
SKYACTIV-X: first commercial gasoline engine to use compression ignition - interconnector
http://www2.mazda.com/en/publicity/release/2017/201708/170808a.html
======
ChuckMcM
A reuters story on how it works: [https://www.reuters.com/article/us-mazda-
strategy-idUSKBN1AO...](https://www.reuters.com/article/us-mazda-strategy-
idUSKBN1AO0E7)

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 Toyota on electric cars so perhaps it is a fall back plan. It
will be interesting to see how it fares. There are a lot of products that are
built as the other side of an industry change bet. Sun created a workstation
on the 68040 in case the SPARCStation didn't meet expectations as an example.

[1] In the dice game Craps, the "Don't Pass" bet is against the current player
'winning.'

~~~
oatmealsnap
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.

~~~
ouid
I visited a Tesla store once in mountain view, and they have a great little
demo where you can check the cost of charging your car in various states.

Washington DC, for whatever reason, gets its electricity from a gasoline power
plant. In Washington, the Model S gets 28 MPG.

This happened a while ago so I could be misremembering, but regardless I don't
believe that the environmental value of electric vehicles has been realized.
In a lot of places, your Tesla is still coal powered. Efficient internal
combustion engines are still a worthy cause, and this will continue until more
electricity is being produced than is normally consumed.

~~~
icc97
Electric cars are the real world example of loose coupling. Once your car is
electric the source of the electricity can change (from Coal -> Gas -> Solar)
and you don't have to change your car even slightly.

So it doesn't matter about any of the arguments about whether an electric car
is more efficient or not when the electricity comes from coal.

What matters is that having electric cars enables us to move to a future of
solar and wind and not notice the difference.

Plus having electric cars that don't pollute in cities where there are lots of
people and generating the electricity with coal fired powerstations outside of
cities where there are less people has immediate benefits.

~~~
bgarbiak
I'm as big fan of EVs as the next guy, and would love to see cities with clean
air and no noise. But, there are few things that we forget about when we talk
about zero-emmision cars.

EVs pollute less, but they pollute too, and in cities as well. They emit dust
(including the most harmful particles: PM10 and PM2.5) from break discs and
tires. Difference between CO2 in power plants and in city centers matters, but
not that much. Once it's in the atmosphere the damage is done. As for NOx, the
biggest offender in the dieselgate, Mazda's engines should not emit these.

Add a fact that in the current grid setup most of the energy is coming from
coal, and that it's very unlikely it is going to change in a near future
(mainly due to political reasons). Also, the waste from batteries is really
ugly.

Given all that factors a 30% less polluting combustion engine is almost too
good to be true. From a macro perspective the gain for environment is on par,
if not better, than from electric cars.

My biggest problem is to believe in the numbers Mazda provides. Have to wait
and see.

~~~
bovine3dom
> From a macro perspective the gain for environment is on par, if not better,
> than from electric cars.

Citation needed. It seems obvious to me that a huge power plant is going to be
less polluting per kWh than a tiny little engine in a car. Otherwise, we'd use
tiny little car engines to power everything - which only happens at the moment
in places where they cannot get electricity by other means (building sites
etc).

~~~
_wmd
Don't forget that electrical grid transmission losses cause massive efficiency
problems before centrally generated power ever reaches that car charging point
-- on the order of 30% or more, and conversion from AC to DC at the charging
port may account for another 10-30%. (Made up numbers, but they're in well
within range IIRC)

I don't think it follows that just because we have historically centralized
power generation, this was obviously due to efficiency. For example,
centralization of management, investment, pollution control, logistical (fuel
delivery), safety (nuclear) and reliability concerns seem far more obvious to
me, although I don't doubt there could be an efficiency benefit to large-scale
generation, I've just never heard of it.

~~~
kw71
> conversion from AC to DC at the charging port may account for another 10-30%

Simple rectification has not so much loss, I think you are thinking about low
voltage DC power supplies, and I think that chargers for large, high voltage
battery piles are likely to be happy with rectified (maybe doubled) mains
supply.

The low voltage supply is first rectifying the input, then using an inverter
to generate high frequency AC, then rectifying and filtering this to give a DC
output.

~~~
londons_explore
Large AC -> DC conversion has to do this too.

The simple "diode" rectification is no longer acceptable due to harmonics put
on the AC side causing grid stability problems and emitted radio interference.

------
Danihan
>Compression ignition and a supercharger fitted to improve fuel economy
together deliver unprecedented engine response and increase torque 10-30
percent over the current SKYACTIV-G gasoline engine.*3

Wow. I already have a 2016 Mazda 3 that gets around 40MPG (even though it's
not a hybrid) and it's already pretty peppy.

Probably the best car I've owned, and I've owned several nice sports sedans.
Getting 40MPG is too convenient when you make longer commutes, not to mention
the thing cost ~20k at 0% APR. Blows any hybrid out of the water for total
COO.

~~~
borski
OK, so honest question: I have a 2012 Mazda 3 which, presumably, gets 40mpg.
But I can't realistically get anything above 29mpg on average. Am I just an
aggressive driver? :)

[edit] I agree, by the way, that the cars are incredibly fun to drive, for
being "fuel efficient."

~~~
greggyb
2012 had half Skyactiv and half .. non-Skyactiv. The expected MPG on the non
is around 30. You'd have a badge on the rear of the car (if sold in US, at
least) that would indicate Skyactiv.

~~~
borski
I have the badge.

~~~
greggyb
I had the 2012 for a few years. When I was driving 80%+ highway, I would
struggle to get below 35MPG or above 42MPG.

On a 50%-50% split, I would be in the mid 30s, usually 36MPG or 37MPG.

When I was 80% city, I would be around 32MPG on average.

That car does not have much low-end torque, so if you accelerate aggressively
from stops you can definitely tank the MPG. I didn't see much impact from
aggressive acceleration at highway speeds (e.g. going from 30MPH to 70MPH on
an on-ramp, or pulling around a slow group of cars going from 45MPH-70+MPH). I
did see a lot of impact from flooring it 0-30.

Hope this context is helpful.

------
lini
Mercedes Benz introduced something very similar to this ten years ago[1]. The
engine was using HCCI at low RPM and conventional spark-plug ignition at
higher RPM.

[1]
[https://en.wikipedia.org/wiki/DiesOtto](https://en.wikipedia.org/wiki/DiesOtto)

~~~
Neil44
That was purely experimental though - Mazda's is going on sale to the public
which indicates that this is a much more evolved product.

Whilst most other manufacturers have persued downsizing and turbos to get
efficciency on paper (at the expense of real world emmissions) Mazda have gone
another road with their SkyActiv technology and it seems to be paying off for
them.

------
stirkac
Mazda is one of those companies just don't stop revolutionizing. First they
got rotary to be actually usable. Now this.

~~~
mikestew
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.

~~~
jsight
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.

~~~
busterarm
Excluding the Miata, when are sports cars ever practical?

~~~
komali2
Anytime it is time to Go Fast.

So always.

~~~
TomMarius
It's always nice to be home in Prague from Munich in 2.5 instead of 4.5 hours
in exchange for just 1.5l/100km more consumption (and going 250 (155 miles per
hour) instead of 130 km/h).

~~~
komali2
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.

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

~~~
mikestew
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).

~~~
busterarm
Lol, I bought my RX-7 from an Ohio state trooper, in Ohio, and we raced the
entire 2.5hr trip out of the state, in the rain. I think he called his buddies
to leave us alone.

------
userbinator
I consider the headline slightly misleading, since compression ignition
engines that run on a variety of fuels, including gasoline, were relatively
popular around the turn of the century:

[https://en.wikipedia.org/wiki/Hot-
bulb_engine#Advantages](https://en.wikipedia.org/wiki/Hot-
bulb_engine#Advantages)

 _Another big attraction with the hot-bulb engine was its ability to run on a
wide range of fuels. Even poorly combustible fuels could be used, since a
combination of vaporiser- and compression ignition meant that such fuels could
be made to burn. The usual fuel was fuel oil, similar to modern-day diesel
fuel, but natural gas, kerosene, crude oil, vegetable oil or creosote could
also be used._

Also known as "semidiesels".

------
maerF0x0
I think this is a great step forward for ICE . Combining this technology into
generators (and cars like chevy volt) will make an extremely convenient and
fuel efficient vehicle.

------
pedrocr
Technologies are always at their best when they're already being obsoleted.
Just as electric cars become practical ICEs are getting great and so are the
transmissions, making for great modern powertrains.

There were rumors last year in F1 that one of the manufacturers was doing HCCI
for it's engine (the same that Mazda has done here). I don't think any
actually did but Ferrari did introduce a jet ignition system[1] that allows
them to run much leaner. I wonder if anyone is thinking of adapting that to
normal road cars.

[1] [http://www.motorsportmagazine.com/opinion/f1/ferraris-
formul...](http://www.motorsportmagazine.com/opinion/f1/ferraris-
formula-1-jet-ignition)

------
IgorPartola
So how exactly does this work? And why is it more effective and how does it
allow you to run super lean while producing the same amount of power? Also,
presumably running lean would mean lower emissions, but is that really true?

~~~
philipkglass
Running lean, highly compressed, and highly efficient reduces expected
production of carbon monoxide and residual hydrocarbons. But it significantly
increases nitrogen oxide formation, as in diesel engines. So I wonder how the
emissions control system deals with the extra NOx -- that has (see Dieselgate
and continuing related fallout) proven quite a sticky problem for high
efficiency diesel engines in passenger vehicles. The cheap "solutions" were
mostly cheats and the actual solutions cost more.

------
elihu
Maybe this is old news to people who pay attention to car news, but the most
interesting thing to me is this line from the press release:

> From 2019, start introducing electric vehicles and other electric drive
> technologies in regions that use a high ratio of clean energy for power
> generation or restrict certain vehicles to reduce air pollution

I've been kind of disappointed that Mazda hasn't gotten into the electric car
market yet; I'm glad to see they're coming around.

~~~
seanmcdirmid
Mazda is kind of small, it would be like expecting an electric vehicle from
Subaru. Ya, it will happen eventually, but the big guys are going to have the
resources to go first (well, and startups built on the concept itself).

Also, hydrogen was supposed to be the big clean fuel in Japan, but that fell
by the wayside when the bigger Chinese market decided it would be electric.

------
devy

       SKYACTIV-X is the world's first commercial gasoline engine to use compression ignition, in which the fuel-air mixture ignites spontaneously when compressed by the piston.
    

Just pure curiosity, I wonder if SKYACTIV-X engine would also also consume
diesel or gasoline/diesel mixtures?

~~~
aidenn0
Almost certainly not, as diesel and gasoline have _very_ different self-
ignition properties.

~~~
ticklemyelmo
I wonder whether this engine will specifically require you to fill up with
NON-premium gas.

~~~
aidenn0
I suspect that when operation in compression-detonation mode, it will inject
the fuel late enough into the compression stroke that the difference between
87 and 97 octane fuel won't be that big of a deal.

If it does make a difference then I would expect they would design for the
higher octane rating gas to prevent user-error.

------
grondilu
A nice YouTube video about what this is about:

[https://www.youtube.com/watch?v=OVWZFdb_AGc](https://www.youtube.com/watch?v=OVWZFdb_AGc)

------
rbanffy
How much more R&D can the internal combustion engine pay for?

~~~
_archon_
How fancy are modern cars compared to the original cars?

------
rsync
Can we please get somebody to create:

blahblah-notelectric-blahblah.blogspot.com ?

Then you can just collect all of these late stage ICE optimization press
releases in one place.

And we can ignore them.

~~~
linksnapzz
I'd like a similar repository, for all the predictions made by electric-car
proponents about when all ICE units will be phased out, and by what date.
Especially when predictions are made regarding the viability of this or that
gascar company who is seen as being insufficiently hitched to the electric
bandwagon, as though powertrain technology was the alpha-and-omega of
carmaking.

------
ajross
Gah, terribly confusing terminology. This is a Diesel engine. "Compression
ignition" is what the Diesel cycle is all about. It's just carefully tuned
such that it can run on gasoline instead of kerosene (i.e. "diesel _fuel_ ").

And mostly I don't get it. This is just a convenience factor. If you want a
high-efficiency diesel right now you can buy one already. Low-volatility fuels
are already more energy-dense (i.e. fewer losses carrying the stuff around in
the tank) and require less energy to refine. This gives you the advantage of
being able to pull into a gas station without diesel available, but otherwise
doesn't seem to add much.

~~~
vvanders
Yes, however common diesel fuels tend to be higher in NOx and particulates.

My understanding is that because gasoline is refined to a higher degree it
burns a fair bit cleaner in similar environments(and also makes it a PITA to
store for more than a few months).

[edit]

We've got a pair of tractors around the house here, '81 diesel(pre-emissions),
and '47 gasser.

I can tell you which one I prefer to run from an exhaust perspective, the
diesel may have torque and is a dead-simple engine but you don't want to be
downwind of it when cutting heavy brush.

~~~
toast0
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 injection will be much earlier
than a diesel, resulting in more complete air/fuel mixture; this is possible
because gasoline has a higher ignition temperature, so fuel can be injected
early and ignition won't happen until the compression stroke; diesel fuel
would ignite during injection regardless of where in the cycle.

~~~
ajross
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 at a lower temperature. But a leaner mixture means lower power
for a given displacement too, which means _lower_ efficiency than a comparable
traditional diesel (which are already hard-pressed to see gains like the 40%
claimed against well-tuned gas engines).

Honestly the whole thing sounds very snake oily to me. I don't deny that it's
possible such a thing could be tuned to operate as well as a traditional
engine, but... it sounds awfully fiddly. I'd want to see numbers from a
production engine in a real car before placing any bets. Electric continues to
look like a much better bet to my eyes.

~~~
tadfisher
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.

