Hi Everyone,

I am running a SC 15 with a #8 plug on 20% nitro and a 6.5x5.5 APC. The glowplug was new and after about 1 and a half hours running It stopped working. On closer inspection I found the element was slightly white.
Any ideas?

Stefan

If this was the engines first glow plug that will happen sometimes. During engine break in small particles of metal fuse themselves to the glow plug wire. Next plug should last longer.

Glow plugs when new have a nice shiny glow wire. As they get older the wire starts to look like it has an aluminum coating on it and that's when they start giving you problems.

As Mettler says, the one thing that will kill a plug is getting a tiny bit of aluminium on the element. This could be either from some swarf or from running in. For that reason you should always use the oldest plug you've got when running in. But in your case it might just be that the plug is too hot for the amount of nitro you're using so try one that's a little colder next time. You really need a tacho though because the best heat range plug is the one that gives the highest revs.

If you are getting more than 2 flights out of your glow plug on 20% nitro, you are not pushing hard enough. I presume that being you are running a prop of less than 7 inches, you are going for maximum speed from your plane like in racing. It is not uncommon for engines being run hard to also be hard on glow plugs. I used to only get 2 to 3 flights out of a plug in my K&B Cox Conquest on 10% nitro turning in excess of 26,000 RPM. The prop was a 6 5/8 by 4 1/4 hand laid glass prop.

Hi!
You run 20% nitro in your SC .15 but in most sport engines one must add a headshim (0,1mm) or more when the nitro content goes over 15%( the nitro rises the compression ratio too much). Have you tried adding a shim?
Also when using so much nitro the OS 8 glowplug is much too warm ...try a colder plug!


Regards!
Jan K
Sweden

Thanks a lot for all your replys.

I think I will try a colder plug next time. The engine is about 2 years old so is definatly run in. Yes i am using it in a wildthing for club racing so I cant expect too much life from them.

Stefan