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SKYACTIV-X: first commercial gasoline engine to use compression ignition

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Re: SKYACTIV-X: first commercial gasoline engine to use compression ignition

#111

Post by DennisP »

spitfire wrote: post #103
ChuckMcM wrote: post #18

A reuters story on how it works: https://www.reuters.com/article/us-mazda-strategy-idUSKBN1AO... So this is 'gasoline' diesel. Or diesel without the NOx. Which, in theory, would give better fuel economy and possibly better torque. And it will ship in cars in the 2019 model year (so possibly as early as late next year). To me, it sounds like a "Don't pass"[1] bet on electric cars. Which they also are working with Toyo…

I believe it's a "luxury/enthusiast" strategy. I believe the auto market will play out something like the watch market did with the introduction of the quartz watch. Most people just want to tell the time, so they buy a quartZ. Similarly most people just want to get from A to B, so will buy an electric (automated) car. Some people enjoy the mechanics of the thing. So they buy a nice mechanical watch. These watches we…

Probably true, but at the same time, some electric cars are pretty darn fun to drive.

Re: SKYACTIV-X: first commercial gasoline engine to use compression ignition

#112

Post by mywittyname »

oatmealsnap wrote: post #35
ChuckMcM wrote: post #18

A reuters story on how it works: https://www.reuters.com/article/us-mazda-strategy-idUSKBN1AO... So this is 'gasoline' diesel. Or diesel without the NOx. Which, in theory, would give better fuel economy and possibly better torque. And it will ship in cars in the 2019 model year (so possibly as early as late next year). To me, it sounds like a "Don't pass"[1] bet on electric cars. Which they also are working with Toyo…

Gasoline engines aren't going away for a while; even when every self-driving car is electric, there will be a market for people who want gasoline engines. If it gives a bump in fuel economy to the next (last?) generation of gasoline and hybrid vehicles, great! I also wonder if the maintainability of these engines will be the same as with diesel. That would be another big benefit.

Diesels aren't inherently more maintainable than gasoline engines. That impression comes from the fact that diesel engines are used in situations where durability is paramount, thus are designed to be robust. Most passenger car engines have several criteria that are more important than maintainability (emissions, power, fuel economy, size, cost, manufacturing simplicity).

People don't hold up BMW passenger diesels as the hallmark of maintainability. Heck, even the diesel offerings in American trucks are pretty bad from a reliability standpoint. Both Cummins and Navistar faced multiple CALs over reliability and warranty-related issues.

Re: SKYACTIV-X: first commercial gasoline engine to use compression ignition

#113

Post by tpm »

robin_reala wrote: post #49
oatmealsnap wrote: post #35

Earlier quoted context omitted.

Gasoline engines aren't going away for a while; even when every self-driving car is electric, there will be a market for people who want gasoline engines. If it gives a bump in fuel economy to the next (last?) generation of gasoline and hybrid vehicles, great! I also wonder if the maintainability of these engines will be the same as with diesel. That would be another big benefit.

Outside of Europe maybe. Inside, well, UK and France have already said no more ICE vehicles to be sold past 2040, and other countries are planning the similar (including India). That’s a big loss of market and consequent economy of scale.

This only concerns passenger cars, not trucks, possibly not even vans. And the discussion is still ongoing.

Re: SKYACTIV-X: first commercial gasoline engine to use compression ignition

#114

Post by bluGill »

mtgx wrote: post #33
bsdetector wrote: post #30

Earlier quoted context omitted.

Or a bet on hybrids. Hybrids enable new types of engines that for instance operate at constant rate or that are under-powered for acceleration from a stop or going uphill.

I don't think hybrids have any future except in the heaviest of vehicles, where batteries won't make sense for another few decades. We're already seeing companies being interested in making battery-only buses, tractors, semis, and even airplanes. Not all models of those types of vehicles may work with batteries, but it's a sign of what the future could bring.

battery only buses make sense because the bug needs to run over rush hour and then can sit all do to charge. Battery operated tractors do not make sense without vastly better batteries because a tractor needs to run for 16 hours at max power (500hp). Sustaining 400000 kw for 16 hours is not easy. For semis and airplanes you need to consider your use: for short in town loads/short flights batteries can work, for longer distances we don't have the battery technology today to make it work.

Someone once told me battery technology has 2-3 more doubling left and then we hit chemical limits and cannot get more out of them. If this is correct batteries can never do the longer distances, but I don't know if it is correct.

Re: SKYACTIV-X: first commercial gasoline engine to use compression ignition

#115

Post by mywittyname »

cmrdporcupine wrote: post #78
bsdetector wrote: post #30

Earlier quoted context omitted.

Or a bet on hybrids. Hybrids enable new types of engines that for instance operate at constant rate or that are under-powered for acceleration from a stop or going uphill.

I bet on plugin hybrids, specifically ones with large batteries. This seems to be an unpopular opinion, but I think the Voltec drivetrain shows what's possible here. Pure EV purists dislike PHEVs because they have the complexity of an ICE car + an EV car, but I think there's some serious advantages. Like you say, Atkinson cycle for electricity generation for when the battery drains beyond smaller commute ranges. Some…

> because they have the complexity of an ICE car + an EV car,

The irony being that most don't. For example, hybrid synergy drive is basically an alternate transmission design that replaces the complex clutch packs used to control Ravigneaux planetary gears with electric motors. The result is a more simple overall design.

Other systems are literally just beefed up starters.

Re: SKYACTIV-X: first commercial gasoline engine to use compression ignition

#116

Post by mikestew »

TomMarius wrote: post #74
komali2 wrote: post #71

Earlier quoted context omitted.

We have the big and beautiful 280 between Mountain View and San Francisco, and I thank goodness every time I make my way to the city for it. I'd never go the speeds on my bike I do on 280 anywhere else, but it's just such a gosh darn huge road I get to make a 45-60 minute trip in like 30 minutes.

I though you Americans have it pretty rough when you're caught going over speed limit?

It very much depends on where in the U. S. one is at. East of the Mississippi River (eastern U. S.): I'm a good boy who doesn't do more than 10mph over the limit. The exception is Ohio: if I can't avoid the state completely, I do THE SPEED LIMIT.

Western U. S.: whatever I think I can get away with. IOW, if I can see for multiple miles with few cross roads and driveways, then it's whatever I feel comfortable with. Though with western speed limits of 70mph and up, one can comfortably get away with 85mph, which is fast enough for me. Much beyond that, on the bike or in the car, and it gets tiring and the difference in fuel efficiency is huge (28mpg or less at "spirited" speeds on a bike that normally gets 42-45mpg). And the last thing one needs in a vehicle with a 5 gallon tank, and an area with few gas stations, is poor fuel efficiency. With increased fuel stops, I'm not convinced that one saves a minute of time after a point.

In this instance, think of the U. S. more like the EU. We have Montana and Nevada, they have Germany. We have Ohio, they have (for lack of a better example) the U. K. with speed cameras everywhere (yeah, yeah, Brexit; bear with me for this example).

Re: SKYACTIV-X: first commercial gasoline engine to use compression ignition

#117

Post by NickM »

spitfire wrote: post #103
ChuckMcM wrote: post #18

A reuters story on how it works: https://www.reuters.com/article/us-mazda-strategy-idUSKBN1AO... So this is 'gasoline' diesel. Or diesel without the NOx. Which, in theory, would give better fuel economy and possibly better torque. And it will ship in cars in the 2019 model year (so possibly as early as late next year). To me, it sounds like a "Don't pass"[1] bet on electric cars. Which they also are working with Toyo…

I believe it's a "luxury/enthusiast" strategy. I believe the auto market will play out something like the watch market did with the introduction of the quartz watch. Most people just want to tell the time, so they buy a quartZ. Similarly most people just want to get from A to B, so will buy an electric (automated) car. Some people enjoy the mechanics of the thing. So they buy a nice mechanical watch. These watches we…

Perhaps, but I wonder if we won't see more countries go the way of Norway/France/Britain and ban gasoline cars altogether once electric vehicles become more competitive and mainstream....

Re: SKYACTIV-X: first commercial gasoline engine to use compression ignition

#118

Post by mulmen »

oatmealsnap wrote: post #35
ChuckMcM wrote: post #18

A reuters story on how it works: https://www.reuters.com/article/us-mazda-strategy-idUSKBN1AO... So this is 'gasoline' diesel. Or diesel without the NOx. Which, in theory, would give better fuel economy and possibly better torque. And it will ship in cars in the 2019 model year (so possibly as early as late next year). To me, it sounds like a "Don't pass"[1] bet on electric cars. Which they also are working with Toyo…

Gasoline engines aren't going away for a while; even when every self-driving car is electric, there will be a market for people who want gasoline engines. If it gives a bump in fuel economy to the next (last?) generation of gasoline and hybrid vehicles, great! I also wonder if the maintainability of these engines will be the same as with diesel. That would be another big benefit.

Nothing about a self-driving car requires it to be electric.

Re: SKYACTIV-X: first commercial gasoline engine to use compression ignition

#119

Post by toxik »

flamedoge wrote: post #75
ddeck wrote: post #23

Earlier quoted context omitted.

This is correct, but they're are also predicting an equivalent improvement in fuel consumption: "Compared to the current lineup of SkyActiv-G engines, the SkyActiv-X line should use between 20 and 30 percent less fuel." http://newatlas.com/mazda-skyactiv-x-compression-ignition/50...

more torque = less rpm @ same hp?

Torque is directly proportional to power, related by angular velocity. So τ Nm of torque at angular velocity ω rad/s will give you power P = τ·ω in watts. In fact this works for three-dimensional τ and ω if · is the scalar product.

Oh and an RPM of N is equivalent to angular velocity ω = N·π/30.

Re: SKYACTIV-X: first commercial gasoline engine to use compression ignition

#120

Post by teraflop »

fnj wrote: post #102
ChuckMcM wrote: post #18

A reuters story on how it works: https://www.reuters.com/article/us-mazda-strategy-idUSKBN1AO... So this is 'gasoline' diesel. Or diesel without the NOx. Which, in theory, would give better fuel economy and possibly better torque. And it will ship in cars in the 2019 model year (so possibly as early as late next year). To me, it sounds like a "Don't pass"[1] bet on electric cars. Which they also are working with Toyo…

> So this is ... diesel without the NOx NOx is not peculiar to diesel engines. Gasoline engines also generate NOx. All internal engines make NOx. As long as you burn fuel + atmospheric air you get NOx. The atmosphere is 78% nitrogen. Some of it gets oxidized.

This makes me wonder whether it would be theoretically possible to use some of the engine's power output to extract nitrogen from the incoming air. You'd effectively be trading more CO2 pollution (because of the reduced efficiency) for less NOx pollution.

My back-of-the-envelope calculations suggest that off-the-shelf oxygen concentrators aren't efficient enough to make this practical, but I don't know whether there are fundamental thermodynamic limits that would prevent the efficiency from being improved.

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