Totally agree...I semi-followed the other explanations, but this was so clearly illustrated, I now totally get it. It's actually an elegantly simple solution from Mazda.
Amazing reaching the compression stroke and raising the actual compression dilivering ignition on its way down makes sense and all the ifficiency in the world. Keep up the good work Mazda.
I own since new a 2009 Mazda 3s hatchback 5 speed auto with 184,000 miles. I have been dumping money lately for suspension parts at all four corners and a trans module. I just got back from a 2000 mile Marathon trip in 50 hours. Car ran like a champ. Did not burn a drop of synthetic oil.
I have owned two Mazda vehicles, 2015 CX5 and currently driving a Mazda3 2018, and both have auto-trans problems. CX5 had entire trans replaced at only 30,000kms, and if you read forums around the world you will see auto-trans are weak and are being replaced routinely. This is Mazda's best kept secret as they have announced no single recall for what is thought to be a design issue. Their engines are superb but reliable vehicles they are not! There is a reason they don't sell well in the US and now I know why.
@@MrTubeniko Agreed the only car I liked from them that was competitive in price and reliable was the Mazda Protege. We had 2 Mazda MPV mini-vans.... NOTHING BUT TROUBLE!
Alex - good job on a tough concept to explain. Another analog to the diesel engine would be the gas turbine (jet) engine. After using igniters to initiate (or what ever word you made up) :) combustion, compression is used to keep the fuel burning from that point on. Broadly speaking there are centrifugal and axial flow compressor designs. I've driven rental Mazda 3s and seen above 40 mpg on the highway. This would really push them into hybrid territory if they deliver. And are reliable. And don't leak oil (or anything else). Mazda is a company I really admire for pushing on the leading edge, even if things don't always work out.
So here’s what I’m walking away with: It achieves conventional ratio + spark mode without detonating by (somehow) prolonging the intake valve, this “wasting” some (pre-fuel) intake air back out the intake valve, thus “spoiling” the effective compression ratio to something conventional. It achieves super-lean combustion mode by going SO lean that it just won’t auto-ignite. It then injects a last-minute “stoich ball” that the spark can ignite. The bump in pressure/temperature from the burning/expanding “stoich ball” then creates diesel-like compression and pow, the super-lean mixture then burns all at once. Whew! Do you agree?
How do you keep the carbon build up on the valve stems from happening with the GDI? Isn't the detonation fighting against the up stroke of the engine and what we have always been told is bad for the engine? How many miles will you test before determining longevity. Why cant my dealer even explain to me as a potential buyer what "Sky active is"?
I suspect it will be less of a problem, because adding some fuel to the intake air is the suggested solution to the carbon problem. See another video that explains direct injection gas engine problems.
This is what I am looking for!!! Great explanation. I hope there is a follow up to this as I have seen that the stop/start feature does wear your engine faster ( as told by mechanics). Although technically they are right I trust these car maker engineers that they have an explanation as to why their technology works better.
Seems similar to Honda's 12 valve CVCC engine back in the late 70's. It used a tiny 2nd intake valve with a cage to ignite a lean mixture produced by the main intake valve.
Any idea about what the miles per gallon will be on this? My 2016 MT Mazda 3 can get close to 38-39 on the highway and usually is around 30 with mixed driving. That's really good for a gas engine. Also I love driving Mazdas! So much fun.
To some entheusists, this is old news. Many of us subscribe to Engineering Explained. On the other hand, I appreciate you helping get this out to the maasses to become common knowledge. I am holding out of my next vehicle to see if I can get a Mazda3 X.
People don't realize how significant this tech is. No other option--electric, natural gas, hybrid, diesel--reduces consumption/emissions as much for as little new cost. It can fit into virtually any gasoline vehicle application, including sports cars, trucks, & SUVs. Merge two of these engines together and you get a 4L V8 producing 350+ hp & lb-ft that gets mid-to-high 20s mpg combined. AND it has plenty of low-end torque & a broad, flat torque curve through the rpm band. If every gasoline vehicle used this tech, the US' oil consumption would drop by ~3 million bbl/day. For perspective, the crash in oil prices a few years ago was caused by an excess in supply of only 1 million bbl/day globally. If others copy the tech (or if Mazda licenses it), or if Nissan's variable compression ratio catches on, etc., the global oil & gas industry could crater with oil prices forever stuck at $30/bbl. And this isn't even the end of the road for gasoline. Mazda's next goal is an adiabatic engine with a thermal efficiency over 50%.
With correct gearing, you can make 350+ horsepower and lb-ft out of any engine and still get mid to upper 20s combined without compression ignition. SBCs V8s are already low-mid 20s in Corvettes and Camaros, but they aren't supposed to be efficient engines and are making nearly 500hp.
Here's the question: high CR in diesels does not ruin their longevity. High CR and resultant higher, more sudden pressure rise after the explosion allegedly _does_ shorten lifespan of engines used for racing. How is that possible and how is a Skyactiv dealing with it?
Great explanation Alex. It will be interesting to see how it is priced vs. hybrid vehicles. Looking forward to try this engine out as I am in the market for a small car this year.
You need to get into octane numbers. Gasoline is the opposite of Diesel if it comes to Octane number. Diesel is using a different number, Cetane..Diesel is extremely eager to self ignite Gasoline very reluctant to self ignite That would be a good starting point for this video. This also explains the entire philosophy of diesel and gasoline engines. The increased efficiency and fuel economy is what is all important! I give it a thumbs up!
Your illustration leaves me with a bit of a complicated question, but a pretty important one. During partial load cycles, you show the engine injesting air, rather than an air/fuel mixture, so I would assume that the engine design does not incorporate an additional fuel injector in the manifold? You also show that only the exhaust valve is open during the exhaust stage. Is this accurate? The reason for asking is that many direct injection engine designs with VVT use variable timing on the intake valves only, and uses this not only to increase engine torque and responsiveness but rather also to perform emissions related functions like EGR and partial load cycles. Thus it would be likely that the intake valve is open during a portion of the exhaust cycle to act as an EGR valve (which can then be omitted). This function is present on e.g. BMW and VW/Audi/etc. engines with direct injection. As far as I know, Mercedes Benz instead uses VVT on both exhaust and intake valves, in order to let the exhaust valves do the EGR function (letting the exhaust valve be open for part of the intake cycle). The problem with this design (other than the Mercedes solution) is that the intake valves carbon, soot and often oil deposits from the crank case ventilation, and that this creates a deposit of material on the intake valves themselves. Fuel on the other hand is injected into the cylinders directly and thus does not clean the valves, neither by "being fuel" nor by having additives added. Volkswagen Auto Group (Audi/VW/Seat/Skoda/...) solves this in their third generation EA888 engine by incorporating a fifth fuel injector in the manifold (like a traditional monopoint injection). This injector would be used when the engine was under partial load as this is when the EGR function would be active. Under full load, the internal injectors (direct injection) are active and the EGR function is inactive. That's one way of solving the problem, but from your illustrations that seem to not be the case on the Mazda since it only injests air. On the other hand, if it's accurate that only the exhaust valve is open during the exhaust stage, then perhaps Mazda still uses the traditional external EGR valves (?) despite the higher cost? Great video and illustrations, by the way. I would offer one suggestion, which would be to have started with the gasoline principle illustration rather than the diesel one. Reason being that the diesel illustration narritive is trying to explain why the spark plug is unnecessary without having first shown why it's necessary in the first place. :)
Thanks Alex! Prior to this video, I thought HCCI (the Mazda version) would be synergistic with Infiniti's VC turbo, but it looks like that's not the case.
I'm thinking of getting a cx-5. should i get the current model or wait for the skyactiv-x? I'd rather not be a beta tester on the first year so i'd probably have to wait a couple years until after it comes out. i just hope my current 16 year old car can last that long.
the clear design shows ....they do nothing to help keep the valves clean by injecting fuel directly into the piston chamber it bypasses spraying gas through the valve. Gasoline if sprayed via valves..can help keep carbon build up to a minimum if at all. Since they bypass that....carbon build up will occur..just like it does in a diesel.
Hi Alex, thank you very much for this video. If I understand this correctly, this engine is using some of the principles of the Atkinson cycle engine, to provide for variable compression ratios. Interesting but ultimately I believe we will all be driving battery electric cars very soon.
As an owner of an e skyactiv x Mazda 3 I can tell you that its your best option if you want a very economical car which drives just like a good old naturally aspirated 2 litre 4 cylinder. No Turbocharger, no lag and power increases with your revs. Just like it used to be.
This would make a great complimentary technology to a range extended electric vehicle.. You could run the compression engine at a steady load for max efficiency while still generating enough power at a light weight to be effective.
"It's so simple I can't figure out why we haven't used it before". This applies to so many things in cars. Disc brakes replacing drum brakes, tubeless tires replacing tubed tires, overhead cams replacing pushrods, etc.
This is incredible! No wonder you look so excited driving it, I would have been too!! Did you get a chance to talk to any engineers about the long-term reliability though? I'm curious if they beefed up components in order to handle spcci-thigh they would lose on efficiency with the additional reciprocating mass.. (so maybe not ?)
How come nobody has put electrical coils around the top of the cylinder to generate electricity created by the explosion of the fuel and the piston moving up and down?
I'm very skeptical. People jump when a manufacturer claims something is "revolutionary", but never do they actually wait for everything to be weighted and proven in reality. The Skyactive-D is a perfect example. It was supposed to take advancements made in gas engines and applying them to diesels, making them simpler, cheaper and cleaner. Well those engines were promised, but they've proven to be crap and they never made it to the US market because of it.
@@mo1kai691 I didn't give them all my designs for the 16X so it is stuck in development. Keeping the final designs of my engine to myself. I know that sounds greedy...but Mazda was greedy first.😋
Realizing that Mazda has stated they want to take the internal combustion engine to as far as it can go before jumping on the electric bandwagon. Because if their size, I think it makes sense, AND I love my current 3's 2.5 and my previous 2.0.
Diesel just like petrol(Gasoline) also ignites at an initial point. The difference in speed of the combustion is due to the higher compression rates of diesel vs petrol.
Well done Alex.. your one of a kind auto reviews are a pleasure to watch. Cool tech.. Can't wait for GM's version, whcih will no doubt self destruct within a year.
In what powerband does this engine operate? Their choice of transmissions and the diesel like torque implies it's lower that the conventional gas engine variant but by how much?
But while the diesel is being injected, the part of the Diesel who being injected first ignites earlier. So it can't be igniting all at once am I right? Or is the ignition only happening when all the diesel is in there so the pressure is reached when all the diesel is in there? Sorry for my bad english i am from Germany
I think it is always gasoline, not diesel. The main gasoline mixture would never reach ignition compression just due to the piston compression. It is a small, richer, explosion near the spark plug that raises the main mixture compression to its ignition compression, thus giving it a fast burn and high torque as though it was diesel.
no, he's talking about the '6' 2018--that has not come out yet...if you're talking about the new Skyactive X engine for the 3, yes that will be fore the 201*9* model year.
Alex, Great review as usual. Last night I test drove a 2018 Mazda CX-9, with the Skyactiv - X, 4 cyl. - 2.5L. Very nicely appointed and with the Touring Premium Package - $1,890 with the car is priced around $38K. Very competitive pricing with a luxury interior (ie. in the Infiniti quality level) and a decent exterior design (headlights and taillights a tad small in my opinion). I currently drive a 2008 Infiniti EX35 Journey, with 295hp under the hood. When I accelerate from a standing position this engine hums beautifully to full speed. However the Mazda 4cyl. engine was noticeably loud until I reached 30mph +. Yes not fair to compare to the 6cyl. Infiniti but this noise was quite unexpected. Did you experience this as well? The Sales guy stated this only occurs when the engine is cold, however they had the car warming up on the lot when I arrived, so this doesn't hold water. Your comment would be appreciated. Thank you in advance.
This Kinda reminds me of the same situation that you have with rifle cartridge. The lean mixture of fuel,which plays the part of the gun powder must be ignited by a richer mixture of fuel which is in my opinion is like the primer cap of a rifle cartridge.
Found the difference in audio levels very annoying throughout the video (normal, to super quite in some parts, back to normal, etc) Great topic though! Thanks Alex!!
so wait, this said that it ends up looking like diesel so what are the advantages over diesel or even a traditional gas engine? I am assuming efficiency.... thanks
My question is if introduced into big clock unleaded and tuned right can Sky Activ technology compete with Diesel engines in terms of torque numbers for towing and payload needs.
Good one. Imo missing note on particulate, especialy because (volatile) gasoline cannot be sprayed at high pressure as diesel. Skyactive x will face that diesel only problem....
Yep, A '75 Civic CVCC for example. The cars needed no Cats they burned so well. My wife had one of these when we met in 1978. I remember taking it to the gas station to get smogged around 1978 or so. This was before the computerized connected networks at smog stations now, and all you got was a paper slip. (and 10 bucks and some beer would get you one for your Firebird ;-) But the fella at the station in Lake Tahoe, where we lived at the time, was around my age, maybe 21-22, came back and said the Civic passed the tailpipe but tried to say he couldn't pass it on the visual inspection because I had taken out the Catalytic Convertor. I think he was looking for a little something from me.. I asked him to look in his books as it didn't need one. I recall that he looked at me like I was a dope. But he came back with the smog certificate. That was a great little car. Had 85,000 miles on it, no trouble at all. I made her sell it to buy a bigger used 1978 Accord so we could have some more room. That was not a great car. Burned oil and smoked. It needed valve stem seals with only 30,000 miles on the odometer. She still blames me for that.
How about using both gas and diesel just a hint of diesel will boost range of travel for a longer stroke on comercial use and a shorter more powerful stroke for domestic application.
Why can't we use a small secondary cylinder which has a plunger to increase the pressure in the cylinder at ignition time? It could take the space of the injector and plug.
Alex, you said the fuel efficiency benefits could be 20%, perhaps even higher like 30% depending upon your driving style. I'm interested to know, under what conditions does HCCI get better efficiency? Are you talking operator style or road/terrain conditions? Interesting to hear that HCCI works best with lower RON/MON rated fuel, how or why is this so? Love your work!
Jalopnik already drove a Mazda 3 with the prototype of this engine which was about 90% finished (not fully refined) and they gave it an 8.5/10. On a prototype.
The problem with this engine is that high compression limits power. It is similar to the Atkinson cycle. You are just trading some power for more efficiency. I would much rather have Nissan/INFINITI’s variable compression engine because it can deliver the power and the fuel efficiency.
As the son of a master mechanic, I learned the basics of the combustion engines at a very young age, and have tried to keep up with all the newer tech. This is a very good explanation of all types, and for the layperson it is likely eye opening. But as with all advancements since the 60's and 70's, it requires so many sensors, controls and a computer to run these systems, and that is where it always goes to shit. People still need less complicated vehicles that don't cost a fortune every time something goes wrong. I am thankful I can still work on my cars, even the newest tech doesn't faze me, and I will always be able to. This sounds great, but like all over complicated systems, it will be interesting to see where it all goes wrong.
In the future (whenever that is) the simplicity of an electric motor will replace all this marvelous technology trying to keep gasoline engines efficient. The heroes in this automotive history will be the folks that come up with greatly improved batteries, or maybe the solution will be 250cc gas engines that are so efficient that they can be used to extend the range of the batteries until you reach a recharge destination. Combustion of gasoline results in serious pollution of our atmosphere and it is only with all this modern tech that we are able to continue to use gasoline engines. 🙂
I think that Honda essentially the same thing many years ago. The only difference was they had a separate small chamber with its own small valves with a relatively rich mixture that would then be used to lite off a lean mixture. It was put into some production cars, Civics I think.
You are incorrect about how diesel ignition works. Diesels use mechanical injectors to introduce fuel to the cylinder. Diesel injectors are like syringes. For example, if the injector is full of diesel, when it comes time to inject the fuel, the plunger will start to inject the fuel into the cylinder through the atomization nozzle where it will start burning. The diesel will continue to be injected and burned until the plunger reaches the end of the stroke. The result is that the pressure created by the burning fuel stays constant for a longer time rather than jumping up all at once and then tapering off as the piston is pressed down. This is what gives diesel engines so much more torque and why automotive diesel engines get so much better mileage than gasoline engines.
I admire Mazda's engine technology, but my personal experience with a new 1990 M6 soured me on Mazda. With less than 17K miles I had a failure of the power steering system along with a failure of the catalytic converter. Both of these were in careful use of the car. I loved the design and ride of the car but these combined failures make me not want to risk another Mazda purchase. Mazda tried to get out of covering these items fully.
Damn it is so simple how come I didn't think of it ? this skyactiv-X setup in an opposite piston engine will be one hell of a winning combination , instead of the fuel being compressed between a moving object and a stationary object it would be compressed between two moving objects .
This has been in F1 engines for a while now . Some systems actually use two injectors , one to inject fuel into the cylinder and one to inject fuel into a small chamber enclosing the spark plug .
You should had inserted generic frames over the blooper that were edited so sharply, giving a jump cut. Otherwise a clean and easy to understand explanation of a complicated technology.
I hope they put the PCV valve at the location easier to access. With gasoline and high compression ratio in the SPCCI engine, the engine can blow the spark plug tube seal under 30k miles. I don't want to take the whole intake manifold out just to replace the PCV valve once every 30k miles.
Mazda... SkyActive XR for the new RX-9. Or how about a rotary engine that works like an alternator. The electricity could charge the battery bank. Theres a capacitor for turning on the vehicle, then it uses batteries long enough for the rotary alternator/dynamo to charge the batteries... Think about it!!!
You explained this engine technology better than anybody. I finally 100% understand how it works. Pretty dang cool, thanks Alex.
Totally agree...I semi-followed the other explanations, but this was so clearly illustrated, I now totally get it. It's actually an elegantly simple solution from Mazda.
The Adventure Mazda Agreed.
Yes, very good explanation.
Now go and buy one , but dont buy the diesel because in some cities going to be banned , or buy electric.
Lino Sammut I may buy a 2020 model year.
How would they ban diesels in certain cities? How would they know?
Alex’s reviews are not only the most useful in detail but also the most viewer-friendly informative. Thank you, Alex. I love you!!
Amazing reaching the compression stroke and raising the actual compression dilivering ignition on its way down makes sense and all the ifficiency in the world. Keep up the good work Mazda.
Awesome. I currently have the 2.5L Mazda 3 and I just absolutely love it. I can't wait for the new Skyactive-X engine.
Yes, very good explanation.
yeah man, im excited to, awesome tech.. btw I read an article that said the new Mazda3 might have AWD
Novice MTBer how is the Mazda 3 in snowy conditions?
Garbage
Will Mazda be using this technology in any other models in the next year or so? How about the CX3?
I own since new a 2009 Mazda 3s hatchback 5 speed auto with 184,000 miles. I have been dumping money lately for suspension parts at all four corners and a trans module. I just got back from a 2000 mile Marathon trip in 50 hours. Car ran like a champ. Did not burn a drop of synthetic oil.
“Ignitiates” - I... am going to start using that word!
Very cool EE style video Alex, love these!
Yea, I tripped on my tongue there didn't I? Woohoo! New word!
I really MUST buy a Maaahzda!!
What a lovely clear explanation of the technology.
Love Mazda . Had many in the family for 20 years. Very reliable. This is Japan's best kept secret. Will keep on buying.
I have owned two Mazda vehicles, 2015 CX5 and currently driving a Mazda3 2018, and both have auto-trans problems. CX5 had entire trans replaced at only 30,000kms, and if you read forums around the world you will see auto-trans are weak and are being replaced routinely. This is Mazda's best kept secret as they have announced no single recall for what is thought to be a design issue. Their engines are superb but reliable vehicles they are not! There is a reason they don't sell well in the US and now I know why.
@@MrTubeniko Agreed the only car I liked from them that was competitive in price and reliable was the Mazda Protege. We had 2 Mazda MPV mini-vans.... NOTHING BUT TROUBLE!
Alex - good job on a tough concept to explain. Another analog to the diesel engine would be the gas turbine (jet) engine. After using igniters to initiate (or what ever word you made up) :) combustion, compression is used to keep the fuel burning from that point on. Broadly speaking there are centrifugal and axial flow compressor designs. I've driven rental Mazda 3s and seen above 40 mpg on the highway. This would really push them into hybrid territory if they deliver. And are reliable. And don't leak oil (or anything else). Mazda is a company I really admire for pushing on the leading edge, even if things don't always work out.
So here’s what I’m walking away with:
It achieves conventional ratio + spark mode without detonating by (somehow) prolonging the intake valve, this “wasting” some (pre-fuel) intake air back out the intake valve, thus “spoiling” the effective compression ratio to something conventional.
It achieves super-lean combustion mode by going SO lean that it just won’t auto-ignite. It then injects a last-minute “stoich ball” that the spark can ignite. The bump in pressure/temperature from the burning/expanding “stoich ball” then creates diesel-like compression and pow, the super-lean mixture then burns all at once.
Whew! Do you agree?
Yes
How do you keep the carbon build up on the valve stems from happening with the GDI? Isn't the detonation fighting against the up stroke of the engine and what we have always been told is bad for the engine? How many miles will you test before determining longevity. Why cant my dealer even explain to me as a potential buyer what "Sky active is"?
Does this setup have the same carbon buildup on the valves that other direct injection have?
I'm sure it does
@@bradfocl this isn't a rotary buddy
@@MilesPrower1992 oops, responded to wrong video
I suspect it will be less of a problem, because adding some fuel to the intake air is the suggested solution to the carbon problem. See another video that explains direct injection gas engine problems.
This is what I am looking for!!! Great explanation. I hope there is a follow up to this as I have seen that the stop/start feature does wear your engine faster ( as told by mechanics). Although technically they are right I trust these car maker engineers that they have an explanation as to why their technology works better.
Seems similar to Honda's 12 valve CVCC engine back in the late 70's. It used a tiny 2nd intake valve with a cage to ignite a lean mixture produced by the main intake valve.
Tha's a precombustion event. Not the same thing.
Any idea about what the miles per gallon will be on this? My 2016 MT Mazda 3 can get close to 38-39 on the highway and usually is around 30 with mixed driving. That's really good for a gas engine. Also I love driving Mazdas! So much fun.
To some entheusists, this is old news. Many of us subscribe to Engineering Explained. On the other hand, I appreciate you helping get this out to the maasses to become common knowledge. I am holding out of my next vehicle to see if I can get a Mazda3 X.
People don't realize how significant this tech is. No other option--electric, natural gas, hybrid, diesel--reduces consumption/emissions as much for as little new cost. It can fit into virtually any gasoline vehicle application, including sports cars, trucks, & SUVs. Merge two of these engines together and you get a 4L V8 producing 350+ hp & lb-ft that gets mid-to-high 20s mpg combined. AND it has plenty of low-end torque & a broad, flat torque curve through the rpm band.
If every gasoline vehicle used this tech, the US' oil consumption would drop by ~3 million bbl/day. For perspective, the crash in oil prices a few years ago was caused by an excess in supply of only 1 million bbl/day globally. If others copy the tech (or if Mazda licenses it), or if Nissan's variable compression ratio catches on, etc., the global oil & gas industry could crater with oil prices forever stuck at $30/bbl.
And this isn't even the end of the road for gasoline. Mazda's next goal is an adiabatic engine with a thermal efficiency over 50%.
With correct gearing, you can make 350+ horsepower and lb-ft out of any engine and still get mid to upper 20s combined without compression ignition. SBCs V8s are already low-mid 20s in Corvettes and Camaros, but they aren't supposed to be efficient engines and are making nearly 500hp.
Reduces compared to what? Old engines that are nowhere near modern turbos when it comes to efficiency.
Will Mazda be using this technology in any other models in the next year or so? How about the CX3?
It wont fit in sports cars unless its controllable by hand. A sports car is a sports car for a reason.
hopefully its reliable
Here's the question: high CR in diesels does not ruin their longevity. High CR and resultant higher, more sudden pressure rise after the explosion allegedly _does_ shorten lifespan of engines used for racing.
How is that possible and how is a Skyactiv dealing with it?
Its not a racing engine. Hope that helps you.
Answering myself after two years:
1.) it's not an 'explosion' at all
2.) mixture is super-duper-lean
why is it not possible to lose the inlet valve altogether and inject the fuel\ air mix directly?
Great explanation Alex. It will be interesting to see how it is priced vs. hybrid vehicles. Looking forward to try this engine out as I am in the market for a small car this year.
You need to get into octane numbers. Gasoline is the opposite of Diesel if it comes to Octane number. Diesel is using a different number, Cetane..Diesel is extremely eager to self ignite Gasoline very reluctant to self ignite That would be a good starting point for this video. This also explains the entire philosophy of diesel and gasoline engines. The increased efficiency and fuel economy is what is all important! I give it a thumbs up!
How are they monitoring air intake, knock, Nox, and timing?
EE says they have a pressure sensor in the combustion chamber. I've seen such sensors in industrial Natural Gas engines for testing purposes.
Very clear explanation. After a long search I finally understand how it works in detail!
Your illustration leaves me with a bit of a complicated question, but a pretty important one. During partial load cycles, you show the engine injesting air, rather than an air/fuel mixture, so I would assume that the engine design does not incorporate an additional fuel injector in the manifold? You also show that only the exhaust valve is open during the exhaust stage. Is this accurate?
The reason for asking is that many direct injection engine designs with VVT use variable timing on the intake valves only, and uses this not only to increase engine torque and responsiveness but rather also to perform emissions related functions like EGR and partial load cycles.
Thus it would be likely that the intake valve is open during a portion of the exhaust cycle to act as an EGR valve (which can then be omitted). This function is present on e.g. BMW and VW/Audi/etc. engines with direct injection. As far as I know, Mercedes Benz instead uses VVT on both exhaust and intake valves, in order to let the exhaust valves do the EGR function (letting the exhaust valve be open for part of the intake cycle).
The problem with this design (other than the Mercedes solution) is that the intake valves carbon, soot and often oil deposits from the crank case ventilation, and that this creates a deposit of material on the intake valves themselves. Fuel on the other hand is injected into the cylinders directly and thus does not clean the valves, neither by "being fuel" nor by having additives added.
Volkswagen Auto Group (Audi/VW/Seat/Skoda/...) solves this in their third generation EA888 engine by incorporating a fifth fuel injector in the manifold (like a traditional monopoint injection). This injector would be used when the engine was under partial load as this is when the EGR function would be active. Under full load, the internal injectors (direct injection) are active and the EGR function is inactive.
That's one way of solving the problem, but from your illustrations that seem to not be the case on the Mazda since it only injests air. On the other hand, if it's accurate that only the exhaust valve is open during the exhaust stage, then perhaps Mazda still uses the traditional external EGR valves (?) despite the higher cost?
Great video and illustrations, by the way. I would offer one suggestion, which would be to have started with the gasoline principle illustration rather than the diesel one. Reason being that the diesel illustration narritive is trying to explain why the spark plug is unnecessary without having first shown why it's necessary in the first place. :)
Thanks Alex! Prior to this video, I thought HCCI (the Mazda version) would be synergistic with Infiniti's VC turbo, but it looks like that's not the case.
I'm thinking of getting a cx-5. should i get the current model or wait for the skyactiv-x? I'd rather not be a beta tester on the first year so i'd probably have to wait a couple years until after it comes out. i just hope my current 16 year old car can last that long.
I loved this video. It makes the differences of engine types so easily understandable. Thank you.
No mention regarding how this technology might have any effect on carbon build up on intake valves. Does anything change in that respect?
the clear design shows ....they do nothing to help keep the valves clean by injecting fuel directly into the piston chamber it bypasses spraying gas through the valve. Gasoline if sprayed via valves..can help keep carbon build up to a minimum if at all. Since they bypass that....carbon build up will occur..just like it does in a diesel.
Mazda engineers said they have developed a new special coating that prevents carbon build-up (they wouldn't share the info of the actual coating)
Hi Alex, thank you very much for this video. If I understand this correctly, this engine is using some of the principles of the Atkinson cycle engine, to provide for variable compression ratios. Interesting but ultimately I believe we will all be driving battery electric cars very soon.
As an owner of an e skyactiv x Mazda 3 I can tell you that its your best option if you want a very economical car which drives just like a good old naturally aspirated 2 litre 4 cylinder. No Turbocharger, no lag and power increases with your revs. Just like it used to be.
One of the best motor channel's on TH-cam, Alex you do the best in explaining! keep it up!!
This would make a great complimentary technology to a range extended electric vehicle.. You could run the compression engine at a steady load for max efficiency while still generating enough power at a light weight to be effective.
"It's so simple I can't figure out why we haven't used it before". This applies to so many things in cars. Disc brakes replacing drum brakes, tubeless tires replacing tubed tires, overhead cams replacing pushrods, etc.
Except LS. Don't know what that is?Get a clue.
This is incredible! No wonder you look so excited driving it, I would have been too!! Did you get a chance to talk to any engineers about the long-term reliability though? I'm curious if they beefed up components in order to handle spcci-thigh they would lose on efficiency with the additional reciprocating mass.. (so maybe not ?)
How come nobody has put electrical coils around the top of the cylinder to generate electricity created by the explosion of the fuel and the piston moving up and down?
This will put load into the pistons and create drag. Sadly there is no such thing as free energy.
Does this mean the skyactive - x combines the otto and miller cycles of combustion? Pretty cool!
Ok Alex....what is the bottom line with Sky Active X? What are the advantages over the traditional gasoline injected engine?
Great explanation Alex, thank you for that. All the other videos almost seem incapable to explain a ''simple'' thing like how this engine works.
I'm very skeptical. People jump when a manufacturer claims something is "revolutionary", but never do they actually wait for everything to be weighted and proven in reality. The Skyactive-D is a perfect example. It was supposed to take advancements made in gas engines and applying them to diesels, making them simpler, cheaper and cleaner. Well those engines were promised, but they've proven to be crap and they never made it to the US market because of it.
Also.......Where the HELL is the rotary RX9 that they've been talking about for most of my adult life?
So you have to fill it up with diesel and petrol? 2 separate tanks?
@@mo1kai691 I didn't give them all my designs for the 16X so it is stuck in development. Keeping the final designs of my engine to myself.
I know that sounds greedy...but Mazda was greedy first.😋
@@mo1kai691 Will likely never be able to meet emissions and fuel economy standards.
mo 1 kai seems to be a little over complicated. It’s really a spark ignition engine with some extra stuff.
Realizing that Mazda has stated they want to take the internal combustion engine to as far as it can go before jumping on the electric bandwagon. Because if their size, I think it makes sense, AND I love my current 3's 2.5 and my previous 2.0.
So, is it mean the injection is working on low pressure? Not like the diesel injection with high pressure which cost much?
Who else absolutely loves Alex's channel...but thinks he needs to change that intro music??? lol
Who cares about the music? The content is what I'm here for.
Yes he does lol
horrible intro music. annoys my ears badly
I dig it
I love the music! It is super unique and catchy
Fantastic, clear, informative vid! The one glaring omission is MPG.
Diesel just like petrol(Gasoline) also ignites at an initial point. The difference in speed of the combustion is due to the higher compression rates of diesel vs petrol.
Well done Alex.. your one of a kind auto reviews are a pleasure to watch.
Cool tech.. Can't wait for GM's version, whcih will no doubt self destruct within a year.
In what powerband does this engine operate? Their choice of transmissions and the diesel like torque implies it's lower that the conventional gas engine variant but by how much?
But while the diesel is being injected, the part of the Diesel who being injected first ignites earlier. So it can't be igniting all at once am I right? Or is the ignition only happening when all the diesel is in there so the pressure is reached when all the diesel is in there?
Sorry for my bad english i am from Germany
I think it is always gasoline, not diesel. The main gasoline mixture would never reach ignition compression just due to the piston compression. It is a small, richer, explosion near the spark plug that raises the main mixture compression to its ignition compression, thus giving it a fast burn and high torque as though it was diesel.
Good Job! Enjoyed it. Really seems to be simple genius. Would the non compression mode not be the same as the Atkinson Cycle?
Is the new mazda 6 2018 review coming soon? thinking about buying one
2019 actually!
no, he's talking about the '6' 2018--that has not come out yet...if you're talking about the new Skyactive X engine for the 3, yes that will be fore the 201*9* model year.
yes, the one they presented at the detroit auto show(i think?) with the new 2.5L turbo gasoline
The 2018 Mazda6 will be out in the spring. Be sure to get the Signature trim
Alex, Great review as usual. Last night I test drove a 2018 Mazda CX-9, with the Skyactiv - X, 4 cyl. - 2.5L. Very nicely appointed and with the Touring Premium Package - $1,890 with the car is priced around $38K. Very competitive pricing with a luxury interior (ie. in the Infiniti quality level) and a decent exterior design (headlights and taillights a tad small in my opinion). I currently drive a 2008 Infiniti EX35 Journey, with 295hp under the hood. When I accelerate from a standing position this engine hums beautifully to full speed. However the Mazda 4cyl. engine was noticeably loud until I reached 30mph +. Yes not fair to compare to the 6cyl. Infiniti but this noise was quite unexpected. Did you experience this as well? The Sales guy stated this only occurs when the engine is cold, however they had the car warming up on the lot when I arrived, so this doesn't hold water. Your comment would be appreciated. Thank you in advance.
11:00 That's been our quick look .... MY BRAIN HURTS!
Alex, thank you so much for taking the time to explain how this works with a very simple straightforward powerpoint!!! Awesome!
This Kinda reminds me of the same situation that you have with rifle cartridge. The lean mixture of fuel,which plays the part of the gun powder must be ignited by a richer mixture of fuel which is in my opinion is like the primer cap of a rifle cartridge.
This is a very good explanation. It also remind me, again, why I wasn't smart enough to study engineering in college.
Very good explanation; clear and complete, and not overly wordy.
I can't wait. It's about time that new engine technology like this came along.
Found the difference in audio levels very annoying throughout the video (normal, to super quite in some parts, back to normal, etc) Great topic though! Thanks Alex!!
so wait, this said that it ends up looking like diesel so what are the advantages over diesel or even a traditional gas engine? I am assuming efficiency.... thanks
Please explain what is the operating pressure of fuel injection system.
My question is if introduced into big clock unleaded and tuned right can Sky Activ technology compete with Diesel engines in terms of torque numbers for towing and payload needs.
Good one.
Imo missing note on particulate, especialy because (volatile) gasoline cannot be sprayed at high pressure as diesel. Skyactive x will face that diesel only problem....
I've been wondering about this new tech for a while, so thanks for the excellent video explanation.
I thought Honda had this way back in the 70s or 80s, an engine with fuel injection in a precombustion chamber in the head?
Yep, A '75 Civic CVCC for example. The cars needed no Cats they burned so well. My wife had one of these when we met in 1978.
I remember taking it to the gas station to get smogged around 1978 or so. This was before the computerized connected networks at smog stations now, and all you got was a paper slip. (and 10 bucks and some beer would get you one for your Firebird ;-) But the fella at the station in Lake Tahoe, where we lived at the time, was around my age, maybe 21-22, came back and said the Civic passed the tailpipe but tried to say he couldn't pass it on the visual inspection because I had taken out the Catalytic Convertor. I think he was looking for a little something from me.. I asked him to look in his books as it didn't need one. I recall that he looked at me like I was a dope. But he came back with the smog certificate.
That was a great little car. Had 85,000 miles on it, no trouble at all. I made her sell it to buy a bigger used 1978 Accord so we could have some more room. That was not a great car. Burned oil and smoked. It needed valve stem seals with only 30,000 miles on the odometer. She still blames me for that.
guitarsncarsnart, what a neat story. Thank you for sharing that.
How about using both gas and diesel just a hint of diesel will boost range of travel for a longer stroke on comercial use and a shorter more powerful stroke for domestic application.
Why can't we use a small secondary cylinder which has a plunger to increase the pressure in the cylinder at ignition time? It could take the space of the injector and plug.
I thought of that In the mid 1970s using hydraulics.
That was the best explanation i have seen on that engine .. thank you.
So it's different from a HCCI engine? Or it can be seen as an evolution of the latter ?
Alex, you said the fuel efficiency benefits could be 20%, perhaps even higher like 30% depending upon your driving style.
I'm interested to know, under what conditions does HCCI get better efficiency? Are you talking operator style or road/terrain conditions?
Interesting to hear that HCCI works best with lower RON/MON rated fuel, how or why is this so?
Love your work!
Where is the advantage, is it mileage, or overall power, or just that its better than other direct gas injection engines?
Jalopnik already drove a Mazda 3 with the prototype of this engine which was about 90% finished (not fully refined) and they gave it an 8.5/10. On a prototype.
What is the difference between Mazda's SkyActive X engine and Infiniti's VC engine?
The problem with this engine is that high compression limits power. It is similar to the Atkinson cycle. You are just trading some power for more efficiency.
I would much rather have Nissan/INFINITI’s variable compression engine because it can deliver the power and the fuel efficiency.
As the son of a master mechanic, I learned the basics of the combustion engines at a very young age, and have tried to keep up with all the newer tech. This is a very good explanation of all types, and for the layperson it is likely eye opening. But as with all advancements since the 60's and 70's, it requires so many sensors, controls and a computer to run these systems, and that is where it always goes to shit. People still need less complicated vehicles that don't cost a fortune every time something goes wrong. I am thankful I can still work on my cars, even the newest tech doesn't faze me, and I will always be able to. This sounds great, but like all over complicated systems, it will be interesting to see where it all goes wrong.
In the future (whenever that is) the simplicity of an electric motor will replace all this marvelous technology trying to keep gasoline engines efficient. The heroes in this automotive history will be the folks that come up with greatly improved batteries, or maybe the solution will be 250cc gas engines that are so efficient that they can be used to extend the range of the batteries until you reach a recharge destination. Combustion of gasoline results in serious pollution of our atmosphere and it is only with all this modern tech that we are able to continue to use gasoline engines. 🙂
and what about the intake valve build up on Skyactive engines??
I think that Honda essentially the same thing many years ago. The only difference was they had a separate small chamber with its own small valves with a relatively rich mixture that would then be used to lite off a lean mixture. It was put into some production cars, Civics I think.
You are incorrect about how diesel ignition works.
Diesels use mechanical injectors to introduce fuel to the cylinder.
Diesel injectors are like syringes. For example, if the injector is full of diesel, when it comes time to inject the fuel, the plunger will start to inject the fuel into the cylinder through the atomization nozzle where it will start burning. The diesel will continue to be injected and burned until the plunger reaches the end of the stroke. The result is that the pressure created by the burning fuel stays constant for a longer time rather than jumping up all at once and then tapering off as the piston is pressed down. This is what gives diesel engines so much more torque and why automotive diesel engines get so much better mileage than gasoline engines.
Interesting, and most certainly viable technology, that, as a loyal Mazda 3 owner, I would be pleased to purchase. Can't wait.
So would this mean you would have the spark plugs wear out a little faster than normal engines?
What SPCCI( spark controlled compress ignition )and HCCI (homogenous charge compress ignition ) are same things ?
Thanks for the explanation. It would be great if your Audio volume remains same as when you explain outside of the car. Great Work!!!
What's a "Maarzda"?
I admire Mazda's engine technology, but my personal experience with a new 1990 M6 soured me on Mazda. With less than 17K miles I had a failure of the power steering system along with a failure of the catalytic converter. Both of these were in careful use of the car. I loved the design and ride of the car but these combined failures make me not want to risk another Mazda purchase. Mazda tried to get out of covering these items fully.
Will Mazda be using this technology in any other models in the next year or so? How about the CX3?
Alex, did you do a review of the Mazda6 behind you? 0:55
I like this explanation. Now, what does this do in terms of numbers? MPG? 0-60 etc. ?
ok but does it increase mileage and only time will tell if the engines hold up but good idea and I hope it works well
Damn it is so simple how come I didn't think of it ?
this skyactiv-X setup in an opposite piston engine will be one hell of a winning combination ,
instead of the fuel being compressed between a moving object and a stationary object it would be compressed between two moving objects .
This has been in F1 engines for a while now . Some systems actually use two injectors , one to inject fuel into the cylinder and one to inject fuel into a small chamber enclosing the spark plug .
Does a highly polish cylinder wall the new way 'verses the traditional cross hatch ??
Is it as durable as traditional designs? Is the maintainable?
This is classical GDI (gasoline direct injection), WHAT is the difference from all others???
Beautifully explained Alex. Technical nirvana!
How is the fuel economy?
Awesome explanation and first-look review. And you drove right past my work - Mazda's across the street from us. :)
Did Alex mention a Mazda 2.5 liter turbo charged engine? Wouldn't that be nice in a Miata!
MZR-CD 2.2 would be nice in a Miata as well :-)
You should had inserted generic frames over the blooper that were edited so sharply, giving a jump cut. Otherwise a clean and easy to understand explanation of a complicated technology.
I hope they put the PCV valve at the location easier to access. With gasoline and high compression ratio in the SPCCI engine, the engine can blow the spark plug tube seal under 30k miles. I don't want to take the whole intake manifold out just to replace the PCV valve once every 30k miles.
Mazda... SkyActive XR for the new RX-9. Or how about a rotary engine that works like an alternator. The electricity could charge the battery bank.
Theres a capacitor for turning on the vehicle, then it uses batteries long enough for the rotary alternator/dynamo to charge the batteries... Think about it!!!
Super good video! Could you do the test drive ? Its way more than a year later. Waiting for that review :-)
ITs april 2019, no Active X, I don't see it happening this year. maybe 2020?