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Old 01-16-2006, 12:44 PM   #1
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4 cylinder trucks

General Motors and Dodge have been promoting "Displacement on Demand" cylinder deactivation technology. Cylinder deactivation reduces engine pumping losses and improves efficiency at low loads. They have installed in on their big V8 engines.

Cylinder deactivation could produce really big mileage gains in small engines. Has anyone heard of a car company that is looking into installing cyliner deactivation on their 4 cylinder engines?

Removing the pistons (rather than just shutting off the gas and air) would produce even better mileage gains because it would also decrease engine friction. It wouldn't be nearly as fast, but this IS a fuel economy forum.

Has anyone removed 2 of the pistons and valve lifters from their 4 cylinder? I suspect that most inline cyliner heads would warp due to differential thermal expansion, but Volkswagen, Porsche or Subaru boxer engines (i.e with 2 cylinder heads each) wouldn't have that problem. (Though they would idle very rough.)

Another good candidate for a high mileage experiment would be a 6 cylinder truck. For example, by removing the pistons from one bank of a GM 4.3 liter V6, you would make a 2.1 liter 3 cylinder engine. This should be almost as powerful as GM's 2.2 liter 4 cylinder, but should be more economical. You could do the same thing with a Ford 3.0 liter to make a 1.5.

Anybody want to try making a 2 or 3 cylinder car from a 4 or 6?
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Old 01-16-2006, 01:04 PM   #2
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Honda has done something

Honda has done something like this with their vtec-e, but that's shutting off the valves in the head, not the pistons in the block.

I don't know how the air going through the engine would work on these pistons that aren't going, but I think it's noteworthy that and engine swap might be easier and that smaller engine would really have to haul *** to move the engine itself around, not to mention the huge truck it's prolly attached to.

I think the best avenue for this idea is with the hybrid and shutting off the ICE altogether, but for DIY it seems a lot of effort and a possibly scary result.
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Old 01-16-2006, 01:12 PM   #3
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Re: 4 cylinder trucks

Quote:
Originally Posted by Sludgy
General Motors and Dodge have been promoting "Displacement on Demand" cylinder deactivation technology. Cylinder deactivation reduces engine pumping losses and improves efficiency at low loads. They have installed in on their big V8 engines.

Cylinder deactivation could produce really big mileage gains in small engines. Has anyone heard of a car company that is looking into installing cyliner deactivation on their 4 cylinder engines?

Removing the pistons (rather than just shutting off the gas and air) would produce even better mileage gains because it would also decrease engine friction. It wouldn't be nearly as fast, but this IS a fuel economy forum.

Has anyone removed 2 of the pistons and valve lifters from their 4 cylinder? I suspect that most inline cyliner heads would warp due to differential thermal expansion, but Volkswagen, Porsche or Subaru boxer engines (i.e with 2 cylinder heads each) wouldn't have that problem. (Though they would idle very rough.)

Another good candidate for a high mileage experiment would be a 6 cylinder truck. For example, by removing the pistons from one bank of a GM 4.3 liter V6, you would make a 2.1 liter 3 cylinder engine. This should be almost as powerful as GM's 2.2 liter 4 cylinder, but should be more economical. You could do the same thing with a Ford 3.0 liter to make a 1.5.

Anybody want to try making a 2 or 3 cylinder car from a 4 or 6?
I tried this by cutting the fuel to the only opposing cylinders in my 4-banger. Unfortunatetly, the firing order provided a large gap between when #3 fired and #1 came back to TDC, and the engine rocked and sputtered unless it ran above 4,000 RPM and it was smoothe. I ran about 40 miles on the interstate on 2-cylinders, but it actually threw a "Cylinder Misfire" code and dumped a bunch of fuel into the 2 running cylinders.

Removing the Cylinders/Rods would open a hole in the bore and oil would splash through the bore and into valve area -- it would have to be sealed somehow.

Also, 4-cylinders are tricky to get balanced if you remove the cylinders -- especially on an auto-trans. You'd have to try it in a shop with the engine outside of the car -- but I could see potential if you're willing to give up the power.

Check out the How-to section on this site for a write-up on injector deactivation.

-RH77
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Old 01-16-2006, 02:31 PM   #4
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rh77 did this on his car

rh77 did this on his car recently, sort of. He simply had switches hooked up to each injector and turned them off for a reactivation. Read about it in the articles (or maybe in the how-to) section.

Anyway, it proved to be too unstable for his car. I for one don't want my car to violently rock while driving/idling.

I do, however, like your idea of removing the piston all together, especially using one of the VW pancake engines.

I have heard of cylinder deactivation technology that makes the engine switch to two cylinders when the car is going downhill. I have also heard of such technology when there is not a heavy load on the engine. Remember, all that you need is about 10HP to get up to speed and to overcome aerodynamic drag. Perhaps while cruising we dont need to have all four cylinders.

I'm sure it would be easy to construct a device that could deactivate the injectors given a certain criteria. I'm not sure how to deactivate the spark plugs though.
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Old 01-17-2006, 01:13 PM   #5
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Cylinder deactivation

Cylinder deactivation by simply disconnecting the fuel injectors won't work well in cars with O2 sensors, since the deactivated cylinders will still pump air into the exhaust manifold. Two things could happen that are equally bad:

1 The exhaust will be much cooler, so the O2 sensor might not work because it's too cold. Under cold exhaust conditions, engine computers usually default to a "start" rich mode.

2) If the O2 sensor keeps working, the extra air pumped by the deactivated cylinders will make the engine think its cylinders are running lean, and the computer will make them run rich.

Operating rich hurts economy. To gain any benefit, the dectivated cylinders need to stop pumping air, not just have their fuel cut off. In GM's Displacement on Demand, the valve lifters stop opening the valves at the same time the fuel is cut off.

SO: If you want to deactivate cylinders permanently, you need to remove the valve lifters (and plug their oil holes if they are hydraulic lifters); and then disconnect their fuel injectors. (It would be better to remove the pistons too, but that's a LOT more work.

Does anyone have a pushrod Vee engine that wants to try this?
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Old 03-31-2006, 06:47 AM   #6
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Where to start.....Well

Where to start.....Well ,first you have to know how an engine works before you try to "fix" it. If you remove a rod and piston, the crank will spit oil out of the hole that lubes the rod bearing and you would lose most if not all your oil pressure. Pull a lifter and the same thing happens, even solid lifters are covering the cam oil gallery and are used for drip/splash oiling the cam/lifter. As far as oil being thrown into the cyl with no piston and getting to the intake?? Ah no, your valves would prevent this. And when your valves are open? If anything, the vacuum created by pcv system would suck air/exh into the cyl.(bad for the obvious reasons). As far as taking a 600lb 8 cyl engine and modifying it to have only four cyl to increase milage..how about dropping in a 300lb 4cyl?
The pumping of air into the exh by just unhooking the inj is correct and would cause problems previously mentioned.
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Old 03-31-2006, 09:10 AM   #7
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I was thinking of using a V6.

I was thinking of using a V6. If it was a GM 4.3, you'd have a 2.1 liter 3 cylinder, which is a hair short of the base 2.2 liter.

The resulting engine should have as similar power as the base 4 cylinder, but less friction and better surface area-to displacement (resulting in less heat loss) than the 4. So it should give better mileage.
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Old 03-31-2006, 10:47 AM   #8
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Re: I was thinking of using a V6.

Quote:
Originally Posted by Sludgy
I was thinking of using a V6. If it was a GM 4.3, you'd have a 2.1 liter 3 cylinder, which is a hair short of the base 2.2 liter.

The resulting engine should have as similar power as the base 4 cylinder, but less friction and better surface area-to displacement (resulting in less heat loss) than the 4. So it should give better mileage.
Since it's a pushrod design with one cam, you might be able to remove the pushrods and and leave the lifters in place to essentially seal the cylinders/valves. The tough part would be to remove the rods and pistons on that side. Next, the balancing might be off depending on the TDC position of that bank of each cylinder, and finally the distributor would have to be altered to address any lapses in firing. I went through a lot of this in my FI deactivation experiment. It's not easy, and it could result in a big failure (in other words, I wouldn't recommend doing it to your daily driver).

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Old 04-26-2006, 09:24 PM   #9
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I think an engine swap would

I think an engine swap would be a lot easier. It presents obvious challenges, but pulling pistons would result in a lot of subtle challenges.

The oiling issue is pretty big... you'd have to weld the crank up to close the rod bearing oil path. Balance would be a huge issue... both the counterweights on each throw and the overall balance. Even if it doesn't blow up, it might get worse mileage than before from a less-than-ideal design.
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Old 04-28-2006, 07:57 AM   #10
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The consensus seems to be

The consensus seems to be that if you pull out 2 pistons from a 4 cyclinder engine, there would be too many lubrication and balance problems.

An alternative might be to remove the valve lifters or pushrods like the GM DOD technology. This would let the engine run on just 2 cylinders, reducing pumping energy loss.

I'm still worried that friction in the deactivated cyclinders would be too great to see fuel economy gain. Piston rings are the biggest source of drag in the engine. What about removing the piston rings in the deactivated cyclinders, but leaving in the rods and pistons?
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