How to make my 4 banger a 3 cylinder

[NoCO2]

Just wondering how feasible it would be to cut one of the cylinders off from the ignition sequence to maybe try and save some fuel.

I know that I have enough power to afford to lose one of the cylinders, but I was talking to a friend of mine who is a Lexus mechanic (for those less informed, lexus and toyota are the same thing mechanically), and he said that if I just removed the spark plug, the injectors would still be dumping in fuel and I would just have a dash light on to annoy me for my efforts, so I wouldn't save any fuel. The only thing he said that might work is if you somehow plugged up the injector for the 4th cylinder, but as to how to do that, I have no idea. He also mentioned that if I did that, the other cylinders might start dumping extra fuel in to compensate for the lose in compression from the one cylinder...but since he has never had anyone try it that he knows of, he doesn't know exactly what would happen.

Can anyone give some more insight into the feasibility of this mod, if there is any?

[NoCO2]

Ok, thanks for the info. Just wanted to clear that up. I figured it wouldn't run right, but who knows, I can dream can't I?

[TheDon]

you gotta pay to play

[3wheeled]

Did you find out if this will work or not?

[diesel_john]

No, that won't save gas unless you takeout a couple pistons, rods, and their valve actuating components, plus unplug the injectors.

Here is a thread on the subject.
Cylinder deactivation discussion

[sdpflag]

Chrysler has done this effectively. I know that the new Grand Cherokee has a V8 that with MDS can turn off 4 of the cylinders when not needed. here is a link Jeep - 2009 Jeep Grand Cherokee - Capability - Powertrain and it is the hemi with MDS

Cheers,
Scott

[some_other_dave]

If you unplug the electrical connector from one injector, and somehow fool the engine management system into thinking it's still plugged in, you would save some gas. But the engine would run quite roughly and unevenly--possibly enough to damage it over the long haul. One advantage of the engines that are designed for cylinder deactivation is that they can set up the remaining cylinders to fire at even intervals, but killing one cylinder of a four-banger and leaving the other three as they were is going to have the engine shaking like crazy.

If you cannot fool the EMS into thinking the injector is still there, the engine will likely go into "limp-home mode", which traditionally means a nice safe rich mixture. Which won't be so good for your fuel economy, or for your engine either over the long haul.

-soD

[Frank Lee]

You've done this?

[Binger]

my moms lumina blew out a spark plug and it ran like crap and it sounded like a big machine from some cartoon....KA-CHUNKA WHUMPA WHUMPA!!! KPPPPPHTTTTT

[taco]

i broke a plug wire while fourwheeling once, and it ran ok at best, ideled rough but ran fine other wise power loose was there i would test with un plugging the injector and tapeing the end first, just to see.

[gofastbobby]

that's an interesting thought. i believe your camry has a firing order of 1-4-3-2, with 1 and 4 firing at the same time, and 3 and 2 firing at the same time.

so my thought is mechanically, you could remove 2 of the pistons and rods, say 1 and 3. this would open the combustion chamber in to the crankcase now, so you would need to disable the valvetrain of the same two cylinders. the easiest way i can think to do this would be to grind the cam lobes so they are not opening the valves.

the question i have is would a twin cylinder have enough power to push the car down the road. maybe maybe not, but unless you have a lot of time and even more money, i wouldn't go to the trouble of trying.

all of this is mechanical i am not sure what would have to be done with the ecm to make it work, but i am sure it would not be easy.

[jamesqf]

Originally Posted by gofastbobby

that's an interesting thought. i believe your camry has a firing order of 1-4-3-2, with 1 and 4 firing at the same time, and 3 and 2 firing at the same time.

I don't see why any engine designer would do that. You want to make the engine run smoothly, which means spacing the firings at equal intervals. 1 & 4 might be at TDC at the same time, but one should be on the compression stroke, the other on exhaust.

[gofastbobby]

Originally Posted by jamesqf

I don't see why any engine designer would do that. You want to make the engine run smoothly, which means spacing the firings at equal intervals. 1 & 4 might be at TDC at the same time, but one should be on the compression stroke, the other on exhaust.

eh, good point.

[hondaworkshop]

So could you put an inline switch on the wires going to the injector, so at highway speed, you manually flip the switch and kill one or more injectors?

[Andyman]

You can turn off fuel injectors with a switch. To protect the electrical system you should also install diodes that would prevent voltage spikes from reaching the computer. In my opinion, it wouldn't be a good idea to deactivate a cylinder unless you have to because a defect in one cylinder. I actually did that on a Ford Mustang with a 2.3 liter engine. The car didn't have fuel injection but I deactivated a cylinder by removing the rocker arms from the bad cylinder. It ran pretty well on the highway. It was a bit rough at low speeds. It ran too rich until I changed something in the carburetor. Maybe I deactivated a power valve somehow. The fuel economy was good.

I also deactivated a cylinder on a car like a Chevy Monza (Maybe an Oldsmobile Starfire) with a Pontiac 2.5 liter engine. It had a worn out exhaust cam lobe. On that engine I took out a pair of pushrods. The varnish on the bottoms of the valve lifters caused them to stick in the lifter bores after the engine was started. If they fell out it would have been a problem because of an internal oil leak that would reduce oil pressure. The engine wouldn't run with all the pushrods in because exhaust gases from the bad cylinder would go into the intake manifold and smother the other cylinders. It could be driven again with the modification.

You may not get any improvement in fuel economy if you just shut off an injector or two. You would also have to do two other things:

1) Close the valves in the deactivated cylinder to prevent pumping losses and a loss of oxygen sensor function.

2) Tune the fuel mixture. It is likely to go too rich unless you make adjustments.

The main reasons I don't recommend this are:

1) The car will shake a lot at low RPM
2) The exhaust pipe will probably break from the shaking
3) The engine mounts will have a short life

[roflwaffle]

Originally Posted by jamesqf

I don't see why any engine designer would do that. You want to make the engine run smoothly, which means spacing the firings at equal intervals. 1 & 4 might be at TDC at the same time, but one should be on the compression stroke, the other on exhaust.

Straight fours fire in pairs every 180 degrees, but due to the difference in piston speed between the pairs most modern straight fours also use a balance shaft. Straight sixes fire in pairs too but don't have this problem because they can fire every 120 degrees, so the fastest pair speed, even though there is still a slowest pair, is offset by the third pair moving a some speed in between.

[roflwaffle]

Also, closing the valves isn't required to reduce most pumping losses, at least those associated with part throttle operation.

[Piwoslaw]

Originally Posted by gofastbobby

the question i have is would a twin cylinder have enough power to push the car down the road. maybe maybe not, but unless you have a lot of time and even more money, i wouldn't go to the trouble of trying.

Look at the Fiat 126p: it has a two-cylinder 650 ccm engine and its 24 hp rushes its 600 kilos from 0 to 100 KPH in just 56 seconds! It does shake, though, you can see the car's rear dancing in idle at a streetlight. FE is 5.2-7.2 l/100km ( 45-33 MPG).

In the case of a four-banger with two dead cylinders, I think it should be enough if you're using it only for cruising and not passing.

[thefirebuilds]

one should consider pulling the rods and pistons will unbalance the crank causing excessive wear on the other moving components. I would assume that the production versions of these are simply forcing valves open to reduce friction resistance, obviously the cylinders aren't removed when disabled in those cars.

[some_other_dave]

Originally Posted by roflwaffle

Straight fours fire in pairs every 180 degrees...

Huh? The firing order on most Honda I4's is 1-3-4-2. Nowhere do two cylinders fire at the same time.

I can't think offhand of any I4 engines that fire in pairs. Most fire one cylinder every 180 degrees of crankshaft rotation, which is every 90 degrees of camshaft rotation--one quarter of a full two-crank-revolution "cycle". I think you may have gotten confused by the difference between the two (which is regrettably easy to do).

-soD