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It's called Spark Controlled Compression Ignition, and Mazda made it work.
Despite rumors to the contrary, the internal combustion engine is far from dead. Recently we've seen several technological advances that will significantly boost the efficiency of gasoline-powered engines. One of these, first reported back in August 2017, is Mazda's breakthrough with compression ignition. On Tuesday, Mazda invited us to its R&D facility in California to learn more about this clever new Skyactiv-X engine, but more importantly we actually got to drive it on the road.
The idea behind Skyactiv-X is to be able to run the engine with as lean a fuel-air mixture (known as λ) as possible. Because very lean combustion is cooler than a stoichiometric reaction (where λ=1 and there is exactly enough air to completely burn each molecule of fuel but no more), less energy is wasted as heat. What's more, the exhaust gases contain fewer nasty nitrogen oxides, and the unused air gets put to work. It absorbs the combustion heat and then expands and pushes down on the piston. The result is a cleaner, more efficient, and more powerful engine. And Skyactiv-X uses a very lean mix: a λ up to 2.5.
(Score: 2) by bzipitidoo on Wednesday January 31 2018, @10:33AM (4 children)
Over the years, there've been a lot of ideas to improve the internal combustion engine. Compression ignition sounds good, but will need more than that to have a chance of competing with electric.
There's the Atkinson Cycle engine, used in some hybrids. It's not used for direct drive because its optimum RPM is a much narrower range, and it doesn't have much torque.
An ICE has a lot of parasitic loads. The water pump is a huge one. Because we do not have materials that can both withstand the peak heat that burning gasoline can reach and still handle the stress of the mechanical motion, we have to cool. Ceramics can take the heat, but are too brittle. Yes, the VW bug had an air cooled engine, but most engines had to use a water based cooling system. John Deere had these "Thermosyphon" tractor engines that used water but no water pump, relying instead on convection. The hoses connecting to the radiators were huge. Eventually John Deere gave up on that idea.
Another idea is this Crowley 6-cycle engine that adds a water to steam cycle. Squirt water into the cylinder and the lingering heat from the previous cycle's combustion turns it into steam, for an additional power stroke that also cools the engine enough to dispense with the water pump. Of course, the car requires a tank of water as well as gasoline. As I recall, the idea had problems, with the worst being that some water gets past the rings and contaminates the engine oil, so the engine needs a device to deal with that, some sort of water trap.
Yet another one is burning a cooler fuel such as methanol. Methanol burns at a low enough temperature that the engine can be air cooled. Not sure I'd want to ever handle methanol on a regular basis. I have heard that drinking methanol causes blindness. What would breathing methanol fumes do to a person, blind you more slowly? There is 100% ethanol, which may burn cool enough that no water cooling is needed.
If we could recharge batteries quickly, we could get rid of the alternator, and that would boost fuel economy by about 10%. Recharge batteries when you refuel.
There was a proposal in the late 90s to move automobile electric systems from the current standard of 12VDC to 42VDC. 42V was chosen as about the highest voltage that was still safe for people to be around. With the higher voltage, wires can be thinner. The mechanical valves can be replaced with solenoid powered electric valves, and we could dump the camshaft and timing belt. We can also dump the mechanical power steering pump for an electric one. Ditto for the water pump and the A/C and the oil pump. Fuel pumps were switched over to electric years ago, when fuel injection gradually replaced the carb in the 80s. However, nothing came of it. One annoying problem was that incandescent filaments of the headlights, brakes, and other indicators had to be thinner to handle the higher voltage, and that unfortunately make them much more prone to breaking. Didn't have super bright LEDs then.
Being a gearhead, you probably know all about headers and port tuning and such like that has now become routine on stock engines. I have heard that some race car engines use a tank of pressurized air to run the valve train, which otherwise is another parasitic load.
So, yeah, lots and lots of ideas. I guess the ones that involve filling up multiple tanks are non-starters with our convenience loving society. Imagine if at the gas pump, you had to also connect an air hose to refill an air tank, and a water hose for a water tank, and a wire to recharge the battery.
(Score: 0) by Anonymous Coward on Wednesday January 31 2018, @01:56PM
It does. But drinking gasoline isn't all that good for you either. Methanol just isn't a particularly good fuel for an everyday engine. It's corrosive and has poor energy density. They use it in racing, especially drag racing, where you only need enough fuel for six seconds, and engines only run for a few minutes before a rebuild.
Or the whole engine.
This seems like a terrible idea. The gain in power from the steam expansion wouldn't come close to making up for the loss in power due to only having 2/3 as much actual combustion activity. You also have problems with the heat being in the wrong place at the wrong time. Relatively little heat is actually transferred into the engine block from the combustion. Most of it goes into the exhaust or into doing actual useful work. Then you'd have to transfer it back from the engine block into the water. Real steam engines have a boiler, they don't try to turn liquid water into steam inside the piston. Steam engines don't usefully produce power at the speeds that gasoline engines do. Spraying cold water into a hot engine is a recipe for cracked cylinders/heads. On top of all that, you need a whole separate plumbing system for the steam that's different from your regular intake and exhaust. Overall, seems like more of an amusing concept than a practical invention.
Oil contamination is unlikely to be any significant part of the problem. Oil already absorbs water, which is released when the oil gets hot enough. They actually put additives in the oil to make it absorb water, to keep the water from corroding the engine. Take enough short trips in the winter, then look in your engine oil, it'll be all foamy. That's the trapped water. Get the engine nice and hot and it will all boil off. Remember water is the main component of engine exhaust.
This has been done (well, the A/C and steering at least), but it only saves so much. Primarily, it saves power by allowing you to run these various pumps at the speed they actually need to run instead of whatever speed the engine happens to be going, improving efficiency and reliability. It also allows the battery to buffer the power needed by these devices - otherwise they draw their maximum power at the same time the engine is working the hardest. But all the power comes out of the engine in the end, just a question of whether it gets turned into electricity temporarily first. It has advantages, just not big fuel savings. And oil/water pumps need to be driven by the engine because the engine would be damaged if they stop but it keeps running.
If you think about it, this isn't going to do anything useful for an everyday engine. If the compressed air were more efficient than the engine end-to-end, they'd just run the whole car on it.
(Score: 2) by Grishnakh on Wednesday January 31 2018, @07:27PM (2 children)
You have a lot of interesting ideas you've obviously read about over the years, but I'm afraid you're way behind and seem to not be aware of how modern cars work.
There's the Atkinson Cycle engine, used in some hybrids. It's not used for direct drive because its optimum RPM is a much narrower range, and it doesn't have much torque.
Wrong; tons of engines now are Atkinson cycle. The one in my car is. The interesting bit is that, thanks to variable valve timing, it changes from Atkinson cycle to Otto cycle when more power is needed.
If we could recharge batteries quickly, we could get rid of the alternator, and that would boost fuel economy by about 10%. Recharge batteries when you refuel.
You can't do that because modern cars have huge electrical loads. What we have now on some cars are "mild-hybrid" systems where the alternator is engaged selectively, keeping it disengaged much of the time, and then engaging it when coasting or braking, for instance, to capture energy to recharge the battery and power the electrical system. It might get you 1-2 mpg improvement, certainly not 10%. I have one of these systems in my car.
There was a proposal in the late 90s to move automobile electric systems from the current standard of 12VDC to 42VDC. 42V was chosen as about the highest voltage that was still safe for people to be around.
It was also chosen because it's 3 times the old standard's voltage (14 x 3 = 42; cars don't run at 12V, they run at ~14V), and because it's under 50V, which is generally accepted to be the maximum safe voltage for humans to work with without worrying a lot about shocks. The main advantages to higher voltage are 1) thinner wires, saving on weight in the car, and 2) smaller motors for the same torque, which again reduces weight.
The mechanical valves can be replaced with solenoid powered electric valves, and we could dump the camshaft and timing belt.
They've been trying to do this for ages. You need really powerful solenoids to operate at that speed, so I think what I read is that the benefits were outweighed by the power needs of the solenoid system. Modern engines with variable valve timing have gotten most of the advantage to be had here.
Also, timing belts are passe; everyone seems to have moved back to timing chains.
We can also dump the mechanical power steering pump for an electric one.
Now this is the one that makes me ask you, exactly what year do you think this is? There is not any car made today that I'm aware of that has an engine-driven mechanical steering pump. Some still have electric-powered hydraulic pumps, which has been common since the 00s, but now most cars are moving to all-electric steering systems, with a motor attached to the steering shaft. My almost-economy car has this even.
Ditto for the water pump and the A/C and the oil pump.
If there were big gains from having electric water and oil pumps, we'd probably see them commonly on production engines now. There's probably little to no gain to be had, because these things have to run all the time, unlike steering for instance, and they need to run faster as the engine runs faster. The A/C is a candidate for electrification, and hybrids now generally do use motor-driven compressors since they have to be able to operate even when the gas engine isn't running. However, the power consumption of one of these compressors is huge, so the motors are high voltage and driven from the car's battery pack; they consume too much power for a standard 12V starting battery.
One annoying problem was that incandescent filaments of the headlights, brakes, and other indicators had to be thinner to handle the higher voltage, and that unfortunately make them much more prone to breaking.
Huh? We've had 110V (and 220V in other countries) light bulbs since Edison's time. I'm sure the military and other industries had bulbs back then which could handle vibration just fine. This should not have been a problem. The likely reason it never happened is because of too much inertia in the industry: no one really wanted to change that badly.
(Score: 2) by bzipitidoo on Thursday February 01 2018, @04:52PM (1 child)
My newest car is a 2001, so, yeah, I am a bit behind. I'm holding out for an all electric car that can do road trips and doesn't cost more than $50k. I'd heard about but forgotten that electric power steering has taken over. Didn't know Atkinson Cycle engines had advanced to become more popular and useful. May I ask, what model and year is your car? Also didn't know of the move back to timing chains. The whole "belts are quieter" reason never sounded like a good justification for the shift to belts in the first place, more like an excuse while the real reason was that they are cheaper, don't need oiling.
Once drove my 1967 car 30 miles (all highway) on battery alone, after the generator quit on me near the end of a 300 mile trip. Only time I ever used the switch that car had to turn off the dash lights. Could have gone further if it wasn't dark. Had to have the headlights, which had gotten very dim, with the engine missing when I crested the last hill before the Interstate. Let up on the gas and the engine stalled, so I coasted the last quarter mile to the gas station at the interchange. Turned out the generator was fine, and that one of the wire terminals had broken off. So, even a 1960s all mechanical except the spark plugs car would need at least 10 batteries to go 300 miles between charges. Of course if batteries could be recharged quickly, we would dump the ICE now and just go all electric.
The point of 42V was everywhere more and more powerful electromechanics in smaller packages. Solenoid actuated valves are just too bulky at 12V. But it seems electrical engineers have improved 12V motors enough that going to 42V is not as big a gain as it was in the 90s. And yes, thinner filaments really were a problem. Automobiles are subject to more and stronger vibration, and temperature and humidity changes. It's a very harsh environment for electronics. As for inertia, yeah 12VDC is darn near a universal standard, cutting across a lot of industries. PCs used to run mainly on the 5V rail, but now the 12V rail is the main one. (The -5V,+5V,+12V PC power supply ought to be retired in favor of a single voltage.) 12VDC and 24VAC electromechanical items such as relays are interchangeable, and the HVAC industry standardized on 24VAC decades ago.
Oh, I misremembered the name of the guy trying the 6-cycle engine. It's Crower, not Crowley.
(Score: 2) by Grishnakh on Thursday February 01 2018, @05:59PM
My newest car is a 2001, so, yeah, I am a bit behind.
You're almost or maybe even more than 2 decades behind, depending on when your car was designed (a 2001 model year came out in 2000, but that generation vehicle may have first come out in 1997). A lot of stuff has changed since then.
May I ask, what model and year is your car?
2015 Mazda 3. Not a very expensive car.
Also didn't know of the move back to timing chains. The whole "belts are quieter" reason never sounded like a good justification for the shift to belts in the first place, more like an excuse while the real reason was that they are cheaper, don't need oiling.
Cheapness is probably the main reason they used them, but too many problems with broken timing belts trashing engines, plus the high expense of routine replacement, probably made them too unpopular to keep using. Modern engines all seem to use chains, so I guess they solved the NVH issues.
The point of 42V was everywhere more and more powerful electromechanics in smaller packages. Solenoid actuated valves are just too bulky at 12V. But it seems electrical engineers have improved 12V motors enough that going to 42V is not as big a gain as it was in the 90s.
Yeah, with pretty much all cars having electric steering now, I am surprised there hasn't been more push to move to a higher voltage.
And yes, thinner filaments really were a problem. Automobiles are subject to more and stronger vibration, and temperature and humidity changes.
Yes, but so are boats, military vehicles, aircraft, etc., and those frequently operate at higher voltages. Boats usually have 24V systems if they're larger than a certain length, and a lot of commercial vehicles also have 24V systems. High-vibration isn't unique to cars, and we've been making incandescent bulbs in various voltages (including 110VAC) for various applications for ages. I just don't see how this should have been a problem. Aircraft have been using light bulbs for many decades and have far, far worse vibration and temp/humidity problems than cars, plus far higher reliability requirements too. Aircraft light bulbs routinely go from warm ambient temperatures on the ground to extremely cold temperatures at cruising altitude and back, on every trip.
Oh, I misremembered the name of the guy trying the 6-cycle engine. It's Crower, not Crowley.
Correct. Crowley [wikipedia.org] was an occultist who founded the religion of Thelema, not an engine builder. :-)