10-15% reduced consumption after "engine split" (physically deactivating 2 of 4 cyl.)

[Varn]

Good project. Keep the posts up.
Welcome.

[Lethedethius]

Could this be done on a honda civic 1.5/1.6L motor? Wouldn't leaving the pistons in create engine knock?

[JohnAh]

@Lethedethius: What do you mean by "engine knock"? I do see a small risk for slow oil-buildup ontop of the pistons even if the average pressure should be atmospheric when all valves are shut. The best reason for this fear is if one valve have a small leakage. I guess this can easily be checked by removing the sparkplugs now and then.

I know nothing about the Honda engines (and verry little about any modern engines) in detail. I would love to see my "split" experiment on a modern engine with injection and also one with turbo. What may make a reversible modification difficult on an OHC engine is if removing the tappets may not give enough clearence between the cams and the valve shafts. This was the case with my Fiat but since the engine was wrecked anyway all I had to do was to cut the clearence needed with my angle-grinder! :-)

On an OHC engine with rocker arms I suppose it may be quite easy to make a reversibe mod by removing the rockers only. (provided there´s no hole where oil starts to squirt like crazy when parts are removed...)

If an engine is to be modified "all the way", still with a chance to turn back, I suggest that the crankshaft oil orefices is shut by another method than welding. There´s always a risk for small drops of metal entering the crankshaft when welding and even if it´s a junk-engine I suggest to first insert some sort of metal plugs before welding starts.

I once read in a military handbook that a seized piston or bearing can be temporary "fixed" by removing the piston and then plugging up the oil-holes in the crankshaft by some layers of tape compressed by ha hose clamp! This is a realy dirty fix thay may both hold just around the corner or forever... I wouldn´t do this if I didn´t have a reliable oil pressure gauge! -A warning lamp may not give the early warning needed to save the engine if the hose clamp slowly gets loose.

[JohnAh]

Think I wrote it before, downsizing the engine is one of three ways to increase efficiency by increasing compression/combustion pressure and reducing ammount of engine friction per driven distance. The same thing can be done by changing gear ratio (modifying/replacing the gearbox or change to much bigger wheels) or switch to "P&G driving".

One thing that may lessen the improvement of fuel economy from the engine downsizing is fuel enrichment on a carburetted engine. Some (most?) carburettors give a richer mixture when operated near full throttle and since the engine will be weak the driver may be tempted to use a heavy foot. This will NOT increase power other than at very high revs. On my Fiat I noticed that if driving at full throttle I got no higher average speed but most of my modification´s 10-15% improvement were lost. The easiest solution to this problem is to put a wedge between the pedal and the floor.

I don´t know how an injection engine will behave but I suppose the airflow sensor will average out the pulsations from each intake stroke so the system will think you are driving with four cylinders on half the load, avoiding the fuel enrichment regardless of how much the pedal is pressed down.

I guess a carburettor will also average out the the pulsations at higher revs to a more continous spray but here the fuel enrichment may be mechanically activated by the throttle opening and not by actual airflow.

I also see a risk for imbalance in fuel mixture between the two cylinders if using a 180 degree config as I did on my Fiat. -If my theori is right the "second" cylinder will get a slightly richer mixture since it gets some of the fuel spray started by the "first" cylinder. Since it will take 540 crankcase degrees until next induction stroke the carburettor spray may have time ease down more than on the following 180 degrees. When I compared my sparkplugs I saw no sign of the cylinders getting different mixture but there may still be something to this theory...

[Cobb]

Interesting.... The newer insight had once advertised that it had cylinder deactivation. It was never clear if it infact would run as a 2 cylinder varable cylinder such as only 1 or up to 4 or if it was all on or all off like the tradational fuel cut, but in this case turning off the rocker arms by vtec as it has dual vtec.

The car sounds like a singer sewing machine at ide with no load at operating temperature and since I havfe a straight pipe exhaust it sounds like my 2 cylidner geo that had a bad cylinder. Then when you touch the gas or turn on the ac the engine comes to life and sounds like a tradational 4 banger.

Guess I could unplug an injector for a start since I got the IMA backing it up and a 4 kilowatt reservce of power for a few hours of driving/?

[JohnAh]

A few days I got an idea on how to improve engine balance when converting från a straight-four to paralell twin: Use a 360 degree configuration and leave the unemployed pistons in place! To reduce friction losses the pistons should be modified by cutting holes in the piston crown and removing the rings. The pumping losses are at a maximum about "halfway" between full throttle with normal valve lift and no valve lift at all. When introducing holes in the piston crown this will also introduce internal pumping losses! The holes must therefore be as large as possible. Perhaps the piston skirt should also be modified to reduce friction even more.

I have seen single cylinder motorcycle engines with a balancing device working as at counterweight to the piston, reducing the vibrations in the same way as a "perfectly symmetric" 2-cyl boxer would do. My passive modified pistons should act in a similar way. The big challenge may be how to cut the pistons for minimum pumping losses and friction while keeping the maximum weight.

[mario.silva]

Good job.

Now you have half the engine (cubic).
Less airflow resistance in engine, less speed, friction...
After all the math, you are getting correct numbers.

Soon will come the day that we will be running on one super giant cilynder with hi compression special aloy. Or 2 opposed linear... Mark my words :-)

[arekkocowicz]

What you have done with this engine is indeed a cruel thing. Last time when I was replacing a ignition coil in my Renault, I came up with an idea: what if I add a little electronic circuit which will switch off fuel injectors in some particular moments when power demand is low, for example when you've already stopped and you are waiting for a green light but you for some reasons don't want to stop the engine. I know that I will not reduce friction loses, but think about that another way: if there are only two cylinders working and they have to produce the same amount of energy (to power up engine accessories) they will be heavier loaded - so they should work more efficiently, am I right?
If I build a circuit which steals signal from gas pedal position sensor I could switch two fuel injectors quite often, for example in situations when gas pedal is pressed less than 15%.
Another think is to change which cylinders are switch off, if I do that quite often no cylinder would get colder so whole engine would be always ready for higher power demand. What do you think? I can build such a circuit

[metromizer]

Originally Posted by JohnAh

@theycallmeebryan: Nice to see that my crazy project can inspire! I did´t think about the possible problem with clean air being pumped and blended with the exhaust. You are probably right about the sensor reading lean mixture making the injectors dumping a lot more fuel than needed in the remaining two cylinders. Dammit! I was hoping to get a some answer about how much of the fuel savings is comming from the harder work in the remaining cylinders and how much is saved by reduced piston friction.

Is there perhaps an easy way to block the intake manifold or to disengage the valves? Don´t remember if I´ve written this before but I want to try removing all push-rods for two cylinders in my old Saab. Removing the push-rods is easy but the question is what will happen when the valve tappets get lose? Removing them is a LOT more work but perhaps they can be lifted up and locked in place by magnets or a thin strip om metal.
Doing the same trick with an OHC-engine demands most likely a destructive operation.

The test is however very interesting. If fuel consumption can be reduced by 5-10% with all piston still in place there may be a way to modify the engine so it can go from standard mode to "split-mode" while driving.

Thanks for posting this, I have a few comments.

only 5-10% reduction in fuel consumption just isn't enough motivation to justify the work, in my mind. By disabling a couple cylinders, but not removing the 'dead cylinder's' friction doesn't seem worth the trouble. If you leave the pistons in, you need to maintain some valve action. If you don't, the piston is compressing air needlessly. Worse, it has no place to go. Ring friction is also a big deal.

Most of the disabling a cylinder or two FE experiments I've read about, have started with a worn out and/or broken engine. I'd like to see someone test a good running engine on a dyno, then remove two pistons and run it.

Pushrod engine: there is a couple ways of dealing with loose lifters after removing pushrods, pistons, permanently disabling a couple cylinders. If you completely remove the lifter, on many engines, you must close off the lifter oiling port or replace the lifter with a plug of somesort. If you remove the camshaft, and precision grind the lobes off round, you can just leave the lifter in place. Another way to remove pistons without having to m9odify the crankshaft, is to modify the connecting rods. Saw the beam and upper end completely off, grind it smooth, and re-install what is left with bearings. That will control the oil leak from that journal. If you don't want it to turn, just add a little .003 shim stock under the bearing shells of the modified rods.

[metromizer]

Originally Posted by JohnAh

A few days I got an idea on how to improve engine balance when converting från a straight-four to paralell twin: Use a 360 degree configuration and leave the unemployed pistons in place! To reduce friction losses the pistons should be modified by cutting holes in the piston crown and removing the rings. The pumping losses are at a maximum about "halfway" between full throttle with normal valve lift and no valve lift at all. When introducing holes in the piston crown this will also introduce internal pumping losses! The holes must therefore be as large as possible. Perhaps the piston skirt should also be modified to reduce friction even more.

I have seen single cylinder motorcycle engines with a balancing device working as at counterweight to the piston, reducing the vibrations in the same way as a "perfectly symmetric" 2-cyl boxer would do. My passive modified pistons should act in a similar way. The big challenge may be how to cut the pistons for minimum pumping losses and friction while keeping the maximum weight.

Rather than cutting holes in pistons, and still having that unwanted friction from the rings, you could just throw away the piston and rod assembly, and add weight to the crank throw. A simple bolt together steel 'split ring' that weighs the same as a piston and con rod assembly would do it.

However, it will still run rough. It's the unbalanced 'power pulses' that will be responsible for that. Lack of a power stroke from the dead cylinders. But if you deactivate 2 cylinders from a 4 cylinder engine, such that a cylinder fires every 360 degrees, it should run reasonably smooth at higher rpms. Idling, it will still vibrate like a tractor.

American car companies had been trying for years to smooth out 4 cylinder engines. Compared to a V8, most customers had historically disliked the 'feel' you experience from fewer pulses per revolution of a 4 cylinder car. Internal engine-smoothing 'balance shafts' were popular for a while, but they are not good for FE or power. Most modern 4 cylinder engines balance shafts have been replaced with these engineered HUGE vibration damper systems, formerly referred to simply as 'motor mounts'. My guess is the engine tuned mass dampers and vibration isolation systems on modern cars are mostly responsible for the smoother feel you get from a modern 4 cylinder car.

Remove 2 power pulses per revolution, and that 'system' might need some rethinking to keep the car from shaking like a Harley Davidson motorcycle