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Nissan Motor Company has announced a new type of gasoline engine

reuters.com

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Re: Nissan Motor Company has announced a new type of gasoline engine

#11

Post by shawkinaw »

From the (much better) Reuters article [0]:

> The higher the ratio, the more efficiently the engine works, producing better fuel economy and, with the addition of a turbo-charger, more power.

> Traditionally, design engineers had to fix a gasoline engine's combustion compression ratio, essentially deciding whether to go for power or economy.

Everything gets better with higher compression ratio, so where's the compromise? As I understand it, the only reason engine makers don't crank the ratio as high as possible is to avoid knocking.

[0] http://www.reuters.com/article/us-autos-japan-nissan-engine-...

Re: Nissan Motor Company has announced a new type of gasoline engine

#12

Post by brownbat »

I have a lot of respect for Nissan's engineers, but somewhat less respect for their lawyers, who hounded Uzi Nissan for a decade trying to get him to turn over his domain.

http://www.nissan.com/Lawsuit/The_Story.php

Cybersquatting is obnoxious, but once they found out it was the guy's actual name, and that he was using it to run his own business, they should have just accepted he had a right to the site and worked to buy it from him or moved on.

Re: Nissan Motor Company has announced a new type of gasoline engine

#13

Post by Aelinsaar »

shawkinaw wrote: post #11

From the (much better) Reuters article [0]: > The higher the ratio, the more efficiently the engine works, producing better fuel economy and, with the addition of a turbo-charger, more power. > Traditionally, design engineers had to fix a gasoline engine's combustion compression ratio, essentially deciding whether to go for power or economy. Everything gets better with higher compression ratio, so where's the comprom…

The drawback is that higher compression ratios require higher octane fuels. Nissan claims to have solved this by some kind of intelligent feedback system that allows them to control compression ratios on the fly. Presumably the compromise there is that it will require more moving parts, be expensive, and may come with issues of its own.

Variability in something like a combustion chamber is a cool idea, so is variability in the angle of turbo vanes. The issue is how you do it, affordably, and in a way that lasts the way that consumers expect from their cars.

Re: Nissan Motor Company has announced a new type of gasoline engine

#14

Post by reidacdc »

I am far from an expert, but there are two ways I know of to do something like variable compression, one is that Saab technique already mentioned, where the cylinder head is displaced to change the size of the combustion chamber.

The other related scheme is the Atkinson cycle: https://en.wikipedia.org/wiki/Atkinson_cycle

The wiki page shows a complicated mechanical arrangement for having a smaller intake volume vs. expansion volume, but the "poor man's" way to do this is to just keep the intake valve open for the first part of the compression stroke. The upside is that you can then adjust the effective compression ratio with valve timing. The downside is that it reduces the intake manifold vacuum by blowing back some of the intake air, not sure how that's handled.

Don't know what the Nissan guys are doing.

Re: Nissan Motor Company has announced a new type of gasoline engine

#15

Post by bmh_ca »

brownbat wrote: post #12

I have a lot of respect for Nissan's engineers, but somewhat less respect for their lawyers, who hounded Uzi Nissan for a decade trying to get him to turn over his domain. http://www.nissan.com/Lawsuit/The_Story.php Cybersquatting is obnoxious, but once they found out it was the guy's actual name, and that he was using it to run his own business, they should have just accepted he had a right to the site and worked to…

Lawyers are tools. (Being one, I feel I can say so, with a humble degree of confidence.)

Certainly there's a give-and-take between lawyers giving advice and clients taking it, but by the "big X" their lawyers essentially do what they are told - lest the big client move elsewhere.

All to say: Lawyers doing a bad thing are often a symptom of an internal disease or conflict.

Which is to summarize a whole host of conflicting emotions: I'm slightly defensive about the profession, wholly sympathetic to the outcomes of wielding lawyers to achieve evil ends, and biased by personal experience – but nevertheless appreciative of comments, like this, that highlight the responsibility that lawyers bear to not only advise and act but to represent the reputations of institutions.

Re: Nissan Motor Company has announced a new type of gasoline engine

#16

Post by qbrass »

tedunangst wrote: post #7
AmVess wrote: post #5

SAAB was working on one of these years ago before GM flew that company into the ground. This link gives you an idea of how it works. https://en.wikipedia.org/wiki/Saab_Variable_Compression_engi...

Variable compression? So logical next step is variable octane, right? One tank of 87 and one tank of 93, dynamically mixed in response to changing compression ratio. :)

A common way to run lots of boost on turbocharged cars is to use 87-93 normally, and E85 under high boost. You get the high octane when you need it, without the 30% hit to fuel economy when you don't.

Re: Nissan Motor Company has announced a new type of gasoline engine

#18

Post by paulmd »

Aelinsaar wrote: post #13
shawkinaw wrote: post #11

From the (much better) Reuters article [0]: > The higher the ratio, the more efficiently the engine works, producing better fuel economy and, with the addition of a turbo-charger, more power. > Traditionally, design engineers had to fix a gasoline engine's combustion compression ratio, essentially deciding whether to go for power or economy. Everything gets better with higher compression ratio, so where's the comprom…

The drawback is that higher compression ratios require higher octane fuels. Nissan claims to have solved this by some kind of intelligent feedback system that allows them to control compression ratios on the fly. Presumably the compromise there is that it will require more moving parts, be expensive, and may come with issues of its own. Variability in something like a combustion chamber is a cool idea, so is variabil…

The obvious precedent for variable-pitch blades are variable-pitch propellers on aircraft and helicopters. I don't want to say it's a solved problem for turbos, but there is almost a century's worth of prior art on the topic. That's one of those things that (in hindsight) really makes you wonder what took so long to think up.

https://en.wikipedia.org/wiki/Variable-pitch_propeller

Re: Nissan Motor Company has announced a new type of gasoline engine

#19

Post by tlb »

shawkinaw wrote: post #11

From the (much better) Reuters article [0]: > The higher the ratio, the more efficiently the engine works, producing better fuel economy and, with the addition of a turbo-charger, more power. > Traditionally, design engineers had to fix a gasoline engine's combustion compression ratio, essentially deciding whether to go for power or economy. Everything gets better with higher compression ratio, so where's the comprom…

Changed the URL from http://www.thedailynewsgrabber.com/nissan-on-gasoline-engine..., thanks.
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