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Glow-Plugs Recommended By OS Engines - 2/4/2006 7:30:11 AM   
DarZeelon



Posts: 7108
Joined: 4/9/2003
From: Rosh-Ha'Ayin, ISRAEL
Status: online 		I looked into the OS web site; not the American distributor's site, but the original, English language, Japanese web site.

Please look here to see which OS glow-plug, OS recommends that you use in your OS engine.


This is for all that recommend running 'F' plugs in big two-strokes, or the A3 in the .91FX.
Also, to all those shops 'giving away' A3 plugs to buyers of all two-stroke engines...


The A3 is recommended ONLY for two-stroke engines smaller than .32 cid; and for LA engines up-to-.40.

The #8 is quite universal, being medium heat.

For the .61-.91FX, .65LA, 1.40, 1.60, BGX, Etc., the right glow-plug is the cold A5; not the hot A3.

And, BTW, have you ever seen any A5 glow plug offered for sale in your LHS, for use in your new, large displacement, expensive OS engine?

I sure have not...


What would you say about this, Bax?


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RE: Glow-Plugs Recommended By OS Engines - 2/4/2006 8:28:20 AM   
Kostas1



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From: AthensAthens, GREECE
Status: offline 		DarZeelon.
my OS 91 FX came with an OS type #8 glowplug.

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RE: Glow-Plugs Recommended By OS Engines - 2/4/2006 11:43:43 AM   
DarZeelon



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From: Rosh-Ha'Ayin, ISRAEL
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quote:

ORIGINAL: Kostas1

DarZeelon.
my OS 91 FX came with an OS type #8 glowplug.




Kostas,


...Which is OK, with the low nitro fuels that you have in Greece.

OS does not limit the #8 glow plug to smaller displacement engines, but still, if OS says the A5 is better for the .91FX, should I need a replacement, I would opt for it and not for the #8.

The A5 should cost a bit less too, compared to the #8.


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RE: Glow-Plugs Recommended By OS Engines - 2/4/2006 12:52:22 PM   
Cyclic Hardover



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From: New Mexico, USA
Status: offline 		I 'm glad we have many other choices in plugs. I rarely use OS due to the cost and my engines run just fine

< Message edited by Cyclic Hardover -- 2/4/2006 12:53:20 PM >

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RE: Glow-Plugs Recommended By OS Engines - 2/4/2006 1:14:53 PM   
Kostas1



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Joined: 12/19/2005
From: AthensAthens, GREECE
Status: offline 		M,good to say this.
A question is that i know that the OS #8 glowplug is hotter than the #A5,but when running the OS 91 FX,
what's the real difference between these glowplugs?
Also,in an 91 FX can i use an #A3 glowplug,if the engine is inverted???


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       Post #: 5

RE: Glow-Plugs Recommended By OS Engines - 2/4/2006 1:33:24 PM   
DarZeelon



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From: Rosh-Ha'Ayin, ISRAEL
Status: online 		Kostas,


I would generally say no.

If the best specific solution is the cold A5 and the universal #8 can also be used, the A3 may be too hot and will require the mixture to be set significantly richer, so as to prevent the engine from suffering from detonation.

You would actually see that you can close the needle further, without risking a lean-run (which is actually detonation), when using the cold A5, compared to using the hot A3.

The price difference between the two is equivalent to the difference in fuel consumption for 15-20 minutes of running...

That is all.

I would not recommend using the A3, unless there is no other glow plug and you must run the engine NOW (and the fuel waste for these one-two flights that you MUST make, is reasonable).

Replace the A3 with the more suitable A5 glow-plug, ASAP!

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RE: Glow-Plugs Recommended By OS Engines - 2/4/2006 3:44:54 PM   
B.L.E.


 

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quote:

ORIGINAL: DarZeelon


You would actually see that you can close the needle further, without risking a lean-run (which is actually detonation), when using the cold A5, compared to using the hot A3.



I believe it would more accurately be described as preignition, which is not the same as detonation although preignition can often lead to detonation.

It has been my observation that a glow engine that is too lean behaves a lot like a model diesel engine that is overcompressed and a spark ignition engine that has it's ignition timing over advanced. This leads me to think that we actually use mixture adjustment to fine tune the ignition timing of glow engines. Glow plug heat ranges and head gasket thickness is used to make course adjustments in ignition timing but the mixture fine tunes it. If you take a Cox .049 engine and add several head gaskets to lower the compression, you will find that the engine wants a leaner mixture for peak power.

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RE: Glow-Plugs Recommended By OS Engines - 2/4/2006 4:46:33 PM   
DarZeelon



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quote:

ORIGINAL: B.L.E.


I believe it would more accurately be described as pre-ignition, which is not the same as detonation although pre-ignition can often lead to detonation.

It has been my observation that a glow engine that is too lean behaves a lot like a model diesel engine that is over-compressed and a spark ignition engine that has it's ignition timing over advanced. This leads me to think that we actually use mixture adjustment to fine tune the ignition timing of glow engines.



B.L.E.,


Pre-ignition is an ignition caused by a hot-spot within the combustion chamber, like a sharp edge on the piston, or the head, or carbon deposits. In a spark-ignition engine, it can even be the electrode of the plug.
In a glow engine it is nearly always the glow-plug coil that initiates the ignition.

So too hot a glow-plug would simply be an overly advanced ignition point. And yes, this can cause the fuel-air charge to detonate, as the piston continues to rise and compress it, after the advancing flame-front had hit it...


About the needles being the ignition timing control, I have been saying it all along, in several past threads here.

With the compression ratio being a given value, as is the fuel you filled the tank with, the prop load you are using and the glow plug you installed, the needle is the only thing that allows you to change the ignition timing.

With a leaner mixture being easier to ignite and faster to burn, it is clear what must be done to increase and optimize the ignition advance. Just screw the needle in a bit.


Using too hot a glow-plug (or too much nitro) requires you to use more fuel, to delay the ignition, reduce the advance.
This fuel is just wasted, just leaving you more gunk to clean off the plane after the flying day.

...Not to mention that you had to pay for all that fuel.


< Message edited by DarZeelon -- 2/4/2006 5:04:27 PM >

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RE: Glow-Plugs Recommended By OS Engines - 2/4/2006 6:36:43 PM   
downunder



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From: Adelaide, AUSTRALIA
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quote:

ORIGINAL: DarZeelon
I looked into the OS web site; not the American distributor's site, but the original, English language, Japanese web site.

Why are their plug recommendations suddenly gospel truth but when it comes to running in engines (on the same site)they don't know what they're talking about? BTW, if you read the instruction manuals it seems that just about every engine is shipped with a #8 plug. The manuals also advise trying different heat range plugs to get the best performance. The original post is too much of a generalisation.

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RE: Glow-Plugs Recommended By OS Engines - 2/4/2006 7:06:38 PM   
DarZeelon



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From: Rosh-Ha'Ayin, ISRAEL
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quote:

ORIGINAL: downunder

Why are their plug recommendations suddenly gospel truth but when it comes to running in engines (on the same site) they don't know what they're talking about?


I was waiting for you to come in, Brian and foresaw this response.

When selecting a glow-plug heat range for an engine, it is a design decision.
Deciding how to perform the break-in, is experience based and also based on being able to change the way you think, about different engine designs.


I was also taught that break-in always requires a slobbery mixture setting.
...And I was also taught that during break-in, an engine may fail, once in a while...

I would have done it that way... But then I started thinking about what I was doing, as well as trying to figure out, who makes more sense about ABC type engines; The geezers with ringed and lapped engine experience, or George Aldrich, Clarence Lee and Harry Higley, with their informed, engineered reasoning.

I chose the later and then wrote about it.

And no, I cannot figure out why OS does not bother to differentiate, between ABC/ABN engines and ringed engines, as Super Tigre does, in regards to the break-in technique in their manuals.


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RE: Glow-Plugs Recommended By OS Engines - 2/4/2006 9:15:39 PM   
Spicoli


 

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From: TERRACE, BC,
Status: offline 		My 91fx seems to run better with a OSF plug compared to a OS8.

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RE: Glow-Plugs Recommended By OS Engines - 2/4/2006 10:08:26 PM   
Kostas1



Posts: 1230
Joined: 12/19/2005
From: AthensAthens, GREECE
Status: offline 		What prop are you running,rpm range and fuel?
Can you post any pics?

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RE: Glow-Plugs Recommended By OS Engines - 2/4/2006 10:26:07 PM   
jaka


 

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Joined: 12/11/2001
From: Upplands Vasby, SWEDEN
Status: offline 		Hi!
There is no glow plug recommendation that should be interpreted like it was the writing of god (or OS)!
Glowplugs are a thing that work different for different engine applications.
saying that the OS .90 FX ...or whatever should always be run on an OS 8 or Enya 3 or ...is not true. It's only a recommendation! Which means that under normal conditions running normal prop sizes, under normal temperature, using normal fuel, having normal cooling for the engine, running at normal rpm, at sea level... or what ever the manufacturer had in mind...then this or that plug will work good.
But saying it's the best plug for that engine for every application is not true!

Regards!
Jan K
Sweden


< Message edited by jaka -- 2/4/2006 10:27:46 PM >

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RE: Glow-Plugs Recommended By OS Engines - 2/5/2006 1:22:58 AM   
Ernie Misner


 

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Status: offline 		>>> Pre-ignition is an ignition caused by a hot-spot within the combustion chamber, like a sharp edge on the piston, or the head, or carbon deposits. In a spark-ignition engine, it can even be the electrode of the plug.
In a glow engine it is nearly always the glow-plug coil that initiates the ignition. >>>

Is this why it doesn't matter that all of OS's "long" plugs are actually a short reach? These so called long plugs leave lots of threads exposed inside of the head. Being used to gasoline engines, I thought this would lead to preignition or hot spots. But apparently not? I would still prefer that OS's plugs would be a true long reach. They could be tightened more safely in the head. Does anyone have a clue why they are such short reach?

Ernie

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