BR9ES is a colder NGK plug than what most people use. I stopped replacing them as they never have shown signs of erosion.
I do the exact same thing.I replace my auto plugs at every condition inspection.
I agreeFor the price, it is cheap insurance just to replace them once a year.
Correct and that is exactly what our Professor found. However, it was the insulation that was starting to fail.
That's why I recommend people don't use high dollar iridium plugs, the metal part isn't the issue.
For the price, it is cheap insurance just to replace them once a year.
Let's back up a moment Bill.
The professor found reduced resistance. Where was this reduced resistance...the center electrode ceramic, or the ceramic body?
Hmmm...'Trust, but verify' (?)
Ever try pulling the cap, removing and re-installing the plug, and rechecking the EI's reading? A simple resistance check, new & after, could be useful data, too.
IIRC, running a 'colder' plug makes conducting tip heat out to the head easier. Would that reduce the heat load in the internal resistor in the plug, extending life?
I would have to dig in my old computer to find his report (and we are leaving for the weekend) to answer if it is the center insulator or the external one.
Here is a description of the behavior that prompted us to send a set off:
The P-mags report the current flow the EIC. A shorted or fouled plug would display as a maximum scale reading (100). A broken or open plug lead would display no bar graph (0). (We set the reported values to a 100 point scale for display purposes.)
When new NGK BR8ES plugs are installed, we typically see a value between 70 and 80. As they accumulate flight time, that value drops off and readings of 40 are not unheard of when 100+/- hours are recorded.
Obviously the plugs resistance is going up, limiting current flow. What I haven't done, is to Ohm used plugs and compared them to new ones because I believe the EIC reporting function.
The odd part is I could not detect any change in engine performance; either roughness or reduced performance. The only indication I had was what the EIC was reporting. Replace the plugs and the bar graphs to back up.
We sent a bunch off to a PHd professor to look at and he found the ceramic insulators were starting to deteriorate.
However, it was the insulation that was starting to fail.
The P-mags report the current flow the EIC. A shorted or fouled plug would display as a maximum scale reading (100). A broken or open plug lead would display no bar graph (0). (We set the reported values to a 100 point scale for display purposes.)
So what is the mechanism that makes a Lycoming eat auto spark plugs. I can understand lead fouling, but why would an 8.5-1 engine "wear out" plugs faster than an 11-1 auto engine?
They don't.
I replace auto plugs on customers aircraft regularly, after a couple hundred hours the gap has grown significantly from wear even on the iridium. I think iridium can go around 200 hrs while the std ones last about 100 hrs before you start seeing wear.
I heard somewhere it is the leaded fuel that does it, makes sense as I grew up working on cars and used to change plugs every 10k mile back when we had leaded auto fuel.
If anything, it is removing a part that is known to be operational, and replacing it with a part which is unknown.
Yes, I know what your point was - but you're painting with a mighty broad brush with that statement.
Seriously, the better question might be "How many hours have you gone on a set of auto plugs, with EI, before noting an abnormal drop, or roughness?"
With the EICommander you can see the condition of the auto plugs and at around 100 hours +/-, they start to degrade. Engine performance seems to be unaffected.
We sent a bunch off to a PHd professor to look at and he found the ceramic insulators were starting to deteriorate.
Quite true. Humor another stroke.
The "replace at annual" common practice has little to do with actual plug condition. Rather, it's an outgrowth of the annual cleaning ritual we all practiced with massive plugs and magnetos. We feel like we're not doing the "proper" maintenance if we don't unscrew them for a look. At $3 each, it's not worth cleaning them, and replacing them feels good.
It's cultural. And woe to the guy who admits he doesn't do it. Unclean! Unclean!
Seriously, the better survey question might be "How many hours have you gone on a set of auto plugs, with EI, before noting an abnormal drop, or roughness?"
It's cultural. And woe to the guy who admits he doesn't do it. Unclean! Unclean!
Seriously, the better survey question might be "How many hours have you gone on a set of auto plugs, with EI, before noting an abnormal drop, or roughness?"
I'd admit to this one. With 1 P-Mag on my O-320, I'm running 4 Iridium plugs on the bottom of the engine so that I DON'T have to ever clean them. I just pull them out and throw them away at oil change.
Yes... I throw them away every ~50 hours. It could be something symptomatic of my airplanes set up, but $20 for 4 new plugs is cheap enough to me. My first flying job was towing banners along the Maryland and Delaware coasts. In the heat of summer, the boss man had us changing oil and cleaning plugs every 25 hours which was sometimes twice a week. (we flew 7 days a week, sometimes 8 hours a day). I feel like I've cleaned a few plugs in my time already... $20 for a fresh plug every few months seems worth it to me.
As for performance:
I recently installed a newly overhauled Carb (amazing difference for me) and 1 P-Mag around the same time. With new plugs, at altitude (10-13k), I can easily run smooth LOP up to almost 100 degrees LOP. Maybe 85-90 degrees, its too rough. After about 20-30 hours, I can barely get LOP without it acting rough. As I type this, it occurs to me that the plugs are probably just dirty. I subscribe to the Mike Busch method of leaning my engine on the ground (and in the air) so I believe I am minimizing the lead build up. So the last 20 hours before an oil change, I don't get my higher altitude efficiency. But a monh or so and $20 later, the efficiency has returned along with my RV Grin
4 Iridium for $20 is a great buy, where do you buy yours. My last Iridium (long reach) was at $11 the cheapest.
As for performance:
I recently installed a newly overhauled Carb (amazing difference for me) and 1 P-Mag around the same time. With new plugs, at altitude (10-13k), I can easily run smooth LOP up to almost 100 degrees LOP. Maybe 85-90 degrees, its too rough. After about 20-30 hours, I can barely get LOP without it acting rough. As I type this, it occurs to me that the plugs are probably just dirty.