Glow Plug Coil
 

I just checked the glow plug on my Magnum GPA 40, and the end of the coil is all messed up. I remember reading somewhere what this is an indication of, but can't remember exactly what, and could not find what I was looking for in a search. Anything anybody could tell me would be greatly appreciated. Part of my problem is that I'm just getting back into flying with nitro engines, been doing the electric thing for awhile, and that after about a 7 year break. All of my engines are still in good shape, and fire up right away, but the 40 isn't running quite right, and I'm suspecting that the plug is the problem, but would like to know the cause of the plug being damaged before I slap another one in and ruin it, too.

RE: Glow Plug Coil
 

To lean or to much nitro causing detonation. To hot a heat range plug can also cause it.

Denis

RE: Glow Plug Coil
 

Thanks djlyon, that helps. I'm going to guess too much nitro, unless I've really lost my touch for tuning an engine. Maybe it will help if I list what I'm using and doing:

Magnum GPA 40
Cool Power 15% nitro
Thunderbolt Standard Long plug w/idle bar
Turn needle in to max rpm, then richen until noticeable rpm drop

The only thing I changed from when I ran this engine in the past was to up the nitro % from 10 to 15. I did this because I am now living at about 2000 ft higher than where I used to fly, and figured it would help compensate for lost power due to altitude.

I'm sure there might be another plug that will work better, also, it's just that I had the Thunderbolts from before, and they had always worked well.

RE: Glow Plug Coil
 

Oops, just noticed something else, the new fuel is all synthetic lubrication, I always used to use something with a little bean oil in it. I wouldn't think this would make a difference, but I could be wrong. Any thoughts on that?

RE: Glow Plug Coil
 

Everything looks alright and I don't think the synth is the problem unless you are getting a little lean. I'm not familiar with the engine or the plug. If the engine is fairly benign in compression the 15% nitro should be OK. Try dropping the nitro and/or richening the engine to a little more than noticeable, such as 4 to 500 rpm. There is some other plugs that might work better ie OS #8, Enya #3, K&B HP or idle bar, McCoy #9. The bean oil will protect the engine but I don't think it will protect the plug from the kind of damage your seeing. That damage is generally the result of detonation. If on my engines it is persistent with good needle settings I lower the compression or drop the nitro. The TT40s on my quickies will destroy a plug with about 20 seconds of even the slightest detonation and those are fairly benign engines.

Denis

RE: Glow Plug Coil
 

Thundebolt plugs are very hot, so a cooler plug might do the trick. I would try the Fox Miricle plug next, or the OS F.

RE: Glow Plug Coil
 

Searched through everything I have, and I do have an OS #8, also have a Fox Standard w/idle bar. Is there an advantage to having an idle bar on a plug, or is it better to not have one? I've been out of this so long, I can't seem to remember anything about plugs. Sport_Pilot, I thought that the 4-stroke plugs were hotter because of ignition only occurring every other stroke? If not, just goes to show how little I know. Is there an advantage to running a 4-stroke plug in a 2-stroke?

As to the engine, it is bushinged, about 10 years old, maybe a little older. If I remember correctly, it was the first non-bearing Magnum to have the 2 needle carb.

It isn't a powerhouse, but until now had always been a very reliable, very smooth engine. It probably has 150-200 flights on it, and maybe 2 deadsticks in all of them, and those due to running out of fuel. I am hoping I can find that "sweet spot" for this engine again, as its always been one of my favorites for just tooling around on an easy flying airframe.

RE: Glow Plug Coil
 

Sorry got the posts mixed up. OS - 8 or K&B 1L would be good. Not OS-F. I know Thunderbolt four strokes is the hottest glow plug I know of, havent tried the two stroke but assume it is also very hot. You shouldn't need an idle bar plug.

RE: Glow Plug Coil
 

'Thumbs,

Your engine is an ABN/ABC type.
Morgan recommends the red Omega fuels for this engine.

Most here would say some Castor oil is needed, as do most ring-less engine manufacturers.

The Cool Power contains none.

The additional nitro you are running just makes your fuel costs double, with very little added power.

Your magnum needs no more than 5% nitro to run well and exceeding 10% is a real waste.

The fuel manufacturers just shovel the 15% brew to most American modelers, who just accept it and pay more for it. Stand your ground and demand nationwide availability of 5% Castor/synthetic!

RE: Glow Plug Coil
 

OK, little update. I tried the fox plug w/idle bar, and the good news is after about 10 minutes of run time, the coil remains undamaged. Bad news is, now the end of the muffler is spinning around, no matter how much I tighten it. Also, after I pulled the muffler apart, I noticed there is a baffle in there, and it looks pretty restrictive. Is there a down side to just pulling that sucker out other than increased noise? Also, any ideas on getting the muffler to stay still would be greatly appreciated.

Thanks again,
Thumbs

RE: Glow Plug Coil
 

Most of the newer Magnums imported here have low enought compression that there is a noticeable increase in power from 5% to 15%. It could be that those sold overseas has a higher compression ratio.

RE: Glow Plug Coil
 

Lefty:

You may do as you please, but the Magnum GP and GPA engines were fitted with plain bearing cranks. Without castor oil in the lube their life is greatly shortened.

Either use the "Pink" Morgan fuel (Omega brand) or add four ounces of castor oil per gallon to your Cool Power.

Or stay with synthetic and accept the short engine life.

Bill.

RE: Glow Plug Coil
 

Bill, like I said before, I usually like to run some bean in it. I just picked up the wrong jug on the way out the LHS door. That will be getting fixed about tomorrow, as I just don't really trust synthetic only fuels. There must be something to the castor oil, why else would so many companies recommend it?


Any thoughts on the baffle in the muffler? In, out, used for a practice target, anything?

RE: Glow Plug Coil
 

Reed:

I had trouble with the wording on the oil post, as you had said you used it. Wanted to reinforce your use of bean in the plain bearing engine.

The baffle? Might work OK with it out. Problems that would show are poor idle from insufficient back pressure, and maybe running lean also due to lowered muffler pressure to feed the fuel. Not to mention it will be noisier without the baffle.

My preference is leaving the baffle, take it out only if I need that last rpm, just a little more power. And sometimes I put it back.

Bill.

RE: Glow Plug Coil
 

Sometimes when the engine runs out of fuel it blows the plug.
Just like any other lean condition, the sudden heat up causes the
coils in the plug to distort. The next time you go to start the engine
you find the blown plug.

MB.

RE: Glow Plug Coil
 

Motorbrain, I always run the fuel tank dry at the end of the flying day on my bearing engines. Have been experiencing a lot of blown plugs lately, especially when starting up the next session. Kind of a dilemma : protect the bearings while stressing the plugs, or???? Any thoughts on this ?

RE: Glow Plug Coil
 

Joe,

I have always run my engines dry after every flight session, yet I have not had a plug burn out on me (in normal use) in about five years.

I invariably retire my glow plugs after they have accumulated a "scale" like substance, on the coil, causing them to glow a bit dim... This happens every few months.

The difference; I use ONLY 5% nitro and 20% oil (including 8-11% Castor) in my fuel; both for all my MVVS, high compression engines and for my past OS engines.
I would recommend this formulation to anyone running a two-stroke glow engine.

Most Americans use 15% nitro and 16-18% oil, for whatever wrong reason, as well as paying more for it and having to use more of it. Most do experience burned out/melted plug elements.

Coincidence? I don't think so.
Prove me wrong!

RE: Glow Plug Coil
 

Dar, I'm with you on the 5% nitro, what is the total oil in the fuel you run? Right now I'm running Fox 5% nitro with 20% castor.

RE: Glow Plug Coil
 

Dave,

I use 20% total oil, out of which about half is degummed Castor oil, for all ball-bearing. ringed and ABC/ABN engines. I have not had, or run, a lapped, meehanite piston, steel sleeve engine in a long time, but for them and for bushing bearing engines, I would use the same formulation, with the oil increased to 22%.

I break-in all engines on 22% oil. I think the richer mixture used for break-in of lapped engines does not require the percentage of oil to be further increased, but for lapped piston engines I would increase the Castor oil's part.

MVVS, by the way, prescribes 25% oil for their Diesels, but this is for another forum.

RE: Glow Plug Coil
 

Dar, I have run engines with 25% nitro and the plugs last! The engine develops more power without the added weight of a larger engine. If the compression ratio and glow plug heat is right for the extra compression they will last just as long as a high compression engine with 5% nitro. But upping the nitro on the high compression engine will indeed blow plugs. Also upping the nitro on high compression engines will gain little to no power, if it detonates power is actually less! Many engines that have low compression ratio's here in the US are often sold with higher compression engines overseas. This is often done buy adding a thick head gasket, where the engine overseas comes with no head gasket. I have some high compression engines I enjoy when I don't need max performance. They run fine on 5% fuel. The low compression engines can run on 5% nitro but they are tempermental to tune, especially on cooler days.

RE: Glow Plug Coil
 

Hugh,


Most European engines are, as you wrote, set up to use 0% nitro and most will use 5% unchanged.
Many engines, even as they are sold in the USA, are set up to run 10% nitro.

15% nitro fuel has begun to become popular in the USA, only in the last few years.
Before that, everyone used 10% nitro, except YS and helicopter pilots.

Clarence Lee and most other US engine review writers, use 10% nitro fuel for their reviews; not only to get a common starting point, but because it is (was) the popular fuel in the USA.

With the upcoming trend to use 15% nitro and with most engines still set up to run 10% nitro, there is no escape from over-compression, which burns up plugs.

Adding an extra head shim to "de-compress" an engine, changes the squish clearance designed into the engine. This squish band allows the engine to use a higher compression ratio, than would be safe without it, without risking detonation and over-heating.

While an extra head shim does decrease the compression ratio, this is counteracted by the squish clearance not being one any longer. This increases the tendency to detonate and overheat, maybe just enough to take out the glow plug.

This glow plug is the "miner's canary" of engines, which dies "telling" us something is wrong.

Using a colder glow plug will allow you to run 15% nitro in some engines set up to run 10%, but not in all of them.

RE: Glow Plug Coil
 

Dar,
I think 15% nitro has been popular for a long time, not just recently. In the 70's my favorite fuel for a long time was Missle Mist with 25% nitro. But when I jumped up to .60 sized engines I noticed it didn't seem to improve performance and I ran through it real quick. I didn't know why at the time but now I know the smaller .35 engines I was using had a real low compression ratio, the larger one was set up for, well I don't know but lower. Most of my engines show a marked improvement with 15% nitro over 10%. The squish band does help, it does so by causing the fuel air to circulate just before ignition. This prevents pockets of lean mixture which can cause preignition. IMO I have never seen a problem with this when just bumping from FAI fuel to 10%. I understand that shimming for very high nitro can cause problems, especially on cooler days when the fuel does not vaporize into the air as well.

RE: Glow Plug Coil
 

Thanks everyone for the replies, suggestions, and help. I threw in some castor and will at least use up the gallon of 15% so that I didn't waste my money on it. After that, I'm just going to go back to the 10% nitro, 20% castor/synthetic mix I always used before, as I've never had any problems with engines on it, or blowing up glow plugs.

Bill, have noticed on other posts you seem to be as big a Magnum fan as me. Always nice to know you're not the only "crazy" person out there that won't run an O.S. just because they are accepted as the standard.

Cheers and good flying.

RE: Glow Plug Coil
 

DarZeelon,

With the exception of your first sentence, everything in your post is incorrect.

MB.

RE: Glow Plug Coil
 

John:
Please support your atatement, sir, or withdraw it.

Thank you.

Bill.