......i have understood from the banter elsewhere that 1.2to1 PC was the standard Lambo figure and not 1.7 .....this figure is too high ........don`t you all think that 1.2 looks like 1.7 if read in a hurry ........for road racing a minimum geometric PC ratio of 1.4:1 is ideally required, 1.5:1 would be better which is more is difficult to achieve without more drastic measures.......because we are only dealing with points of a whole one the amounts removed from the crankcase are more easily achieved than first thought......with the tapering effect of the transfers is where a lot of cc can be achieved towards the LPC..... ....the true (or trapped) primary compression of the mixture starts not at TDC but when the back face of the piston closes the inlet port. The vast majority of the gas to be pumped up the transfer ports comes not from the crankcase but from under the piston as it descends, and the gas has to do a 180 turn to go up the best tapered transfers. Note that there is no pumping action from the crankcase. There is however a ramming effect from a correctly designed inlet tract which can greatly increase the gas pressure prior to primary compression starting..........by the way, i hope i am not included as a passer by, i did my apprenticeship with bikes in the early sixties and at Brands Hatch.........
PS
..........although the engine with the HPC ratio greatly increases the pumping losses and can decrease the power ....... a longer stroke unit that uses small transfer ports, even though pumping losses do increase there is an increase in power.........
