4 Cylinder to 2 Cylinder Project

[Frank Lee]

It'll move. Well, I'm a flatlander and have no steep hills to climb. It would still move, in low gears. It's easy for me to imagine having 1/2 the horsepower, as much of my stuff does have 1/2 the horsepower people think they need these days. Old VWs anyone? 36 HP in a van? 48 HP in a Rabbit diesel? If I took out 2 cyls in my 100 HP Tempo I'd think it would be good for about 50 HP which would make it somewhat comparable to the Rabbit.

[LittleBlackDuck]

Originally Posted by Frank Lee

FWIW I'd disable the valves on cyls 1 and 4 and pull the non-working pistons and con rods. Then I'd have to plug the oil ports on those two crank pins. I'd want cyls 2 and 3 to be the working cylinders because the rocking couple would be minimized. I don't think I'd try it on a turbo engine unless as someone said earlier a right-sized turbo was fitted. Stock flywheel should suffice. Stock manifolds too. O2 too. I'd put resistors equal in resistance to the injectors on injector leads 1 and 4. Might be naive but if ECU listens to the O2 sensor the mixture richness should be fine in spite of the reduced air volume moving through? It should be able to highway cruise just fine, although acceleration will be glacial vs stock. Fuel economy should be improved but not doubled; my WAG estimates better than 15% but less than 50% improvement. Mind you I haven't done this but this is how I'd start off.

Pulling the pistons like this would result in a huge primary imbalance as well as the secondary rocking couple. The thing would be like a pogo stick at idle and most likely self-destruct catastrophically at higher revs du to the bending forces on the crankshaft.

Mixture would be totally out of whack too, as the ECU would use injector opening times based on four holes being opened instead of the two operating injectors. The oxygen sensor would detect this and probably throw a few codes to boot.

Simon

[Frank Lee]

I doubt it. The crank is fully equipped with counterweights after all.

I would semi-balance the lack of the two pistons and rods and plug off the crank pins simultaneously by cutting off and remounting the big ends of some crap rods, as long as they don't hit the block.

[wdb]

Originally Posted by redpoint5

My WAG is 0 MPG as the thing won't move.

^^^^^ This. The whole idea is dipping toes into the Unicorn Corral. But I'm in for the video.

[LittleBlackDuck]

Originally Posted by Frank Lee

I doubt it. The crank is fully equipped with counterweights after all.

I would semi-balance the lack of the two pistons and rods and plug off the crank pins simultaneously by cutting off and remounting the big ends of some crap rods, as long as they don't hit the block.

Yep, and by doing the chop saw modification you will be approximately 500+ grams out of balance. This is not an insignificant amount when you consider balancing tolerances for street engines are in the order of 5 grams and a race engine can be 0.25 grams.

If you are planning on it being drive able and not destroying the drivetrain I would seriously look into this aspect of the project.

Google "washing machine brick" and consider that the machine is designed for a large imbalance in its load and only operates at around 1000 RPM...

Simon

[ChillyBear]

I would say that pretty much any kind of lean burn or egr strategy would be better than a cylinder delete.

I'd rather play with flame speed and a cushion of egr than play with an imbalanced 2cyl engine. I've never known the math, let alone forget.... But 4cyl's are naturally imbalanced due to power stroke degrees of rotation. You would have to run two cylinders rich or near stoic, so you may eliminate some throttling losses or something, but with a turbo, I don't think that's a big enough factor.

I ran my Ford on an Atkinson cycle, it worked. And it still wasn't worth pursuing.

I think a megasquirt and a couple months of research on timing and flame speed would yield better results than a cyl delete. Plus..... A tune can cruise at an illegally lean AFR, and still produce 200hp at wot. A 2 cyl jetta will just be an unreliable piece of garbage worth an extra 5mpg MAYBE! Plus, with a solid tune, you don't need to hypermile, you've just gotta watch your egt's and you're good!

[MPGeo]

Originally Posted by Ecky

I disagree. This way, OP will still get pumping losses. Plenty of manufacturers offer systems to close valves completely and quit firing several cylinders when cruising at low load, because the air inside acts as a spring, rather than simply sapping power by being pumped through.

I disagree with your disagreement... (that doesn't even sound right)

But seriously, I can understand the rational, and I guess it makes some sense... And although I respect your opinion, I don't think the line of thought is completely accurate. Let me explain my position, and please feel free to counter anything I say, after all is only my opinion...

-If you keep the pistons in the equations it is a given the there will be pumping losses, because that's what the piston does - pump air. This part of the suggestion was not an attempt to eliminate losses, but simply to minimize them. I would prefer no pistons at all as I stated in prior post... that would in fact eliminate the pumping losses of the useless pistons.

-If for whatever reason the pistons are not removed, they would be practically useless on this particular application... And with only two other pistons to carry the load, the obvious next best would be to minimize as much of those parasitic power losses as possible, and with this in mind...

-It is a fact that it takes more power to compress air than to move air. The syringe example is almost as good as any for this purpose. Try pushing air through the syringe with the orifice plugged w/ your finger, and then with the orifice unplugged. Compression takes much more force... But also if you increase the size of the orifice it will reduce the amount of force required to push the syringe piston.... and that was the premise behind leaving both ports fully open, greater orifice sizes... bigger orifice size = less airflow restrictions = less power consumption per rev. But for practicality I suggested to only leave the exhaust side open just so that minimal modifications have to be made to engine and it can be reassembled easier if he decides to do so.

-As far as the OEMs using a closed valve method, in my opinion it has nothing to do with a benefit of "spring" action... But rather with practicality, pricing, manufacturing challenges and the like.

Because before they can "spring" into action, those air molecules have to be compressed... And again, it takes more power to compress than to simply blow to the atmosphere... And I'm sure OEMs have calculated these power losses into their equation, after all that's what they are after, they are after lowering the power output at specific scenarios so that the engine can operate at higher percentages of power output... lower the power, the percentage increases.

But it really makes no difference because you can electronically cut them on-and off as needed to offset any power losses instantly.... vs. the car in question will not have that option, and with only two cylinders to carry the load, he needs to get rid of as much losses as possible.

What you think?

[Ecky]

My Civic hybrid closes all of the valves in the motor when coasting in gear. Honda advertised this as reducing drag, as opposed to leaving the valves open and pumping air.

You're right in that it takes power to compress air, but that power isn't lost. It's stored in the air, and transferred back to the piston after TDC. Pumping air takes more energy.

[Frank Lee]

NO successful cylinder deactivation schemes pump or move air. NONE.

[MPGeo]

Originally Posted by Ecky

...but that power isn't lost. It's stored in the air, and transferred back to the piston after TDC...

The first thing that came to my mind the first time I read this thread... which goes along with your statement Ecky, was of an engine I had seen some time ago that uses waste exhaust gasses and transfers that energy into a separate piston, as a secondary stage of sorts and removes extra power from that stored energy and then dumps it into the turbo... And it has some impressive performance #s... I finally found the site...

It's called a 5 stroke engine.

dfelddt91 if you can do this to your the VW engine, then that would be awesome!