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

www2.mazda.com

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

#101

Post by Neliquat »

jonsen wrote: post #94
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…

Someday someone might invent an efficient process for making gasoline from renewable energi sources.

Like ethanol? Biogas? Methane from farming and landfills? We are already doing all of those.

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

#102

Post by fnj »

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.

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

#103

Post by spitfire »

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 went from being simple utility pieces to works of art.

Similarly I expect that car companies will continue to sell a set of "enthusiasts" models for a long time. They might revert back to manual gearboxes, and become more and more outrageous works of art - turned polished engine bays (Think Perlée, etc).

When all your actual needs can be met by a self driving electric car, why do you own a physical mechanical car? For the enjoyment of it.

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

#104

Post by fnj »

kbenson wrote: post #86
cmrdporcupine wrote: post #78

Earlier quoted context omitted.

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…

> 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. I would imagine most the complaints are for when the ICE actually powers a drivetrain. If it's essentially a generator to keep the batteries from depleting too far, that's not much extra complexity it all. Have a problem with the generator? Just swap it out with a new or rebuilt one…

> a Tesla uses about 300 Watts a mile @ 55 Mph

This is nonsense. The dimensions are wrong. Watts are instantaneous power. To be meaningful, you would have to give either kWh/h or kWh per mile or km.

Besides that 300 W is only 0.4 hp. Sorry, but that is just not credible.

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

#105

Post by timerol »

kbenson wrote: post #86
cmrdporcupine wrote: post #78

Earlier quoted context omitted.

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…

> 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. I would imagine most the complaints are for when the ICE actually powers a drivetrain. If it's essentially a generator to keep the batteries from depleting too far, that's not much extra complexity it all. Have a problem with the generator? Just swap it out with a new or rebuilt one…

The units in the linked thread are slightly wrong, which was corrected later in the thread. 300 Wh/mi * 55 mph = 16.5 kW.

The most powerful generator I see on Honda's site is 10 kW for $5400.

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

#106

Post by tadfisher »

ajross wrote: post #84
toast0 wrote: post #37

Earlier quoted context omitted.

NOx emissions from a diesel engine are from atmospheric nitrogen and oxygen, not from the fuel. I welcome further clarifications, but my understanding is that this engine will not produce NOx like a standard diesel because the fuel/air mix will be tightly controlled like in a gasoline engine, and temperature and pressure will be significantly less than a standard diesel. Additionally, it seems the timing of the fuel…

I'm struggling with the same reasoning: NOx is the result of high combustion temperatures, which is a pure function of the compression ratio (and fuel mixture), which is the thing that defines the high efficiencies you can get with a diesel cycle. The argument in the linked wikipedia entry is that combustion temperatures are lower in this cycle because the better fuel/air mixing means it can burn much leaner and thus…

I don't buy the wikipedia argument either, but I do believe the homogenous charge mixture will burn at a lower temperature for a given compression ratio than the equivalent stratified charge.

Throwing f/a into the mix, the HCCI mode is apparently only active during low-power cruise, so the lean mixture is fine. The Mazda innovation is controlling the changeover from HCCI to SI when more power is demanded.

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

#107

Post by fnj »

komali2 wrote: post #55
mtgx wrote: post #33

Earlier quoted context omitted.

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.

Total individual perspective here, but my dad took me on his worksite like 15 years ago to see the big super gorram awesome trucks (seriously those things are HUGE). When I asked about the engines, he said the trucks had massive diesel generators that powered motors, that in turn powered the wheels and hydraulics. So in a way, lots of construction equipment has kind of already been "hybrid."

An electric power transmission is hardly hybrid. You just have two extra conversions in your transmission, mechanical to electric and electric back to mechanical.

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

#108

Post by chipsa »

kbenson wrote: post #86
cmrdporcupine wrote: post #78

Earlier quoted context omitted.

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…

> 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. I would imagine most the complaints are for when the ICE actually powers a drivetrain. If it's essentially a generator to keep the batteries from depleting too far, that's not much extra complexity it all. Have a problem with the generator? Just swap it out with a new or rebuilt one…

Yeah. I expect the unit being used is 300 Watt-hours. IOW: (300 Wh/mi 55mi/h) =16500 W, or 16.5 kW. Which actually sounds about reasonable, being 22 horsepower.

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

#109

Post by mikestew »

_ea1k wrote: post #47
mikestew wrote: post #19

Earlier quoted context omitted.

The rotaries leaked oil and got terrible mileage, and good luck finding someone to work on them. Other than that, they were zippy. "Usable" they might have been if you keep a low bar, but "practical" they were not.

Rotary engines do not "leak oil", they burn oil a modest amount of oil by design. If you think about it, there really wasn't another way to lubricate them. Practicality was pretty low, though, as you rightly point out.

Rotary engines do not "leak oil", they burn oil a modest amount of oil by design.

I was thinking of the seals, which by about 50K seemed to be a common failure point. But, yes, they did burn a bit by design; no argument there. OTOH, a lot of Wankel defenders in this thread mention RX-8s. I'm remembering RX-7s, and the economy cars that used the Wankels. Those economy cars of the 70s are where the Wankel reputation for poor fuel mileage comes from. Cute TV commercials ("piston engine goes 'boing, boing, boing', Mazda engine goes 'hmmmmm'"), not really the best engine choice to go up against Honda and Toyota at the time.

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

#110

Post by fnj »

cromulent wrote: post #63
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…

It's good work, but I suspect Mahle's TJI (as used in current F1 cars) is a better bet. - Fuel efficiency gains over 17% - over 40% thermal efficiency - over 99% reduction in NOx - significant reduction in CO2 http://www.f1technical.net/news/20316 http://www.mahle-powertrain.com/en/experience/mahle-jet-igni...

- over 40% thermal efficiency

- significant reduction in CO2

CO2 production is directly inverse-linearly related to thermal eficiency. It is silly to list both.

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