Dear friends in the ecomodder community, my name is Anatoly Kishinevski. I am a Russian engineer.
This thread is about a modifying a car engine to half of it's original displaced volume with the goal of
increasing fuel efficiency drastically while
maintaining driveability of the car (safely).
I have been planning the conversion of a 4 cylinder car to a 2 cylinder car for about 2 years. I recently acquired a rust free 2000 Nissan Altima with a 5spd transmission and 2.4L KA24 engine. This car is going to be the machine to which this modification and test is done. The engine is favorable because it has a very long stroke to bore ratio.
The idea is to remove two pistons and connecting rods. Typical firing order of a 4cyl engine is 1-3-4-2, so for this modification pistons 1 & 4 will be the ones I remove. Reason being, having pistons 2 & 3 remaining together will help engine stay as warm as possible. This will make the new firing order x-3-x-2-x, essentially the engine will fire-miss-fire-miss-fire-miss. It will be firing half as often as it normally would.
I have heard of people doing variations of this modification, but not necessarily with the goal of increasing fuel efficiency. I have searched quite a bit and found very little information on anyone else who has attempted this for the sole purpose of fuel efficiency. I have been very interested to see how well it works and if the car is still driveable. I anticipate it will be. Any comments or thoughts that you have on this process will be greatly appreciated. Please feel free to add constructive comments, questions, etc. below.
Points of consideration in this effort:
a.) engine will be off balance- Because pistons 2 & 3 move in phase e.g. move up and down at the same time. This lack of balance may be bearable without any effort to correct it, however I expect the car will vibrate quite significantly. To correct the lack of balance, doughnuts of very dense metal, for example wolfram (tungsten), may be manufactured and clamped onto the crank journals where the connecting rods have been removed. This would probably help with balance, but also introduce harmonics the engine was not originally designed to deal with.. it will probably work fine either way.
b.) oil pressure- If two connecting rods are removed from the crankshaft/engine, then something needs to be done to block the oil passages on the crank so oil pressure remains adequate. The best solution would be to cut the connecting rods to keep their original bottom on the crankshaft. This would maintain factory tolerances and oil pressure. Alternatively, using a hose clamp and some sheet metal would probably suffice.. or using epoxy or threaded insert into oil passage.
c.) valves of cylinders with missing pistons- The camshaft lobes for cylinders where pistons are removed will have to be ground to base circle so that the valves are no longer opening on disabled cylinders. Easy task
d.) MAF sensor (mass air flow sensor) will see incorrect amount of incoming air- It is possible the air/fuel maps programmed in the ECU would be able to accommodate the significantly reduced volume of air, however possibly not. In order to correct this problem, if needed, a venturri or reduced cross section tubing can be used in intake to compensate. The MAF sensor would be placed within this reduced diameter intake pipe. You can make the MAF sensor think that the same volume of air is passing by it as if there were still 4 cylinders pulling air in. To monitor air fuel ratio a wide band will be installed.
e.) lumpy power distribution- Due to the engine firing half as often with only 2 cylinders, it may feel lumpy in it's driving throughout various RPMs. To correct this, a heavier flywheel can be utilized. This will cause the engine to run smoother. For the initial attempt the stock flywheel will be used.
f.) fuel injectors- Fuel injectors on cylinders with missing pistons need to be blocked. In order to keep the computer happy and prevent it from knowing the fuel injectors aren't actually doing anything, instead of removing them, fuel compatible epoxy will be used to block them off. Then the computer can still fire them, but no fuel will be passing through.
g.) cooling capacity of stock system would be too great- The engine with only two cylinders may not be able to get up to full operating temperature with stock cooling system. In order to remedy this utilization of an under-drive water pump pulley may be helpful. It is possible the thermostat alone will be adequate.
The power of the engine will be measured on a dyno before this modification takes place.. and then the power will be measured after the modification takes place.
This whole project stems from the problem with cars being geared poorly with no consideration for fuel economy. Even in 5th gear in a normal car, on the highway when you stomp the gas, you can still accelerate at a considerable rate. Instead of dealing with taller tires or trying to figure out how to re-gear the car, if you simply reduce power output, then you can maximize use of the transmission's gears
I would be very happy to hear people's thoughts on this. I will continue to provide updates as the project progresses.
Sincerely,
Anatoly Kishinevski