Hypothetical cylinder deactivation question
 

I have been thinking about the idea of cylinder deactivation, and I understand that the only successful route to take is by disabling all of the valves to basically make an air spring with the "trapped" air, as well as cutting off fuel.

I was thinking about fully deactivating a cylinder, not just at cruising speed. The car in question is a 2000 dodge neon, with a 2.0 liter, 4 cylinder, 16 valve motor. The idea that I'm thinking about would be to remove the rocker arms for the valves in that cylinder, and then pulling the electrical connector to the injector.

By removing the injectors, it would disable the valves, and the springs would just keep them closed, and removing power and/or ground to the injector, the fuel supply would be cut off.

In theory, this should work. The cylinder pressure from the trapped air would keep enough pressure on the rings to prevent excessive oil burning.
The lack of air into the exhaust would prevent faulty O2 sensor readings.
If this was done for cylinders 2 or 3, there shouldnt be too bad of any "hot spots" by the lack of combustion, as the aluminum head and coolant flow should keep things moderated.
A lock of power shouldnt be too much of an issue, the motor would still basically be a 1.5 liter with a heavy rotating mass ;) And at 130 hp, cutting off 25% would still leave 97.5 hp, which would be enough for basic daily driving duties.
Balance could be an issue, although with the deactivated cylinder still being there, the piston and rod would keep things in balance except for the "kick" from combustion. - but lets be honest, these neon motors all shake a lot anyways:p

The only thing that I can't picture in my mind is the actual rocker arm setup. The majority of my engine experience is with older Chevy motors, with a very simple pushrod design, which would allows for extremely removal of a rocker, but I dont really know how these neon's valvetrains are set up. Also, do the neons use a shaft mounted rocker? Would it be possible to remove only some of the rockers?

What do you guys think? Is it worth the cost of a valve cover gasket and some time?

I do understand that this would probably throw the check engine light due to a cylinder misfire, but would that result in any fuel changes?

For the Neon 2.0 SOHC engine, the rocker arms are mounted on pivot shafts that are above the cam. Hydraulic lash adjusters are built into each rocker arm that link the arm to the valvestem. There are separate pivot shafts for intake and exhaust. The pivot shafts are also part of the oil supply, as they supply pressurized oil to the lash adjusters in the rocker arms. The intake rocker arms each control two valves, while the exhaust rocker arms each only control one valve. This implies that, for each cylinder, there are two exhaust rocker arms and only one intake rocker arm.

Now, you could remove the rocker arms for a given cylinder, but then you'd have to put in some sort of sleeve that would prevent your oil supply from spewing out the holes in the pivot shafts and starving the remaining valvetrain components.

As for engine longevity? Eh. Your oil pump might not like the resultant vibrations from having one cylinder become dead, meaning that the gerotors might crack apart.

Try it- it probably won't even start, if it's like my 2.3 HSC on 2 cylinders.

Oil pump fall apart from vibrations? Really?

Oh, I'm sure it'll start. This engine is fairly stout. I once hydrolocked one of these engines, and could get it to start with only 3 working pistons. Surprisingly, it ran pretty good, too... even after the dead piston got chewed up by the crank and allowed oil to get sucked into the intake manifold.

As for longevity, the motor already has 200 000 kms on it, and the body has only got about 1 summer left in it.. ;)

I am intrigued about the oil though, is there an actual oil feed line, do you know if it would be possible, or reasonable to actually take care of the oiling issue?

Yah, it's the pivot shaft.

If you remove the rocker arms, you'll see holes in the pivot shaft that feed the rocker arms. If you're going to leave the arms off, you'll need to plug those holes. Otherwise, your remaining rocker arms will rather quickly fail and your engine will run like garbage until it dies.

Hmm, okay then, does it all feed inline? Like for example if I removed the rockers for cylinder number 3, and plugged the oil hole, would cylinder #4 now not receive any oil? Or are they all separate.

http://www.factorychryslerparts.com/...e/i2113783.jpg

This picture should help.

If you remove the rocker arms for #3 cylinder, you'll need to install sleeves over the pivot shafts to replace the rocker arms. Otherwise, the oil supply will just shoot out the bare holes in the pivot shafts where the rocker arms used to be, and you're going to end up starving the other valvetrain components.

Sweet thank you, that is a huge help. So the oil supply is right down the middle of pivot shaft.

Seeing as my brother is a machinist, I wonder how tough it would be to make some sleeves to clamp over the oil ports and actually seal.

sorry to keep hounding you with questions, but how large are the oil holes? And does the rocker shaft itself stay stationary?

1 - It's been a long time since I messed with Neon engines. Tempted to say on the order of a millimeter, but could be off. Shouldn't matter if you use a sleeve, though. It just needs to block the holes enough so that the rest of the valvetrain can still have an oil supply. Aluminum sleeves, with the same diameter and length as the rocker arms, should work well enough for your needs.

2 - The rocker shaft itself is stationary. The mounting bolts even go through it.

Okay cool, thanks I appreciate any input you have!
I'm just worried about sealing between the shaft and the sleeve with oil pressure on it. Although I guess even if it doesnt completely seal, oil will simply drain back to the pan and the later rocker arsm should still get oil.

Oooooh, I just noticed you are only disabling one cylinder, not two. It will start and run, but you will hate the exhaust note so much you will wish you had never done it. Disabling one is pointless.

I'm intrigued, what do you mean about the exhaust note?

You don't make a nice even-firing triple out of a 4-cyl by disabling one cylinder; you make a lopey odd-firing triple, unless you fab up a new cam and crankshaft. You will hate the way it sounds and runs, I guarantee it. I tried it once, and wrote all about here.

I know it wouldnt be as smooth as when running as 4 cylinders. What specifically about the sound was so bad? Do you have a link to your write up?

Search it. It was just plain bad, in the way that a malfunctioning engine sounds. But go ahead and try it; another data point is always welcome.

What do you suppose the potential economy gains are? They'll be well under 10% if you can stand to drive it. Hey... maybe that's the secret! Make driving suck so bad you will do anything to avoid it!

I'm not sure what the potential gains would be, although I doubt that I would see a loss. I'm seeing a lot of discussion on this, but not your write up. Although I dont want to shy away from something just because someone else says I wont like it. A lot of people thought that my El Camino with its cam, compression and exhaust would be way too loud, and I love it! ha h

Also Frank, how did you actually disable the cylinder?Did you keep the valves closed, or simply cut fuel to it?

There are many threads on cylinder deactivation here.

I took the rockers off the valves and pulled the injector wires.

And if many say that car is too loud, it is. Denying that and terrorizing the neighborhood with it is just plain rude.

Terrorizing the neighborhood, when I drop the mufflers at the track? Really?
And no offense meant, but it's always people over the Internet who have never heard the car that say it's too loud. I have yet to have anyone in person say anything.

The car runs through true mufflers whenever it is on the street. I also don't "terrorize" the neighborhood at all, all my fun is at the track.

So all these people were over the internet, imagining things? Could be, but then again I hear stupid redneck crap exhausts all day long... those are real.

Yes, people who read about my cam, and compression ratio, and can apparently accurately determine that the exhaust will be too loud for me when I race it.

Are you going to try and say that my exhaust is too loud or crappy sounding too without knowing a single detail about the car?

ADD much? You said people said it's loud and I went with it. Now you know my position on loud exhausts. Are you going to disable a cylinder or what? :rolleyes:

I'm going to keep exploring the possibility and looking for Constructive criticism.

When you did it, did you do just one or two cylinders? Was there an actual mpg gain? What engine?

Don't mind Frank. If I had a nickel for every time someone took offense to his opinions on here, I'd buy you lunch.

Please, do try it and report back with your findings/opinions. I hadn't ever seriously entertained the idea of disabling just one cylinder before.

I attempted a quick fuel cut on 2 of 4 cyl on my corolla one day, ran fine, vibrated quite a lot, could have been driveable but desided to clear the check engine light and drive home. My big 105hp engine cut in half + other losses would probably make a turd but maybe great mpg.

I would like to see more attempts on a cyl delete. The cars I drive directly push on the valves, so only way to "delete" them would be to grind off the lobe on the cams.

I suspect a 1 cyl delete would run pretty off, but shouldn't be super bad, depending on how the engine is designed, and what the ECU does because of the delete. I would say not one answer covers all cars.

On a side note, I do have an extra set of cams for my Camry from an engine that ran out of oil, could be interesting, but too old for instant MPG feed back :(.

A new car may be in the works in the next month or two, if that happens, then this will end up a 3 cylinder motor before it hits the scrap yard :D