A shrinking/growing engine

Moving the crankshaft won't help, the length of the stroke will not change.

What about a sleeve around the piston that can either be stationary or move with the piston?

Why not just turn off half the cylinders?

I got this brilliant idea in the cereal box this morning. (Snap crackle pop).

In addition to switching off why not use an electronic cam. One can get V8 performance by using 2 stroke mode. And improve the economy on steady drives by selecting 6 stroke mode.

Where can I get such an electronic cam? I need one now!

Cadillac tried this on the 4-6-8 cylinder engine, but while the concept was fine, there were a multitude of problems.

This is similar to what a turbocharger does. Larger amount of air/fuel when it's on boost. Smaller effective displacement when off boost.

Also do you remember the Cadillac 8-6-4? I think thats what it was called. It was an attempt at something along similar thought paths.

How about swash plate pumps? Another similar idea. They actually vary the stroke as you tilt the plate.

Hello,

I believe BMW also had a V12 engine (850 series?) that could shut down a bank and become a slant 6, if I am not mistaking it involved a mechanical disconnect and was intended to aid transitioning from city to highway driving - fuel economy.

Back to the shrinking engine - well we could have 2 engines, one small one, and one large one with perhaps 3 cylinders each. I think real answers we are seeking are in fuel efficiency, and dramatic results may be found by alternative fuels, or by starting a new engine design from scratch without the influence of current low efficiency designs allowing our economy to be balanced by the need for gasoline.......This balance needs to be leveled slowly, it could be economically disasterous. I am sure there are some great prototypes in crates somewhere, perhaps even a growing engine - just add water???

Mirco.

Nothing is more beautiful than nature itself.

It is a wonder how such a large variety of beings and plants all run on water and solar power.

Randolph, excellent point - what is the efficiency of animals and humans vs a combustion engine? I think it is safe to assume that due to evolution alone we are not likely to beat nature in efficience with technology created in 100 years, or are we?

Imagination beyond limits!

Mirco.

I'm sure this approach has been done before, open the exhaust valve (making sure the piston won't smack it) and close the inlet, or maybe the inlet too.

Maybe that would work at idle... just keep 1 or 2 cylinders going.

Heck I know...ask Ragavan... he'll know how to do it..

Del

Heck I know...ask Ragavan... he'll know how to do it..

Ouch.

You don't say?

So sad.

Mediocrity is on the rise.

If the inefficiency in these engines is cause by load of the piston drawing air in why not use a larger intake valve or place two. Which has been done on some engines to increase performance.

The adjustable crankshaft would not alleviate this. Moving the crank shaft closer to the engine head would change the compression ratio.

"If the inefficiency in these engines is cause by load of the piston drawing air in why not use a larger intake valve or place two. Which has been done on some engines to increase performance."

but that would cause a lean burn. The reason why the air/fuel valve is near shut, is because the engine does not need that much fuel, and so it must have less air as well to keep it at equal ratio.

If the fuel is being mixed with air in the intake manifold then drawn in to the cylinder the volume being set by the displacement. How would opening the opening cause a lean burn. The amount of fuel being introduce in to the air is a function of the injectors not the orifice size of the intake valve

Back in the 70's we had the dodge Mopar the first in primitive turbo's a basic piston drive.What you probably should do is rethink.Think rotary.More efficent than your basic piston drive.But thats my opinion

variable valve timing http://en.wikipedia.org/wiki/Variable_valve_timing

In conjunction with a turbo, would let you get by w/a much smaller motor.

The lean burn adjustment [from the other thread ]would need to be conditional to the load.

electric or pneumatic valves would let you run on less cylinders, but would take some tricky programing.

Chrysler currently has a V8 that shuts down 2 or 4 cylinders as the load is reduced.

Gm has AFV Active Fuel Management which shuts down half the cylinders on a V-8 and a V-6.

Shawn

Indeed a good point. Shrinking the engine when cruising.

Playing with the engine capacity and even with the compression ratio is an important way forward to better fuel economy.

You will find some examples on
the Saab VCR engine in production. Additional link here and on page 4 of this document. Also follow what Envera is doing.

Cylinder cut off is also applied to have better combustion. Indeed the Caddilac 8-6-4 is an example and there are others too. Alfa Romeo had a cut on one bank of their V6 at a time.

What you can also do is optimizing fuel economy when cruising while having enough torque when needed as is done with hybrids when the additional torque comes from an electromotor.

I hope this gives you some better understanding of the matter.

Best Regards,

Randolph Toom

Aren't there any rotary people here Hello??/ Your crank is right there and is part of your drive more efficent less moving parts??//?///Lets talk

Okay. I love the Mazda RX-8, but the mileage is nothing to write home about, despite the weight advantages.

So what's up with that?