Hi there all,

I was just wondering that there are assorted glo plugs available, some have long heads, some have short heads, some have open filaments, some have a metal strip on the top of filament crossing from one end to another. My question is, if a gloplug has long head does it make any difference in any engine or short head one would work better? Gloplugs can be used for any engine either 2 stroke or 4 stroke and whatever the engine displacements are? or recommended or some particular gloplugs should be used.

Thanks

Mody

"long" plugs have longer threaded portions and if used where a "short" plug is required COULD actually hit the piston. If a "short" is used where a "long" is required it may not get down into the combustion area. The "strip" accross the plug is called an "idle bar" and is used to keep cold fuel from splashing on the element and cooling it too much and making it stop firing the mixture.

Always use the proper length as recommended by the manufacturer. The use if an idle bar is kind of option al in most modern engines although they are use more often in side mounted or inverted engines.

Bruce's advice is, as always, right on the money.

Just for a point of reference, short plugs are generally only recommended on engines smaller than .25 cu in in displacement. A short plug will be marketed as "short" whereas "standard" or "long" are normally the same thing, and if a glow plug only has it's heat characteristic listed and not length, it's usually safe to assume it's a standard long plug (Tower Hobbies Medium Sport Plug, e.g.).

Short plugs get used more frequently for car/truck glow engines rather than aircraft, but there are plenty of .10 and .15 sized glow engines on the market for aircraft that may use short plugs.

yup size matters.



my wife told me so[:-]

Thank you very much for the reply, I got your point Bruce & bigedmustafa. I would always use recommended gloplugs. In my .61 HB 2C engine can I use O.S. standard gloplug or any other standard glo plug?

Well OzMo, according to my wife, size really doesnt matter, how one uses it, that is what really matters

Mody

Your .61 HB should accept most O.S. glow plugs just fine. The #8 and A3 are quite popular for 2-strokes, but you might want to use a colder plug if you're using high nitro content fuel. Higher nitro fuel often calls for a colder plug while lower nitro/no nitro calls for a hotter plug.

Generally speaking, most 2-stroke aircraft engines will run fine with a Hot (A3) or Med Hot (#8) plug with 15% or lower nitro. If you're running 30% nitro helicopter fuel in your 2-stroke engine (waste of money), you'd probably want to go with a Med or Med cool plug.

Hope this makes sense!

just to add to that, i have a particular thundertiger 46 that never runs really well anyway, but almost always deadsticks on me with idle bar type plugs. it runs ok with the standard glow plugs though.

Long plugs are really only used for four stroke engines. Maybe some two strokes for giant scale use them, I'm not too sure. For most two strokes, you'll always be using a short plug.

I recommend the OS A3 plug for most two strokes. It's a hot plug. From personal experience, I've found the engine runs better with the hotter plug. For most flying, you will not need a cool plug since most glow planes should only be run on 5-15% nitro, unless otherwise specified.

Once again you are completely wrong. OS recommends the #8 for most of their engines in the .25-.61 size range and this in a standard LONG plug.
http://www2.towerhobbies.com/cgi-bin...?&I=LXCB27&P=M

Please get your info correct prior to posting.

the A3 is a hotter version of this plug. It is also a LONG plug. They also tend to burn out a bit faster for the obvious reasons.

http://www.osengines.com/accys/glowplugs.html

Excuse me? You're the one who is completely wrong my friend. The A3 is not a long plug. It's the same size as the #8.
According to OS, strait from the link you posted The A3 is "A long-lasting hot plug for most 2-strokes up to .60." I use the A3 in my OS 46FX, 61FX, and Evolution NT46. All engines run very well with 10-15% nitro.
Not that there's anything wrong with the #8. I just like the A3 better.

The only air plug that is a long plug is the type F. Other long plugs are for cars.

So the words:
O.S. 8 Glow Plug Standard Long Medium Hot

mean it's a short plug to you? Strange.

Eh Bruce is right on the money...

Here's proof...



From left to right:
Stock Evolution 1.00NX 2 Stroke Glow Plug
O.S. "F" 4 Stroke Glow Plug ( can be used on 2 strokers )
Stock SuperTigre .75 2 Stroke Glow Plug
O.S. A3 2 Stroke Glow Plug

There's some confusion here with long and short plugs. The OS (and also Enya) plugs are actually a medium length plug, no one knows why those two companies make that particular length. A true short plug is one or two threads shorter than the OS.

Virtually all engines now a days take a long reach plug but getting down to around the .15 size it's worth checking the manual for the recommendation. If unsure then take off the head and screw in a plug. If it comes very near flush with the combustion chamber then that's the length to use. The only engines where you have to be especially careful about plug length (including the idle bar if it has one) is on the early baffled piston engines where some of them had the plug offset into the baffle groove in the piston (the OS Max-III is an example). Modern flat top piston engines will all have more than enough clearance for virtually any length plug.

Most 4 stroke plugs have an extended nose on them (the OS F plug in that photo has the same thread length as the A3) and this can be handy to use in an inverted engine because any slight overpriming doesn't get inside the plug cavity to put the fire out so the engine will start easier. It's better to learn not to overprime of course .

Heat range is the more important part of selecting a plug but really only if you're after the last few possible revs from the engine. For normal flying with lowish nitro fuels any medium to hot plug is fine because they'll also work well at idle.

As always sage words from "Down Under".

Well Thank you all for your fruitful advices,

I have bought 2 O.S. #8 plugs. They are quite shorter in size, but so far they seem to be working fine, all I have a problem is the carburetor, my carb had loose nipple, I changed it, I borrowed another carb from senior flyer, screws got so tightened, it broke[:@] then I got metallic one, with the needle valve , the - minus and + plus plate was also moving causing my engine to stop, another wasteful sunday without flying but extremely hot day[]. Finally I got another carb of HB own manufactured, its not Perry, but it's HB's carb, but the lower part is smaller and little loose in engine, I have tightened it good, but I don't know how long its stay held on, we would find out in a week day when we goto flying. Im so far unable to fly my plane properly, its damn carb. If this carb doesnt work right, Im gonna throw this engine away.

Over here in Pakistan, I haven't seen hardly anyone using Nitro, here people use simple fuel 80% methanol 20% castor oil mixed this is what I have been using and never had any problem unless the carb is messy or other things are going on with engine.

I'd let you know about my flying if engine doesnt play up

Mody

That fuel mix is often referred to as FAI fuel. Used a lot, I'm told, thoughout Europe. If the +/- plate you are talking about is the idle mix plate on the Perry carb it can be removed (pulled out) and the o-rings lubed or replaced.

Thanks bruce for the reply,

Well, as I got another carb, its not Perry its exactly like Perry and HB is written on it. Im gonna try this carb coming week, either or saturday or sunday, and Im gonna post how did it work, and as you adviced that idle mix plate can be pulled out, Im gonna do that with other mettalic Perry carb if the carb I have of HB doesnt work. I hope it would work, if not the I'd have no option but to arrange some money as im going thru tight financial position and get another engine and its gonna be ASP's 2 stroke.

Mody

A friend of mine has Super Tigre 90 2C engine, as my plane is 60 size and honestly I have not measured fuselage's length and wing span, is it possible to use that engine which is 2C on that plane? is it too heavy and is it an overkill for my plane? if it is possible then what size of Prop can be used?

Mody

Hello, I have a used os .40 fp. I can't seem to get it to idle without stopping. It seems to idle ok with the glow plug starter attached. any ideas. Thanks

Usually this is the result of a bad plug, or too rich of a mixture.

When you remove the igniter your glow plug is effectively cooling off.

Try setting the low speed needle even lower in small 1/4 increments and see if you can get it to idle this way.

If you are unsuccessful, try a hotter plug too.

Thanks opjose, i'll give it a try.