Skyactiv-X: Mazdas Revolutionary Engine Explained
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Date: 2019-05-30
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Comments and reviews: 10
Nicoleise
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. Thats 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 its 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 its necessary in the first place. :)
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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. Thats 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 its 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 its necessary in the first place. :)
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automobilseelsorge
complete wrong you do not understand the Otto and the Diesel cycle the diagramm shown on 3: 43 is mixed up. The Diesel has a same pressure process because the firework begins 0. 2ms past injection, it begins to burn in the ms the mixture builds up and keeps on burning as long diesel is injected (so the pressure is kept on a high efficient level) there is no mixture that makes boom as you explained before (this is only the knocking if the diesel is cold and the mixture builds up while the piston is compressing to a higher temperature. The Otto in your wrong diagramm is told to burn down slowly, but no, it has a same room process it burns down the mixture very quickly, much quicker than the Diesel. The point is that for this process there has to be a Lambda 1 mixture in the whole Cylinder and this is what SPCCI solves in low speed cycles. They start the self ignition of the lean mixture with high compression heat and the spark. Less HC Cinder and NOX as the Diesel, because mixture has time to build up and no hotspots on the edges of burning mixture. short lesson by a german automotive engineer
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complete wrong you do not understand the Otto and the Diesel cycle the diagramm shown on 3: 43 is mixed up. The Diesel has a same pressure process because the firework begins 0. 2ms past injection, it begins to burn in the ms the mixture builds up and keeps on burning as long diesel is injected (so the pressure is kept on a high efficient level) there is no mixture that makes boom as you explained before (this is only the knocking if the diesel is cold and the mixture builds up while the piston is compressing to a higher temperature. The Otto in your wrong diagramm is told to burn down slowly, but no, it has a same room process it burns down the mixture very quickly, much quicker than the Diesel. The point is that for this process there has to be a Lambda 1 mixture in the whole Cylinder and this is what SPCCI solves in low speed cycles. They start the self ignition of the lean mixture with high compression heat and the spark. Less HC Cinder and NOX as the Diesel, because mixture has time to build up and no hotspots on the edges of burning mixture. short lesson by a german automotive engineer
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Tim Hallas
Have you ever heard of the Honda CVCC system of the late 70s and early 80s? This was a carb engine (pre fuel injection. It sends a very lean fuel/air mixture through the main intake port, into the cyl. At the same time it sends a richer air/fuel mixture through a separate intake port with its own valve and valve timing, into a small chamber atop the combustion chamber, where the spark plug ignites it. The resulting flame is able to ignite the lean mixture in the main combustion chamber. This is how Honda was able to sell us a car that got 50 mpg in the years BEFORE fuel injection was common on production cars. So, Mazda hasnt invented anything new. This is just a fuel injection version of the Honda CVCC engine. So, you might ask, what ever happened to the CVCC? It was made obsolete and unneeded by modern fuel injection systems, and advanced engine control electronics. Mazda is selling you a solution to a problem that doesnt exist.
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Have you ever heard of the Honda CVCC system of the late 70s and early 80s? This was a carb engine (pre fuel injection. It sends a very lean fuel/air mixture through the main intake port, into the cyl. At the same time it sends a richer air/fuel mixture through a separate intake port with its own valve and valve timing, into a small chamber atop the combustion chamber, where the spark plug ignites it. The resulting flame is able to ignite the lean mixture in the main combustion chamber. This is how Honda was able to sell us a car that got 50 mpg in the years BEFORE fuel injection was common on production cars. So, Mazda hasnt invented anything new. This is just a fuel injection version of the Honda CVCC engine. So, you might ask, what ever happened to the CVCC? It was made obsolete and unneeded by modern fuel injection systems, and advanced engine control electronics. Mazda is selling you a solution to a problem that doesnt exist.
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Jesse Percifield
Doesnt mention what octane is required. If its a lower octane like 87 or E85 that would be cool enough cost wise. If it requires 91 or higher you you might get 40 miles per gallon but at what extra expense at the pump. I have a 2016 MX5 that consistently gets 37 highway with 91 octane. The only issue with the higher octane Ive found that in some states the price is usually 60 cent per gallon more and have seen it as high as 1 per gallon more. This summer I drove my MX5 on an 8 week trip totalling a little over 10, 000 miles towing a small motorcycle camper getting as low as 27 mpg to 32 mpg. Great trip, great fun and noticed in some states the premium fuel only being a 30 cent per gallon hike from regular unleaded. The whole idea of more torque and power sounds good. I will be following this technology to see how well it holds up because it sounds pretty good.
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Doesnt mention what octane is required. If its a lower octane like 87 or E85 that would be cool enough cost wise. If it requires 91 or higher you you might get 40 miles per gallon but at what extra expense at the pump. I have a 2016 MX5 that consistently gets 37 highway with 91 octane. The only issue with the higher octane Ive found that in some states the price is usually 60 cent per gallon more and have seen it as high as 1 per gallon more. This summer I drove my MX5 on an 8 week trip totalling a little over 10, 000 miles towing a small motorcycle camper getting as low as 27 mpg to 32 mpg. Great trip, great fun and noticed in some states the premium fuel only being a 30 cent per gallon hike from regular unleaded. The whole idea of more torque and power sounds good. I will be following this technology to see how well it holds up because it sounds pretty good.
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Paul Pflaum
Mazda has always been ahead of the times. I bought a Mazda RX-3 (rotary engine) from Westcott Mazda in San Diego (National City/South Bay) in 1972. It was shaped like all 2 door Japanese cars. like a Toyota Corolla. but it was a pocket rocket. Dear God the thing was fast for its size I put 80, 000 miles on it. still ran like a scalded dog. no problems with the engine or anything on the car AT ALL. but Mom (the one who must be obeyedthe wife) said we need a family car in 1977 as we were then in a family way. I regret selling it to this day. We ended up with a Datsun POS. The rest is as the munchkins say: Itll be hiss. itll be hiss. itll be history ( History note: I did enjoy beating a Pontiac Bonneville 421 in a drag race on Camelback Rd. In Phoenix to 120 MPHand then he blew past me (he won). on New Years Eve 1972/1973. We werent arrested. thank God. )
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Mazda has always been ahead of the times. I bought a Mazda RX-3 (rotary engine) from Westcott Mazda in San Diego (National City/South Bay) in 1972. It was shaped like all 2 door Japanese cars. like a Toyota Corolla. but it was a pocket rocket. Dear God the thing was fast for its size I put 80, 000 miles on it. still ran like a scalded dog. no problems with the engine or anything on the car AT ALL. but Mom (the one who must be obeyedthe wife) said we need a family car in 1977 as we were then in a family way. I regret selling it to this day. We ended up with a Datsun POS. The rest is as the munchkins say: Itll be hiss. itll be hiss. itll be history ( History note: I did enjoy beating a Pontiac Bonneville 421 in a drag race on Camelback Rd. In Phoenix to 120 MPHand then he blew past me (he won). on New Years Eve 1972/1973. We werent arrested. thank God. )
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old time farm boy
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.
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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.
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kalelopaka
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 60s and 70s, 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 dont cost a fortune every time something goes wrong. I am thankful I can still work on my cars, even the newest tech doesnt 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.
reply
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 60s and 70s, 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 dont cost a fortune every time something goes wrong. I am thankful I can still work on my cars, even the newest tech doesnt 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.
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Craig Meyer
So heres what Im 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 wont 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?
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So heres what Im 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 wont 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?
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ernie brink rotary hemi
Mazda invited us out to a press day at their headquarters to show us their new engine technology. Could this be the new Mazda rotary engine? We didnt know Turns out it was their new Skyactiv technology --specifically SkyactivX. While we were a little bummed it wasnt the rotary, our dismay was alleviated as we started to learn all about this impressive technology. This [largely] SPARKLESS engine relies on insanely high compression in coordination with a slew of other engineering marvels to maintain a stable gasoline ignition. Zoom zoom muchacho.
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Mazda invited us out to a press day at their headquarters to show us their new engine technology. Could this be the new Mazda rotary engine? We didnt know Turns out it was their new Skyactiv technology --specifically SkyactivX. While we were a little bummed it wasnt the rotary, our dismay was alleviated as we started to learn all about this impressive technology. This [largely] SPARKLESS engine relies on insanely high compression in coordination with a slew of other engineering marvels to maintain a stable gasoline ignition. Zoom zoom muchacho.
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Charlie Maiorano
Im not convinced this is anything revolutionary. My understanding from watching your video, is that this is a new name for what Honda called CVCC and patent in the 1970s. Exactly as Mazda illustrated, but using a dual chambered combustion to maximize power and efficiency. How can Mazda be calling this combustion ignition if they still need to use a spark plug? I like the technology, just think the PR its slightly misleading.
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Im not convinced this is anything revolutionary. My understanding from watching your video, is that this is a new name for what Honda called CVCC and patent in the 1970s. Exactly as Mazda illustrated, but using a dual chambered combustion to maximize power and efficiency. How can Mazda be calling this combustion ignition if they still need to use a spark plug? I like the technology, just think the PR its slightly misleading.
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