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#11
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O. Sami Saydjari wrote:
I just received a booklet from TCM called "Tips on Engine Care" (a very good book...available from TCM's website...http://www.tcmlink.com/). On page 12 it says "Never but never attempt to "burn out" a magneto drop with ground run-up. This 'time-honored' procedure succeeds only at the expense of the engine's mechanical health." Well, I was taught this time-honored way. What the book does not say is what you are supposed to do when you get roughness in one magento. Ideas? -Sami N2057M, Piper Turbo Arrow III Sounds to me like they are trying to err on the side of caution. John Deakin's series of articles are a worthwhile read; the first is he http://www.avweb.com/news/columns/182179-1.html Of course, you have to have an injected and instrumented (EGT and CHT) engine to use his advice. -- Jim Pennino Remove -spam-sux to reply. |
#12
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In article ,
O. Sami Saydjari wrote: Well, I was taught this time-honored way. What the book does not say is what you are supposed to do when you get roughness in one magento. Ideas? If you lean aggressively during taxi and avoid full-rich descents you probably won't have any fouled plugs to worry about (we are talking about OWNED aircraft, right?). And then engine roughness on the mag check is probably NOT plugs, so why abuse the engine to try and fix it? -- Ben Jackson http://www.ben.com/ |
#13
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Obviously not someone who is familiar with GAMI Injectors or the
Advanced Pilot Seminar where they have data to say opposite! Contrary to what the self proclaimed gear head states here, your engine should always be leaned when on the ground to avoid the fouling that gives you the roughness when one mag is switched off during runup. On Sat, 28 Feb 2004 10:37:00 -0500, " jls" wrote: When you lean your engine and rev it up on the ground you are super-heating the heads, the sparkplugs, the pistons, the valves, seats, and guides --- just to clean a fouled plug or two by burning the lead or carbon fouling off the electrode. It's best to clean the fouled plug. Of course, the problem is NOT with the mag. My instructor (who was not at all a gearhead) once did that burn-it-off thing in a 152's O-235 Lycoming, and it wasn't long before that engine was in the shop for new cylinders. I remember well the heat. We could feel it and smell it coming through the firewall, and being a gearhead I knew that THAT was not good for that engine. Besides, an aircraft revved up on the ground can hardly cool itself, irrespective of the fact you have leaned the **** out of it. I haven't seen it but have heard of burning holes in pistons by overleaning. By the mag drop you already know which set of plugs, upper or lower, and then all you have to do is find the misfiring cold cylinder. That's easy enough and what if the problem is a sparkplug wire or injector? You've just managed to fry your cylinders in the hopes of getting one out of four or six to fire. Leaning an engine takes a little finesse. It shouldn't be done on the ground unless you're in Denver or on a high-altitude ramp. A small fraction of that fuel charge is cooling your heads as it evaporates and flows through the combustion chamber and out the exhaust port. Ideally it is rich enough to give you a perfect stoichiometric charge plus just a little for cooling. If you burn it all by leaning you have lost your mixture's ability to dissipate heat. In addition, some of a lean charge is burning as it departs the combustion chamber because a lean mixture burns more slowly than a rich one. Damned if I want my exhaust valve to glow just to clean a sparkplug. |
#14
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BTW, since my FBO started using some fuel additive (sorry- I don't know
what it is offhand) they've experienced NO plug fouling. I can corraborate that based on 30+ hours of flying since then- not one plug fouling whereas it used to be quite common (and, yeah, we always burned it off). O. Sami Saydjari wrote: I just received a booklet from TCM called "Tips on Engine Care" (a very good book...available from TCM's website...http://www.tcmlink.com/). On page 12 it says "Never but never attempt to "burn out" a magneto drop with ground run-up. This 'time-honored' procedure succeeds only at the expense of the engine's mechanical health." Well, I was taught this time-honored way. What the book does not say is what you are supposed to do when you get roughness in one magento. Ideas? -Sami N2057M, Piper Turbo Arrow III |
#15
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Ben, Yeah. Actually, this has not yet happened in the Piper Turbo
Arrow III that I just bought. It happened pretty frequently in the Skyhawk Millenium that I used to rent. I am asking because the TCM booklet seems to be pretty hard-over on NOT doing burn-out procedure. -Sami Ben Jackson wrote: In article , O. Sami Saydjari wrote: Well, I was taught this time-honored way. What the book does not say is what you are supposed to do when you get roughness in one magento. Ideas? If you lean aggressively during taxi and avoid full-rich descents you probably won't have any fouled plugs to worry about (we are talking about OWNED aircraft, right?). And then engine roughness on the mag check is probably NOT plugs, so why abuse the engine to try and fix it? |
#16
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It's best to clean the fouled plug. Of course, the problem
is NOT with the mag. Does that mean that you would shut your airplane down in the run up area, get out, open the cowling (top and bottom), get out your tool box, pull the spark plug and clean it on the spot right there? That might look a little odd, especially at a busy airport. Perhaps I am not understanding you correctly. -Sami |
#17
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"O. Sami Saydjari" wrote in message ... It's best to clean the fouled plug. Of course, the problem is NOT with the mag. Does that mean that you would shut your airplane down in the run up area, get out, open the cowling (top and bottom), get out your tool box, pull the spark plug and clean it on the spot right there? That might look a little odd, especially at a busy airport. Perhaps I am not understanding you correctly. -Sami Obviously you don't work on your own airplane. Fry it if you like, and in spite of warnings from TCM. The previous poster talked about an additive. If you've read all that has been said (other than some jabbering) and the two Sacramento Sky Ranch links, you probably have a few ideas about prevention, including the legal additive, Alcor TCP. It is an old formula quite successfully used in auto gasoline way back when to prevent lead fouling of sparkplugs. |
#18
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jls wrote: "O. Sami Saydjari" wrote in message ... It's best to clean the fouled plug. Of course, the problem is NOT with the mag. Does that mean that you would shut your airplane down in the run up area, get out, open the cowling (top and bottom), get out your tool box, pull the spark plug and clean it on the spot right there? That might look a little odd, especially at a busy airport. Perhaps I am not understanding you correctly. -Sami Obviously you don't work on your own airplane. Fry it if you like, and in spite of warnings from TCM. Well, I was not trying to be sarcastic, I was just asking a stratight question about what exactly you were suggesting one do if one is running up his plane and encountered this situation. I honestly could not tell from your post, what alternative you were suggesting. Other than prevention, I have not yet heard a good alternative on the thread yet. Perhaps I am being dense. The previous poster talked about an additive. If you've read all that has been said (other than some jabbering) and the two Sacramento Sky Ranch links, you probably have a few ideas about prevention, including the legal additive, Alcor TCP. It is an old formula quite successfully used in auto gasoline way back when to prevent lead fouling of sparkplugs. |
#19
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Hey, don't worry about it. We get anal retentive engineer types in here from
time to time. They either suck back in to the wisdom we've collected over the past few years or have eventually disappeared back into their own wrong groups. Welcome, if you choose to stay as a member of this group... " jls" shared these priceless pearls of wisdom: - -When you lean your engine and rev it up on the ground you are super-heating -the heads, the sparkplugs, the pistons, the valves, seats, and guides --- -just to clean a fouled plug or two by burning the lead or carbon fouling off -the electrode. It's best to clean the fouled plug. Of course, the problem -is NOT with the mag. Jim Weir (A&P/IA, CFI, & other good alphabet soup) VP Eng RST Pres. Cyberchapter EAA Tech. Counselor http://www.rst-engr.com |
#20
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For a fouled plug, running up and leaning is an old as old as aviation,
and very proven, method of clearing the plug I have been doing it for a half century, works for me... If it doesn't clear, then you taxi back in and have it serviced... As far as all the dire warnings from the manufacturers, if you followed their SB's to the letter, you literally would not be able to fly... Those SB's are often cya position papers crafted by their legal department, not engineer recommendations... cheers ... denny "O. Sami Saydjari" |
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