Combustion chamber & twin plugs

[jac at wave.sheridan.wy.us]

I have added an automotive type plug to some 
single plug Continental ground power unit heads. 
It is possible to install the new plug much 
closer to the center of the combustion chamber 
that the standard location of the large aircraft 
plugs.

These jugs were used one generators that 
serviced aircraft.  They were built with a 
different intake and exhaust orientation but are 
very similar otherwise.  They bolt up exactly to 
aircraft crankcases. The Continental GPU jugs 
were built with a single ignition.  The plug is 
located in the same place that it is for the 
aircraft version.  

With the more centrally located plug in 
operation, the RPM drop from switching the 
aircraft plug off is almost negligeable.  The 
drop from switching the central plug off is 400 
- 500 RPM.

I don't think that it is reasonable to expect as 
anywhere near much power gain from adding a plug 
to a system designed with one plug, as there is 
power loss when a plug is removed from a two 
plug system.  It is important to remember that 
there is no advance adjustment at all in the 
aircraft magnetos under discussion.



john carroll
jac at wave.sheridan.wy.us
 
---------------Original Message---------------
> All piston aircraft engines from about 1915 on 
have twin plugs per 
> cylinder.  Switch one set off - engine RPM 
drops about 500 rpm or
> so.  Must contribute both to power and 
reliability.  Just part of the
> background on why I want a bigger flame.  (in 
the combustion chamber
> - remember I have asbestos pampers)

Piston Aircraft have a complete duplicate 
ignition system in case the
first one fails.

Does anyone know what had to be done in order to 
make a twin plug head
still work with 1 plug?


	RF.

-------------------------------------------------
------------------------
83 R100			DoD 749			
Robert Fridman
84 320i						
fridman at cpsc.ucalgary.ca


----------End of Original Message----------



-------------------------------------
john carroll
 jac at wave.sheridan.wy.us