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

[Christ]

Originally Posted by Frank Lee

It has been discussed and I think somebody did it or is going to do it. I was considering it pretty seriously for a long while but the bottom line is, as long as the car runs well, I'm not all that motivated to mess with it, especially since some of us have predicted the potential econo improvement to be less than 20% which for my car would be less than 7 mpg.

I'm surprised you took out #3 and #4- did it shake and/or sound bad? I'd take out pairs 1-4 or 2-3.

This I'd considered once on a Geo Storm, taking out the center cylinders (had a broken rod) and running on just the outers (1 and 4). Ended up selling the car to a guy who thought he'd "just buy a new engine" and "drop it in", then ended up junking the car when he priced NEW engines for it instead of listening to me and figuring out that engines from about 100 other cars bolt right in.

[IsaacMTSU]

That's awesome! I had wondered if anyone ever tried this...

[MetroMPG]

Thanks for posting - great project.

I made your links active.

[JohnAh]

The seized big-end bearing was on cylinder 4 so I could chose between keeping 2 and 3 och 1 and 2. If I had kept piston 2&3 the engine would be a more common twin with "symmetric" firing order of 360 deg. On the other hand it would also get the same problems with mechanical balance as any single cylinder engine. In that case I would have to add some counterweigths at the crankshaft but would still have had vibrations at any speed.

I also have a smaller Fiat 126 with a 600cc paralell twin in the rear. The only reason this engine SEEMS to run smooth is because it rests on a big soft coil-spring. The engine itself is constantly rattling itself to pieces. It´s air-cooled with at lot of sheet-metal that cracks everywhere if you push it to the maximum. (which you mostly do because it only have23 hp...)

A single cylinder och 360 degree P-twin simply can´t get good balance unless a balance-shaft or similar solution is added. This is why I chosed to go for the 180 degree configuration on my Fiat 127. The two counter-acting pistons doesn´t give perfect balance either but the need for counter-weight is less critical I think. Since the 1050cc straight four is quite long i block and it´s crankshaft have five bearings the weight of the block will reduce the rocking vibrations. I guess the front-drive gearbox at the end of the engine also add some extra momentum.

Anyhow, my somewhat unusual cylinder arrangement gave a well balanced engine at any speed, but due to the long separation of 540 degrees every second firing the engine´s power-strokes felt a lot at low rpm. I also guess that the car would have been slightly easier to drive if I had chosed the more common 360+360 config but I´m sure the vibrations at ANY speed would have driven me crazy and perhaps killed the engine.

It would be verry interesting to try the same modification but saving piston 2 & 3 to get a comparison.

[JohnAh]

I now want to try this down-sizing cruelty on my Saab 96 V4, but such an engine makes the selection of pistons to rip out a lot more difficult. The engine, a Ford V4 designed in the early 1960´s I guess, have an even 180 degree firing order with pistons in opposite corners travelling in paralell. -It doesn´t share the same crankshaft throws for two opposing cylinders as a traditional american V8 or a Harley V-twin. A V4 engine must have a counter-rotating balancing shaft to run smooth. This shaft is driven from the crankshaft by the same cogwheel as the camshaft and is made by a fiberous plastic. A few weeks ago my balance shaft stopped working (and so did the fan, alternator and waterpump since their driving pulley is attached to the balance shaft and not to the crankshaft -a stupid solution) Anyhow, this failure gave me the experience of feeling a V4 without balance shaft and this was a lot worse than the vibrations in my modified Fiat. It was quite nasty vibrations of higher frequency.

I realy have to think twice if I decide to repeat the "engine split" on my Saab V4...

[euromodder]

Welcome to ecomodder, and that's some intro


I've been in Vallentuna last July - visiting Åke Jansson's aircraft collection along Väsbyvägen.

Originally Posted by JohnAh

Anybody who havre hearde about this kind of crazy and brutal modification?

A few users have done so - or at least contemplated doing so.

And of course VW have recently introduced their 1.4L TSI with dynamic cylinder deactivation .

[euromodder]

Originally Posted by JohnAh

The engine, a Ford V4 designed in the early 1960´s I guess, have an even 180 degree firing order with pistons in opposite corners travelling in paralell.

Wouldn't that make it possible to deactivate one side of the engine, and just use 1 bank of the "V" as a standing twin ?

[JohnAh]

Ooops, I made this reply to some posts at the first page of this thread without seing that I already had answered. But I´ll leave it here since people are always asking me why I did it the way I did and not like a more traditional two-in-line engine.

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Frank, have you tried to run a four cylinder engine with only three pistons? Long ago I heared about a man who bought an old car with V8 engine that felt slightly "off". The buyer suspected something was wrong with the ignition system or perhaps a stucked valve. He finally put a thin welding rod down the sparkplug hole and ended up in the oilpan... -No piston at all! But that was a heavy slow V8. Removing a single piston from a four-in-line is probably something completely different that never appeared as an alternative to me.

When the idea of removing pistons first appeared to me perhaps ten years ago I thought of it as a way of saving fuel only. My experiences from single- and two-cylinder-in-line engines told me that if I hade chosen to keep the two pistons running in paralel without modifying the crankshaft counterweights I would have ended up with an enginen that SOUNDED smooth but with terrible vibrations.

Earlier in life I had a coupple of small Fiat 126 with a two cylinder in-line engine in the rear. These engines are designed for this like most 2-cyl motorcycle, but there´s no doubt that they still give nasty vibrations. The 126-engine is resting on a soft coil-spring in the rear. I once tried to replace the spring with a common rubber cushion (?) and got terrible vibrations.

A two-in-line two-stroke engine have a 180 degree crankshaft with the pistons going opposite directions. There still is a rocking imbalance but that is smaller than the total vibrations from a single cylinder engine of same size. I have a 600cc 12Hp Kubota diesel that also utilizes the 180 degree configuration. So choosing this for my Fiat engine modification wasn´t a difficult decission.

[JohnAh]

Now with some distance to this project I think of the "engine split" as one way of three possible ways to reduce fuel consumption almost the same way. The other two "similar" methods is to reduce gearing/engine rev and to perform "pulse & glide-driving". In all thre cases an oversized engine is operating at a higher combustion pressure than normal near maximum torque for most of the time its running. Having extra power when needed is definitely nice in some situations so the "engine split" as a way to save fuel only is the worst method of the three. But as a desperate repair it´s a nice comfort that it also save a lot of fuel.

[Cd]

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