I tried to find info about this very subject on the internet with no luck.
However, because it's called "Active Fuel Management," my guess would be it
simply shuts off 4 fuel injectors. Then the question arises, "what about the
compression of the four cylinders not receiving fuel?"
I haven't found any documents explaining exactly how the system works, but
if someone does, I would like to know as well.
OK, after a bit of googling, I found GM's 'Displacement on Demand' uses
collapsible/telescoping lifters which allow them to absorb the once-solid
drive from the cam thru the valves. Hence, during deactivation (4 of 8
available cylinders being used) every other piston in the firing order is
deactivated--the fuel & spark are cut off and the valves stay CLOSED. Just
prevents a compression stroke. Evidently, it takes a considerably small
amount of energy to allow these pistons to move up & down inside the
cylinder EVEN while the valves are closed.
Did I promise to shut up and sit back down? HTH, s
Did you find this article?
I'm still not sure what's going to happen inside that engine. In your note,
valves CLOSED, there will be compression and decompression on each stroke.
The air in the cylinder can function like a spring, except for leakage and
In the description I found, open vs closed is not specified. Clearly,
however, they're doing something a little tricky with the valves.
By the way, this:
mentions an all-aluminum engine. In a big behicle, like a Suburban, the
weight savings will be no big deal. However, it will be interesting to see
if this development moves down to smaller motors. I guess they've decided
that after 30 years, the memory of the Vega has been lost.
This describes it pretty well
they say the reason it works now is the throttle by wire so the computer can
adjust the throttle at the point it cuts the others in or out unlike the
old days where you would feel it.
Looks like it might not be too hard to retrofit to an existing engine.
Maybe hook up a switch on the dash and label it turbo boost or something :)
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