Spark plug lifespan

RyanB

RyanB

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What’s the typical lifespan one can expect out of a plug? We’ve got 200hrs on a set of Champion 38E’s. I’d like to just replace them all as preventative maintenance. How much more time can we realistically expect?
 
I was wondering the same. Mine are a mix with some @ ~ 300 hrs and some ~ 600 hrs. Spark Plug P/N UREM40E. I was thinking this upcoming annual to just ask my mechanic to replace them all.
 
RyanB said:
I’d like to just replace them all as preventative maintenance.
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From a preventative mx standpoint, all things equal, I usually recommended 400 hours on massive plugs and double that on fine plugs. Didn't mess with fine wire plugs much so that figure maybe a tad low but 1000 hr would be a max number in my book. Regardless, those numbers are heavily dependent on your operational style and regular mx of the plugs.
 
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Well, spark plugs(massives) used to be relatively cheap, $25 or so. I think it’s more with the condition & care. I’d think massives could go 400 hours or so, on average. The normal procedure is to clean, inspect, re-gap, then fresh thread anti-seize.

One could inspect, maybe test resistance, replace any as needed.

5AFF360C-6CC6-46DD-BB53-F1A58C638665.jpeg
 
sourdough44 said:
Well, spark plugs(massives) used to be relatively cheap, $25 or so. I think it’s more with the condition & care. I’d think massives could go 400 hours or so, on average. The normal procedure is to clean, inspect, re-gap, then fresh thread anti-seize.

One could inspect, maybe test resistance, replace any as needed.

View attachment 117362
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That plug seems to have about half its life used up.

They last much longer with low lead fuel, since far less abrasive blasting to get rid of lead deposits. We kept a box of spares in the big tool and supplies box. we used to change them about every 4 oil changes, so they were always in top shape. Effective leaning and low lead fuel made a big difference.

We changed to fine wire, and they lasted forever....
 
Auburn had a 400-hour warranty on their plugs, and I routinely got 800 hours out of them. Champion bought them and shut them down. Arrrgh.

If you can use REM37BY or tempest UREM37BY, I would do that. Very fouling-resistant. Check the Tempest plug applicability chart for your engine.

upload_2023-5-17_18-34-9.jpeg

37BY at the top, typical 38E or 40E below it. I think they also give a little better performance, getting the spark farther out into the mixture.
 
Dan Thomas said:
Auburn had a 400-hour warranty on their plugs, and I routinely got 800 hours out of them. Champion bought them and shut them down. Arrrgh.

If you can use REM37BY or tempest UREM37BY, I would do that. Very fouling-resistant. Check the Tempest plug applicability chart for your engine.

37BY at the top, typical 38E or 40E below it. I think they also give a little better performance, getting the spark farther out into the mixture.
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I use the 37BY spark plugs in everything they fit. With the exception of a couple o-235 engines, I’ve never had to clean one. I also think they offer better performance thanks to the projected tip.
 
sourdough44 said:
Well, spark plugs(massives) used to be relatively cheap, $25 or so. I think it’s more with the condition & care. I’d think massives could go 400 hours or so, on average. The normal procedure is to clean, inspect, re-gap, then fresh thread anti-seize.

One could inspect, maybe test resistance, replace any as needed.

View attachment 117362
Click to expand...
That is a beautiful picture of a electrode and the wear/erosion that occurs.
 
Dan Thomas said:
If you can use REM37BY or tempest UREM37BY, I would do that. Very fouling-resistant. Check the Tempest plug applicability chart for your engine.
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Aircraft Spruce shows the same price for Tempest UREM40E v UREM37BY @ $33.55 per spark plug. The Tempest Application Guide has both of those listed for my engine. Is there a reason the mechanics have so far been continuing to use the UREM40E or is it more likely that they are just using what is already in there without consideration to a change?
 
Mongoose Aviator said:
or is it more likely that they are just using what is already in there without consideration to a change?
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More than likely this. It might also depend on how proactive the mechanics are. Perhaps ask them directly and compare their input to what was discussed here?
 
Right now I have 330 hours on a set of UREM37BY and they are going strong. I expect to get another 200 hours. Every oil change during the compression check they get cleaned, checked (resistance/football), and gapped as needed.

Spark plug maintenance tools:
PRECISE GAP SPARKPLUG SET TOOL 12-11600 $18.90
http://www.aircraftspruce.com/catalog/topages/precisegap.php
http://www.aircraftspruce.com/catalog/topages/1201682.php

ELECTRODE SPREADING TOOL 12-51520 $17.95
https://www.aircraftspruce.com/catalog/topages/expansiontool12-03391.php
You likely have something laying around which will do this just fine.

CT-450 RETRACT. GAP GAUGE S 12-00797 $22.50
http://www.aircraftspruce.com/catalog/topages/gapsettingtool2.php
The automotive L-shaped wire feelers work well.

Spark Plug Erosion Gauge 12-00791 $4.35
https://www.aircraftspruce.com/catalog/topages/ct482gauge.php
Go-NoGo gauge - hole is 0.260" in diameter. You can make your own. If it fits over the electrodes when properly gapped the plugs are beyond acceptable wear.
 
Proper rotation of plugs will equalize wear on the electrodes.

Top to bottom may not do it.

I’m not a fan of abrasive cleaning.

Often installing lower plugs in the upper position will provide some self cleaning.

Gravity sucks!

Run-up and shut-down per LYCOMING Service Instruction will reduce the need for removal and blasting.
 
Do you know that just about all aviation spark plugs can be traced to one individual?

Albert Champion - AC

Looks like a unique person.
 
mondtster said:
I use the 37BY spark plugs in everything they fit. With the exception of a couple o-235 engines, I’ve never had to clean one.
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We had an O-235 in a Citabria. They run really cool, and foul their plugs quickly in the flight-training world. Sometimes we'd have to clean those plugs less than 50 hours after the last cleaning. I put the UREM37BYs in it and the fouling stopped completely and forever.

Did the same to the other engines except for the O-540, which is a long-reach (long thread) plug. No extended-electrode plug available for those engines.
 
Magman said:
P
I’m not a fan of abrasive cleaning.
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The spark plug cleaners use silicon carbide grit. That stuff is hard, sharp and erodes the electrodes. I went to using the bead blaster, using glass bead, which cleans without so much erosion. But one has to carefully, with a light and magnifier or strong reading glasses, make sure that no bead is wedged into the bottom of the plug well where the ceramic meets the steel. Bead is tiny and white and hard to spot otherwise, and if it falls out into the cylinder you get scoring. If carbide grit gets into your cylinder, the scoring is FAR worse.
 
Many small engine mfg discourage cleaning for the reasons Dan mentioned.

Many years ago I came across a small engine cleaner that used water.

Plugs looked like brand new. Never saw another.
 
Papa Pilot said:
The electrode on massive plugs tend to wear down to an ellipse shape. I've seen it referenced many times that you replace massive plugs when the minor radius is 1/2 the major radius.

Ellipse Calculator - Monolithic Dome Institute
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The center electrode will wear like that, but the outer electrodes also erode. Which one get it worst depends on the plug's firing polarity, which is why we rotate plugs when we clean them. Magnetos are AC devices, firing one plug center positive, the next plug center negative. IIRC it's the positive electrodes that get eroded the fastest.

When those outer electrodes wear thin, they can start acting like glow plugs, causing preignition.
 
I usually change oil at 40 hours and clean and gap at 80 hours. The plugs are never cleaned and gapped 3 times.
 
A bit of an addendum to my earlier post...
Every 50 hour oil/filter change, I do a few other maintenance tasks. Service and rotate the spark plugs as noted above. Run a compression check while the plugs are out. Generally, I do oil changes after a short flight to heat saturate the engine, so these compression checks are warm, unlike most during annual inspection. It's nice to get both cold and warm numbers.

I haven't had a fouled plug in 100s of hours. As Magman stated, following Lycoming's run-up and shutdown procedures helps prevent fouling. While I'm not sure of Lycoming's run-up suggestions, I do follow their shutdown procedure. Since I lean <b>aggressively</b> on the ground, step one is covered. At the hangar I goose the throttle for 20-30 seconds while turning tail toward hangar, then shutdown with mixture.
 
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Domenick said:
I haven't had a fouled plug in 100s of hours. As Magman stated, following Lycoming's run-up and shutdown procedures helps prevent fouling. While I'm not sure of Lycoming's run-up suggestions, I do follow their shutdown procedure. Since I lean <b>aggressively</b> on the ground, step one is covered. At the hangar I goose the throttle for 20-30 seconds while turning tail toward hangar, then shutdown with mixture.
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Lycomings don't have the big fouling problem that the small Continentals do (up to the O-300). The lower plugs in the Continental cylinders are very close to the bottom of the bore, and the oil that gets past the rings during idle (due to the closed throttle creating terrific suction on the cylinder's intake stroke) will flow into the plugs and get baked in there. The runup before shutdown helps scavenge that oil out.

The Lyc O-235 is, however, a plug-fouling machine. It runs too cool and fouls its plugs easily.
 
Lycoming did a few interesting things regarding the O-235 L2C due to issues with deposits.

The 37BY plug helps are lot.

30 secs at 2000 really cleans things out. Good time to check mags to see if ok for
next flight.

I met an L2C that had deposits on pistons meeting the deposits on the head as
the prop rotated! Lycoming has a procedure using something like wheat or rice to
blast the installed cylinders.

In my prior life 112 plugs required some monitoring. Even with the Ignition Analyzer ( Chinese Television? ) we did post flight run ups to assure next flight readiness.
 
Magman said:
Run-up and shut-down per LYCOMING Service Instruction will reduce the need for removal and blasting.
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Which SI is it? All I see in the Lycoming Operator's Manual is this:

upload_2023-5-19_18-11-56.png
 
I don’t recall the number.

it is a Service Instruction from about 30 years ago.

I’ll try to look it up in paper.
 
How did you ever come up with that? Problem has been around for a while. Squids got their act together on it.

Btw - ignition part is about 3/4 down.


Sorry it’s NOT an SI. It is Service Letter L192B. Briefly , the Lyc Folks say 1800 RPM for 30 sec prior to shutdown.

When returning from a flight the power is generally reduced during the descent. This action reduces temps in the combustion chamber and lead scavenging is reduced . The temps stay low during taxi through shutdown. The accumulated deposits are still there at the next start. Often they can be burned off during the run- up .
This is easier to do with a hot engine rather than a cold one. Hence the Lycoming procedure.
 
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