New Chevy

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.

Steve

It has hyd actuators that open the intake valves too when cylinders are cut off. It is a remake of the system that they used on caddies in early

80's that they gave up on and are trying again.

It is even simpler than that. The microprocessor simply cuts the spark and fuel to the cylinders, same as with the Chrysler system

mike hunt

I'm gonna research later, but I believe it would just about have to keep open a valve(s) to keep load off crank caused by providing a compression stroke. Else, I'll shut up and sit back down. s

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 heat loss.

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 :)

Everything old is new again. Who else remembers the Cadillac 4-6-8 engines of the 1980s?

Cylinder deactivation is now becoming a relatively common technology.

John