spark plug to hot to touch ?
 

After starting and checking idle, transition and top rpm ok and then running for a few minutes at midrange my gas engine (spe 26) quits. This happend several times.
Checking the spark plug ,I´ve never seen the spark plug so hot to touch.
What happend ?. I suspect the spark may have failed, but this plug so hot is new to me.
Any ideas ?.

RE: spark plug to hot to touch ?
 

It is possible you are running the engine too lean and overheating it.

How did you determin top rpm was ok?

RE: spark plug to hot to touch ?
 

Plugs normally get very hot. Did you try a new plug? Different brand? Are you sure the problem isn't with your ignition?

RE: spark plug to hot to touch ?
 

It was too lean (1/4 turn)

RE: spark plug to hot to touch ?
 

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You can't run a gas engine "too lean" and have it produce enough power to fly a model. Gas engines don't work that way, glow engines work that way.

Spark plugs and any other part on the cylinder of a gas engine get extremely hot and will burn the pi$$ out of you if you touch them immediately after the engine has been ran.


Ed Cregger

RE: spark plug to hot to touch ?
 

Ed, I don't know how many times we have to cross paths on this one. :eek: But you are wrong. Stop making these comments and giving people bad advice. People wouldn't burn up engines from lean runs if you couldn't fly with a lean engine. If you fly level and pull verticle and hear the engine sag it is too lean period! You can fly all day long like that, run your engine too hot and burn it up. Go a tad bit leaner and it will still fly the plane without problems. When finding peak rpm you could if you wanted to go 100 or 200 rpms past peak to lean and still fly your plane even. It would probably overheat badly and dead stick in the middle of the flight but it can be done nps.

You have made this exact comment 3 or 4 times in the last 6 months and everytime you make it people correct you. :eek:

RE: spark plug to hot to touch ?
 

sinergy - *absolutely* correct in your statements. If our toys could NOT fly with improperly-leaned engines, the DA and BME repair shops would be a lot emptier!!! I've observed planes sag so badly on rotation that they would ALMOST die.... yet the driver jus' kept on chuggin'..... they flew the plane, and were critically over-lean.

It is *the* sure way to destroy a perfectly good gasoline engine...

RE: spark plug to hot to touch ?
 

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Gas engines have a much narrower range between unacceptable fuel-to-air ratios and acceptable settings than glow engines. Because this is true, they must be treated and thought of differently from glow timed engines. The rules are not the same. Yet I see folks trying to treat them as though they are the same. They are not.

A glow engine is fairly tolerant of less than perfect fuel-to-air ratios. It is possible to set most glow engines too lean to the point that engine damage will occur, but which will still fly the model adequately. When someone isn't paying attention, or is preoccupied with other issues, they can zone-out enough not to notice the overly lean condition. This is very difficult to impossible to do with most gas fueled, sparkplug fired engines because the engine will run so poorly that the pilot cannot ignore the poor running engine and therefore terminates the flight long before the glow pilot will terminate his flight. In essence, the gas powered model will be far less tolerant of being mistuned, forcing the pilot to land the model for an adjustment.

I don't know how to make it any clearer than that.


Ed Cregger

RE: spark plug to hot to touch ?
 

Ed - you probably cannot make *your* opinion clearer, but clarification of erroneous information doesn't "correct" the info.

As hard as it is to imagine that there even could be a difference of opinion on whether or not a gas model engine can be OPERATED and FLOWN in a damaging -lean - maladjusted condition, evidently it is so in this case.

Go post a poll.... "Can airplanes be flown with gas engines when they are set lean enough to damage the engine?"..... I'd put money on the results you'll gather, and maybe it will help clarify the issue further with fact.

Any one of us can improperly lean an engine and fly with that setting, and damage them in doing so.

RE: spark plug to hot to touch ?
 

Hey Ralph, Dick, SS and RCBugman, you guys care to jump in here and give us the benefit of your opinions.....pretty please :D

Karol

RE: spark plug to hot to touch ?
 

Bob, you and Ed sound like you are on the same side, that is, "you don't want to fly your gas engine when it is too lean". Bob I certainly don't see the bad information that you think Ed is putting out. A touch lean and you might not notice it. Too lean and the performance will really suffer as well as the longevity of the engine.

Guys, tuning a gasoline engine is not rocket science. Start with both needles about 1 1/2 turn out. Adjust the LOW needle for good transition. Too rich and it will burble on transition. Too lean and it will sag on transition. Use a tac and adjust the HI needle for peak RPM and back off 1/8 turn or about 200 RPM. Check the transition from low to high again.

Bob it seems like you really have it in to get Ed. I think both of you have a lot to contribute but try to do it without the attitude.

RE: spark plug to hot to touch ?
 

Your opinion noted, Ken... thank you.

RE: spark plug to hot to touch ?
 

Just another two cents worth. Have we considered that some people run fuel/oil ratios others wouldn't even think about? As an engine runs lean there would be less oil to lube the recip parts "Possibly" causing damage. I see where there are many factors involved in whether a lean run will harm an engine. One very important factor is C/R as it has a lot to do with whether detonation is going to occur on a lean run. I also personally don't run my stuff at 100:1 oil mix (much more oil in fact) and I have had dozens of lean runs where the engine eventually died out in the air and after a hard 5 years my good ole G-26 is still humming like new (I still do not use an electric starter on it). I have had friends who do use considerably less oil and seem to have more engine wear/problems than I do so maybe it is more than just a lean run that is the culprit in "gas" engine death. Again, Just my two cents. Have a bessed and wonderful day. [8D]

P.S. That's a G-26 with CH ignition on the Spacewalker in my avitar.

RE: spark plug to hot to touch ?
 

You are missing the point... Ed said you can not run a gas engine too lean This is not true and bad advice period

RE: spark plug to hot to touch ?
 

OK. Here is proof positive that running a gas engine too lean will destroy it. This engine was run lean. Not so lean it was running bad, just lean engough. It was a brand new engine and this is less than 6 flights. No intake or case leaks, I checked that. It was just too lean. Being new it was more prone to this type of damage. This engine ran fine through the range but was a little low on power. That was the only indication. The guy who had it, never had this engine before so he did not know the difference. The point is you can fly your plane with a lean running engine. It will not go right away, but it will go eventually. Lean on any engine is not good. On a glow we can get away with it more because of the high oil content. Gas on the other hand runs a far lower oil content, and also burns and runs hotter than glow. So it is more prone to this type of damage.

The moral of the story, tune your engine. Do not rely on "factory needle settings"

RE: spark plug to hot to touch ?
 

If the setup is too lean (1/4 turn) the engine runs for about 1 minute or 45 seconds and quits.
The time it needs to get too hot. I perfomed this test on the ground.

RE: spark plug to hot to touch ?
 

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I just remembered how I had to pull my Pinto wagon over along side the road, less than a few hundred feet away from the NJ inspection center outside of Salem, NJ, pull the air filter and adjust the carb so lean that the car would barely drive, just to pass the emissions test in the station. No way would I have ever considered driving it home that way (fifteen miles). It was simply intractable when tuned that way, but it would pass inspection. After getting my sticker for another year's worth of driving, I would pull over right outside the inspection station and reverse the tuning procedure by richening up the engine engine until it was running right once again.

So, with all of that said, what I was trying to say before was that you can't adjust a gas/spark engine "too lean" and still have a usable engine. Certainly, someone without experience might not know what to expect and they could tune it lean enough to cause damage. But my original idea was right. I just didn't preface it with the statement of "having a usable engine". Better? <G>


Ed Cregger

RE: spark plug to hot to touch ?
 

Now fly it 1/8 or 1/16 of a turn too lean and you will be able to fly all day.. might sound ok to the untrained ear... will even fly pretty well. However long term its doing damage. If ity's way too lean you will get your results evrytime.

Ed: I am done beating the dead horse... we have had the same conversation 3 times and you can keep clarifying it all day long.. but you can fly a plane for quite sometime with being a 1/16 of aa turn too lean... get great performance, and a couple months down the road (if that) your engine will be burnt up for running too lean.

I think it's important that the correct info be shared so people get long life out of their engines.

Your comments were very broad and easily misunderstood for people who are new to gas engines...

RE: spark plug to hot to touch ?
 

I used to belong to your club for a couple of decades, if you're flying at the Lum's Pond field. Last I heard, the retention of that field seemed doubtful because of noise. Sorry to hear about that.


Ed Cregger

RE: spark plug to hot to touch ?
 

Gas engines are not very tolerant of tuning on the lean side. They prefer an air to oil mixed fuel ratio in the area of 16-1. This differs from a straight gasoline burn ratio of 14.7-1. You can run an engine rich and only foul plugs on a frequent basis if you manage to keep the engine running. OTH, running a gasser lean will cause immediate damage, but it may not be immediately noticable due to the amount of damage incurred. Small loss of compression is usually evident, later sticking of the ring becomes an issue, precipated by the earlier lean run. Excessively lean runs melt pistons and leave aluminum trails on the cylinder wall on the first flight, as do running without or too little oil in the gas.

So I agree with Ed, one lean run will cause damage. The issue is whether you immediately notice it or not due to the level of being excessive lean.

RE: spark plug to hot to touch ?
 

But Ed first said it is impossable ti run an engine lean and fly it. Not true. Building as many engines as I have, over 800 now. I have seen the results of lean run more than once. Thes people were flying thier planes when it happened. No it did not take long to do. It is a fast process. It all depends on just how lean it is. I live here in the great white north. Snowmobiles are everywere. Tell all of the guys here that burn thier engines up that it will not run lean. It makes the most power it ever did, until it burns down. If an engine is not grossly lean it will still run OK and start to score the piston. As it does with continued running it will get worse very fast until it does get to the point of the picture I showed. This has an even greater effect on a new engine because of the allready tight fit and extra heat.

RE: spark plug to hot to touch ?
 

Actually the club is doing fine and no noise restrictions besides we cant fly gassers after 6pm on Fridays and Sat. However Sunday to Thursday can fly them up till it gets dark. We have I believe 175 members this year. I am actually the club VP / trainer there thsi yr.

RE: spark plug to hot to touch ?
 

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A friend of mine, with whom I am still in touch, also belongs to your club. I forget how long ago it was, but he said that the campers were complaining about the noise. I suppose the curfew that you mentioned was the club's response to the noise complaints.

Don't know if you ever heard of it before, but I was one of the founding members of the Salem County R/C Club, outside of Salem, NJ. They fly behind the Vo-Tech Center on Salem-Woodstown Road. That used to be a big open field with no powerlines down the highway. Now those guys are just about completely boxed in with another school, power lines and a huge water tower. I sure wish I could hop into a Star Trek transporter and magically appear at the field for a flying session now and then. Lots of good people in that club and lots of great memories at that field.

I'm having trouble with my memory. You and Bob jump in there any time you think I'm saying something that is out of whack. At the very least, we can have a good, civil discussion.

Ed Cregger

RE: spark plug to hot to touch ?
 

Ed, Yes I know of that club although I have never been there. Lived in DE for 7 yrs and been dow at the Lums club for the last couple of yrs. I heave heard stories from Vinny about a couple people managing to land on top of that tower almost :D

You will probably remember some of the guys that still fly at Lums like Joe Denest, Vinny Damianie (sp), probably Dick Stuwart as well.... there are still a fair amount of active members from the time you were a member. Ya campers complained and that's what the outcome was. It's not too bad.. although I like to fly as long as I can :)

I don't mind a good civil conversation and always like to learn something new!

RE: spark plug to hot to touch ?
 

Scott, and all,
It all depends largely on the definition of "lean" running.
In literature, the normal mixture is stochastic. There is just enough air to burn all the fuel. With this mixture, the engine runs quite hot, and delivers not the best power. We modellers would call this lean running, and unless the engine is cooled very well, the piston will fail soon.
with larger jet sizes, the mixture is made richer up to about 20%, when best power is available, but the engine still runs hot, though not as hot as with a stochastic mixture. This is what we call a normal leaned out setting.
Going still richer, the engine temperature falls of quite a bit, and so does power. This is what we woud call a rich mixture, just before four-stroking (missing beats) sets in. With such a rich setting, plugs tend to foul or oil up. It does make up however for bad engine installations with lacking cooling flow.

Again, from the stochastic mixture going leaner, the engine temperature will drop again, because the fuel has to heat up too much air. Getting the mixture to ignite becomes harder and harder. This is the realm of modern lean burn engines with controlled over-stochastic pockets in the mixture near the spark. These engines have best efficiency, but not best power. Air cooled two stroke engines will never see this, because they have fried a piston long before that.

Also check out NACA technical note #328 (1929), where the mechanics of power, jetting and cylinder head temperature are researched. I cannot at the moment find my copy of Ricardo's work, where he explained the mechanics of mixture strength and combustion speed. I will keep thatin mind for an other occasion.