, for me, no thread problems. The cylinders were from Lycoming.
PS easy to get a 14mm compression adapter
Peter

In the past have had poor success with Automotive 18mm plugs, be very careful about heat range too hot = too bad
Peter
 
I just recently switched to 386 from BR8ES with adapters... I too had detonation on climb out. Mine was on the number 3 cylinder. I pulled the power back and when the CHT cooled off, it ran fine at cruise.

I took that plug out and the center electrode was no where near the center of the plug. I put one of my BR8ES that I removed back in and I have had no issues.

I am wondering if these plugs are too hot for a 9.5 to 1 -540 ?

I hate the adapters, but I might go back....

Doug Rozendaal
F-1 EVO
 
14 mm plug holes, other than ECI

Hi gang:

Are new cylinders available with 14 mm plug holes from Lycoming?

I assumed that ECI was the only source for this option. Unless ECI has gotten their act together on the cylinders I felt that I would be using new lycoming cylinders and the adapters.



Thanks, Terry.
 
Mag harness conversion

osxuser said:
I've had customers run Autolite 386's without a problem. Champion also hand-makes plugs that are 18mm with auto ends (you can only get them a the Reno Air Races...:p)

I would never order an aero engine with 14mm plugs, BUT champion also makes 14mm aircraft plugs, so you aren't SOL if you do and want to run mags eventually, just have same rare plugs to track down.

It's also not that big a deal to put together a mag with Auto leads for the cap either.

So go with whatever makes you warm and fuzzy. I only run Aero plugs in my personal airplanes.
Click to expand...

Here a link to my G3i website for the step by step stock magneto harness conversion to automotive spark plugs. http://www.g3ignition.com/magmod.html
Cheers,
 
Autolite 386 is not the coldest plug in that series of 18mm plugs.
The Autolite 373 is the coldest one I see on their chart.
Has anyone tried it? I would rather find an 18mm plug and not use 14mm adapters.
As for Autolites, I've never had a bad one, and use Autolite aircraft plugs in the Cessna too.
 
I just reviewed this thread after reading about Ground Power Unit conversions on another site. Lots of O-290G GPU's were converted to power Thorp T-18 and other early homebuilt aircraft.
Continental designed a whole series of GPUs based on aircraft engines like the C-90. These and the 4AO84 GPU's use an Autolite 2223 shielded spark plug just like the aviation plug, except the tip looks like an automotive tip. This plug has a heat range of "3". The 386 has a heat range of "6" which is hotter. With 386's testing too hot, I'm thinking the 2223's might be the ticket.
The 2223 has the 5/8-24 top terminal and 18mm x 1/2" thread like an REM40E
Based on that data from the Autolite site, and no response when I asked if anyone had tried these, I ordered a set of 2223 plugs to try....
$5.13 each, free shipping on orders over $25 @ Amazon . http://www.amazon.com/Autolite-2223-Copper-Shielded-Spark/dp/B000ET3W98
This is a possible alternative to bushing adapters and retains the shield and stock harness.
If the 2223 is too cold, Autolite also lists a 2225, which is one level colder than the 386. These are listed @ saturnsurplus (with the champion ED-16 and others) for $7.50 ea, new 100+ in stock.
 
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So how did the plugs work out?
In a word, slowly.
We just got a test going in an O-235 high compression engine, it's in a Wagabond.
We have an O-290G converted to D, which is in a Thorp T-18. Just got it this week. It sat 9 years, but started up and ran well yesterday. Once we get it flying, and establish that the airframe and engine are ready, I'll try some Autolite 2223 plugs. If those don't satisfy, then other heat ranges or bushings and 14mm plugs.
I know this isn't an O-320 or O-360 commonly used by this group, but it is what it is...
 
SHIPCHIEF said:
Autolite 386 is not the coldest plug in that series of 18mm plugs.
The Autolite 373 is the coldest one I see on their chart.
Has anyone tried it? I would rather find an 18mm plug and not use 14mm adapters.
Click to expand...

No chatter on this thread in a while. I'm curious if anyone has tried the 373? Or if there is any other news for plug options.

I've been running Autolite 386 plugs on Electro-Air EI (IO-320) for 4+ years without a problem. But it seems that for PMag there has been to many issues with the autolites, so I don't want to try it on my P-Mag system.
 
I was reading another post on measuring spark plug resistance on Champion aircraft plugs when I got an idea.
NGK offers resistor covers for spark plugs. Those of us who want to run 18mm auto (tractor) plugs find only the Autolite 386 to have a resistor, but it's too hot of heat range for many Lycomings. The NGK AB7 or AB8 might be a better heat range but are not resistor plugs. If resistor plug leads like MSD Superconductor 8.5mm wire can't suppress EMI the NGK Resistor caps may add the missing R?
I recently had radio trouble that I traced to the left mag. The leads were old, so I made a new harness from MSD 8.5mm Superconductor wire & 90 degree plug boots. I used NGK BR8ES plugs gapped .016" same as aircraft plugs. I got the idea for that from G3i Ignition's previous post. Older Bendix harness plates are even easier to mod, they have threaded gland nuts for the harness wire and don't require any drilling.
Those plugs & wires worked fine, but the mag was the problem after all. I upgraded to a Pmag and regapped the plugs to .035". That "fixed" the radio.
When the aircraft plugs get worn, my auto conversion harness will go on the remaing mag to spark AB8 plugs.
This plug testing is a long drawn out process.
The Autolite 2223 sheilded resistor plugs for Jeeps, GPU's etc were never tested because the 'cigarettes' on the aviation plugs are bigger and don't fit in the GPU style plug. I bought enough to try on a plane, and 8.5mm wire will fit inside, but the nut at the plug end gets Mickey Mouse, and auto plug caps are a better, time tested solution.
 
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