Melting glow plug coils!
 

Today I was at the track running the engine rich at stock needle settings - 4.5 turns out - HSN, 3 turns out - LSN, Flush with carb body - MSN. Usually I do this for a few mintues to reset everything and flush out any dirt. Well after about four laps (smoke at full throttle, raw fuel spitting out at idle) I shut her down. After about 30 seconds I attempted restart the engine with no luck. Upon inspection the glow plug coil had melted - brand new! Then it did it again within three laps on another brand new plug!

After I burned two plugs out and none left, I packed up my things.

I have a Nova TN12 (based off RS12), Byrons Race 3000 (30%), and O.S. #8 plugs, 90-95 degrees out, engine is totally stock (no shims added). At the end of the last race I noticed the car was having problems.

Is it possible that the car is too rich? This isn't making any sense to me. Thanks in advance.

Should I be using a colder plug?

Hmmmmm, the same problem I had before.
Does your engine vibrate too much? Does the button head in the combustion chamber a little rough?
Check the piston, bearings, and excessive play on the connecting rod brass bushings.
Replace them if necessary. Or try to add 0.1mm shims to minimize detonation.

I'm almost positive it is the 30% nitro and the OS #8 that do not match. Can anyone confirm this?

Just one question... why use an OS #8 plug? Just use the Nova or RB ones... less fuzz and problems. Is normal or Turbo?

Normal/Standard. I'll be honest I am very disappointed with these. My Novas never gave me problems other than one. Where can I get them in the states?

Just use a Nova 7Cold or RB #7. Pay attention to the Combustion chamber height. If you find some Sirio #7 they work really fine too (Yep... are available on standard 1/4 UNF thread size - Are the buggy ones).

Can someone breakdown the RB Concepts plug number and heat ranges, thanks.

I would try to use a shorter plug. OS #8 is a standard plug as your said.

You probably save couple bucks using OS #8, but it is just better to use NovaRossi plug....

i blew every OS standard pug i ever had (A3 ,#8) (when i used a OS12TR) i found that they werent that good, i always ran the engine rich and i wasnt the only one having probs with them, i ended up selling the engine cheap and the other guy started using the R5 plug on 15% nitro

os plug
 

The os plugs are shorter than novarossi and the #8 is too hot for 30 percent fuel.

Can anyone break down the RB heat ranges/plug codes?

Yeah, I went through $20 worth of plugs. You live and learn I guess. :(

What's the difference between long and short plugs?

Check your engine's spec. the shim that come with stock engine has a limitation. most engines are good up to 25% nitro without adding a 0.1mm shim. (0.1=5% nitro) 30% nitro creates lots of compression. your problem is shimming.
i am almost sure that once you find out the max nitro for the stock setting and adding the right shimms your problem will go away.

I had the exact same problem on my JP .21. on another thread the guys suggested running shims on higher nitro. Well i went the conservative way with my .12 TZ and it worked a treat. i added two head shims, ran it on 30% and it screamed and sounded sweet. no weird noises (detonation) and had tonnes of power. ill strip the engine tonight to double check everything tho.

RB does this on their FAQ page. Here is the link to it.
http://www.rbproducts.com/mainEn.php...ght%20glowplug

Hope this answers your question.

Thanks! Should have looked there - I was all over the plug section.

Melting coils = too much compression.

Add 0.1mm shim(s) or use lower nitro content.

What is the difference between F and C on the Nova turbo plugs?

F = Freddo
C = Caldo(sp?)

A C7TF is Very cold while a C7TC is cold.

I only run 7 plugs and the temperature outside determains weather I use a F or C plug.

I also suggest you read this on all the info on glowplugs you will need.

http://www.rbproducts.com/mainEn.php...ght%20glowplug

The numbers and characters on the plugs, are the product number, wire thickness, and thermal range of the plug’s body. Example: The Novarossi C6TG (F) or (C)
Product: C (Conical)
Wire Thickness: 6
Plug Type: T (Turbo)
Plated: G (Gold)
Thermal Range: F (Fredda = Cold) C (Calda = Hot)

The plugs with cold thermal range F (Fredda), have a body with thinner walls and shorter body, so they dissipate heat better and faster to the engine head. The plugs with hot thermal range C (Calda), have a body with thicker walls and longer body, so they dissipate heat better and faster to the engine head. The number of threads is the same on both types of plugs.

How to select the proper plug:
·When the ambient temperature is high, we have to use a plug with thicker wire.
·With higher compression, we have to use a plug with thicker wire.
·Humidity determines if we use a Cold (F) thermal range, or Hot (C) thermal range.
·With high humidity percentage we should use a Hot (C) thermal range plug.
·If we have high temperature and high humidity, we should use a plug with thick wire and a Hot(C) thermal range.

On Another note: The Old OS standard plugs such as the Nº8, Nº5 have fewer threads than Nova based plugs, so they sit higher in the combustion chamber of a Nova based engine, and won't work addecuately, thus your problem.

AFM

Well Done AFM :cool: :cool:

I would to add another tips to eliminate melting glow plugs.

Increase shim thickness by 0.1mm
Use thicker wire ( colder ) glow plugs ( I prefer this one )
Lower nitro content

I also found out that Long Plug tends to last longer... :) That's what I've been using.

Before I get flamed, they're available locally, how are MegaTech plugs?

An OS #8 is fine with 30% nitro but you should not use an OS plug in anything but an OS or Go Tech engine. Those engines are designed for "short" plugs. All other engines should be run with standard reach plugs.

How old is your engine? A common cause of engines eating plugs quickly is a worn lower rod bushing. If this is the cause then it should be difficult to get the engine to idle well too.

It was the wrong plug and high %.

How are Megatech plugs?