At the extremes - if you are getting detonation because the plug tip
continues to glow, go colder. If they are fouling (like with oil),
go hotter. Had a motorcycle that burned oil that would start running
on 3 of 4 cylinders unless I ran hotter than stock plugs to keep the
oil burned off the tip.
Tony
At 09:52 AM 4/24/2015, Barr, Scott via Fot wrote:
>So, if the plugs are too dark despite your EGTs and/or air-fuel
>meter showing the mixture is good, would you move up a heat range?
>
>If not, what would indicate a need to change the heat range of your plugs?
>
>Scott (B.)
>
>-----Original Message-----
>From: Randall [mailto:TR3driver@ca.rr.com]
>Sent: Friday, April 24, 2015 8:31 AM
>To: Barr, Scott
>Subject: RE: [Fot] Spark Plugs
>
> > OK, so here's the stupid question of the day - what is it that makes a
> > hot plug "hotter" or a cold plug "colder". Is a "colder" plug more
> > resistant to absorbing heat? And if so, why?
>
>Basically, hotter plugs have more (thermal) insulation between the
>tip and the shell. Do a quick Google and you'll find lots of
>diagrams showing the longer/shorter path for the heat to follow.
>
>The reason for the differences in heat range (hotter or colder) is
>that the plug tip needs to get hot during operation, to burn away
>and prevent combustion deposits from fouling the plug; but not too
>hot. Stock engines tend to have relatively low temperatures in the
>combustion chamber, so use a hotter plug to avoid fouling. As the
>engine is modified for more power, the temperatures go up, and a
>colder plug is sometimes needed to keep the plug from
>overheating. Too high a temperature at the plug tip can damage the
>plug, but more importantly also lead to detonation. The plug tip
>can get so hot that it lights the mixture early (before the spark
>happens), causing loss of power and even engine damage.
>
>I also found that, with the MSD 6 ignition, colder plugs would last
>longer on the street, but of course that's not an issue with a race car.
>
>-- Randall
>
>_______________________________________________
>fot@autox.team.net
>
>http://www.fot-racing.com
>
>Donate: http://www.team.net/donate.html
>Archive: http://www.team.net/archive
>Forums: http://www.team.net/forums
>Unsubscribe/Manage:
>http://autox.team.net/mailman/options/fot/tony@tonydrews.com
_______________________________________________
fot@autox.team.net
http://www.fot-racing.com
Archive: http://www.team.net/archive
|