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Old 02-15-2008, 01:50 AM   #1
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removing a spark plug for better economy

I was thinking about this when I pulled off my wire and the god dam metal piece fell off, which I still have to fix, but I was thinking of leaving it off for better mileage. The injector would have to be disconnected to, cause fuel would still be dumped in that cylinder.

I'm thinking it wouldn't give me better mileage though, cause I'd have to give it more throttle then I would normally in any given situation..... but why does a metro get good mileage? its a 3 cylinder. or a bike for that matter. are cars made with way more power then they need or is it a weight thing. where that 3 banger only needs x small amount of power at it's weight and still be effecient.
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Old 02-15-2008, 05:27 AM   #2
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If you remove a plug on a 4 cylinder for economy you'll end up ruining the engine. The camshaft is divided up into 4, where it's divided up into 3 on a 3 cyl. (Oversimplification) Basically it will drive under power on 3 cylinders but the 4th won't be powered, meaning that effectively you will be driving the cam around 1/2 turn on 1/4 power. Good way to wreck an engine.
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Old 02-15-2008, 07:00 AM   #3
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Well you still have to lug around the weight of the extra cylinder, it becomes dead weight at that point.

Also, you're going to introduce lots of imbalance in the engine. The reason that your firing order is 1-3-2-4 instead of 1-2-3-4 is harmonic balancing, which will go away if you kill a cyl. You'll get all sorts of stresses all through the engine, mounts, etc.

And removing the plug opens the cyl to the elements, it'll rust inside and ruin the engine.
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Old 02-15-2008, 08:21 AM   #4
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youll loose close to 50% power if you do that to a 4 cylinder. also you might have problems down the road with the crankshaft not being balanced as it rotates in the block
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Old 02-15-2008, 09:30 AM   #5
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If you do try this, put a good filter onthe spark plug opening, and a spark plug on the wire or you will ruin the coil, and you might ruin the coil that runs the injector as those get a high voltage pulse as well.
and I agree with everyone else on your engine eing out of balince.
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Old 02-15-2008, 10:22 AM   #6
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a couple people have tried cylinder deactivation by disconnecting it and it always sucks. horribly off balance and you lose a greater than proportional amount of power because you aren't just removing power, you're losing engine speed to friction (in engine) and drag (of car) that has to be made up before you deal with maintaining the same power from the other cylinders....in short, it always ends poorly.
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Old 02-15-2008, 12:40 PM   #7
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Removing TWO sparkplugs is as foolish, but can maintain the balance in a four cylinder four stroke engine if the right ones are removed.
The problem is that the friction of the piston rings doesn't go away, the water pump has the same load, the alternator load remains, and the energy needed to move the vehicle through the air at some speed remains the same. The work produced by the remaining operating cylinders doubles to make up for the lack of effort from the dead ones. The net result is a loss of power AND a loss of fuel efficiency.
The factory de-activation schemes involve perods of extremely low load when internal combustion engines are pathetically inefficient at turning fuel into heat energy. By doubling the load on half the cylinders the improvement in thermal efficiency in the few working ones makes up for the dead weight of the deactivated ones.
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Old 02-16-2008, 10:31 AM   #8
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^^ the good ones also hold valves open so the piston isn't working against compression/power strokes.
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Old 02-16-2008, 02:02 PM   #9
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the honda civic hybrid head that I checked out that could run on one cylender kept all the valves closed it looked like for the 3 cylenders that it turned off, but I think civic hybrid works simalerly to the insight, in that it uses the motor as the fly wheel, alowing it to absorb that imballence in rotational speed.
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Old 02-16-2008, 04:37 PM   #10
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Real world 2 cylinder

Last Year I had a Mercury Topaz, the Ford Escort boxy wedge version, I got the car through the family and it had a very tired 1900 4 cylinder automatic, the car ran like a vibrator, but it was transportation. While trying to iron out its problems, I found that it had almost no compression in the 2 middle cylinders, but perfect compression on the outer 2, it got 16 mpg. I tried plugs, wires, and ocationally number 3 would fire, but would die at idle. I did try unplugging number 2 and 3 injector and I got 24 mpg, the one thing I did notice is that with the 2 middle cylinders unplugged I realy had to keep my foot in it on the hwy. The vibration was terrible and screws started unscrewing themselves. The only thing I could recommend would be trying an injector kill switch for the 2 inner cylinders and olny use it on the hwy, at idle in city traffic the thing wants to shake its self apart. The car ran for under a year and was junked. If I had a perfectly running car, I would not do it, the idle vibrations are terrible. Hope this helps.
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