Quote:
Originally Posted by glazr69
When deactivating cylinders, the valves on the inactive ones are held open. This helps resuce mechanical losses, as you dont want to be compressing air on the compression strokes, and dont want to be creating a vaccum on what would be the combustion stroke.
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Not in GM's version. They keep the valves closed, so the air being compressed acts like a spring during piston travel to BDC. Supposedly, Chrysler's 5.7 V8 acts the way you described. And it seems to work better, because they're getting another mpg more out of the system.