Spark Plug Change Interval Recommendation?

[Aeric]

I bought my C-150L in mid-2010 and about 800 tach hours have accumulated since then. The last 400 tach hours have been put on exclusively by me, and that includes aggressively leaning during taxi and cruise. When I purchased the airplane the plugs had a few hundred hours on them already. Up until recently the engine would fire up within 1 1/2 turns of the prop every time when cold (2-3 when hot). Lately it takes just a bit more. Fuel consumption remains steady at 4.7-4.9gph tach (I fly conservatively, aggressive doesn't go far in a 150).
The plugs have looked good at the last few inspections.
My question, is a little over 1000 hours a lot on a set of massives? And what is a typical number of hours until a change of plugs is called for?

 

[Let'sgoflying!]

My service history says 500hrs its time to get new.

 

[Clark1961]

you've got your money's worth out of them at 1,000 hours...have the mags been IRAN in the last 500 hours?

 

[Henning]

I bought my C-150L in mid-2010 and about 800 tach hours have accumulated since then. The last 400 tach hours have been put on exclusively by me, and that includes aggressively leaning during taxi and cruise. When I purchased the airplane the plugs had a few hundred hours on them already. Up until recently the engine would fire up within 1 1/2 turns of the prop every time when cold (2-3 when hot). Lately it takes just a bit more. Fuel consumption remains steady at 4.7-4.9gph tach (I fly conservatively, aggressive doesn't go far in a 150).
The plugs have looked good at the last few inspections.
My question, is a little over 1000 hours a lot on a set of massives? And what is a typical number of hours until a change of plugs is called for?

On a massive electrode, a good rule of thumb is when the center electrode gets skinnier than a football shape, it's getting worn out; if it hasn't failed before then.

 

[Aeric]

you've got your money's worth out of them at 1,000 hours...have the mags been IRAN in the last 500 hours?

Yep, and the timing set to 28BTDC with Millenium cylinders.

 

[Aeric]

On a massive electrode, a good rule of thumb is when the center electrode gets skinnier than a football shape, it's getting worn out; if it hasn't failed before then.

Seems as though it's pretty much time for replacement as Clark mentioned.

 

[Henning]

Seems as though it's pretty much time for replacement as Clark mentioned.

1000 hours on a massive electrode is a pretty solid lifespan, I would expect the electrodes eroded down. Now the question is do you spring for Irridium fine wires?

 

[Tom-D]

1000 hours on a massive electrode is a pretty solid lifespan, I would expect the electrodes eroded down. Now the question is do you spring for Irridium fine wires?

Have you priced a set of Irridium fine wires lately?

 

[Aeric]

1000 hours on a massive electrode is a pretty solid lifespan, I would expect the electrodes eroded down. Now the question is do you spring for Irridium fine wires?

$750 vs. $200, I'll stick with the massives. Normally I never cheapie-out when it comes to my airplane, but I probably won't own the plane for another 1000 hours.

 

[Henning]

Have you priced a set of Irridium fine wires lately?

Yes, they are three times the price and supposedly last 4 times as long with supposedly less service requirement. It's a gamble whether they pay off for sure. I haven't tried a set yet to see if I see a performance difference.

 

[Henning]

$750 vs. $200, I'll stick with the massives. Normally I never cheapie-out when it comes to my airplane, but I probably won't own the plane for another 1000 hours.

Then it likely wouldn't be worth it for you. I always kinda questioned them unless at overhaul, unless I was dealing with a fouling problem and was trying to stretch an overhaul, then I might, and just keep them for the overhaul.

 

[Clark1961]

Yes, they are three times the price and supposedly last 4 times as long with supposedly less service requirement. It's a gamble whether they pay off for sure. I haven't tried a set yet to see if I see a performance difference.

I put in a set of fine wires last summer. They seem to perform better at high altitudes so so far so good.

 

[Henning]

I put in a set of fine wires last summer. They seem to perform better at high altitudes so so far so good.

Good to know. Did you replace Champion massives? I think they would help getting deeper LOP smoothly as well.

 

[poadeleted20]

I consider plugs an IRAN (Inspect, Repair As Necessary) item. Check them every time you change the oil and pitch the ones worn too much. Clean the rest, check the gaps, re-gap if necessary, swap them top/bottom, and return them to service for another 25/50 hours.

 

[Clark1961]

Good to know. Did you replace Champion massives? I think they would help getting deeper LOP smoothly as well.

Tempest massives. I've never bought a Champion plug for the airplane...I think the last I ever bought a Champion plug was for a lawn mower...

 

[Henning]

Tempest massives. I've never bought a Champion plug for the airplane...I think the last I ever bought a Champion plug was for a lawn mower...

Good, I was wondering if it was the difference between massive and fine wire or between defective Champion and non defective plug.

 

[Clark1961]

Good, I was wondering if it was the difference between massive and fine wire or between defective Champion and non defective plug.

The plugs had been cleaned, gapped, and tested about 30 hrs prior to the performance that drove me to change them. They had about 400 hours on them and had been rotated regularly/wear was even. The cylinders had about 30 hours on them and oil consumption was low - no oil added in the past 28 hours. The mags have about 250 hours since IRAN and they were timed when the engine was topped. The ignition harness has about 150 hours on it. Injectors were cleaned and fuel flow was set when the engine was topped. I believe the engine was set up and operating properly except for the stinking plugs. The behavior was strange because the engine just developed an irregular but persistent miss while in level cruise. I could adjust mixture and get it to settle down for awhile but it started missing again. When I finally gave up on it and descended, the engine remained smooth.

I was trying to run 2300/30" when the problem developed. I've run those parameters for many hours but usually at lower altitudes than I was that day. I was up at 15,500 to get over some clouds. The one thing that bothers me a little is that the fuel controller has altitude compensation so I wonder if that isn't set quite right and the weak plugs just expose a minor problem.

 

[Henning]

The plugs had been cleaned, gapped, and tested about 30 hrs prior to the performance that drove me to change them. They had about 400 hours on them and had been rotated regularly/wear was even. The cylinders had about 30 hours on them and oil consumption was low - no oil added in the past 28 hours. The mags have about 250 hours since IRAN and they were timed when the engine was topped. The ignition harness has about 150 hours on it. Injectors were cleaned and fuel flow was set when the engine was topped. I believe the engine was set up and operating properly except for the stinking plugs. The behavior was strange because the engine just developed an irregular but persistent miss while in level cruise. I could adjust mixture and get it to settle down for awhile but it started missing again. When I finally gave up on it and descended, the engine remained smooth.

I was trying to run 2300/30" when the problem developed. I've run those parameters for many hours but usually at lower altitudes than I was that day. I was up at 15,500 to get over some clouds. The one thing that bothers me a little is that the fuel controller has altitude compensation so I wonder if that isn't set quite right and the weak plugs just expose a minor problem.

You may have something there, but I would think that deck pressure would over ride the altitude down that low, but that engine has that morphodite system and I'm not quite sure how they have it referenced. It would be worth looking at only if you are seeing TIT or CHT issues, or aren't making speed. The better plugs may be good enough to deal with it.