KDXRIDER.NET

Now where did all this come from? CC causing trouble with my explaination. I guess I should have included the "where the heat goes" section to my post. I'll have to watch my step from now on!

Not at all Rob.
One of the goals on this site is to get as much information as possible. With the visual representations and explainations, you have to admit... everything is much clearer to everyone.

Good read!! Keep it up guys.

With all this team work the questions have been answered!! I bet we all learned something about the spark plug today

I sure did! That's why I like it when a bunch of people ask a question, share their point of view, etc. One thing can cause another person to ask/say something which causes another person to learn.


EVERYONE can contribute something, no matter how small and whether they know it or not.

This was actually a great discussion with excellent information. Hard to believe a little spark plug can do so much. I was surprised by the volume of great info posted since I last check the thread.

Inda, thanks. I was actually joking about the watching my step. CC does a great job playing devils advocate...and he was correct in his assessment that only a portion of the info was presented. At the time, I assumed I had presented enough info to clarify the spark plug issue. You know what happens when you assume! It's always good to have a second or third perspective to look at things from a different angle. Great job on this thread guys!

Later
Robb

Re: Pictures, circles and arrows, etc....

Nothing new in any of that...nothing I haven't read many times. Understood just fine, too.


Still doesn't answer the question. Consider: A change from a '7' to an '8' plug will cause more heat, 70-100ºC, to be transferred to the head/water jacket.

So...switching to a colder plug makes the engine coolant temp run hotter?

My infrared temp gun, gurgling noises from the rads and a spitting overflow tube tell a different story. Saying 'A '7' runs hotter than an '8',' says EVERYthing engine-wise runs hotter.

You don't find a heat range that ends up looking good. You choose the heat range to match the engine characteristics and then jet to make the plug look good (WOT plug chops..otherwise by response/performance).

NGK tech wrote:When a manufacture (sic) selects spark plugs for an application they perform a series of pre-ignition tests. The spark plugs used have thermal couples built into the center and ground electrodes. This allows us to read internal firing end temperatures of the spark plug. Based on the engine design i.e. compression, fuel and timing we can determine the correct spark plug for the application.

...but that's beside the point.

I'm referring to 'heat removal' of the plug and engine/coolant temp.

Who wants to tell me that a colder plug makes an engine run hotter?

If a colder plug is removing heat from the firing chamber, (and I belive it is) then, like the diagram shows, it is going out to the head and to the air. Removing the 100 degrees or so from such a small volume and mass as the compressed combustion chamber can't be that much heat. I would have to see a BTU rating of heat exchange to deside if it's enough to notice a rise in coolant temperature.
I'm guessing the volume inside the combustion chamber is about 15 to 17 cc's and a compression rate of what? 11:1. That volume of gas isn't holding much BTU's in the 100 Degree (or less) delta.