Date: Wed, 03 Dec 2003 03:54:57 GMT
From: "Hyperdog" <>
Subject: Re: NGK Spark Plug Question

The variable here is the number that NGK uses to rate the "heat" of the plug. A "hot" spark plug will have a deeper recessed "groove" separating the center porcelain core insulator from the steel, threaded shell. This empty space becomes filled with intensely hot gas upon combustion and, with limited paths to export this heat, the tip of the plug remains hotter than a similar plug constructed with a more shallow "grove". Hot plugs stay cleaner. The objective is to run the hottest plug you can with out the porcelain turning "toasted brown" after hard driving. DANGER. Run a too-hot plug for too long and you destroy pistons (Rare). If you use high octane fuel you can run a hotter plug. If you drive HARD use a colder plug. All the plugs you listed are "mid range " plugs. Not "cold" (racing) plugs or hot (anti-oil-fouling) plugs. With NGK, the LOWER the number the HOTTER the plug. Opposite with Champion. Check your plug's color. Black or nearly so... too cold. Toasty brown.....too hot. Warm tone of light grey....juuuuuuuuust right. HINT: If your '91 uses a distributorless direct ignition system, do not use BOSCH Platinum Plus plugs!! They eat ignition cassettes. I learned the hard way. Twice. Fool me once, shame on you. Fool me twice, shame on me. Hyperdog "jon banquer" <> wrote in message news:bqbh7d$1vnhrd$ > What is the difference between NGK BCP5EV, NGK BCP6EV and > NGK BCP7EV ? > > I have a 91 900S 16V non-turbo. The car currently has BCP6EV's. > How do I know which one is right ? The car is completely stock. > > jon > > >

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