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From: "Barry Gardner" <barrygardner@gmail.com>
To: "Rotary motors in aircraft" <flyrotary@lancaironline.net>
Subject: Fw: [FlyRotary] Re: Spark Plugs
Date: Sun, 19 Nov 2006 08:51:59 -0600
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Guys,

There's a diagram and discussion from Champion over at:

http://www.edelbrock.com/automotive/sparkplugs.html

Here's another discussion:

http://se-r.net/engine/specialty_spark_plugs.html

Bosch also apparently makes surface air gap plugs in their Platinum+4 and 
Platinum2 lines. I've not seen any of these plugs but they might be worth 
chasing. Here's Bosch's description of them:

"Q. What are the advantages of surface air gap plugs such as Platinum+4 and 
Platinum2?   A. To validate the improved performance of surface air gap 
plugs with a pure platinum core and multiple ground electrodes, extensive 
testing was conducted in the laboratory and in the field:
  a.. The first test measured the energy transfer efficiency of the 
four-electrode platinum plug compared to conventional and other premium 
plugs with a single ground electrode. This certified laboratory test 
measured the additional pressure generated by the spark discharge in a 
pressure chamber. Higher pressure equals a higher energy transfer by the 
spark. The test showed that the four-electrode platinum plugs transferred 
more energy to the air/fuel mixture resulting in improved driveablility and 
lower emissions.
  b.. As a spark plug wears via erosion and corrosion, the gap between the 
center electrode and ground electrode gets larger. The larger the gap, the 
more voltage is required to produce a spark, until the capability of the 
ignition system is exceeded and the plug misfires. It was found that the 
multiple ground electrode, pure platinum center electrode plug reduces gap 
erosion and increasing voltage requirements over time.
  c.. Roush Industries, an independent test lab, measured the fuel 
consumption for the four-electrode platinum plug, as well as, that for 
original equipment and other premium single ground electrode plugs. Fuel 
savings up to 4.8% were found in the four electrodes, platinum core plugs. 
Tests were conducted in accordance with Federal Test Procedure 75FTP and 
HFE.
  d.. Tests for carbon fouling were simulated in a cold cell by repeatedly 
cooling, starting and operating the engine without letting the spark plugs 
reach their self-cleaning temperature. This cycle does not let the spark 
plug reach its self-cleaning temperature and allows the formation of carbon 
deposits. The tests found that the four ground electrode spark plugs had up 
to 33% better cold restart reliability than conventional plugs."
Of course, surface air gap or not, the nose of the plug still can't project 
into the housing where it can be swept by the apex seal.

Barry Gardner
Wheaton, IL

>>
>> Anyone know whether these plugs are still available? It would seem that 
>> if nothing else, it might make cleaning the lead a bit easier.
>>
>> Charlie
>>
>>
> Actually,Charlie,  they still make them and they are available.  Jason had 
> them in his engine at Pecan Plantation.  I looked into using them but when 
> I read that one of the possible short-comings of this type of "surface 
> gap" plug was fouling, I decided not to even buy a set, but wait until 
> Jason reported back on how his were working out.  I agree they would 
> appear easier to clean once they fouled, but if they fouled twice as 
> readily, not much gained {:>)
>
> Ed
>
>
> --
> Homepage:  http://www.flyrotary.com/
> Archive and UnSub:   http://mail.lancaironline.net/lists/flyrotary/ 

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