All production engines with cylinder deactivation keep both intake and exhaust valves closed.
If you leave one open, it will pump air and become a drag on the system.
With both valves closed, the trapped air acts as a spring and returns the energy it takes to compress the gas when the piston is on the down stroke..
If you open both valves and keep them open, it will pump fresh air into the exhaust and throw your O2 reading off.
Interesting thread on the subject-
Transmission, Driveline, Hybrid Drive engineering - Shade tree cylinder deactivation?
BTW, before reading the above thread, I would have agreed with you.
I posted a link on EGR in another thread here. EGR is the simplest way for a DIY variable displacement engine IMHO.
Spent exhaust gas is a source of inert gas- pump 1 litre of an inert gas into a 2 litre engine and you now have a 1 litre engine. Plus the combustion will be cooler, so you can run leaner, and more timing, without NOx forming.
Quote:
Originally Posted by Christ
Better to leave all the "dead" pistons with their valves open - constantly. Still take advantage of exhaust pulses, although not as much.
There was an experiment done *youtube, of all places* where someone ran the exhaust on his Geo 1.0 liter engine from 2 cylinders into the last cylinder in the firing order (I think it's 1 - 3 - 2, so 1&3 get run into 2) and just reburnt the exhaust gasses without introducing any more fuel or air into the mix.
I never thought into it very far, and I don't plan on it, but maybe someone could comment on the validity of something like that?
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