The work of Michael May has always attracted my interest. When we study
burn patterns left on combustion surfaces, it becomes obvious that heat has
a huge impact on combustion. May devised a clever way to combine this with
mixture motion, it was promising enough to make it into production. Personally
I believe the concept has huge potential if further developed. If anyone has
more information on his work let me know.
It's difficult to find much information on the design, I thought you might be
interested in the views of one Jaguar power train engineer:
"I'm quite familiar with the May Fireball head. Over here on 5 star 100 octane
fuel that engine was supplied with a 12.5 : 1 CR in production!
In retrospect however we've moved on: although that chamber had good
initial burn characteristics, (0-10 %), later in the cycle it didn't burn all that
fast. Also, that engines CR made it supremely suitable for part load
operation, but it was quite knock limited all the way up the rev range even
with quite modest VEs at WOT. For after market performance applications of
this engine I recommend using the flat head as the ports flow better then
thge swirl inducing May ones.It should be noted that one CAN have too much
of a fast initial burn that leads to knock also!"
"I think squish/quenching the intake side of the chamber the way the Jag may
head did is actually good for combustion stability. This means the engine can
run lean and still remain stable without running into the lean misfire limit. In
modern day terms it can also mean that the engine can have a high EGR
tolerance at part load and still have stable combustion-again good for fuel
economy if you design your package to take advantage of this."
"In terms of tumble, swirl and squish-for me squish is used in tandem with
tumble. Swirl decays less then tumble ( as the piston comes up)and isn't
so confined and contrained to peak gas velocities during the intake stroke.
squish can be used to make the tumble motion into smaller eddies -which is
ideal to speed up combustion in some situations."
"Squish on its own, as here doesn't necessarily do much (It takes place too
late in the cycle and the speed at which the crown approaches the head at
lower engine speeds is fairly slow). In practice this may seem rather vague,
as it often is with combustion, it's alot less clear cut even in terms of trends
then something like maximizing your VE for full load performance."
"To be fair to the old May head -in the V12 it was barely lower then the more
conventional flat head design in terms of outright WOT performance -but this
was WITH the high CR versus the lower CR!"
