Thanks, Mike. I experienced some raised eyebrows when I read this passage,
too. A spark
plug has just a (relatively) small copper wire down the center, which would
act as just about the sole conduction path for heat for the plug, as
compared with just more cylinder head. Where does this wire (which by the
way is a lovely heat conductor) lead? To the spark plug wire. Which is NOT
a good heat conduction path. The rest of the plug is typically iron or
steel which doesn't conduct even as well as your aluminum cylinder head.
So I have to say the plug likely conducts very little heat. The only heat
conduction path that has any potential puts the heat right into your
distributor, which is not where you want it to go. So, I'm going to make a
stretch here and say the idea that your spark plug acts as a heat conductor
is totally incorrect.
What is more likely is that your spark plug sticks out into the combustion
environment and so gets a lot of heat loading. This plug will eventually
come up to an equilibrium temperature that is a function of its thermal
resistance to the prime thermal sink in that part of the engine, which is
the cylinder head (and from there into the water jacket). So a "hotter"
plug will likely have a higher thermal resistance and will have a higher
equilibrium temperature. So the function of the plug is NOT to conduct heat
out of the combustion chamber, but part of the function of the plug is to
conduct heat out of ITSELF so that it operates at a temperature that is both
efficient and not conducive to pre-ignition.
This is just an engineer's assessment. As always I have to defer to Mike
when it comes to how things REALLY work.
Dave
-----Original Message-----
From: mike kojima [mailto:[EMAIL PROTECTED]]
Sent: Sunday, May 20, 2001 11:08 PM
To: Sentra Mailing List
Subject: Re: SML-NON-P: spark plugs
The amount of heat that the plug removes from the
chamber is not signicant, a colder plug has a shorter
conducting path from the center electrode to the plugs
main body. Thus the center electrode runs cooler.
You can see this if you look at a hot and a cold plug
side by side. The center electrode of the cold plug
is much shorter when you look down into the plug body.
Remember, this sight is funky translated Japanese
english.
Mike
--- Jason Bosaw <[EMAIL PROTECTED]> wrote:
> Oh shit! I was just looking at the site to confirm
> what I thought I
> understood. I had it backwards. The 6 will take more
> heat out of the
> chamber. The NGK site does confirm that a plug's job
> is to dissipate heat
> though.
__________________________________________________
Do You Yahoo!?
Yahoo! Auctions - buy the things you want at great prices
http://auctions.yahoo.com/
+----------------------------------------------------------------------+
To unsubscribe, put "unsubscribe" (by itself) in the subject and send to
[EMAIL PROTECTED] or use the form at http://www.sentra.net/sml
+----------------------------------------------------------------------+
Have questions about your car? Try here: http://www.sentra.net
