MDS system question

[Wagon Collector]

Hopefully this is the right forum for this question... I see there arent' too many posts here, so I'll ask my question here: I've read what I can find on the Multiple Displacement System, but I still can't figure out how it works. Maybe I'm just a bit slow :oops:

Anyway, I understand that the lifters sort of "bleed down," allowing the valves to stop moving. I also understand that the fuel and spark can be cut off FROM the the four cylinders that are shut down.

But here's what I don't understand. Once the valves are closed on the "dead" cylinders, how is the cylinder pressure releaved? You can't just have a piston moving up and down in a cylinder with no intake or exhaust valving. I would think that the valves (or at least the exhaust valve) would have to remain open. Does anyone know how this is addressed?

Thanks in advance to anyone who can get this theory through my thick skull

[liquid]

You can't just have a piston moving up and down in a cylinder with no intake or exhaust valving.

Sure you can. The trapped air becomes a spring for the pistons.