Quote:
Originally posted by 928ram
Two questions I haven't found an answer for: How they overcome the drag of running the piston in a sealed cylinder, surely the valves are left partialy open; Does the deactivation alternate between (sets of) cylinders, it would almost have to or the 4 that run always would surely wear more.
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Drag? All you're doing is eliminating combustion. The cylinder is still lubed. The piston works against vacuum on the downstroke, but is aided by it on the upstroke. The net net is zero energy loss. (and before the physics guys have heart attacks, I KNOW some energy is lost to friction and air escaping past the rings, but this is negligible overall).
The deactivation is always on the same 4. THere isn't "additional wear". The active cylinders wear as if all were running. The inactive ones would wear minutely less because of the lack of combustion stress.