Terence,

whether it is engine or prop
rpm


They are connected at a fixed ratio (1:1 on direct drive engines), so
the distinction doesn't matter.

May I recommend John Deakin's engine management columns at avweb.com to
shed light on this? They are priceless in understanding your engine,
specifically these four:

Pelican's Perch #15:
Manifold Pressure Sucks!

Pelican's Perch #16:
Those Marvelous Props

Pelican's Perch #18:
Mixture Magic

Pelican's Perch #19:
Putting It All Together

http://www.avweb.com/news/pelican/182081-1.html
http://www.avweb.com/news/pelican/182082-1.html
http://www.avweb.com/news/pelican/182084-1.html
http://www.avweb.com/news/pelican/182085-1.html

--
Thomas Borchert (EDDH)