[Andyman]

I tried cylinder deactivation on three vehicles I've had. The engines were a 5.8 L V8, a 4.3 L V6 and a 2.0 L inline 4 cylinder. Only the V8 conversion really worked well. The highway fuel economy went from 18 MPG to 24 MPG. It was sluggish at getting moving from a stop but the power was good enough above 30 MPH. The engine had a performance camshaft which reduced low speed torque.

The easy way to do the conversion is to remove either the pushrods or the rocker arms (if the engine is overhead cam) in every other cylinder in the firing order. On a V6 this means disabling three cylinders on one side. If four cylinders were running, the firing pattern would be more uneven and there would be more vibration. If the engine has multiport fuel injection, the unused cylinders should have their fuel injectors disconnected by unplugging the electrical connectors.

When I tried the experiment on a V6 Astro van, I just removed the six pushrods on the right side of the engine, reinstalled the valve cover and disconnected one of the two fuel injectors on the the throttle body fuel injection unit. I depended on some varnish buildup on the valve lifters to make them stick in the lifter bores above the camshaft without falling out. A new engine would have required removal of the intake manifold to hold up the lifters with hose clamps. I was not satisfied with the results for three reasons.

1) The starter motor had trouble starting the engine when hot because there were two compression strokes at a time.
2) The engine torque was not sufficient to climb up a steep driveway in reverse.
3) The worn timing chain rattled more because of fewer valve lifters pushing on the camshaft. Therefore the torque to turn the camshaft was more uneven.

In about an hour I restored the van to work on six cylinders.

I also converted my Accord to run on two cylinders. It worked pretty well that way but accelerating required some patience. It moved like a bus. It did a good job cruising on the highway as long as I was satisfied with 60 MPH. Higher speeds would have required downshifting to third gear. There didn't seem to be much fuel economy improvement, at least in local driving, and the extra vibration at low engine speeds was damaging exhaust parts. I restored it to four cylinder operation after about 700 miles.

I've decided that cylinder deactivation is a good idea if it can be switched on and off automatically while driving. It would be useful to have a kit to allow this modification on older six and eight cylinder engines. My test showed that it can improve fuel economy by 33% on a V8 car.