Nomen Nescio wrote:


Quite simply, a piston on the down stroke (suck) has no idea why it's
on the downstroke. Is it being droven by a windmilling prop, or the other
cylinders firing? It doesn't know............it doesn't care.

For a given RPM and throttle setting, MAP will be a constant.



No, cause engines don't have 100% volumetric efficiency. On the exhaust
stroke, with combustion happening, there will be a higher volume of
exhaust, which is discharged less completely, resulting in less
intake... and a higher MAP when the engine is running compared to not
running (firing); RPM and throttle remaining the same.