Lotus developing HCCI engine, claims 10% efficiency increase
 

Interesting to see Lotus doing work on efficiency related items, but it seems they are working on their own gasonline HCCI (homogeneous charge compression ignition - ah la diesel) engine. Its also claimed that it can run on almost any liquid fuel because it has variable compression ratio via a movable puck the the head.

Lotus: Omnivore engine is 10% more efficient with more to come - Autoblog

http://ecomodder.com/forum/attachmen...1&d=1260542017

...a compression ratio "puck"?

...I've wondered why two "opposed" cylinders with variable "timing" on the dummy-compression piston hasn't been popularized more...especially with today's smart ECU controllers.

Daox -

I'd like to see a comparison chart between that one and the one that GM has had "in the works" for a really long time. It sounds like Lotus is claming to solve the HCCI puzzle.

CarloSW2

That would be great to see. How long has GM been working on their HCCI anyways? I know its been quite a few years, but unsure of exactly how long.

Traditionally 2 stroke engines generate 50% more power and use 50% more fuel than 4 stroke engines. If they eliminate the fuel usage problem inherent in 2 stroke carbs that give it such terrible emissions then it sounds good to me. Having a working prototype is probably Lotus' main point. But increasing compression from 10:1 to 40:1 is pretty handy. 10% improvement on Gasoline means if it ran on Alcohol or Diesel it could be even better. Mixed with turbocharging we're talking about cutting engine sizes in half and then by a third. Which means a theoretical 2.0l engine could be replaced by a TurboCharged 660CC motor! :thumbup: And run on just about any fuel of your choosing.

Mixing oil with gasoline is obsolete already since they switched most 2 strokes here in the US over to wet sump years ago. Some of the comments, sheesh :D.

Yeah, really. :) But then I thought about it a little bit and realized it wouldn't be that hard to do. All you need is a bit of moveable real estate on the cylinder head side of the combustion chamber. Move it further into the chamber to increase compression ratio, and move it out of the combustion chamber to reduce it. It can't be a flat plate, it needs to have sides; make it round and you have a "puck".

I have one of those, a two stroke diesel model airplane engine that fits in the palm of your hand with a nob on top to change the compression.

Lotus new development engine
 

An engine developped by Lotus for mixed fuel ,variable compression, two stroke, high efficiency.

Run the engine

http://www.grouplotus.com/manageshow...sthru/8628.swf

...excellent technical illustration of "...what's going on..." but I have to worry--too many mechanically 'moving' things for my mechanical-comfort-zone.

Maybe you've never seen how the various VTEC systems work. They can be pretty complicated, and people routinely get multiple 100K miles out of the engines.

I'm fascinated -- and a bit confused -- by the exhaust port Trapping Valve.

I'm trying to find out why no manufacture has implemented variable compression ratio technology. In part load conditions most engines only have an effective compression ratio of 6:1 or less (The published compression ratio only applies in high load conditions) So this makes me think of using a sliding plate that dynamically slides in a controlled manner into the combustion chamber (to displace some of the unoccupied volume) in part load conditions bringing the effective ratio back to 9.5:1 and slides out in high load conditions. It's probably not as simple as attaching this "slider" to an accelerator cable and I see lubrication and getting really tight tolerances as one of several challenges to be overcome. While I may be over simplistic here, why this low hanging fruit is still not implemented by any manufacturer as this idea has been floated for decades.
I just found some info here. This site www dot prodrive.com/up/vcr.pdf

I recall seeing an old magazine from the late 1940's that had an article about variable CR.
It was done on a flathead Olds engine, I think, and CR could be varied to go higher with light load.
Ray Mac

I was mistaken. The engine this was done on was a '40s flathead Olds but the article was in the Aug. 1953 issue of Popular Science. Oil pressure was used to drive a piston up and down in the cylinder depending on load to vary compression from 6-1/2 to 1 to 14 to 1.
Ray Mac

...the GM-Allison XM-1 "tank" that went up against the Chrysler "turbine" XM-1 tank used a variable compression ratio diesel engine.

...both got about 1 MPG or 1GPM (take your pick).

Updated link

Lotus Engineering - omnivore interactive demo

It appears all the VCR solutions I've read involve varying the combustion chamber volume by applying a force normal to a flat structure parallel to the piston head which necessitates the use of very high pressure specification, high force actuators. On the other hand a sliding profiled plate that slides parallel to the combustion pressure forces would require a far lower specification actuator. Remember the volume of the combustion chamber does not have to vary by much to have a large effect on compression ratio. The displacement profile of the slider plate would be optimized such as to preserve symmetry and avoid pockets of uneven combustion. Optimizing the profile for the part load condition would be the priority as that is where the majority of the engine operation time would be spent. I hope this technology becomes mainstream soon as it would enable an optimum use of E85 which needs a high compression ratio to get the most out of it.