thermocouples and mixture.

[Edward Hernandez R]

"If combustion is taking place in the converter, (the mixture is rich)
the outlet sensor will probably be the hotter of the two and visa
versa."

Rich mixtures do not raise catalyst temperatures, they lower them.
It's a well known fact that this is how OEMs make cats last longer.

"Now both two-strokes and rotaries have more power 'strokes' than
four-stroke motors.  Is this significant?  What does it mean vis-a-vis
four-stroke engines?"

It means that the plugs are colder and would likely foul if used in 
a car engine. I think somebody mentioned they couldn't find ones
hot enough for a car. PS for the person who suggested that this kind
of plug may alter the shape of the flame: the flame front is a dis-
torted sphere(depending on how much swirl is in the chamber at igni-
tion). Plug design does not affect this shape, but it can affect the
the shape of the kernel right at ignition. Kernel shapes and growth
rates affect how lean you can run before you misfire(lean limit), but
not power or anything a DIYer(who normally runs rich to be safe) might
care about.

Ed Hernandez
Ford Motor Company
ehernan3 at ed8719.pto.ford.com