DonMuncy Posted September 17, 2013 Report Posted September 17, 2013 My 231 has been running fine, but I had the cowling off for something else and decided to check a few of my plugs. I read somewhere that the resistance in the plug should be around 3 - 5,000 ohms. These are massive Champions. I pulled two and both showed "open", (as in the same reading as when the ohmmeter probes are not touching anything). I checked with both my meters, and I don't think I've suddenly forgotten how to read an ohmmeter. What do the geniuses on this forum think is going on.
KSMooniac Posted September 17, 2013 Report Posted September 17, 2013 You have bad Champion plugs. There are a lot of them out there these days, despite declarations from Champion that nothing is wrong. Switch to Tempests (either massive or fine) as yours fail or all at once. I did it last year (fines) after getting a couple failed Champions within their first couple hundred hours.
Parker_Woodruff Posted September 17, 2013 Report Posted September 17, 2013 Excellent experience with Tempest Fine Wire spark plugs when I changed them last year. Lower TIT and much better ignition up high. Absolutely no misfiring at high altitude.
carqwik Posted September 17, 2013 Report Posted September 17, 2013 I just put on Tempest massives on my Bravo...about 5 hours of flying since then. Too early to judge but I switched because Mike Busch of SavvyMX said the Tempests were better in one of his webinars. Plus they're cheaper than the Champions.
DrBill Posted September 17, 2013 Report Posted September 17, 2013 When I tested my "old" plugs, I found it very difficult to get a good connection on each surface. Had to "scratch" both probes to get any reading. Had the issue even with the new plugs. BILL
DonMuncy Posted September 18, 2013 Author Report Posted September 18, 2013 Naturally, if I knew the answer, I would not have asked. But I am having a little difficulty with the idea that two plugs both failed between the last time I did a run-up and today. If they had both shown 6, 8 or 10,000 ohms, I would not have been surprised. At this time I am more inclined to go with Dr Bill's theory. The contact surface down inside the plug is bright and shiny, but the nose may have enough crud that my scratching didn't get down to good metal contact. I will try again tomorrow. Thanks guys. 1
tony Posted September 18, 2013 Report Posted September 18, 2013 As a side note, when you get ready to switch your plugs, the tempest plugs require a deeper socket than the champions. I got surprised.
MARZ Posted September 18, 2013 Report Posted September 18, 2013 Not to divert the thread but I found that I had massives on the top holes and wires on the lower - haven't changed it but just curious if anyone else has seen or heard of this
BigTex Posted September 18, 2013 Report Posted September 18, 2013 Not to divert the thread but I found that I had massives on the top holes and wires on the lower - haven't changed it but just curious if anyone else has seen or heard of this Mike - Using fine wire plugs in the lower side is a very common technique if the engine has a tendency to fowl plugs.
larryb Posted September 18, 2013 Report Posted September 18, 2013 Naturally, if I knew the answer, I would not have asked. But I am having a little difficulty with the idea that two plugs both failed between the last time I did a run-up and today. If they had both shown 6, 8 or 10,000 ohms, I would not have been surprised. At this time I am more inclined to go with Dr Bill's theory. The contact surface down inside the plug is bright and shiny, but the nose may have enough crud that my scratching didn't get down to good metal contact. I will try again tomorrow. Thanks guys. Just because you read open doesn't mean you won't get a spark. You could have a tiny gap inside, and spark across both that gap and the main gap. Another theory I have read is that the Champions are temperature sensitive and will show a lower resistance once heated up. So it doesn't mean that your bad plugs failed since your last run-up. I had a few of my plugs read high a year ago, and switched to the Tempest fine-wires. I've got about 100 hours on the Tempest. My run-ups are more consistent than with the Champions. Larry
DonMuncy Posted September 18, 2013 Author Report Posted September 18, 2013 Dr Bill was right. I sharpened the ends of the probes of my ohmmeter and wire brushed the center electrode of the plugs. Voila, I get an ohm reading. The bad part is they both read about 9,000 ohms. I plan on looking at how many hours I have on these plugs and then make a decision about tossing them. Being cheap like I am, tossing $350 in plugs for some unknown (and likely small) change in potential fuel burn and/or power, is going to take some contemplation. Would all of you replace these plugs if they have 100 hours on them?
N601RX Posted September 18, 2013 Report Posted September 18, 2013 See if your mechanic or someone around your filed has a tester that will fire them under pressure. My IA has one that will clean the plugs, and then fire them. You can adjust the air pressure while doing this. I had a champion with 26 hrs on it that would fire fine at ambient pressure, but around 80psi it would stop firing.
Danb Posted September 18, 2013 Report Posted September 18, 2013 I also switched to the fine wire plugs in my Bravo and I could not be happier, temps. are better in the flight levels no fouling etc. a great choice. Safe flying
Danb Posted September 18, 2013 Report Posted September 18, 2013 Btw I have over 500 hrs on the fine wires to boot
kmyfm20s Posted September 18, 2013 Report Posted September 18, 2013 Fine wires here and very happy with them!
BigTex Posted September 18, 2013 Report Posted September 18, 2013 FWIW i swapped my plugs for the fine wires and my little C model couldn't be happier. It made a huge difference. The engine still has a smile on its face.
PTK Posted September 18, 2013 Report Posted September 18, 2013 Running Champion massives with no apparent problems. I haven't checked resistance. When the time comes I'd be tempted to go with Tempest fine wires. The way I see it the cost is a wash because they last at least twice as long as massives. Here are recent flight test profiles. An in-flight lean mag check and a GAMI lean test, both at 9k. Besides the timing which I'll have better tweaked, can anybody comment? Is there anything out of the ordinary?
DrBill Posted September 18, 2013 Report Posted September 18, 2013 When I found a plug out of spec, I changed the 4 highest. The next annual, I changed the other 4. Spread the cost over a year and now I have some "good" spares. Courtesy of my A&P I have some really bad ones. I'll take some pictures tomorrow and post here. It's amazing how egg shaped the electrode can get. So, besides a high ohm reading, and oblong electrode is what my A&P looks for. Oh yea, I use Tempest Massives since I don't have a fouling issue. BILL
DonMuncy Posted September 19, 2013 Author Report Posted September 19, 2013 I don't know whether it is a blessing or a curse, but Tempest doesn't sell fine wire plugs for K models (turbos).
PTK Posted September 19, 2013 Report Posted September 19, 2013 ..It's amazing how egg shaped the electrode can get. So, besides a high ohm reading, and oblong electrode is what my A&P looks for. These we donate to the American Bonanza Society!
Parker_Woodruff Posted October 3, 2013 Report Posted October 3, 2013 I don't know whether it is a blessing or a curse, but Tempest doesn't sell fine wire plugs for K models (turbos). They had them last year for my plane.
DonMuncy Posted October 3, 2013 Author Report Posted October 3, 2013 Parker, I think you are right. It has been a while, but I think I looked at their chart and my brain said that the "Xs" meant they didn't have them. It appears that the xs are which ones are available. Thanks for the correction. For anyone I misled, I apologize.
carusoam Posted October 3, 2013 Report Posted October 3, 2013 Maybe the check mark would be better than the X.....? -a-
testwest Posted October 6, 2013 Report Posted October 6, 2013 Hi everyone I wrote an article about this issue for the Aerostar Owner's Association a while ago, it is a reasonably technical discussion of spark plug center electrode resistance. You may find it interesting. The article is in PDF format, hosted here: http://www.openclip.net/Benchmark/AOALog2011SpringTwoSparks.pdf Thanks. 2
carusoam Posted October 7, 2013 Report Posted October 7, 2013 Really nice writing skills for a highly technical guy! Norman, you made it interesting to read about spark plugs. Best regards, -a-
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