Ed, thanks for that article.
I installed the hotter plugs, BUR6EQ leading and BUR8EQ trailing a
month or so ago.
I guess I'll have to start burning 100LL to see if it fixes the fouling
problem.
I usually only burn it when I'm travelling and have no other choice,
but don't have any trips planned soon.
For me, it only takes 4 hours of continuous 100LL use to get SAG and
fouled leading plugs on the next takeoff.
Is there any data anywhere that might tell us what temperature BUR6EQ,
7EQ, 8EQ, and 9EQ plugs operate at in an RX-7?
Perry
http://www.ductedfan.com
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Regarding spark plug fouling, I knew I had come across an article that
indicated achieving certain minimum temperatures was a key factor in
improving (lessening) the fouling of spark plugs. IT sure seems that
hotter plugs may be part of the answer.
Ed
Here is the URL for that article in case
anyone is interested
..........Operating temperature of the spark plug insulator core
nose is one factor that governs formation of troublesome combustion
deposits. To help overcome this problem, selection of spark plugs with
the proper heat range should be made. Spark plugs are susceptible to
carbon deposits when the operating temperature of the core nose
insulator is at or below 800o F, but an increase of just 100o F is
sufficient to eliminate formation of these deposits. Also, lead
deposits form because the bromide scavenger contained in tetraethyl
lead is nonactive at low temperatures. At 900o F temperature, the
bromide scavenger is fully activated, disposing of lead deposits with
combustion gases during exhaust cycle. In this case, an increase of
just 100o F was sufficient to make the difference between a smooth and
rough running engine. To eliminate or keep this problem at a minimum,
avoid prolonged idling at low RPM, avoid power-off let downs, and after
flooded starts run engine at medium RPM before taxiing.
Deposits formed between 1000o F and 1300o F are low in volume
and electrical conductivity and are least apt to cause spark plug
fouling. This is the reason for selecting a plug that will operate
within the aforementioned temperature range at all power settings.
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