Greetings,

I have an OS FX 46, I bought a bunch of Fox Long Glow Plugs with the Idle Bar, based on the guy at the club's recommendation. Someone else said the idle bar was useless on this engine.

I really don't even know what the idle bar is, and the plugs work fine, but I'm out and before I buy more I was wondering what glow plugs everyone else uses.

Also, what is the idle bar and if it bit me on the nose, what would it look like?

GB

I have an OS46FX also and use either OS #8 or A3 plugs. Both work equally well.

Not sure about the idle bar... sorry.

Mike

GB
The idle bar plug was developed in the days of loop scavenging (deflector top piston) engines that had no mufflers. Without muffler back pressure plugs had difficult times staying lit at idle and (this is why most old RC engines had coupled exhaust baffles that closed with the throttle) couple this with fresh mixture deflecting directly up into the plug at idle it tended to quench the fires. The solution was a plug with a bar welded or machined on directly above the coil that acted as a shield for the coil. Most modern *****ie's (an entirely differant type of induction porting) do not require this type plug. There are however many older loop or cross ported engines still in use that do benefit from glow bar plugs.

John

Like John said, idle bar plugs are a bit of a hold over from earlier days. In my .46fx I use OS A3 plugs. I use them in a couple of other 2-stroke engines as well. Either I'm doing something right, or I'm lucky, as I don't go through but one or two glow plugs per year. I've got friends that balke at the dollar or two more the A3 costs over K&B or Fox, but they end up switching glow plugs every 3 or 4 flying sessions. So much for any savings, eh?

There is a science to selecting the right glow plug. Different plugs have different heat ratings. Finding and selecting the proper heat rating for your engine will make your life a lot easier. Unfortunately, you'll have to find someone who's more familiar with the process to tell you about it. IIRC, if when you remove the ignitor the RPM drops you're not using a hot enough plug. Beyond that I'm useless.

use OS # 8

I've run about 15 gallons through my .46 FX and it has done just fine on a standard Fox long plug...that is to say that it is still using the Fox standard long plug I put in when it was new.

The 46 fx, like most new engines doesn't need an idle bar.

My experience with fox plugs is that they rarely burn out unless you over drive them by turning up the amps on your power panel.

The idle bar has a second function other than shielding the coil from the fresh mixture... It also retains heat, making it easier to tune for a smooth idle. I prefer to use them. That being said, I have heard of the idle bars breaking loose, and damaging the engine, so routine inspection is a good idea.

I missed the point...If you already have a bunch of Fox idlebar plugs, there is not a reason in the world not to use them. The Fox idle bar is machined into the plug and it cannot break off and damage the engine.

Use up the fox long idlebar plugs, then, when you are out of them, you can switch over to fox standard long plugs or any other plug that floats your boat.

I believe the instructions for the .46 say to use the No. 8 and they work well for me

buy OS #3 or #8 both work on your engine.-
these glow plug laaassstttt.

When you take off your glow plug ignitor and the engine speed drops a few hundred RPM...that is one sign of the WRONG plug for your engine/fuel combination (or your fuel is full of water). For my 2 cycle engines I personally like the OS #8 plug. They seem to last forever and they burn a bit hotter so as to not have the RPM drop as mentioned above. The OS #8 is NOT the "perfect" plug for EVERYTHING though...different engines/fuels require different plugs in some cases. Brand to brand engine/plug/fuel results WILL vary...it is a matter of finding what works BEST for YOUR engine/fuel combo and go from there.

Sorry, but there is NO simple easy answer here since there are SO many variables to the question.

Uncle Dad

Here is a chart I picked up awhile back see if it help's, applies to O.S plug's so not sure if it's any good for other brand's

OSMG6300 #0 Economy standard plug similar to the #8
OSMG6304 #1 Hot plug for low nitro (0-5%)
OSMG6308 #3 Medium plug for medium nitro (5-25%)
OSMG6312 #5 Cold plug for high nitro (25%-plus)
OSMG6316 #7 2-stroke engines requiring an idle bar
OSMG2690 #A3 "The new standard" for use in all 2-strokes, any nitro
OSMG2691 #8 "The standard" for use in all 2-strokes, any nitro
OSMG6320 #9 For general use in 2-stroke engines
OSMG2692 #F For O.S. and other 4-stroke engines
OSMG2688 #RE For the O.S. Wankel Rotary engines

Okay, Folks, let's use our heads instead of trying to find "pat" answers. First, the Fox R/C Long glow plugs work fine. Besides retaining heat, they tend to protect the glow element from any blasts of raw fuel hitting it. I tend to use about 3 of these glow plugs per season per engine. You should also know that I use about 5 gallons of fuel per season per airplane. I have seen many a beginner try the stock plugs that come with the O.S. 46 and have a hard time keeping the engine running, then they try the #3 and #8. Sure, O.S. recommends them! The Fox plug tends to be more forgiving of a lean or rich condition. Also, if your engine drops a couple of hundred RPM after removing the glow driver, it's probably more due to a rich carb setting than the plug.

That's a rather "pat" answer, John. You're just relaying your experience, which is what most of us did.

If I were Ghostbear, I'd pick up a couple of the plugs people recommend. There's no need to buy just one kind in bulk. Take the time to experiment a little. You'll get your own "pat" answers soon enough that way.

All,

Thanks everyone for the recommendation. The chart from mrisis is very nice.

I'll get a couple of the OS plugs and see how they do.

GB

not glow plug related but if you remove the glow starter and the rpm drops, it can also mean you are running too rich

Yeah, it's a hornet's nest

Unfortunately there's no standard for heat ratings between manufacturers, some will use a low # to indicate a hot plug and another will use a high # for their hot plug. OS seem to confuse it even more by having numbers all over the place

Although there's only ONE correct plug for any combination of engine/prop/fuel/phase-of-the-moon, for normal sport flying you can get away with a reasonable range of plugs. That's why almost everyone says use an OS #8 (although why the Enya #3 hasn't been mentioned I've no idea, it's considered to be a far better plug).

But to understand what they do and why it's important to use a reasonably correct plug the best site I've found is at http://www.modeltechnics.com/glowplug/firepower.html

I have an OS FSR 61 that dropped about a third of its rpm when the glow driver was removed. Without touching the engine settings, I changed plugs and the problem immediately stopped. Unfortunately I have no idea what plug was in the engine, or what I replaced it with as it was just a plug floating around in my flight box. The only reason I'm relating this is because it proved to me that the wrong plug can certainly cause the problem of dropped rpm when the glow driver is removed. Thanks for the link, downunder!

Just hilighting what appears to be a problem. You stated that you had used up the "bunch" of plugs that you had bought. How many do you typically go through in what period of time.

My personal experience has been to change them once a year unless they blow (which is rare). If you are burning them much more often (as your note seems to imply), perhaos there is more to look at.

For example if you are using a glow attachment from your power panel and keep blowing the Fox plugs by overcharging, the same will happen to the OS.

Just wanted to confirm this wasn't the case.

Bob aka Nuker

ps I use OS #3 in my .15 bushing combats, OS F in all my 4-strokes and OS #8 in everything else

The bunch was four. I gave one away. The rest probably didn't need to be changed, but whenever the engine gave me problems (about twice) the guy at the club said "just change the glow plug and see if that fixes it."

Anyway, I haven't had a chance to fly lately so I haven't gotten to the store to buy a few spares.

I always use A3 plugs with my TT 46 Pro and could tell absolutely no difference from the #8 plug. So I stuck with A3's considering they were much cheaper. I once tried a fox idlebar plug in my TT and it woudln't run worth a crap. In fact, the motor wouldn't run long enough to get the plane off the ground. SO I scrapped that idea real quick.

Another aspect of the heat range and how it affects engines is ignition timing (speaking glow engines here). As plugs are changed from cold to hot, this effectively advances the ignition timing ("lead") which will give the noted increase in RPM and sometimes, power. Of course this can have a detrimental effect if you have an engine that's tuned to the edge of destruction (lean) to start with......


Sam

You are all have good points. Some have good luck with OS plugs, some Fox, some Enya. I have had good luck with Fox, but I have also had new Fox plugs that were bad right out of the package. I don't think I have seen anyone mention though that if you are changing to a different glow plug be prepared to have to change your carb setting, low and/or high speed needles. I would recommend that you stay away from 'bargain' plugs. I believe that any of the main 3 will work with almost all engines if you get everything adjusted correctly.

as a rule of thumb what i've been doing for the last 20 yrs.
exhaust system is very credicule on 2 stroke glow motors
on stock mufflers use a idel bar plug best one i've used and think at one time or another i've used them all is a kb1l good all around plug if you're useing a performance pipe or muffler use a non idelbar plug os 8 a3 enya 3 also if you'r burning plugs in a motor
thats say a sport motor not a high performance engine you'r proberly running on the lean side low end or high end when you take the driver off at a idel it should drop slightly the old pinch test is a good way to check it should run for about 5 sec. before it quits thats speed up and quit if it doesn't its proberly lean. rich engines run a little sluggish lean engines burn up.

roy