Re: Spark Plug Question

[Priit Varik <Priit.Varik@xxxxxxx>]

Hi,

>indexing?  Maybe plug life?
>I suspect the latter.
>Anyone know for sure why BMW picked this plug type?

The Service bulletin in TIS says about this topic following.
(Sorry for english, as this text is translated from german by http://www.freetranslation.com/)
I quote:
\"With the new 3-series E46 a \"Longlife\"-Spark plug was released for the first time. As of model year 1999 also other BMW models are equipped with this spark plug.  In addition these sparks plugs can be used from immediately for certain motors (see retroactive releases). This new spark plug has following construction features:
- - four ground electrodes
- - middle electrode with platinum disk
- - semifloating spark technology
In this technology the electrodes are arranged so that the spark glides always over the insulator, before it jumps.
Herewith soot deposits are worn out and dropouts caused by short circuits are avoided. The spark jumps to the ground electrode always at the place, where the most favorable conditions for the combustion rule. Therefore a uniform wear of all electrodes is achieved over the total service life. The platinum disk on the middle electrode offers high stability against spark degradation.  
This Design enables a constant optimal function during the total operation time between the change intervals. Advantages of the semifloating spark technology:
- - outstanding cold start characteristics.
- - better inflaming characteristics, resulting in high idling quality and improved acceleration behavior.
- - no dropouts in load change or WOT.
- - highest ignition security also in extreme short stretch and stop & go traffic offers protection from catalyst damage.
- - constant optimal function during the total running time.
- - up to double service life depending on engine model.
- - high security reserves in aggravated applications.\"

So, the double service life is listed among the reasons.

Priit

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