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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

#131

Post by coredog64 »

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…

Higher compression ratios mean higher temperatures. Higher temperatures means more NOX in the output. As it is cars _already_ have to run richer than stoichiometric in order to keep from melting the catalytic converter. I would expect this will require some extraordinary pollution control measures as well.

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

#132

Post by bluGill »

micaksica wrote: post #55
asimuvPR wrote: post #31

Here is a simple explanation gathered from this image http://o.aolcdn.com/hss/storage/midas/de3e84cf46030cd7b3ea39... : The difference from a conventional engine is that the engine stroke is increased or decreased automatically. The stroke is the distance the piston travels up and down in order to turn the crankshaft. A shorter distance that is closer to the combustion chamber increases the compression ratio because…

> Possible issues with this design could be: Let's also recognize that shortblock costs will be much, much higher with this design when you need a rebuild. Many engine builders won't touch this, and I'd suspect the Nissan OEMs will say that these engine shortblocks are "factory replaceable only". Who is going to make aftermarket bearings for the multilink setup? How does the engine operate under actuator failure?

> Many engine builders won't touch this

That depends on how popular rebuilds are. If this design proves out many engines will go to this and then a rebuilder who refuses to touch this design won't be in the business anymore.

If this design takes 1/10th of a second off lap times rebuilders will quickly not work on anything else, even if for every other application this engine is junk. (in most other applications the engine will outlast the car without a rebuild)

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

#133

Post by _archon_ »

paulmd wrote: post #18
Aelinsaar wrote: post #13

Earlier quoted context omitted.

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

Variable geometry turbos are a thing, and have been for some time. The larger trucks and semis use this technology. Typically they are hydraulically controlled.

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

#134

Post by HeyLaughingBoy »

dsfyu404ed wrote: post #124
larrydag wrote: post #114

Earlier quoted context omitted.

Clever design but that looks like a lot of moving parts. I wonder about longevity of the engine.

Figuring out longevity will probably wait until they've been shipping for a few years.

Or... maybe, just maybe, after they've done longevity testing!

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

#135

Post by zglennie »

TheSpiceIsLife wrote: post #68
TheSpiceIsLife wrote: post #66

Earlier quoted context omitted.

I don't follow how the stroke length changes. The conrod (upper-link in the image) is a fixed length, therefore the stroke length is fixed. The compression ratio changes because the mechanism changes where TDC (Top Dead Centre) is. Or have I misunderstood something? Edited to add: If TDC moves then the bottom of the stroke moves with it because the conrod is a fixed length, right?

Never mind, I see now how the mechanism changes the stroke length.

Can you elaborate? I'm trying to figure it out. I'm also confused about where the crankshaft is supposed to be in this picture.

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

#136

Post by Annatar »

Neil44 wrote: post #122
Annatar wrote: post #106

Earlier quoted context omitted.

First of all, timing by injection is still simpler than timing by spark: in gasoline engines, the computer must time both the injection and the ignition. Second, timing by spark means that spark plugs are necessary, so that is more parts, and more parts means higher probability of failure. Third, spark plugs are needed to start a chain reaction of igniting fuel, because gasoline fuel is volatile enough as not to be c…

I'd say that modern disel injector problems were more common than spark plug problems, so I guess we'll have to agree disagree :) I could also draw your attention to the cost and ease of replacement of a spark plug vs a diesel injector, or all the extra emissions treatment equipment that modern diesels need that petrol doesn't, but I don't think we're going to convince each other here :)

How long have you worked on diesels in order to be able to claim that?

How many cases of diesel engines with injector problems have you had during your career as a mechanic?

How much does, on the average, a diesel injector cost?

How often do they have to be replaced?

I've worked on diesel engines since I was a little kid, and have yet to work on one with injector problems.

The following are ultramodern mazda injectors, for instance; if you look at the spray pattern and the capability of these programmable injectors, it's pretty obvious it's going to be tough for them to experience problems:

https://www.youtube.com/watch?v=fDFgiLrEX1o

modern piezoelectric technology is wonderful, isn't it? And wouldn't you know it, all modern diesel engines sport piezoelectric injectors.

But let's suppose for a moment that you are correct, and that I'm wrong. Your logic has one flaw, and that is that in a diesel engine, I will (and have) get three times the kilometrage that you will get with a gasoline engine. Even if I had to replace all of the injectors, I will still have come out ahead. How?

Assuming that you are running the simplest, ultramodern gasoline V8 (I picked V8 in particular because that is the most reliable of the gasoline engines), if you maintain it according to the extreme maintenance schedule, you might get about 460,000 km out of it before requiring a rebuild. By that time, I will have gotten almost 1,300,000 km on the diesel and maybe need an engine rebuild, and that engine rebuild might not even need new injectors, if I changed my fuel filter every 15,000 km (which I do), and every 30,000 km added one liter of biodiesel to my tank!

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

#137

Post by barney54 »

codeulike wrote: post #117
lutefisk wrote: post #116

Earlier quoted context omitted.

So all companies related to gas technology should just close up shop? Something that may or may not work is on the horizon, so all the engineers that have been researching gas technology for years should throw in the towel and quit? There is no chance that electric overtakes gas in 5 years.

er, electric cars work fine. They just need to get cheaper and have longer range. That will happen easily in the next 5 to 10 years.

...But it hasn't happened in the last 100 years--it also hasn't happened over the last 5-10 years. The Nissan Leaf, for example, is over 5 years old.

There are good reasons why EVs haven't dominated yet--cost, range, flexibility, etc. Battery technology hasn't changed all that much either: http://www.cnet.com/news/why-batteries-arent-getting-better/

Someday EVs may dominate, but it's doubtful that will happen in the next 5-10 years unless there is a large technological leap.

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

#138

Post by sliverstorm »

Aelinsaar wrote: post #119
sliverstorm wrote: post #35

Earlier quoted context omitted.

I suspect it does two things- 1) lets the engine have high compression AND a turbo. Typically a turbo is run with lower compression, because even today nobody can make an engine run 14:1 with a turbo. Speculating, when you floor it the compression might drop to 8:1 and the turbo kicks in; then when you highway cruise, it runs 14:1 for efficiency. 2) lets the little engine still hit big torque numbers at low speeds. T…

Ahhhh, those both make a lot of sense. This could be a nice feature on higher-end cars that try to use smaller engines, with more turbos, for the sake of fuel and emissions then?

Right, I think it's most interesting in the context of the little-engine-big-turbo archetype.

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

#139

Post by Annatar »

TylerE wrote: post #123
asimuvPR wrote: post #86

Earlier quoted context omitted.

Depends on the brand. Nissan engine quality has gone down in the last 15 years. Their flagship engine the VQ3XDETT has been good but the rest of the lineup has suffered. Its not yet as cas as a chrysler9 engine, but its not what it was during the 80s and 90s.

I seriously doubt their actual levels of quality have gone downhill. Automotive quality has been on an enormous upswing - the WORST cars of today are better than the BEST cars of 25 years ago.

No worries - where there is management, especially middle management, there's always trouble.

And at PSA concern, there is a lllooottt of management! NISSAN is nowhere near the ingenuity and quality they were back in the '80's and the '90's, after all, most of the engineering comes from Renault now, and not Japan. And the Japanese get all the low end engineering designs from Renault, while Renault, Peugeot, and Citroen get all the good engineering in the European models. Ah the "benefits" of being part of the PSA concern!

I remember studying a NISSAN Cherry back in 1988 and my jaw was on the ground with how much cutting edge technology that little car was loaded with (and it was just a city car!), and I look at all the garbage cars NISSAN has been pumping out today... it's an atrocity. Even if I compare the 280 ZX turbo and today's offerings... the 280 ZX is impressive, while today's assortment is something I would be ashamed to be seen in.

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

#140

Post by nwmcsween »

asimuvPR wrote: post #31

Here is a simple explanation gathered from this image http://o.aolcdn.com/hss/storage/midas/de3e84cf46030cd7b3ea39... : The difference from a conventional engine is that the engine stroke is increased or decreased automatically. The stroke is the distance the piston travels up and down in order to turn the crankshaft. A shorter distance that is closer to the combustion chamber increases the compression ratio because…

The piston wear shouldn't be an issue as Nissan will have to cycle (high/low compression) the pistons anyways otherwise the split ring will catch on a the lip that normally occurs, it would be nice if they used sleeves in case there is an issue but I doubt they will. How would the turbo over boost? The ECM controls what the turbo does and if the waste gate is open or not. It would be interesting to see if and how they control compression to each cylinder, maybe a waste gate at each cylinder on the manifold.

The issues I see:

* Regular gasoline explodes from too much compression, if this engine requires premium gasoline it's sort of dead out the door.

* NOX emissions increase with efficiency and in general efficiency increases with compression, there are two prevailing ways to fix this: cheat and inject urea.

* It greatly complicates where all the force is being generated which will probably lead to more failures.

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