Nissan Motor Company has announced a new type of gasoline engine • Hacker News Board

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

#61

Post by 13of40 » Mon, Aug 15, 2016, 5:52 AM UTC

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…

Maybe the trick would be to have two crank shafts, with two pistons per "cylinder" (or combustion space), and run them slightly out of phase with each other to vary the compression....

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

#62

Post by asimuvPR » Mon, Aug 15, 2016, 5:52 AM UTC

pdonis wrote: post #56

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…

> A shorter distance that is closer to the combustion chamber increases the compression ratio because there is less space for the fuel/air mixture. When the system is operating in low compression mode the piston travels more and does not reach as high. I think this is partly inaccurate. The images show the piston at the top of the stroke; when the compression ratio is high the piston is higher at the top of the strok…

Yes, you are correct. It was a mistake on my end. Thanks for pointing it out. I cannot update the post to fix the mistake. Hope people upvote your post to make sure it stays visible.

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

#63

Post by asimuvPR » Mon, Aug 15, 2016, 6:12 AM UTC

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?

I figure these engines won't be rebuilt. Its simpler to swap one in since its a four cylinder.

The engine should operate OK in case the actuator stops adjust the stroke. There really isn't anything new in terms of parts. They simply took proven implementations of each part and applied them in a new configuration. The biggest issue might be cylinder bore degradation due to the variable stroke. I need to learn more about its lubrication system before I can pass judgement. It probably has some additional jets in the middle shaft that sprays the piston and the bore on different angles. Nissan already uses jets on their turbocharged engines. I just sondas how they might pull it of here. The oil galleries shouldn't be so different from a conventional engine.

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

#64

Post by SigmundA » Mon, Aug 15, 2016, 6:15 AM UTC

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…

Well you could do like diesels and use urea injection in the exhaust to neutralize NOx, this add complication, but nothing like this new design.

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

#65

Post by asimuvPR » Mon, Aug 15, 2016, 6:16 AM UTC

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…

Yes, high compression chambers are tricky and require pistons that incorporate part of the chamber shape on their domes.

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

#66

Post by TheSpiceIsLife » Mon, Aug 15, 2016, 6:16 AM UTC

pdonis wrote: post #56

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…

> A shorter distance that is closer to the combustion chamber increases the compression ratio because there is less space for the fuel/air mixture. When the system is operating in low compression mode the piston travels more and does not reach as high. I think this is partly inaccurate. The images show the piston at the top of the stroke; when the compression ratio is high the piston is higher at the top of the strok…

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?

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

#67

Post by l0neranger » Mon, Aug 15, 2016, 6:18 AM UTC

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?

Audi is working on a type of electric turbocharger that spools the turbo ahead of the exhaust gas pressure, to eliminate lag . VW is working on one that uses an air compressor to pre-spool the turbo charger. And Eaton has an electric assisted supercharger that helps the supercharger spool, it can also can start the engine, and recover energy from engine braking.

I'm wondering if something like stored kinetic energy like that on the Audi e-tron (a carbon vacuum sealed flywheel) could also be used to ram air into the intake, and how much resistance the air would have against the stored energy.

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

#68

Post by TheSpiceIsLife » Mon, Aug 15, 2016, 6:19 AM UTC

TheSpiceIsLife wrote: post #66

pdonis wrote: post #56

Earlier quoted context omitted.

> A shorter distance that is closer to the combustion chamber increases the compression ratio because there is less space for the fuel/air mixture. When the system is operating in low compression mode the piston travels more and does not reach as high. I think this is partly inaccurate. The images show the piston at the top of the stroke; when the compression ratio is high the piston is higher at the top of the strok…

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.

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

#69

Post by asimuvPR » Mon, Aug 15, 2016, 6:23 AM UTC

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?

Not at all. Problem is that ir has been an uphill battle to develop such technology. The energy required to move a turbo compressor fast enough ti generate boost is very high. A hydraulic approach has also been under works but proved challenging. Although Garret has promoted turbochargers with embedded motors to speed up the compressor speed and reduce lag.

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

#70

Post by usrusr » Mon, Aug 15, 2016, 6:27 AM UTC

tapeman wrote: post #48

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…

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 development.