Mazda Creates The Holy Grail Of Gasoline Engines - HCCI SkyActiv-X

Take it from a competitor - Nissan calls HCCI “the highest potential heat efficiency among internal-combustion engine systems” and “the ultimate combustion method for achieving both CO2 reduction and clean exhaust.” This is big news that we’ll see it in a production car soon! Follow along on Instagram: www.instagram.com/engineeringexplained/

Japan : "let's think of a new way to make engine more efficient and eco-friendly" Europe : "ugh, let's lose one more cylinder and add another turbocharger"

"Sustainable Zoom Zoom 2030."I can't say that out loud without laughing.

Japanese Engineer: Let's think of a unique approach to solve this. European Engineer: That's too much work, let's just cheat.

Was in Hiroshima a couple of weeks back and speaking to one of the Mazda staff about this engine. They stated (and it was repeated in their release video YouTube: wEh8MgFLNh8) that the work they did for their clean sheet approach to the Skyactiv-G and Skyactiv-D engines was intended as the path to this Skyactiv-X engine. Of course with those, the non detuned G had a compression ratio of 14:1 (very high for gasoline) and the diesel had the same compression ratio (14:1 very low for diesel). The diesel follows on from numerous studies of low compression diesel using a single cylinder (Example "A Survey on Low Compression Ratio Diesel Engine" - Bridjesh P et al) where there was lower NOx and soot, however cold starts were an issue. Mazda sorted this out by redirecting exhaust during startup (I experience this daily because I have a Skyactiv-D, and even on the coldest mornings it takes just a few minutes to warm up where you cannot exceed 50km/h). The bonus however has been lower NOx and lower soot. Both of these were illustrated recently. Japanese government investigations into diesel engines post VW dieselgate, showed that Mazda's engine was the only engine to meet standards and had NOx emissions as stated in both real world and laboratory tests, whereas all other manufacturers had between 6 to 10 times more that the standard when comparing real world tests to the lab. With regards to deposits, AutoBild in Germany Dauertest (which is an intensive 100,000km test), came to completion on a CX-5 with the Skyactive-D, they noted no deposits on the cylinder (which contrasted greatly to the 18:1+ also in their Dauertest. The other advantage to lower compression has been weight. The old Mazda 18:1 diesel had an iron block. So the question I posed when in Hiroshima was what compression ratio the Skyactiv-X would be. The answer was simple.... what compression ratio have both G and D been heading towards? The answer - 14:1. Watch the Mazda video on youtube wEh8MgFLNh8 and this is basically hinted.

Knowing nothing of engines, and going based on the pictures alone I assume gasoline engines run on lighting bolts, diesel engins run on fire and HCCI runs on magic.

First thing I thought was there'll be issues with engine failures if one little thing goes wrong. So basically if one component fails, it will be a catastrophe for the whole engine. I suppose the fail-safe will be the spark plugs......... which will be useless in a lean running engine because of premature detonation, and holes in the piston crown. Looking down the thread seems like many will agree. But here's an idea. Instead of borrowing $50,000 for a new car, then chasing your tail to pay it off. Why not buy a used car for under $5000, with a fuel efficient engine, it'll use 30-40% more fuel but cost $45,000 less. If you spend $5000 overhauling the engine and transmission over its lifetime, you'll have saved $40,000. Then there's accrued interest, which offsets any 30-40% saving in fuel on the newer car. Then there's the amount of energy that goes into making a whole new car and the emissions that causes. Recycling existing cars by restoring them and retro fitting more fuel efficient engines will actually save more on crude oil usage. So lets be a society that is concerned about fossil fuel usage, and keep throwing away this energy on creative destruction, and then throwing away the savings to fossil fuel usage on creative destruction.

Hmm, some of this is accurate, some not so much. It looks like Mazda's version of HCCI is very similar to programs most automakers are working on though they may have expanded the operating window a bit. HCCI is essentially the process of introducing fuel into a combustion chamber which contains large amounts of hot exhaust gasses from the last combustion cycle. This is accomplished by closing the exhaust valve before the piston reaches the top of its travel. The exhaust gases which are trapped by the early closure of the exhaust valve remain in the cylinder during the intake stroke which mixes fresh air (no fuel) with the hot gases. By using direct injection (the fuel is delivered into the combustion chamber, not the intake manifold), fuel is sprayed under high pressure into the mixture of fresh air and hot gases. Because a percentage of the gases in the cylinder contain no oxygen (the previous cycle burned it) there is less oxygen available for combustion, this means less fuel is injected. Also less power is produced. The residual heat in the mixture is adequate to ignite the fuel and thus, no spark is required. If compression ignition were used: gasoline, unlike diesel burns very quickly and with compression ignition would ignite entirely at the same time. This would create a very large, and brief pressure spike (explosion) which would damage hardware and waste energy because all of the force would be applied over a very short distance of piston travel. The amount of fuel injected during HCCI operating mode is considerably less than the amount normally provided. This means less power and is the primary reason HCCI is used in steady cruise conditions when minimal output is required to keep the vehicle moving.As a smaller amount of fuel is injected into the cylinder, it is effectively a very lean mixture that would not ignite reliably with a spark plug nor would it burn completely because the fuel molecules are too far apart for the flame front to span the distance between them. However, because it is injected into combined gases, the heat ensures that all molecules burn and at the same time control the rate of pressure build. This reduces mechanical loads and provides a more even "push" on the piston over more degrees of crankshaft travel so improved efficiency. This also solves the greatest problems associated with lean combustion; NOx, and HC emissions. Lean mixtures burn at very high temperatures, creating NOx. They also (counterintuitively) leave behind unburned fuel because the flame front fades before all the fuel is burned. The catalyst can clean up the HC by burning it as it passes through but that means wasted energy. NOx is more difficult. HCCI is like EGR (Exhaust Gas Recirculation) on steroids. By having large amounts of inert gas in the cylinders, mixed with the fresh air: the combustion temperature is lowered and NOx can be pretty much eliminated. By controlling the closure of the intake valve as well, compression can by regulated and this does permit higher compression ratios (Atkinson Cycle). I believe the Atkinson cycle was documented many decades ago and has been used on hybrid engines for quite some time so no news there as it has been proven reliable. Supercharging/Turbocharging permits higher air volume through the engine and would likely be used to reduce the engine's displacement which improves efficiency. There are millions of turbocharged engines on the road today and despite predictions to the contrary are proving out very well. So, that does leave some new technology and a lot of software management to ensure everything works smoothly. This has proven very difficult and with the amount of effective EGR involved there are legitimate questions regarding how some components will stand up over time. I would be concerned about buildup on valves, residue on fuel injectors, possible spark plug issues, etc but I think eventually they will work out. I think Mazda has expanded the operating window closer to idle and perhaps under higher loads (maybe the reason for the charger if they actually do install one). Consumers also need to understand that like nearly all powertrain improvements: 8+ speed transmissions, downsized turbo engines, variable displacement/cylinder deactivation, electrical load management, aerodynamics (shutter, louvers) etc have the same characteristics: they work under specific conditions. For example: an HCCI vehicle pulling a trailer, with a hardtop carrier, climbing hills, driven at high speeds, etc, etc. Will be unable to maintain HCCI mode as often as in lower load conditions. This means that the gap between best and worst fuel economy will widen. This creates a lot of dissatisfaction and mistrust of the claims made regarding projected versus "real world" fuel economy. However, on a positive note: understanding your vehicle better can result in impressive increases in mileage realized.

Deisel efficiency without blowing cancer into the lungs of all the baby children. This really is big news. My hat off to Mazda, mighty effort.

This news just came out like 2d ago. Can't believe how fast you got this video out

This technology is amazing. I love Mazda for doing it.

You tube better be paying your ass good coin for teaching us these engine setups .... bless your heart for going out of your way to teach people about engines

Jason - by supercharging, I think mazda means a compressed air injection system. it's still 'super charging' but not in the way we think. I presume they'll accumulate compressed air in a cylinder, similar to volvo's compressed air turbo spooling system but instead of dumping the air into turbo exhaust turbine, mazda will directly inject it into the cylinders. that way they can make very precise alterations to the air fuel ratio based on feedback from fuel quality sensors and change the effective compression ratio on the fly; even providing different amounts to each cylinder if necessary. HCCI is quite sensitive to pressure, temperature and fuel quality so this flexibility and granularity will be very helpful.

The year zoom zoom 2030, where the boomy boom engines were made more efficient for the vroomy vrooms

I could picture all of those dudes at Mazda sitting at a table and one dude picks up a spark plug and says, “zoom zoom baby!” And that’s how that engine was born.

Interesting, we own a car that isn’t sold in the U.S., a Skoda Octavia 1.6 SE diesel. On a long run, long at least for us in the U.K., of say, around 75 miles or so, We have been getting around 70 m.p.g. on mainly motorway driving mixed with some city roads. Driving sensibly and sticking to speed limits my wife and I have managed to achieve these figures, so it will be interesting to see what this Mazda engine can achieve on real roads in the real world.

just imagine how awesome a HCCI Freevalve engine would be

I want a straight six with this tech

Explained brilliantly.

10/10 Great engineering video, good simple to understand practical explanation