False reasons for rejecting the 'Blackburn Cycle'
With 8 strokes in the cycle there is more friction - The only way to get more strokes and friction is to change the overall gearing. This is obviously not needed and not done. There are simply half as many combustions for cruising and idling. One full power 8 stroke 'Blackburn Cycle' gives the same power and speed as two half power 4 stroke cycles for cruising. The important aspect is friction losses per mile. Friction per combustion is not relevant while cruising. If pumping losses are included with friction, total mechanical losses are less than 4 stroke.
BC is the same as Cylinder de-activation - Both systems reduce the number of combustions and raise the compression pressure while cruising but there the similarity ends. The 'Blackburn Cycle' is totally different and much more fuel efficient than the 4 stroke cycle which is always used by Cylinder De-activation.
Lean burn increases 4 stroke fuel efficiency, while BC runs richer - Lean burn has two effects on 4 stroke engines. Excess air cools the charge at the start of the cycle which helps efficiency, but also cools the combustion temperature which is unhelpful. 'Blackburn Cycle' already has a cool charge due to the alternate cool 'air only' inductions, so there is nothing further to gain from lean burn. All heat engines achieves maximum efficiency with a high combustion temperature. This is why 'Blackburn Cycle' achieves maximum efficiency in theory and practise with a stoichiometric fuel/air mix.
Emissions - Higher temperature and pressure combustion is more efficient with lower HC, CO and CO2 but produces more N0x. There are several N0x exhaust solutions including urea/Ad Blue. Alternate opening exhaust valves allow usual catalytic converters to be used. For low power the exhaust is like Diesel, with excess air but with less smoke and particulates. Total CO2 is about the same as electric vehicles where power is generated by oil/gas/coal.
Roughness - 'Blackburn Cycle' may benefit from torque smoothing but this presents no problem. It is smoother and quieter than Diesels.
Heat Engines - More heat is not always helpful. Heat from the exhaust is not used to preheat the air entering the engine. Homogenous Charge Compression Ignition (HCCI) was claimed to make petrol engines more efficient like Diesel. However, HCCI has dispersed, diluted, slow and incomplete combustion with a high temperature at the start of the cycle and a low heat added by combustion. 'Blackburn Cycle' is the opposite of HCCI with fewer more efficient combustions for cruising with a low temperature at the start of the cycle.
There are no valid reasons to reject the 'Blackburn Cycle'.