Bosch spark plug deciphering

[C1J1Miller at aol.com]

You are not interpreting the spark plug heat range correctly.  The plugs don't make the cylinders run hotter or colder.
The temperature range is refering to the temperature of the plug.  If the plug gets too hot, you can have autoignition (bad thing, especially if the engine management is trying to suppress spark).

Bosch does an ionic current test with the engine on a test stand, looking for highest operating temperatures over long periods of running.  Be careful when arbitrarily changing plug heat ranges...
Chris


In a message dated 5/2/2003 3:09:21 PM Eastern Standard Time, bradym at sympatico.ca writes:

>
>
> Why not stick to what the manufacturer recommends? I would if the engine was
> stock (Lehmann ECU and more boost) I also took some advice off the IA site
> (Ned suggests W7DTC) and I wanted to know of the plugs were hotter or colder
> than stock.
>
> According to what you quoted, I think Bosch has reversed the definitions of
> hot and cold plugs. I always thought that a cold plug kept the combustion
> chamber colder, and therefore had _high_ heat absorption ability???!
>
> Cheers,
> Brady Moffatt
> Montreal, Quebec, Canada
> 83 UrQuattro with 51,000 miles
> 86 4ksq with 309,000km
> 86 4ksq parts car
> 72 Datsun 240Z with 180,000 miles
> 92 VW Golf with 200,000km FOR SALE
> in middle stages of quattrosis accumulatus
>
>
> ----- Original Message -----
> From: <C1J1Miller at aol.com>
>
>
> > Bosch says "...a low heat range number indicates a "cold plug" with low
> heat absorption through its short insulator nose.  A high heat-range code
> number applies to a "hot plug" with high heat absorption through it's long
> insulator nose"...
> > So, 2-4 is cold, 7-10 is hot...
> >
> > why not stick with what the manufacturer lists?
> > Chris
> >
> >
> > Brady Moffatt writes:
> > -----------
> >
> > Hi All,
> >
> > Is a 7 a hotter plugs than a 6 in Bosch-speak?
> >
> > I was just at the NGK site www.ngk.com . In NGK-speak, a higher number is
> > colder (dissipates more heat).
> >
> > Cheers,
> > Brady Moffatt