Originally posted by click, dublin
Hi,
A No. 8? I could not get the engine to run on a 6, a 7 seemed even worse?
In my case TopGun suggested I go down to a 5 or even a 4?
I thought the higher the number the colder the plug. You tend to run 7 & 8 in .21's
I've always run 6 in my .12's because they tend to need a hotter plug.
I thought the lower numbered plugs have a thinner wire which get hotter which tends to be needed in a .12 because of the small compression & most run 16% fuel.
With the .21 you have higher compression & most run 25% fuel so you don't need as hot a plug.
Have I got this right or am I completely wrong??
All the above relates to Novarossi glow plugs.
Thanks in advance
Hi Kevin,
You are right in your theory. Most .12's do require a hotter plug and on my RB I was using a No. 3 OS Plug.
However, when you remove a shim you increase the compression level and induce pre-detonation. To counter this you need to put in a colder plug.