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-   -   Nissan announces 2.0L variable compression ratio engine (https://ecomodder.com/forum/showthread.php/nissan-announces-2-0l-variable-compression-ratio-engine-34189.html)

Daox 08-15-2016 12:58 PM

Nissan announces 2.0L variable compression ratio engine
 
1 Attachment(s)
http://ecomodder.com/forum/attachmen...1&d=1471279636

Hmm... very interesting.

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

Quote:

The result of all this is an engine that gets 27 percent better fuel economy than Nissanís 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 08-16-2016 08:24 PM

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 08-17-2016 04:44 PM

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 08-17-2016 07:52 PM

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 08-18-2016 02:36 PM

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 08-18-2016 09:08 PM

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 08-22-2016 09:15 PM

Here's another variable compression scheme:

http://blog.caranddriver.com/wp-cont...cr-876x535.png
(Click on image for link)

Xist 08-23-2016 06:30 PM

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

Fixed

Frank, what do you think would be more effective?

gone-ot 08-23-2016 08:53 PM

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 08-29-2016 06:45 AM

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

http://www.topgear.com.ph//images/20...c-t_engine.gif

NeilBlanchard 08-29-2016 08:58 AM

If the crankshaft rotation was counterclockwise - would the power stroke have better mechanical vectors?

The radius of the crank pin is much smaller, and based on that, the torque would seem to be MUCH lower for the left side diagram.

niky 08-29-2016 01:31 PM

Quote:

Originally Posted by NeilBlanchard (Post 521655)
If the crankshaft rotation was counterclockwise - would the power stroke have better mechanical vectors?

The radius of the crank pin is much smaller, and based on that, the torque would seem to be MUCH lower for the left side diagram.

Interesting thought. I see what you mean... this is basically the reverse of a stroker modification... instead, you're getting the engine to act like a short-stroke one with the same effective movement range. I don't know if it's noticeable, but the piston on the VC-T actually accelerates slower at the start of the downstroke than the standard piston, where all the power is supposed to be made... and contrawise, due to the eccentric movement of the upper link, if you reversed the motion, the VC-T piston would indeed move faster on the downstroke, which *should* give more torque. (...uhh... right?)

But I'm assuming Nissan makes it rotate that way due to side loading and efficiency. Plus, it will probably rev higher (if these other considerations outweigh the extra friction caused by the extra link assemblies) Besides... with a turbo, they can probably cover up any torque deficiency inherent in the design... they're claiming V6-like power... meaning 250-300+ hp... though that's not too terribly far out for a two-liter turbo nowadays.

California98Civic 08-29-2016 08:01 PM

Thanks Daox... interesting bit of news.

Fingie 08-30-2016 07:49 AM

This is certainly interesting.

We'll see how well these will last.

It's amazing how far you'll go with money, many cheaper manufacturers haven't even changed to direct injection, and here we have some manufacturers reinventing the wheel (Or should I say crank)

NeilBlanchard 08-30-2016 12:21 PM

Quote:

Originally Posted by niky (Post 521675)
Interesting thought. I see what you mean... this is basically the reverse of a stroker modification... instead, you're getting the engine to act like a short-stroke one with the same effective movement range. I don't know if it's noticeable, but the piston on the VC-T actually accelerates slower at the start of the downstroke than the standard piston, where all the power is supposed to be made... and contrawise, due to the eccentric movement of the upper link, if you reversed the motion, the VC-T piston would indeed move faster on the downstroke, which *should* give more torque. (...uhh... right?)

But I'm assuming Nissan makes it rotate that way due to side loading and efficiency. Plus, it will probably rev higher (if these other considerations outweigh the extra friction caused by the extra link assemblies) Besides... with a turbo, they can probably cover up any torque deficiency inherent in the design... they're claiming V6-like power... meaning 250-300+ hp... though that's not too terribly far out for a two-liter turbo nowadays.

I was thinking along the lines of what Honda (and I am sure others as well) did, which is to offset the centerline of the cylinder to the down (power) stroke side. This puts the connecting rod in a better position at TDC to push the crank more effectively at the beginning of the power stroke.

niky 08-31-2016 10:09 PM

Quote:

Originally Posted by NeilBlanchard (Post 521759)
I was thinking along the lines of what Honda (and I am sure others as well) did, which is to offset the centerline of the cylinder to the down (power) stroke side. This puts the connecting rod in a better position at TDC to push the crank more effectively at the beginning of the power stroke.

The way I see it... it's already offset that way... but I don't know how much of that vertical push goes into the crank.

Funnily enough, some readers pointed out Honda's EX-link, which I knew nothing about... which uses almost the exact same multi-link system, only with a continuously moving lower pivot, basically making it an atkinson's engine, with a longer intake stroke achieved mechanically rather than through valve trickery:
https://www.youtube.com/watch?v=P68W5jOR0bA

(the animation is a bit off, though... in the final Honda prototype, the connecting rod also pushes straight down on the power stroke)

Thinking of covering this one, also, since it was mentioned... but that's going to be a pain in the butt to animate. :D

NeilBlanchard 09-01-2016 12:30 PM

That's a different design than the Nissan engine.

niky 09-02-2016 06:56 AM

Quote:

Originally Posted by NeilBlanchard (Post 521967)
That's a different design than the Nissan engine.

Yes, it is, but interestingly, Honda's final engine uses a very similar multi-link geometry:

http://world.honda.com/news/2011/p11.../images/10.jpg

rmay635703 09-02-2016 09:21 AM

Interesting that Honda uses that engine for natural gas cogeneration and heat.

Its unfortunate that cogeneration systems (which are just a motor and heat exchanger) can't be mass produced and reasonably priced.

If they were priced at the same rate as any other small engine we could produce energy at home more efficiently than the grid with about the same level of reliability. Solar when you have it NG when you don't and need heat.

RedDevil 10-01-2016 04:04 PM

Road&Track had it featured nicely:

Variable Compression Engine - How Infiniti VC-T Works

niky 10-02-2016 09:43 PM

Quote:

Originally Posted by RedDevil (Post 523911)

I covered it more thoroughly months ago... :turtle: :p

cRiPpLe_rOoStEr 10-15-2016 04:30 PM

Quote:

Originally Posted by niky (Post 521675)
they're claiming V6-like power... meaning 250-300+ hp... though that's not too terribly far out for a two-liter turbo nowadays.

That's why it doesn't seem so likely to reach production. And with direct injection becoming more widespread, a fixed high compression ratio is actually more suitable than a variable one.

MetroMPG 12-27-2018 01:05 PM

This is not going to help the cause:


Quote:

Infiniti QX50's New Engine Falls Short in CR's Fuel-Economy Testing

The automaker says its technology delivers best-in-class mileage, but our results show it’s among the worst

https://www.consumerreports.org/fuel...economy-tests/


CR registered 22 mpg in their "real world" test, vs. an EPA rating of 26 mpg combined.

Vman455 12-27-2018 07:13 PM

That's too bad for Nissan. The hammer of bad publicity is about to come down on them.

I've come to really dislike CR. They play to the public's overconfidence in its own intelligence with their air of scientific inquiry, when their process is, "Hey, we removed the controls on all the variables that actually allow you to compare things like vehicle fuel economy with any consistency. Now we're going to scream about how our results varied! Oogie boogie!" Meanwhile, John Q. Public thinks that because they write, "...CR runs its own tests to simulate what consumers are more likely to experience in daily use," their results are perfectly valid and applicable to Mr. Public's own use case because they used science-y words like "test" and "simulate."

MetroMPG 12-28-2018 10:47 AM

Whereas I don't like them simply because they hate the Mitsubshi Mirage.

What's not to like in a spiritual successor to the Geo Metro??? :D

MetroMPG 12-28-2018 10:53 AM

1 Attachment(s)
I want to give CR some credit for making claims in a somewhat controlled fashion. They're at least doing track driving only, at set speeds, and correcting for temperature variation.

The government’s tests vs. ours

Quote:

Road tests. Consumer Reports’ fuel-economy tests are conducted on our track and on public roads. Testers splice a precise fuel meter into each test car’s fuel line to measure how much gas is consumed. Each car is then run through highway and city drive loops, with each performed multiple times by two drivers.


The city test is conducted on a loop that’s set up on our track to reflect driving in a suburban area. It’s marked so that a driver must maintain specific speeds in certain sections and stop the car at specific points for set idling times. Highway mpg is measured by driving on a particular stretch of sparsely used freeway near our test track at a steady pace of 65 mph.



Each driver runs the test in both directions to compensate for wind and the slight difference in grade.


Our raw results are corrected for temperature using a formula established by the Society of Automotive Engineers. But we don’t test if it’s too hot, too cold, too wet, or too windy. Our overall mpg is a weighted composite of city and highway mpg measurements.
From: https://www.consumerreports.org/cro/...-gap/index.htm



An interesting trend from their conclusions (I believe this refers mainly to city driving):



https://ecomodder.com/forum/attachme...1&d=1546012357

hayden55 12-28-2018 06:15 PM

I've never been a fan of diesel. But since we're talking about killing diesels here... It sure wouln't be hard with the current fuel prices.
In my city in AR gas: $1.829 Diesel: $3.039
That pretty much kills diesel right there, even enough for me to consider a gas burning f250 over a diesel version.

Angel And The Wolf 12-28-2018 07:02 PM

Quote:

Originally Posted by ksa8907 (Post 520848)
I thought hydraulically actuated valves were going to allow complete and independent control of effective compression ratio?.

Yes Start with the highest compression ratio your fuel can handle, for maximum displacement, and delay the intake valve closing as needed to lower the compression ratio as low as possible for the power needed. Of course, adjust the fuel injection map.

This system has too many reciprocating parts.

samwichse 12-29-2018 09:12 AM

Fiat's Multiair system is mechanically a lot simpler and seems to do a pretty good job.

https://www.youtube.com/watch?v=Td9Gz_h7Qpg

I've been very impressed with the cold start gas mileage.

Rumor has it, the turbo GSE 1L engine with multiair II (direct injection) will be replacing the NA 1.4L in the base Fiat 500 in the US for 2020!

rmay635703 12-29-2018 11:52 AM

Quote:

Originally Posted by samwichse (Post 587295)
Fiat's Multiair system is mechanically a lot simpler and seems to do a pretty good job.

https://www.youtube.com/watch?v=Td9Gz_h7Qpg

I've been very impressed with the cold start gas mileage.

Rumor has it, the turbo GSE 1L engine with multiair II (direct injection) will be replacing the NA 1.4L in the base Fiat 500 in the US for 2020!

I always hoped for the twinair diesel

samwichse 12-31-2018 11:20 AM

Quote:

Originally Posted by rmay635703 (Post 587304)
I always hoped for the twinair diesel

Does that exist?

rmay635703 12-31-2018 11:29 AM

Quote:

Originally Posted by samwichse (Post 587433)
Does that exist?

Nah just the 1.3 ltr multijet diesel which would still be a good offering with the 6sp stick

niky 01-03-2019 02:07 AM

Not surprised much. A downsized turbo is only going to be as economical as its acceleration profile. If the "standard consumer behavior" includes hitting the boost more often, it's going to drink more gas than normal.

What I'd like to see is how it drinks in traffic, where a downsized variable compression engine should have an advantage over regular ones... or if the heat issues inherent in turbocharged installations make that a no-starter, as well.

teoman 01-03-2019 03:16 PM

I have driven the 1.3 L multijet punto and the 1.9 multijet doblo. The engines are fairly good. I was pleased with the performance and the fuel consumption of both cars (3.5l and 5.5l respectively in city traffic). I did try to avoid rush hour but my city has 18M other people so there is always traffic.

euromodder 01-03-2019 04:52 PM

Quote:

Originally Posted by rmay635703 (Post 587304)
I always hoped for the twinair diesel

The petrol and CNG TwinAirs are nothing spectacular in real world driving, returning far worse FE than advertised


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