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#4588633 - 11/29/17 10:36 AM Infiniti First to Market with Variable Compression Engine ?
SubLGT Offline


Registered: 01/31/06
Posts: 2646
Loc: Idaho
Quote:
...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

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#4588651 - 11/29/17 10:51 AM Re: Infiniti First to Market with Variable Compression Engine ? [Re: SubLGT]
PimTac Online   content


Registered: 03/04/17
Posts: 4285
Loc: Soviet State of Washington
As I understand it, the Mazda SkyActiv can change its compression ratio depending on certain circumstances. It may be more common than we know.
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#4588655 - 11/29/17 10:53 AM Re: Infiniti First to Market with Variable Compression Engine ? [Re: SubLGT]
andyd Offline


Registered: 09/25/04
Posts: 7145
Loc: Marshfield , MA
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.
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#4588669 - 11/29/17 11:01 AM Re: Infiniti First to Market with Variable Compression Engine ? [Re: SubLGT]
PimTac Online   content


Registered: 03/04/17
Posts: 4285
Loc: Soviet State of Washington
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.
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#4588671 - 11/29/17 11:03 AM Re: Infiniti First to Market with Variable Compression Engine ? [Re: SubLGT]
StevieC Offline


Registered: 08/21/08
Posts: 17116
Loc: Ontario, Canada
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.
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#4588695 - 11/29/17 11:17 AM Re: Infiniti First to Market with Variable Compression Engine ? [Re: SubLGT]
meep Offline


Registered: 02/20/07
Posts: 3552
Loc: Southeast
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.
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#4588712 - 11/29/17 11:27 AM Re: Infiniti First to Market with Variable Compression Engine ? [Re: andyd]
Linctex Offline


Registered: 12/31/16
Posts: 6148
Loc: Waco, TX
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

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#4588715 - 11/29/17 11:30 AM Re: Infiniti First to Market with Variable Compression Engine ? [Re: SubLGT]
StevieC Offline


Registered: 08/21/08
Posts: 17116
Loc: Ontario, Canada
Nissan doesn't build aircraft and I'm thankful! LOL


Edited by StevieC (11/29/17 11:31 AM)
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#4588853 - 11/29/17 01:02 PM Re: Infiniti First to Market with Variable Compression Engine ? [Re: SubLGT]
ARB1977 Offline


Registered: 06/12/05
Posts: 5168
Loc: North Texas
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.
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#4589358 - 11/29/17 09:17 PM Re: Infiniti First to Market with Variable Compression Engine ? [Re: Linctex]
andyd Offline


Registered: 09/25/04
Posts: 7145
Loc: Marshfield , MA
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

This design is used in airplane engines? I didn't know that. Please elaborate.
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1994 Ranger ,the Rat, 5w30 dino, STP filter

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#4589503 - 11/30/17 01:19 AM Re: Infiniti First to Market with Variable Compression Engine ? [Re: ARB1977]
DoubleWasp Offline


Registered: 05/21/12
Posts: 5236
Loc: Fort Lauderdale, FL
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.
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#4589512 - 11/30/17 02:14 AM Re: Infiniti First to Market with Variable Compression Engine ? [Re: SubLGT]
Shannow Online   content


Registered: 12/12/02
Posts: 39858
Loc: 'Stralia
I remember 1980s magazine articles on Nissan working on that engine...it's been in development for a LONG time

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#4590403 - 11/30/17 09:16 PM Re: Infiniti First to Market with Variable Compression Engine ? [Re: SubLGT]
cronk Offline


Registered: 01/06/09
Posts: 1287
Loc: Watertown, New York
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!
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#4590438 - 11/30/17 10:07 PM Re: Infiniti First to Market with Variable Compression Engine ? [Re: SubLGT]
Merkava_4 Offline


Registered: 01/30/07
Posts: 17501
Loc: Clovis, CA
- variable compression
- variable valve timing
- multiple cylinder deactivation
- direct fuel injection

That should be a nice reliable engine. crazy crazy

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#4590759 - 12/01/17 09:19 AM Re: Infiniti First to Market with Variable Compression Engine ? [Re: SubLGT]
StevieC Offline


Registered: 08/21/08
Posts: 17116
Loc: Ontario, Canada
Just needs a CVT! LOL
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