OK so now we are on the same track, lets investigate the issue of firing up two pots simultaneously as opposed to one:
On any engine, when the power stroke occurs it is not only applying force on the associated piston, it is applying force on all pistons via the crankshaft. So at any instant the mass of the all the pistons are being accelerated/decelerated. All will be experiencing different opposing forces due to valve position, side wall loading, compression, blowdown etc., but the piston mass will be be constant.
If indeed two pots were fired simultaneously the liberated energy would be roughly the same for the same power. It's questionable if there wouldn't be any
AFR change, because, say with a V8, it would be like two four pot engines sharing a common crankshaft.
The core of the claims 100MPGe is that the current control of the engines is so poor there is an opportunity for a manifold increase in efficeincy, merely by precise calibration. Somewhere I think he mentions factory engines have an efficiency of figure of 10% or 15%? That simply is not true. Simple maths tells otherwise..e.g.
lets say petrol has a specfic energy value of 35mJ/litre and an average specfic weight of 0.72. At 30% engine efficiency that works out to ~70mg/kW or 0.096cc/kW at stoich. Check that against the actual fuel rates currently required and it's pretty close. In other words significant gains in the order of magnitude claimed, just don't stack up.