You've got that completely backwards.amr wrote: ↑27 Apr 2018, 10:43You have to deactivate the valves in the open position, otherwise you will have pumping losses. Imagine you deactivate the cylinder after the intake stroke, with all valves close, in the compression stroke you will have pumping losses. Next , in the what should have been a power stroke, the pressure (which is atmospheric pressure if is normally aspirated or maybe double if is turbo, multiply by the compression ratio) is too small to do meaningful work and compensate for the pumping loses.
That is because the crank shaft will spin faster then what the pressure in the deactivated cylinder can achieve. The piston is pull down by the inertia of the flywheel/other cylinder work faster than it is pushed by the pressure in the deactivated cylinder.