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Tell me what you know about glow plugs!

Old 07-24-2005, 09:15 PM
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laker500
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Default Tell me what you know about glow plugs!

Hello,
In a previous post of mine, (early spring) I discussed an OS FL70 in which the consensus was that they are junk. I still feel this way but since I lost my receipt and can't return it and feel guilty about selling it to unload the problem onto someone else, I've decided to attempt it once more and put in into a junker airplane and use it for a practice plane I'm likely to crash. My problem was that it turns only low RPM at high throttle and would only idle at around 3500 RPM. I changed props from the recommended 13x6 to a 12x5 and now turn about 10800 rpm at WOT. I can live with this. This motor uses an air-bleed carb so the adjusting of it is a new experience for me. I have spent a lot of time adjusting it a little at a time and it idles and transitions only so-so at about 3000-3200 RPM. I would like to get that shaved down to 2500 RPM. I read an article recently about engines and glow plugs and they discussed the differences in heat ranges and plug length. I am wondering how much difference there really is in heat ranges of plugs. They don't sell them by heat range so how do you know if its colder or hotter? As for plug length, the article said it affected compression ratio. It makes sense if the length is dramatically different but is there really difference enough in plugs to address length in a finicky engine? I was also wondering if an idle bar helps in four-strokes. Is my idle problem due to the plug being doused by raw fuel or is the plug just to cold? How do you know? I just don't want to throw more money at the engine by buying one of every plug made so where do I start? Any experiences you have regarding different plugs would be of great help. Thanks, Jeff
Old 07-24-2005, 09:21 PM
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w8ye
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Default RE: Tell me what you know about glow plugs!

With the exception of the Enya #3, you are going to be restricted to four stroke plugs of which there are not that many.

Each company usually only makes one four stroke plug.



Enya #3
OS "F"
Y-S four stroke
H9 super plug four stroke
McCoy four stroke
Fox Miracle
Hobby People sell some plug like a Thunderbolt or something?

Enjoy,

Jim
Old 07-24-2005, 11:01 PM
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Rcpilot
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Default RE: Tell me what you know about glow plugs!

Check the following:

Tank position. Is the tank CL even with or very close to CL of the carb?

Did you do the break in right? It's a ringed engine. I'd have used at least a gallon to break it in. If you didn't, and the sleeve and piston are worn or cooked--then you'll never get consistant running from it.

Hows the fuel? Are you running too much nitro? Not enough?

On the compression, and plug length--I think it can make a difference. If your running 15% nitro and a hot plug, you may be experiencing detonation. I doubt that you could really use too little nitro. Most modern engines for general sport flying will easily handle 5%--10% nitro without problems. Getting up into the 20%--30% fuel and a hot, LONG plug could cause heating problems.

The combustion chamber on these little engine is only a few CC's at best. So putting a long plug in can DRASTICLY effect the compression ratio. Removing 1/2CC or even 1/4CC from the total volume of the combustion chamber by using a long reach plug will most definetly effect your compression. Head shims are another thing to think about.

Unfortunately, noone is really going to be able to tell you EXACTLY what plug to use on your particular engine. Your going to have to experiment with different plugs, fuels, and props to get a finicky engine working well. I ended up using an OS #8 on a 120 Surpass once.

Check your carb for leaks. Worn seals. Bad needles. What about the intake manifold and the gaskets and associated seals? Got any air leaks there? Maybe time for a gasket set?

Are you adjusting the air-bleed carb correctly? Turn the screw out for a leaner idle. Turn it in for a richer idle. If you turn it all the way out and the engine is still loading up and getting rich at idle--then you can drill out the air-bleed hole in the carb to let in more air. Is it idleing at 3500RPM because it's too rich to run any slower without loading up? This may be the problem. Is the hole clogged up? No air going in at all?

Check your airflow over the engine when in the cowl. We all know the rule for ventilation on a cowled engine.

Old 07-25-2005, 07:35 AM
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Flypaper 2
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Default RE: Tell me what you know about glow plugs!

http://209.15.36.61/rdrc/gloplugs.html As you see all the manufacturers make different heat ranges. If, when you take the glow starter off, the engine slows down, the motor is to rich or the plug is to cold. The plug length is determined by how long the manufacturer makes the thread, be it long or short. Looking down the plug hole, it's pretty obvious whether it's long or short. Plug length has nothing to do with heat range, although it can run hot or cold if you use the wrong plug length in it.
Old 07-25-2005, 08:32 AM
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Gene Chernosky
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Default RE: Tell me what you know about glow plugs!

Since this engine came with an OS 'F' plug when new it would be a good idea to stick with it. Per instructions...use 5%-15% nitro fuel with minimum 18% oil content and a 12x7 or 13x6 prop. Practical RPM's are supposed to be from 2300-12000 so yours could idle down somewhat more. Since this is the 'el cheapo' model of the OS .70 4 stroke engine I wouldn't expect a whole lot out of it though. You could have bought a Magnum .70 4 cycle for the SAME price and had a LOT more engine than this OS will EVER be. ...oh well...live and learn.
Old 07-25-2005, 12:20 PM
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Default RE: Tell me what you know about glow plugs!


ORIGINAL: Gene Chernosky
Since this engine came with an OS 'F' plug when new it would be a good idea to stick with it.
I disagree. When I got my first OS 120 Surpass, it wouldn't idle below 3500RPM. All the "experts" at the filed told me to stick with the F plug--no mater what.

I ended up using an OS #8 plug in my Surpass--but only after wasting boatloads of money on several F plugs.

Every engine is unique. They all get broken in differently, and at different temps and rates of expansion. Just because it's an OS 4-stroke engine doesn't necessarily mean that it needs an F plug.
Old 07-25-2005, 12:56 PM
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Default RE: Tell me what you know about glow plugs!

ORIGINAL: Rcpilet



Did you do the break in right? It's a ringed engine. I'd have used at least a gallon to break it in. If you didn't, and the sleeve and piston are worn or cooked--then you'll never get consistant running from it.


I thought that this one was NOT ringed? Isn't the FL like the only four stroke, non-ringed engine out there?


And by the way laker500, thanks for not putting it up for sale!
Old 07-25-2005, 03:14 PM
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Default RE: Tell me what you know about glow plugs!

Hi!
Sorry about your experiences with the OS .70 But during my 30 years in this hobby/sport I have never experienced an OS that didn't run perfect. I have seen some OS engines that people couldn't run but that was only their on fault , using wrong glow plugs and bad fuel and wrong techniques.

First...it is a general rule among model flyers worldwide that when you run a fourstroke you should to use an OS F glowplug. That is if you run 0-15% nitro.
There are other glowplugs available like the SAITO P1 and P2 and the Y&S four stroke plug and the FOX fourstroke plug that will work too, but the OS F plug is the one you should use.
Enya four-stroke engines are equipped with Enya 3 glowplugs but even these engines work better with the OS F glowplug. So don't try to use the Enya 3 glowplug in your OS it will only make it run bad.

The first you should do is to get fresh fuel...get 10% nitro and 20% oil ...whether it is all Castor oil or synthetic or a mix doesn't matter. Over here in Sweden it is very common to run 10-15% all synthetic oil in all our engines, but the oils we use could be hard to obtain in the US. (Motul "Micro" and Aerosynt 2 and Aerosave) so get fuel from a well known manufacturer.
I also recommend a 13x6 prop and preferable APC, Not master Airscrew.
As for tank use a 240cc -300cc (8oz-10oz) tank, not bigger. And the center of the tank should be in line with the center of the carb intake orifice when the airplane sits horizontal. This is very important!
Fuel lines should be of silicon of course with an inner diameter of 1,5-2,5mm, and a "Uniflow" tank set-up should be used (that is two clunks, one for pressure and the other going to the carb, one slightly shorter then the other). A ordinary tank set-up with just one clunk will of course work too.
Always keep the tank set-up simple...that means never use a commercial filling valve and keep the fuel lines as short as possible.
I would also recommend that you always mount your engines sideways...or slightly tilted to the left (vied from the front), that way the carb will be in line with the tank more easily.

The OS 70 has an airbleed carb ...that means that the carb is "bullet proof" and it is not really possible to "make any mistakes" with it...due to the carb being so easy to set. There is only one high speed needle and an airbleed adjustment screw that doesn't do much any way. So making mistakes with this carb is just not possible.
I expect that you have run the engine for some tanks so that it is fairly run-in,
so when you start your engine adjust the highspeed needle for nearly maximum rpm...I did not say max rpm! You must adjust the highspeed needle so that you hear that the engine runs a little rich.
I would expect that the OS .70 would turn an APC 13x6 at around 9000 rpm on 5%-15% nitro.
Then throttle down and see what happens...you should now have a throttle opening of about 1,5-2mm.... and now the engine should idle fine at around 2500rpm. But do not worry if it idles more. Now check how the engine responds to throttle! When you give full power the engine should burst into life and immediately turn maximum revs...if not... adjust the idle mixture screw (IN ...gives more fuel. OUT ...gives more air). The idle screw is placed in the middle of the 2mm hole that you can see if you look at the engine from behind and this is the standard setting from OS and usually you have to open up the idle screw somewhat to achieve the best throttle response.
Try the above and see what happens.
Regards!
Jan K
Sweden

Old 07-25-2005, 07:09 PM
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laker500
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Default RE: Tell me what you know about glow plugs!

Thanks for all the info. I'll answer some of the things brought up in the replies. The fuel I'm using is 15% nitro, 18% oil Wildcat fuel. I broke it in on 10% nitro of the same type and brand. The gallon is brand new, I just opened the seal on it. I switched from an OS F plug to the Fox Miracle plug. I use them in my Magnum four strokes and they work very well. It took a couple hundred RPM off of the idle down to where I am with it now. It only turns a 13X6 at a little over 8000 RPM so I switched to the 12X5 thats on it now(turns at 10000 or so). It has improved my top RPM and did not change the idle, as I expected it would'nt do. The head temperature runs about 380-400 when checked with an infrared temp gage. I know these aren't perfect but its what I have. If I richen it up any more, even a couple clicks it loads up even at higher throttle settings so I'm pretty sure its about where it should be there. Someone suggested leaks in the intake, etc.. The engine is basically new, somewhere near 8-10 tanks thru it so I am confident that nothing is leaking, all the screws are tight. All the fuel line is new and the same diameter I use on all my other engines, a Magnum 70 included. I will double check the tank height because I cant remember for sure but it should be right. I usually am pretty meticulous about setting that stuff up. I have disconnected the crankcase vent from the muffler which someone told me to do once before. OS has 2 pressure taps on this muffler, one to the tank and the other to the crankcase vent? Go figure! The engine is not ringed, its more like an ABC but I don't think they even call it that. As for venting the cowl, its never ran well enough to ever have put the cowl on. Its vented pretty well anyway but its not a problem now as its not installed. I am also aware I could have had a Magnum for the same money. I have 3 of their four-strokes already and bought this only because it was the same money and on the shelf of the LHS. I subscribed to the notion that it's made by OS so it must be good. The ads stated it was easy to set up and designed for beginners. My Magnums ran, untouched, right out of the box. Believe me it won't happen again. I don't think I will buy another OS, to many other companies out there that are not turning out junk and selling them as "beginners four-strokes". Thanks for all you replies. I'll keep tuning and let you know what if anything improves it for me. Jeff
Old 07-25-2005, 10:44 PM
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Default RE: Tell me what you know about glow plugs!

Jaka- as far as your opinion that ALL o.s. problems stem from the user, I suggest that you do a bit of research on the o.s. 70 Ultimate- a real lemon. These things were so consistantly bad, that they have stopped selling them for the time being while they work their problems out. Tower lists them as "Temporarily Unavailable", and Hobby Services replaces them no-questions-asked. Laker500 could very well have a legitimate complaint here. I have also heard that the FL70's reputation is less than stellar.

Laker500, it looks like between the two of us, we both bought the only real junk that O.S. has ever put out- I for one believe that fourstrokers should not be ABC (or whatever the FL70 is). But don't let that turn you off from O.S. entirely. I have an FS52 Surpass and an FS91 II fourstroke, and they are both excellent motors. I also own a Saito 82, and that thing is a monster. Try the Saito 72 if you want a similar displacement- or, if you want a real powerhouse that is actually lighter than the Saito 72, go with the 82. Bit longer breakin process than an O.S., but I'm grinnin'!

Life is too short for bad motors.
Old 07-25-2005, 11:41 PM
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Default RE: Tell me what you know about glow plugs!

Hi Jeff: With all rumors you get a variety of opinions and no real meat. Some folks swear by this or that engine and will use nothing else. I've used them all and probably have more 4 strokers than anyone else. For example, the Magnums can be a good engine and some folks think they are junk and only use OS or some other brand.
Personally, they are all pretty damn good. Just think of them as you would a car. Just about any car you buys now days is going to be pretty good.
I have used F plugs in all my 4 strokers and some of them have lasted for three or four years and would suggest you use them as well.
If it ain't turning up the way it is supposed to, just be patient and send it back to the importer and have them run it. I think it is Horizon and they have a very good service center and I highly recommend them.
All these folks want you to be satisfied and will knock themselves out to make you happy.
No, I don't work for them. But I know them from personal experience.
I have, incidentally, owned several 70's and they all ran great. I use a variety of fuels and always add an ounce or so of castor oil in the event I get a too lean run. The extra castor burns off at a much higher temp than the synthetic oil and will save an engine. 20% oil for sure.

3dbob
Old 07-26-2005, 03:29 AM
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Default RE: Tell me what you know about glow plugs!

Jeff,

(turns at 10000 or so)
Seems about right for a four stroke.

The head temperature runs about 380-400 when checked with an infrared temp gage.
Seems very high. Most oils will start breaking down at around 450 to 480 F. Just for curiosity what is the head temperature of your other four strokes?

Bill
Old 07-26-2005, 07:11 PM
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Default RE: Tell me what you know about glow plugs!

Bill,
To answer your question. I have no idea what my other fourstrikes run at. Perhaps there is someone out there that may already know where it should run. Like allot of other flyer's I only get out the temp gun when I'm having problems. I know its an everyday tool for the car guys but I bet most flyer's don't even own one. I will have to check that out next chance I get. It would be a good place to get some basic reference data.
I also have another opinion question for you guys. I re-checked my tank position and the centerline of the tank was about 1/2" -3/4" below the center of the carb. This is as high as you can mount the tank while keeping it immediately behind the firewall. If I switched to a 6 ounce tank and used a flex tank I could get it up where it should be in elevation but this would pull the tank another inch plus back from the firewall and motor. Which do you feel is more important, the elevation of the tank in relation to the carburetor or the closeness to the engine. I'm am interested to hear what everyone thinks.
And flycfii, I think JAKA owns stock in OS or something. He has lots of good information and I appreciate his attempts to help me out but I've seen in other posts he always defends OS. He must have stock in the company! I know as well in other posts that people that work for some of these company's answer some of our basic questions but they always seem to stear clear of the discussions about the products everyone is having trouble with, Imagine that! Thanks again, Jeff
Old 07-27-2005, 06:45 AM
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BillS
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Default RE: Tell me what you know about glow plugs!

Jeff you might want to explore the engine temperature more fully. I think you are going to find the temperature is at least 100 F. to 150 F. high.

On the bench is the best palace to chase tank height and engine problems. More can be discovered if 15 minutes on the bench than working for days in the airplane. If you think the tank height is incorrect it takes seconds to put a piece of foam under it. It only takes seconds to swap to a spare tank. If it won’t run on the bench it sure won’t run in the airplane.

Bill
Old 07-27-2005, 07:58 AM
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Default RE: Tell me what you know about glow plugs!

Just a thought.

Check both valves are seating correctly. I understand the engine is new, but things can go wrong...

Leaking valve(s) can cause high head temperatures. Could also explain the other symptoms.
Old 07-27-2005, 08:20 AM
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Rodney
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Default RE: Tell me what you know about glow plugs!

Bodge's advice to check valve settings is well worth heading. I've seen New Out Of Box engines missadjusted and almost all need to be checked again after the first couple of tanks of fuel are run through them as initial breakin can cause serious changes. After that, they do not need to be checked very often unless you notice some significant change in performance.
Old 07-27-2005, 08:57 PM
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laker500
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Default RE: Tell me what you know about glow plugs!

Check both valves are seating correctly
I have done this only to the extent of making sure they both closed by checking that the rocker arms were loose on the compression stroke. I should get out the feeler guages and actually check the tolerances.
Jeff you might want to explore the engine temperature more fully. I think you are going to find the temperature is at least 100 F. to 150 F. high.
Is it true that this could be from the engine being still relativiley new? What can be done about it?, If the engine is already as rich as it will run there is'nt much else you have control of to cool the engine, is there? Should I maybe switch to an all castor fuel? I've heard that it provides more cooling effectiveness than synthetic which is what I'm using now. Jeff
Old 07-27-2005, 09:31 PM
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Default RE: Tell me what you know about glow plugs!

Jeff,

Sorry oil will not fix a problem of the magnitude you describe. Please check another engine or two.

Bill

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