Cylinder deactivation for improved fuel economy

I have a 1990 Dodge Omni. I know, I know: “A 1990 Dodge Omni! Why not get a tricycle?” It’s in great shape and has sentimental value and, because it’s not my day-to-day car, it’s a convenient experimental platform.

I’ve been thinking about all the newer engines that are coming out with push-button cylinder deactivation. Why not do the same to the Omni?

As I’ve brainstormed it, this is what I’ve come up with:

* Deactivating fuel delivery to 1 (or 2) cylinders is easy. Just unplug the fuel injector. Is there any advantage to which cylinders should be deactivated? My first thought is “No” since it’s an in-line 4-cylinder.

* Remove the spark plug or plugs and plug wires for the cylinders to be deactivated. If the plugs are left in, those cylinders will still go through the compression phase and that will rob some power.

* Install a “false” plug in those cylinders to prevent lubricating oil from being blown out the plug hole and all over the engine compartment.

* I know that the “Check Engine” light will come on. As far as the ECU is concerned, something will have gone very wrong. Is it possible using a scanner to tell the ECU to ignore those abnormal conditions? Will the ECU have a panic attack and prevent the engine from even running?

What I hope to end up with is econo-box producing half the original power, so 35-50 horsepower and city MPG in the mid-30s (last time I checked, I was getting around 28 MPG with all four cylinder).

So, is this a workable idea or am I just going to waste a lot of time and maybe start a fire?

Won’t work, because all cylinder deactivation engines also disable the valves, turning the inactive cylinders into air-filled springs. If you really want to try this, and don’t mind potentially trashing the engine, you need to deactivate the fuel injection to the 2 chosen cylinders and somehow deactivate the valve opening. How? Beats me. Don’t worry about the plugs, doesn’t hurt them to fire. What you’ll be left with is an extremely slow, noisy, vibrating car that won’t probably save any gas, because you’ll have to keep it floored just to keep up with traffic.

I know of no car with “push button” cylinder deactivation. The cylinder deactivation is controlled by the computer, not the driver.

This is NOT a do-it-yourself project.

Who says starting this vehicle on fire is a bad thing? Maybe you could donate it to the local fire academy for training purposes (extinguishing vehicle fires). That way, when it goes up in flames, it will be in a relatively safe, controlled environment, plus the next class of first responders gets some valuable experience.

I would think you’d be afraid of a 1990 Dodge Omni not catching on fire.

Won’t work, because all cylinder deactivation engines also disable the valves, turning the inactive cylinders into air-filled springs.

Don’t need a spring. The amount of energy gained from the spring effect of the compressed air is LOST by the amount of energy it takes to compress the air. There is no gain.

I still don’t think this is going to work even if you get everything to work the way you want it to. The firing order is NOT going to give you a very smooth engine. You’ll loose a LOT more then 1/2 the hp. You’ll have one complete cycle of the engine not firing. I’ve driven 4-cylinders where a plug wire disconnected. With just 1 wire off…the car lost a LOT of power.

Right, net energy lost with valves closed is about zero. If the valves operate, you have pumping losses, big time.

I know that very few people have any affection for Omnis, but I do, at least this one. My mother bought it from some little old man who only used it to go to the liquor store. She herself used it very little. Her mechanics loved it when she brought it in for basic maintainence, because they never had any nasty surprises. They even gave it a nickname: The Elvis-Mobile. It’s white with burgandy interior and Elvis had a white/burgundy Cadillac. And the car has been rock solid. No problems, no rust. This is a good car! When my mother stopped driving, it was passed on to me. I like simple cars and this is a nice simple car. Basic transportation.

Also, my father is a Chrysler retiree. And say what you may about Chrysler products and US autos in general, I benefited greatly as the son of a US auto worker: A secure childhood, good medical care, nice teeth and a knock-out education. And I’ll continue to buy Chrysler products (or US products) as long as I can justify it. And I haven’t been disappointed yet: A Mitsubishi-built Colt (1979?), a 2000(?) Neon (170,000 miles, running strong when I sold it) and a 2004 Neon.

Thanks everyone for there input.

The “knock-out education” must have been heavy in liberal arts.
You skipped math,physics.

Oh I agree…Great loss in engine performance…It would be far less hp then a 2-cylinder engine that weighed the same.

Well, given your long experience with this car, you should pass. This is the kind of thing you do right before the wrecker comes to take it away. Put the time you would have spent on this improving it, you’ll enjoy that every time you get in.

I agree with all the replies you’ve received. However Texases’ reply got me thinking.

You have a lot of youthful enthusiasm to try this experiment. I would bet that most (or all) of us who work on cars have tried our own experiments over the years. The worst thing you can do is to squash your enthusiasm.

So, as Texases noted, do this “cylinder deactivation” experiment just before the wrecker comes for the car. You’ll have fun and you’ll learn a few things.