Hi,
I have posted a few times on this topic regarding the Papp engine. Now heres the thing - I think the papp engine is actually a water engine.
Regards using the piston as one electrode in discussions on this page, the Papp engine has 4 LARGE electrodes that protrude down from the underneath of the cylinder head into the combustion chamber .
In fact the papp engine pistons have 4 large hemispheres dug into them to allow for the protruding electrodes.
Could it be that we need this extra "oomph" electrically to get things happening? At a guess, if we are using 4 ELECTRODES, maybe we need that much contact with the water ( water/fuel mix ) using 4 electrodes instead of one normal spark plug, to get things going?
Just a thought....