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Date: Thu, 23 Nov 2006 19:00:49 -0600
From: Charlie England <ceengland@bellsouth.net>
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To: Rotary motors in aircraft <flyrotary@lancaironline.net>
Subject: Re: [FlyRotary] Re: Spark Plug Fouling and Temperature
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Perry Mick wrote:

> http://www.ngksparkplugs.com/techinfo/spark_plugs/overviewp2.asp?nav=3D=
31000&country=3DUS
>
> "the spark plug tip temperature must remain between 500C-850=B0C. If th=
e=20
> tip temperature is lower than 500=B0C, the insulator area surrounding=20
> the center electrode will not be hot enough to burn off carbon and=20
> combustion chamber deposits. These accumulated deposits can result in=20
> spark plug fouling leading to misfire. If the tip temperature is=20
> higher than 850=B0C the spark plug will overheat which may cause the=20
> ceramic around the center electrode to blister and the electrodes to=20
> melt. This may lead to pre-ignition/detonation and expensive engine=20
> damage. In identical spark plug types, the difference from one heat=20
> range to the next is the ability to remove approximately 70=B0C to 100=B0=
C=20
> from the combustion chamber."
>
> http://www.sacskyranch.com/eng23.htm
>
> "Also, lead deposits form because the bromide scavenger contained in=20
> tetraethyl lead is nonactive at low temperatures. At 900o F=20
> temperature, the bromide scavenger is fully activated, disposing of=20
> lead deposits with combustion gases during exhaust cycle. In this=20
> case, an increase of just 100o F was sufficient to make the difference =

> between a smooth and rough running engine."
>
> Lynn: it sounds like I might be risking detonation by using BUR6EQ-L=20
> and BUR8EQ-T instead of stock BUR7EQ-L and BUR9EQ-T? Maybe with the=20
> hotter plugs I SHOULD  burn higher octane fuel?
>
> But since I experience lead plug fouling with 100LL, wouldn't that be=20
> an indicator the stock plugs run too cool? It appears air-cooled=20
> aircraft engines might tolerate higher spark plug temperatures, maybe=20
> because of higher octane fuel? NGK says 850C max, while Skyranch says=20
> it takes 900C to avoid lead deposits.
>
> Race car guys don't use leaded fuel anymore?
>
> Perry


The quote for carbon uses C; the quote for lead uses F. Is one  a typo?