'Blackburn Cycle' advantages
Ideal combustion mixture is maintained from idling speed up to half load. Each cylinder contains an ideal charge of 1:14 fuel/air with no exhaust gas from the previous cycle.
Faster combustion, Exhaust gas which slows combustion is removed. Faster combustion can start and finish when the piston is nearer to TDC, when the effective compression ratio is higher. There is less negative work as the combustion pressure increases before TDC. The full pressure after combustion is effective earlier, on the power stroke, to do more useful work.
Combustion temperature increase, the 'air only' cycles removes all incombustible exhaust gas, allowing a higher combustion temperature increase which helps fuel efficiency in theory and practice.
More complete combustion, more air and oxygen in the cylinder and a higher temperature and pressure.
Charge cooling, the maximised alternate 'air only' 4 stroke cycles in each cylinder in turn, gives a lower temperature at the start of the cycle, this increases efficiency like a very effective intercooler.
Raised compression, for half load in BC mode, the inlet is fully open. This gives full compression when the 4 stroke throttle is half closed causing about half compression pressure.
Lower pumping losses, for half load BC mode, the inlet valve or throttle is fully open with no inlet vacuum. There is also no throttle and no vacuum for the 'air only' induction for all speeds.
Less heat is lost to the cooling system, with half as many combustion cycles for cruising and idling, there is half the time for heat to drain from the charge to the cooling system.
Gains in 4 stroke mode, for 51% load BC uses the 4 stroke cycle with 100% load on one cycle and 2% load on the next cycle etc. This averages at 51% load but allows 98% of the fuel to be burnt at 100% compression and load, rather than 2 combustions at 51% load in the usual 4 stroke.