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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

#91

Post by Gravityloss »

dclowd9901 wrote: post #53
jacknews wrote: post #51

This looks cool, but complicated. The problem addressed seems to be that turbocharged (and supercharged) engines are sub-optimal at lower powers. IMHO mild electric hybrids, or full serial electric hybrids would be a more elegant solution - only run the combustion engine when full power is needed, and use the electric motor otherwise. "full power" could be used to top the battery if it's not all required for motion.

Would an electrically powered, computer-controlled turbo be silly?

Well, somewhat, if you mean an electric only compressor. Turbos actually increase efficiency because besides intake compression, they extract energy from the exhaust with the turbine.

Formula 1 cars have a mixture: there's an electric motor / generator in the turbo, so that the turbo can be spun up when there's not enough exhaust yet, but the engine needs a lot of air (when you start accelerating). Or the opposite: when there's excess exhaust energy that you don't need for intake charge anymore (when you've stopped accelerating), you can run the motor as generator providing electricity for batteries. Since the turbo rotation speed is so high and torque small, a relatively small motor-generator will suffice.

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

#92

Post by hvidgaard »

usrusr wrote: post #70
tapeman wrote: post #48

Earlier quoted context omitted.

That article is kind of shitty too. Higher compression ratio = better combustion = more power with less fuel, regardless of turbo. Higher compression will always mean better fuel efficiency. My moms Mazda CX-5 runs a 13.5 compression ratio and gets 27mpg. The power/efficiency trade off appears when you're talking about turbocharged engines. Turbos compress air into the combustion chamber, so when you compress compres…

So this only reduces inefficiency while the the engine revs too low for the turbo to kick in? Then it is competing with electrically assisted turbocharging (spin the turbo electrically when there is not enough exhaust pressure, basically a super/turbo hybrid using electric transmission), as both are addressing the same inefficiency. I know where I would put my bets in terms of price, reliability and ease of developme…

At lower revs the turbo is more likely to boost the engine if you demand power, of course depending on the dimensions of the turbo, but it doesn't make sense to put a performance turbo that works in the upper rpm range, in a regular car.

In any case, an electrically assisted turbo is not a replacement for this. This is a way to have high compression at low loads, such as highway crusing, and ability to lower compression when boost is needed for performance.

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

#93

Post by hvidgaard »

asimuvPR wrote: post #44
Unklejoe wrote: post #39

Earlier quoted context omitted.

I think you are incorrect. Most production cars (all that I know) have only a single fuel tank, thus nothing to mix.

I think the point of the person you replied to is that any variation in octane is handled by the fuel injection system. This renders having two tanks unnecessary (unless you require more distance between fill ups).

It can adapt to lower octane fuel by adjusting the timing, it's far from optimal, and at high enough boost level you need higher octane regardless. At non boost levels, you need less octane rating to prevent knock, but under boost you need higher octane rating. So you run the higher octane fuel all the time, and that is less efficient.

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

#94

Post by hvidgaard »

reidacdc wrote: post #14

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. e…

This is what Mazda is doing with their Skyactive-G engines if I'm not mistaken. It works reasonably well.

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

#95

Post by hvidgaard »

ArkyBeagle wrote: post #83
jacknews wrote: post #51

This looks cool, but complicated. The problem addressed seems to be that turbocharged (and supercharged) engines are sub-optimal at lower powers. IMHO mild electric hybrids, or full serial electric hybrids would be a more elegant solution - only run the combustion engine when full power is needed, and use the electric motor otherwise. "full power" could be used to top the battery if it's not all required for motion.

Turbocharging and supercharging grew up in aviation , where there is much more variable air pressure due to altitude. They were more a "hack" to get more envelope out of an engine system. Started seeing them on consumer ground vehicles in the '80s, when everything had to have a "turbo" button because PCs had one. It's never been clear to me that they are really all the great of a fit with terrestrial engines. Part co…

Much better low rpm power, and a more or less flat torque curve is possible. You can have a smaller engine, resulting in increased efficiency, while still having the power equal to a larger engine.

Not to mention that diesel engines are pretty much useless without a turbo.

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

#96

Post by hvidgaard »

ArkyBeagle wrote: post #84
dclowd9901 wrote: post #53

Earlier quoted context omitted.

Would an electrically powered, computer-controlled turbo be silly?

The electric motor to be used would have to be a pretty unusual motor. IMO, supercharging is "better" because the PTO side of an engine is less ... trouble than the exhaust side. Superchargers are generally heavier.

Super chargers generally result in a fairly large parasitic loss to power it. Turbo more or less harvest free energy with only a minimal loss due to increased back pressure.

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

#97

Post by tonylemesmer »

So if this engine changes the compression ratio (the amount the mixture is compressed) how is all this complexity better than a supercharger which changes the amount the air is compressed? Surely increasing the compression of the mixture and compressing the air before it goes in is pretty much the same thing? Except...that all that variable stroke length mechanism is a lot more complicated, and patentable?

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

#98

Post by cromulent »

sliverstorm wrote: post #27
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…

High compression ratios produces high combustion temperatures. This leads to the formation of nitrous oxide (NOx). We have a lot of techniques to improve mpg that increase NOx. If you can figure out how to easily inhibit NOx formation inside the combustion chamber you could be a rich man. Incedentally this is one way direct gasoline injection can improve economy. The injector sprays directly into the cylinder, and ca…

Mahle claim 99% reduction of NOx with their Turbulent Jet Ignition system.

http://www.f1technical.net/news/20316

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

#99

Post by Johan-bjareholt »

creshal wrote: post #78
themodelplumber wrote: post #49

Earlier quoted context omitted.

> Make sure to wait two years Haha, this reminded me of a friend who did a summer engineering internship with a U.S. automaker. He came back and related one of the most important things he learned: "never, ever buy a first-run car." I remember hearing him tell about tolerances still being adjusted after all these cars had shipped, cringing to think of all the problems that could cause.

Engine control computers are even more fun . A friend of mine works for Audi's/VW's supplier, and honestly my biggest surprise about the emission scandal was that the code actually worked. (They had to write their own linter, because they need to ship slightly broken code written by code generators, and last I heard Windows XP is still part of the compilation chain…)

I'm guessing you refer to AutoSARL when you talk about the code generation. Its insane that its an industry standard.
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