Hi, I thought it might be useful to add some comments because I've tried using cylinder deactivation in several engines. One was my Accord with a 2 liter 4 cylinder engine. I ran it for about 700 miles on just cylinders 1 and 4. It worked fairly well. It could cruise at 60 MPH in fourth gear, climb most hills without slowing down in third gear and climb a really steep hill (maybe about an 8% grade) in second gear at 50 MPH.
The biggest problem was the vibration when the engine ran less than 2000 RPM. It was damaging the exhaust system. I had to replace the flex pipe and weld the pipe next to one of the hangers after it broke there. I'm not sure it got better fuel economy. It seemed disappointing. I think it was better on the highway and worse in local driving. It might have been running too rich at low engine speeds.
Here are my suggestions for making your engine useful again. Remove the oil pan and disconnect the #1 connecting rod cap. You will probably find a damaged bearing. Examine the crankshaft journal too. If it's rough you can use a long strip of wet fine sandpaper to make it smoother. Clean off the crankshaft and install a new bearing into the connecting rod, oil it and connect the rod back to the crankshaft. Then install the oil pan. This method will preserve the balance of the engine. Then you have to decide whether to use cylinder #1 to make power or deactivate it. If you use it to make power, the new rod bearing might wear out fast if the crankshaft is worn badly.
If you want to use only two cylinders you would deactivate #1 and #4. After you remove the rocker arms for those cylinders you will need to block any exposed oil holes on the rocker shaft. I did that with some small hose clamps. It might be good to put brass shims inside the clamps the if the clamps are not very smooth.
You need to unplug the fuel injectors for the unused cylinders. On my car, there was no need to connect any resistors to the wiring harness. The computer didn't complain. On my car, there are two oxygen sensors so I had to disconnect one and connect the one operational oygen sensor to both cables. My car had almost no power to get moving at first. It improved after I used a restrictor inside the vacuum hose that leads to the MAP sensor. That reduces flucuations of the vacuum. I think it made it run leaner. I used a couple of wires to short out the unused spark plugs. I wasn't sure if the sparks could cause any trouble in the deactivated cylinders.
I like the idea of using deactivated cylinders for extra expansion of the exhaust gasses but I don't think it could be done at a reasonable cost. The expansion cylinders would have to have a different kind of valve control so they would operate on a two stroke cycle. The intake valve would be open while the piston goes down about halfway and then close. The exhaust valve would open when the piston is near the bottom and then close before it gets to the top. It is best if the pressure in the cylinder is the same as the exhaust pressure from the normal cylinders when the intake valve opens.
I found the article about the Mother Earth V8 to V4 conversion. It is on the internet and here is the link:
Can you convert a V8 engine to a V4 and save gas?
This plan is a little different because the exaust valves are removed from the deactivated cylinders. That makes cranking easier because it avoids having a compression stroke in two cylinders at a time. I think it probably wastes some power when the engine runs fast.