How does displacement on demand work? Do the pistons actually stop moving in the cylinders? Do the valves stop opening and closing? What gives?
Now called Active Fuel Management, General Motors previously used Displacement on Demand as the name for its cylinder-deactivation feature, which disables cylinders for better fuel economy, meaning a V-8 can effectively run on four cylinders at highway or cruising speeds. Other automakers have features that do the same thing, like Honda’s Variable Cylinder Management.
Active Fuel Management does, in fact, stop the valves from opening and closing. The pistons are still moving inside the cylinder walls, but the valves have been disabled and remain closed on half of the engine’s cylinders.
GM’s cylinder deactivation system is found on V-6 and V-8 engines in GM trucks and SUVs, including the Chevrolet Avalanche, Silverado, Tahoe and TrailBlazer; GMC Sierra, Yukon and Envoy, and the Saab 9-7X. It’s also used on cars, including the Chevrolet Impala, Buick LaCrosse, Pontiac Grand Prix and Pontiac G8.
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look in the first ilike to say every car maker had astratgy and policy to make cars get economic melage fuel consumptions and saaab as example had movable head cylinder
and honda vtec motors was had diffrant timeng to cam shaft working and mercedes benz was make valves changing timmeng to open and shut intake valve and exhust valve bydiffrant way to make the v12 engine to decreasing fuel consumptions into qrawded streets in town or city looks like 6 cylinder engines only and in hight way its turn into it self as av12 engine powerfull to get it completly hourse power finaly i like to said its all talent idea to best performance without hight coast or polluotions .
In another site, two statements were made that sounded contraditory to me. I had written them but I thought that I would leave these with you for your assessment.
The statements are: “activate specially designed lifters which prevent the valves from opening,” and then “Also the 'dead' cylinders don’t drag energy from the working four, due to air being pumped through those cylinders that are temporarily out of action.”
It looks like they agree with you on the matter of keeping valves closed when cylinders are deactivated, however, what about this air being pumped? Through what? Closed valves or is there something else or maybe no air is pumped. If the latter, then the engine will probably experience some compression cycles, thereby robbing power. What don't I understand here?
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look in the first ilike to say every car maker had astratgy and policy to make cars get economic melage fuel consumptions and saaab as example had movable head cylinder
and honda vtec motors was had diffrant timeng to cam shaft working and mercedes benz was make valves changing timmeng to open and shut intake valve and exhust valve bydiffrant way to make the v12 engine to decreasing fuel consumptions into qrawded streets in town or city looks like 6 cylinder engines only and in hight way its turn into it self as av12 engine powerfull to get it completly hourse power finaly i like to said its all talent idea to best performance without hight coast or polluotions .