Reading plugs

[BradV]

My CMB1.0 has been running well lately but I am now wanting to optimise its performance.

Can anyone recommend an ideal plug for this motor? I'm currently using 50% nitro but will move to 60% soon.

Also I've noticed some material appear on the plugs after a few hard runs. Looks like carbon melted onto the glow plug casing as speckles. Is this a sign of detonation?

 

[Dan_Cousin]

A sure sign of detination is a sandblasted look on the head button and piston top.

A little is OK but a lot is robbing your power and stressing your rod and bearings.

 

[bbnate804]

not trying to steal the thread but....what do you do when your gettin detonation?

nate

 

[Tim_Duggan]

Nate,

Basic answer : increase the bowl volume in the head to reduce compression.

Head design, engine temp, pipe, load from prop, fuel and so on can all cause it.

 

[BradV]

Thanks for that, the speckling is what I thought.

Only thing is it ran very hot because the water cooling came off, so I will check it out with a fresh plug before reducing compression as it might have just been the heat.

Any suggestions on the best plug for these motors?

 

[Tim_Duggan]

Most guys running those in my area run mccoy MC-9's or K&B HP. A few of the guys prefer a hotter plug and less compression in them and use MC-8's.

If you lost the water line that could have caused your deto.

Tim.

 

[waterbug]

Tim

On my OS 21 OB I noticed after 4-5 heats I see a greyish-lite tan fuzzy on the first two coils... This normal ?? 2% caster oil

 

[Tim_Duggan]

A greyish lite tan fuzzy?

Do you have a hopper tank in that boat? Do you run it until it runs out of fuel? Sounds like it's close to ideal mixture. If it's shiney - it's rich.

 

[waterbug]

Tim

:lol: Yes I have a hopper tank....no I don,t run it empty !! and that plug has about 9 hrs. run time I have run that plug for a year !!!! on 60%.. :lol: I changed it this past weekend when I saw the build up on the coils.... K&B-1-L

Butch

 

[Jerry T]

Here is a chart that might help in reading the plug.

http://rcunlimiteds.org/webpages/specialar...heglowplug.html

 

[Dan_Cousin]

What about when your blow the pin and ceramic right out of the top!

 

[Jerry T]

Dan, I said the chart may help. In my opinion when the plug gets really hot like to blow the center out, the plug is not dissapating the heat, it's holding it in. Is the head button anodized? An anodized head button will not transfer the heat from the glow plug to the rest of the motor. Make sure the contact between the glow plug washer and the head button is metal to metal and clean. You can also measure the resistance from the glow plug the the engine block with an ohm meter.

Hope this helps.

 

[Terry Flynn]

What about when your blow the pin and ceramic right out of the top!

91917[/snapback]

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I bet it was a Mcoy

 

[Russell Bear]

What about when your blow the pin and ceramic right out of the top!

91917[/snapback]

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I bet it was a Mcoy

91983[/snapback]

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Dan, Wasn't it those cone locks that this kept happening to?

 

[not2bright]

when i was having the pins blow out of my 11cc it was because i had way to high of compression. of course i didnt realize that until i went through about $60 worth of plugs, expensive lesson. so my guess would be if your blowing them all the time try shimming the head up a little

 

[Don Ferrette]

when i was having the pins blow out of my 11cc it was because i had way to high of compression. of course i didnt realize that until i went through about $60 worth of plugs, expensive lesson. so my guess would be if your blowing them all the time try shimming the head up a little  

92015[/snapback]

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Jacking up the head clearance is not always the best way to go as you want to keep a tight squishband area. A better approach might be to look at the actual head button bowl volume & increase that depending on what you find. :blink:

 

[[email protected]]

Add a dental pick to your collection, it'll help w/the plugs

 

[BradV]

What's youre favourite brand guys?

So far I've found the Nova Rossi one of the better ones, any others out there that give good performance on high nitro fuel?

 

[Dan_Cousin]

Too high of compresion was the right answer.

It was the MC-9. Surprising enough, I had some tower hobbies RC plugs (sans idle bar) and they did not do this but they they came back with no coil. <_<

The head was a .27cc on a CMB 45. :lol:

No the head button was not anodized.

Another issued I've asked on the "other" board and never got a real answer is having MC-9s turn blue/black after a run. The coil was perfect but a little frosted but the plug turned burnt blue.

Never did this before with MC-9s.