Nissan announces 2.0L variable compression ratio engine

[Daox]

Hmm... very interesting.

The World's-First Variable Compression Ratio Engine Could Kill Diesel Forever

The result of all this is an engine that gets 27 percent better fuel economy than Nissan’s 3.5-liter V6, at roughly the same HP and torque. According to Reuters, at a press conference Nissan engineers said the new engine matches turbodiesels in torque, and is actually cheaper to build than modern turbodiesel engines.

What they fail to mention is this technology could also be used on diesels to further improve their efficiency as well (I would imagine at least). It would help deal with emissions as well as NHV and cold start conditions as well as efficiency... But you can't say that and also have a sensationalistic article title I suppose.

[ksa8907]

I thought hydraulically actuated valves were going to allow complete and independent control of effective compression ratio?

I think this is slick engineering, but I'm skeptical of it performing well in longevity tests.

[rmay635703]

Nissan variable compression ratio tech - Insight Central: Honda Insight Forum

Hmm even on wired, see if this goes anywhere or if its like the 90's era Chrysler 2 cycle car.

Imagine trying to rebuild an engine with that thing in there though?

[Frank Lee]

I wonder if the performance gains are worth the cost and complexity penalties?

I don't see wide-spread adoption of this. I don't even see long-term Infinity adoption of it.

I think there are simpler ways to achieve similar goals.

[Daox]

It would have been nice if they would have provided a apples to apples comparison of the mileage improvement. Yay, it makes as much power as a 3.5L. That is great. But, how does it compare fuel economy wise to a run of the mill 2.0L?

[niky]

Looking at it, it seems complex, but plot out the movement and it's pretty elegant.

First off, the power stroke is offset way to the side, and the conecting rod moves almost completely vertically, limiting side load and minimizing friction. Also, you have less horizontal movement at the bottom of the con rod than in a regular piston with the same stroke, and the counterbalance on the other side of the crank moves even less...

This all means less counterbalancing, less weight, smoother operation and... supposedly... the elimination of balancer shafts.

Sure, it's a little more complex... but with more parts under... presumably... less stress... it should all balance out.

[NeilBlanchard]

Here's another variable compression scheme:


(Click on image for link)

[Xist]

Could The World's First Variable Compression Ratio Engine Kill Diesel Forever?

Fixed

Frank, what do you think would be more effective?

[gone-ot]

The GM-version XM-1 tank had a variable compression ratio diesel engine (AVCR-1360), but ended up getting exactly the same "one-mile per gallon" mileage that the Chrysler XM-1 turbine did...so, the "peanut oil" burning turbine was selected (wink,wink).

[niky]

Here's a little diagram I worked up last week: