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Engine basics => Engine set up tips => Topic started by: Ty Marcucci on September 04, 2006, 01:15:37 PM
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In the last three days I have gone through five glow plugs on two St .46 engines. This is very unusual. I use the Fireball long RC plugs, never a problem on OS engines especially the OS .40/46/35 FP or LA engines. Same on Fox L&J engines. But five plugs in three days seems very high usage, even for me. 10% nitro, 28% oil, all castor as reccomended by Tom Lay. One engine on a Cardinal, one in my scratch Cobra. Both planes by the way fly beautifully, right until the engine suddenly stops.
Ideas, answers, comments, questions?? ::) ??? :P :!
Don't have a clue as to what is causing your problem, Ty. What does the plug look like when you pull it?
I have been using the Thunderbolt, either the 4 cycle plug or the R/C long. No problems with mine blowing plugs. ???????????????
Bill <><
Bill <><
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Something's not right, if the compression is too high it will blow plugs but a few other things can also be the cause.. Tell us what the plug looks like when you remove it. Not running your glow driver too hot are you?
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Hi Bob. No, these are the normal glow drivers most of us use. In fact, one was down.
I think I better contact Tom Lay and ask about the compression ratio on these. Do you guys know if he kicks it up a tad??
having used several of Tom's engines, I can't say that he kicks the compression up enough on a stunt engine to burn out plugs. ?????????
My T&L ST G51 went two seasons on one plug, and then it was still good.
Never had to change plugs in my 46s either.
Better give ol' Tom a call! y1
Bill <><
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Is the coil deformed? If so it's likly over compression..
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Just a comment, and I don't really know how or why it might cause this effect, but Tom recommends 22% - 24% all-Castor fuel, I think. At least on his ST V.60s.
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Ty -
28% sounds like a lot of oil, even if Tom relieves the ring groove for running all castor. I've run nothing but 22% 50/50 in all my ST's for the last several years, hundreds of flights, yet to wear one out. I'd not want to contradict the engine tuners instructions, but I also would be tempted to ask him if running Sig Champion is ok.
If your 46 is a newer model, with muffler lugs, it could very well be the version with the high compression head with the huge squish band.
Throw in a .10 head shim and switch to a K&B 1L (long idle bar) plug. I'd bet your problems vanish.
EricV
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Tom Lay recommended 22% all caster in the ST 46 he did for me. Never had a problem. It was the one with muffler lugs. I use the K&B long with the idle bar. It just runs and runs etc........... Although if you have bad bearings or a ring gone south, dirty fuel etc.?
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Look for signs of scuffed aluminum parts... backplate, rod and piston being the likely source. Aluminum particles will kill the plug real quick. Not likely on a BB engine, but maybe the shaft end-play isn't right. I've had that situation on early ST's before they put the little spacers in behind the front bearings. Might also be worth taking a look at the mufflers, to make sure they aren't clogged up with carbon. :X Steve
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Ty,
Went through plugs like mad with my ST .46's & .60's. I quit using Armorall and the problem
went away.
Ted
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Hi Ty,
Strange you are running 28% oil. Did I read that right? Tom told me to use 22% all castor in the ST 46 I got from him ???