Spark plugs

[Bruce]

From: <bill.shurvinton at nokia.com>
Subject: Spark plugs
> Back to DIY with a quick theory question on spark plugs. I was reading
> some conjecture
> somewhere that plugs with >1 ground strap actually shroud the spark and
> that you would get improved performance by grinding off the extra
> straps. Proviso being that if you go from 4 straps to 1 you also get a
> 4:1 drop in plug life.

If the erosion rate of the plug is what is limiting it's service life.

> On a related topic for those of us who are still new to the arcane arts,
> is there a good primer on how to tell if you plugs are too hot/cold.

Examine the center porclean to center electrode area, on a new plug,
closely, you'll notice no (most generally) bonding goo being exposed there.
If you used plug has the appearance of an excessive (any more then was there
originally), goo showing the plug is too hot.  If the side electrode has a
*fish scale* appearing blue / green hue to it it's too hot.   One other
sometimes is the rounding off of the center electrode quickly could be an
indicator of too hot of plug.
   If your absolutely sure of your AFR, and running conservative timing, and
your still seeing detonation sights on the plug, you might want to try a
colder plug.

>It seems to be one of those areas where it's deemed that if you don't know
> then you shouldn't be messing with them. All I know is that mine are
> well worn after 2000 miles, which seems to indicate something is wrong.

Rarely will going with a cooler then oem plug cause you any serious grief.
If in doubt, just try a set, and then pull em and take a look.  If motor get
real cold blooded, ot the plugs are too dark well, the warmer ones were in
fact right.

All spark plugs do is supply an air gap for where a spark may occur.  They
vary in design and materials, but when all is said an done, that's it.  A
plug will erode.  Bits and ions are generated from the material for the
spark to follow.  A **soft** easily erodable plug will do that well.  But
life will be short.  A harder plug will require a little longer for the ion
path to occur, and require a slightly higher voltage for it too happen.
   All any plug can do is help compensate for a poor ignition system.   If
the basic system is fine then you should be able to run a hard material
plug, just fine (Autolite).  In hardness of side eletrodes in conventional
plugs you have Autolite, AC, and then the others.  On a street car projected
nose plugs will help with being resistant to fouling.  On a hypo engine you
want to get the center electrode out of the chamber so it doesn't help
introduce any detonation.  If someone get the systems right would be nice to
have surface gaps plugs.   Problem with most (if not all) surface gaps is
that they have so little heat in them that they can foul easily.  A fast
rise ignition system can help min that.
Bruce

 Note:  The sender is not responsible for your interest or lack thereof in
the contents of this posting.  The Warning is included in part to ensure
that people who ARE NOT LIKE ME are in no way offended or disadvantaged.


> Rgds
> Bill


----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org