Infiniti First to Market with Variable Compression Engine ?

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...At the Los Angeles Auto Show, INFINITI revealed the all-new QX50—a premium mid-size SUV featuring the first production application of the VC-Turbo variable compression ratio engine, transforming on demand…

...The VC-Turbo changes its compression ratio seamlessly with an advanced multi-link system, continuously raising or lowering the pistons’ reach to transform compression ratio—offering both power and efficiency, on demand….

...As the angle of the multi-link arms changes, it adjusts the top-dead-center position of the pistons—and the compression ratio with them. An eccentric control shaft changes the compression ratio of all the cylinders at the same time. As a result, the engine capacity varies between 1,997 cc (for a low 8:1 ratio) and 1,970 cc (high 14:1 ratio)….

...Equipped with the VC-Turbo engine, the QX50 delivers gasoline fuel economy of 27 mpg (US combined, front-wheel drive; 26 mpg all-wheel drive). In front-wheel drive specification, this offers a 35% improvement in fuel efficiency over the V6 gasoline engine in the previous QX50, while the new all-wheel drive model’s 26 mpg represents a 30% improvement...


More technical details here:
http://www.greencarcongress.com/2017/11/20171129-qx50.html
 
As I understand it, the Mazda SkyActiv can change its compression ratio depending on certain circumstances. It may be more common than we know.
 
There are too many extra reciprocating parts in there to make me comfortable. The 4 banger in my Camry gets 35.7 MPG in a 25~ mile drive to my daughter's house. I'm happy with that.
 
Reading that insert further this is a different way than what I was thinking. Mazda just keeps valves open at certain points in the combustion process to achieve the effect. Infiniti is going with a complicated method involving the rods. I would be cautious yet I applaud Infiniti for their innovation.
 
I will wait until Nissan (Infinity) has their failures like early CVT's first and then when the bugs are worked out have a look.
 
I really like the skyactive solution. lots of moving parts in the infinity design. I wonder if infinity found a wider performance/efficiency range or other advantage with their design? There's got to be additional losses from the multiple friction points and inertial mass, so there must be another payoff. I tell you what, when one of those throws a rod, the carnage will be unmatched.
 
Originally Posted By: andyd
There are too many extra reciprocating parts in there to make me comfortable.


1000's and 1000's of reliable flight hours say your fears are unwarranted

xr600-radial-master-link-rods.jpg
 
Since turbos are more common now and days. How about variable waste gates. More psi when needed. Instead of reaching a certain psi to releave pressure.
 
Originally Posted By: Linctex
Originally Posted By: andyd
There are too many extra reciprocating parts in there to make me comfortable.


1000's and 1000's of reliable flight hours say your fears are unwarranted

xr600-radial-master-link-rods.jpg

This design is used in airplane engines? I didn't know that. Please elaborate.
 
Originally Posted By: ARB1977
Since turbos are more common now and days. How about variable waste gates. More psi when needed. Instead of reaching a certain psi to releave pressure.


That's been done for a long time. Some vehicles change the boost pattern based on settings, and some based on atmospheric conditions.

I remember one of the rags doing a high altitude test of "hot" wagons, and the SAAB was walking away from a 540i wagon due it's boost pressure having elevated to 28psi to compensate for the lower air density.
 
I remember 1980s magazine articles on Nissan working on that engine...it's been in development for a LONG time
 
It is certainly an interesting concept. Variable compression along with variable valve timing could really optimize efficiency and power.
If this design proves reliable it could really be a game changer. I would definitely let someone else buy one and be the Guinea pig to test reliability!
 
- variable compression
- variable valve timing
- multiple cylinder deactivation
- direct fuel injection

That should be a nice reliable engine.
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Many years ago a car company had an engine that had variable compression ratios. I want to say it was Lotus. When the turbo was used, it went to a lower compression ratio, and with operations without the turbo it would go to a higher compression ratio. The cylinder head was pivoted on one side, and the other side was raised or lowered mechanically.
 
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