Point of clarification on compression ratios......
First rule, generally speaking
An increase of 1 point in compression = 4% increase in HP
Second rule
Manufacturers have shied away from high compression ratios because of two things, A) KISS engineering and B) The common use of regular or 87 octane gas
Current Efforts
The race now is to get major horspower out of small displacement engines. For example: 100 HP/liter was, a few years back a very respectable figure. For comparison the most powerful Chevy 350 engine was rated at 370 HP, that calculates to 5.3l/370 HP = ~ 70 HP/l, certainly not a high figure by the then standards. Today, most of the 600 cc bikes put out 110 HP and that calculates to ~ 183 HP/liter !!!!!
Of course to get that kind of output everything has to be optimized and high compression is one of the parameters.
The problems with high compression are varied, sealing (not a major obstacle with today's hard coatings and ring designs), temperature (better design of the water jackes and higher capacity cooling) along with squish and swirl of the fuel mixture.....here is where major gains can be made.
Combustion chamber design is a major engineering exercise considering that the bikes intended for public sale are not like race bikes that will have the engine torn down after three or four races.
So, in closing, cheap HP can be made with increased compression. as such cyclinder head design to manage and improve mixture squish and swirl are at the forefront of today's engine design.
