In making head buttons for your engine, the configuration
of the Squish Band is a PRIMARY CONSIDERATION. You also need a squish
velocity sufficient to create a strong plugging effect toward the center of the
combustion chamber. The velocity of the squish charge accelerates
at the top of the combustion cycle and the maximum squish pressure
ratio is developed at about 5-10 degrees before top dead center.
The maximum squish velocity AND the maximum squish pressure MUST
occur at between 5 and 10 degrees before top dead center for maximum power. How
much squish velocity should you look for in your engines? My
21 Nova Rossi has a maximum squish velocity of between 55 and
60 Meters per second (Why the metric measurements? - The Blair software uses the Metric measurement.).
My engine specs for the Nova Rossi 21 yield
a Squished Kinetic Energy of .73 mj. This really tells you the
amount of power that the squish band is producing in the total
picture of the combustion chamber. I run a trapped compression
ratio of 10.3:1 and exhaust timing of 183 exhaust open at 88.5 degrees
after top dead center (This computes to an open duration of 183
I calculate that my MAXIMUM engine RPM is approximately 34,000
RPM. I use a squish area ratio of 65% of the total bore (In
other words I look for a squish band that represents an area equal
to 65% of the total bore area). How do I know that these figures
are what I have on my BEST engine? I applied the Engine Analysis software
and the software from Dr. Blair, to my engine specifications, to document my BEST engine.
The Blair Software and The Engine Analysis Software
will solve the complex formulas necessary to do this documentation!
The Blair Software adds further refinements to my knowledge base in
addition to the documentation of the base engine in " The
Engine Analysis Program".
I can build as many engines as I want, that are equal to my BEST engine with the use of these
two most valuable tools. Anyone who know me well, know that
I try to make it possible to "duplicate successes"! (This is not to say I don't learn from failures - quite the contrary,
I probably learn MORE from my failures!).
What do I mean by that? I want to be able to duplicate my best
engine, my best prop, my best pipe setup and my best boat setup.
There are "WAY TO MANY" variables in model boating (and model
car racing) to be able to keep up with them without tools for
I have developed " The Engine Analysis Software"
and " The Prop Duplicator" to do this for me. I knew
that it would be helpful to everyone(a necessity to some). You can have
both of these aids from MWD & Associates. The Blair book & software can be purchased from SAE (Click Here