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Camless Internal Combustion and the Digital Age (hackaday.com)
szczys writes: The internal combustion engine is amazing, and it continues to evolve. Carburetors gave way to fuel injection, and a computer now monitors all kinds of sensors to ensure these engines operate at peak efficiency. But there is one thing that has remained largely unchanged: the cam shaft. This is a device responsible for mechanically timing the operation of the cylinders. It's possible to build an engine that uses digitally controlled actuators instead of a camshaft to decide when each cylinder should fire. These exist as prototypes — we have the technology, so why aren't we building with it? The answer is that change is hard, and as with the carburetor it could take an outside force (in that case mandatory efficiency benchmarks) to get automobile manufacturers to wager a bet on new technology.
The fundamental parts of the engine are all mechanical. They work without a battery.
Resilience to electrical failure is important.
Camshaft hooked up to my Raspberry Pi. Ruby on Rails controlled Iot webserver platform with home automation built in. Insteon X10 platform protocols provide robust social media sharing.
rumor is the hydraulics used a ton of power. The thing was much less efficient than a traditional cam driven engine. Sure, the valve timing and lift was perfect, but it was otherwise a nightmare.
Ever break a timing belt on an interference engine? Very bad.
One of our competitors trademarked the term "hypothesis". From now on, we will call them "boneheaded ideas".
http://jalopnik.com/what-its-like-to-ride-in-a-car-with-the-camless-engine-1529865968
I gather the price is still prohibitive...
It's possible to build an engine that uses digitally controlled actuators instead of a camshaft to decide when each cylinder should fire.
Camshafts don't control when cylinders should fire, that's an already replaced component called the distributor. Camshafts control the timing of inlet and outlet valves, and there are already formula one and other engines using electronically actuated pneumatic valve lifters.
The problem is that cam shafts are very reliable, and a single fault in valve timing, in an interference engine especially, results in catastrophic engine damage, so the software and hardware has a very high bar to meet for it to replace mechanical cams.
Also firstpost.
-puddingpimp
These exist as prototypes â" we have the technology, so why aren't we building with it?
Probably because a camshaft will last for 200K+ miles, and this new technology will not.
Inefficient, noisy, polluting, maintenance intensive, expansive, complex, why are we still trying? There's no alternative?
I'm far and away not an engine guy, but I always thought the reason was limited lifespan of solenoids.
A cam is just a spinning part. A solenoid would have to electrically activate perfectly every time, thousands of times a minutes, for 15-odd years of usage. To match that kind of usage, you're talking some serious solenoid. Probably they do exist but they're not exactly standard hardware, as far as I know.
And even the article suggests you tinker with models where the pistons can't crash into the valves. When you're tinkering, maybe that's okay. When you're designing engines it's not really okay.
Like all things, it's not that it can't be done. It's that the investment to make it work, work right, work first time every time, and prototype it to oblivion so you know that, probably far outweighs what you'll get back in any kind of efficiency saving on a non-trivial engine. Even rotary engines are comparatively rare compared to other types.
Things are most certainly heading all-electronic. But if you're going that way, almost certainly your investment is better of in electric drive, rather than huge investment into a critical piece of technology that - if it goes wrong - means a new car, for the sake of an slight efficiency increase.
One of the big limiting issues in this field (BTDT) is energy consumption by the actuators and associated circuit components. Valve are heavy relative to the accelerations needed by the motion profiles. This results in ferocious energy use and dissipation.
If this power consumption is more than the engine power/efficiency gains from tinkering with profiles, the answer is an easy No.
My only relevant direct experience was for an R&D engine to test different cam profiles without having to grind sets of camshafts. It used plant electrical power, can't remember exactly how much but the equivalent horsepower was in the teens.
Bent, folded, spindled, and mutilated.
Seriously. If the technology is mature (regularly survives a 500 mile race) while providing tangible benefits (more horsepower meaning a faster car with better fuel economy which means fewer pit stops) customers will demand it.
Otherwise, it's of no perceived value to customers and might be seen as just another piece of electronic junk that is being foisted upon them (like anti-lock brakes for those of us who remember people who couldn't see their value).
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Automakers embrace whatever gets people to chose their car over the competitors car, is cost effective to manufacture, and is reliable enough to get past the warranty period but not so reliable the car last too long past the warranty.
There were fuel injected cars long before it was practically mandatory. I believe there were Corvette's from the 1950's that had early fuel injection. I test drove a 1982 Fiat that had it. Fuel injection was slow to be adopted due to cost benefit ratios along with performance. Early fuel injection wasn't always better than a well tuned carb, in fact it was very popular among enthusiast to remove fuel injection systems from 1990's Mustangs and put carburetors back on.
Cars still use camshafts because camless systems haven't been developed to a point that mass production and implementation makes sense to a manufacturer. Not just a custom built lab system, not just a small run on rinky-dink 3D printers, but something that can be churned out by the 1,000's.
I was hoping new Slashdot ownership would steer us away from these pro-regulation propaganda pieces.
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Its because all the "safety" equip mandatory on cars now, all those extra pounds are killing PMG
Who cares about efficiency in an internal combustion engine? What you really want is lots of noise and smoke when you stomp on the gas pedal! (So you can look impressive! Or, more accurately, so you can look childish as the electric car next to you quietly leaves you in the dust.)
Being able to vary the valve timing under computer control could have some advantages,
Yes. And there are some schemes that can modulate the relationship between each DOHC shaft relative to the crank position. And that pretty much achieves what TFA proposes with much lower actuator power and nearly the same flexibility. So, problem solved.
Have gnu, will travel.
What it really means is that the efficiency improvements are so poor it is not worth the additional cost. Unless some government agency, for good reasons or for bad, forces the manufacturers to change it is not worth it.
sed -e 's/Chuck Norris/Rajnikant/g' joke > fact
Here is an example of a cam-less engine that has been in development for over 10 years.
http://www.dukeengines.com/
46137
Just a reminder, when your fuel injector goes tits up, you just replace the fuel injector. When your timing belt/chain breaks ("digital" or mechanical), you replace your engine.
Why bother?
More parts to break.
"If any question why we died, Tell them because our fathers lied."
Because the new car is heavier.
Tell me about it. I had a 95 1/2 Tacoma and an 01 Celica. Both about 34 MPG in practical conditions and use.
My wife's 03 Cavalier still gets about 33 MPG.
Very few modern cars get mileage that good, and when they do they're usually shoe-box sized cars. Not that any of the stuff I named was huge, but they weren't Smart Cars.
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I thought electronically controlled pneumatic valves were old tech (as in almost 20 years old)? Im surprised they haven't evolved into modern cars yet.
My Ducati has cams for opening and closing the valves.
Will I need a larger battery when they go all electric valves?
A bullet may have your name on it, but artillery is addressed to " Whom It May concern"
I have a 1991 Mazda RX-7 with a rotary engine in my garage, no cams there!
Just because it is possible doesn't make it a good idea.
Many engines are interference engines, where the valves sweep through the same space of the pistons during different parts of the cycle. This is largely due to the need to have high compression ratios (IC engine efficiency is strongly driven by compression ratio). Timing is crucial - if the timing is off, valves crash into the pistons and your engine tears itself to pieces. Timing belts, chains, or even gears are used to prevent this. It is particularly important to get timing belts serviced regularly, because they are a cheap part that can cause destruction of the engine if they fail. However, it is only a single point of failure.
The digital solution introduces at least two and possibly more points of failure per piston Loose or frayed wire? *BOOM* - destroyed engine. Mechanical failure of a single lifter? *BOOM* - destroyed engine.
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Sounds good. I'll take two.
Have gnu, will travel.
The forces involved in a valvetrain, coupled with the speed of operation needed are going to call for some chunky power electronics driving the valve actuator solenoids. Given that the typical failure mode for power MOSFETs is to go short circuit, this would drive the affected valve wide open and hold it there. The open valve then gets bent over and possibly driven through the top of the piston.
I can't ever see this kind of high power (multiple kW), high speed electronic switching system being as reliable as a timing belt that typically runs 100k miles before recommended replacement.
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No, wait... We're already talking about cars... Hmm, where does one go to for an analogy when the subject is already cars?
The advantage you gain is not just the ability to vary the timing of the valve events, but you can change the duration and lift as well. A camshaft only lets you vary how much sooner or later you open the valve but it's always open the same duration and the same lift.
Theoretically, with enough fine control over the valves and a good computer to control it, you could do away with the throttle altogether and use the valve duration, lift, and timing as the throttle.
You may be right, but the technology might be useful elsewhere. Also, if they choose the right kind of actuator they might be able to reduce or eliminate the spring tension, which would make it easier. Also also, don't forget that the camshaft robs the engine of plenty of power on its own, so the electronically actuated ones don't have as far to go as we might think.
Lucas was working on this 36 years ago.
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Because its heavier and cleaner running. It probably has heavier tires and lots of other features your old one didn't have. Not to mention more power.
http://www.motorauthority.com/news/1101737_video-shows-inner-workings-of-koenigseggs-camless
Firstly changing how soon you open a valve and how late you close it can be translated to duration, so you kinda contradict yourself there. But more importantly if you change the shape of your cam and you change the lift. The Honda VTEC system has multiple lobes which are engaged at various throttle and rpm levels. This has the effect of changing the duration and the lift. Specifically it changes the lift far more than the duration.
The biggest change that can be made to the valve system is to move away from springs and to a manual close system. This way your valves can physically move faster and hence have a longer period of time open without valve bounce or smashing into the piston.
They call it a "Digital Cam" because when you graph valve lift vs time it literally looks like a square wave. The ramps really are that steep!
This compares to a conventional cam with a sudo-sinusoidal shaped wave lift profile (neglecting the effects of high RPM valve float).
Criticize as much as you want, but a truly functional electronically controlled camless engine would be the holy grail of internal combustion engine design. You can easily pick up 20 horsepower on many engines just by swapping to a performance cam, but you often compromise efficiency. But with a camless engine, in theory, you could have cylinder deactivation, low compression starts, the elimination of throttle plates (lower pumping losses), "full race-cam" profiles for performance, a cam profile for smooth idling, low emissions, etc....
Truly the best of both worlds!! That being said, there are disadvantages....
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I read an interesting SAE paper 20+ years ago describing a working prototype camless engine. The performance gains were impressive, but as I recall, there were two main obstacles:
1) Noise, Vibration, and Harshness. (NVH)
2) The valves landed harshly leading to valve seat wear. The SAE paper suggested using a method for softer valve landings.
The force required to open a valve comes from the size of the spring that closes the valve. There isn't anything about engines that inherently requires that level of force but most valve systems are self closing with the cam only being responsible for opening. The force in the spring needs to be high enough to close the valve as fast as the cam allows and to be able to prevent the valve bouncing when it hits the seat.
In an ideal world we would be mechanically closing the valve as well as opening it. It requires significantly less force, and allows higher valve head speed and longer lift times. The disadvantages are you have to maintain the system a lot more and it is more complex. This is called a desmodromic valve system, Ducati motorcycles are the most common example.
While the desmo system still uses a cam if you could replace that system with an electrical system you could potentially see higher performance outcomes.
The OP was talking about engines that can advance or retard a single pattern cam. And when you have just one cam profile, you can only change the relative timing. The duration and lift stay fixed. Duration is the number of degrees of camshaft rotation that the valve is open. Adjusting when a camshaft opens the valve doesn't change how long it stays open, or how far it opens for that matter. Electrically controlled valves can vary all 3 of those things.
Sure, the VVT tech changes from one camshaft profile to a second one. But that's all they can choose from. You either use one or the other. You might be able to squeeze 3 profiles in there if you use a DOHC setup that splits the intake and exhaust lobes between two physical camshafts and gives you room to fit the multiple patterns. But it would be a lot more complicated to do that. And you're still limited to a few fixed profiles. Electrically controlled valves do not have this limitation.
Electrically controlled valves, in theory, have "infinite" adjustability (within certain limits). You can have dozens, hundreds, probably even thousands of profiles to choose from. All you have to do is have the computer pick the profile based on load, throttle position, etc. and it changes instantly.
It has one camshaft for operating the intake valves and one for the exhaust valves. What it does have is separate cam LOBES for the opening and closing followers. A single solenoid for each phase could open both intake/exhaust valves, and another pair could handle the closing. With the twin, though, that's four solenoids/head, which would need to be cooled, and the vertical cylinder is already a packaging hassle.
I have both an air cooled 2-valve and a liquid cooled 4-valve, and, while it might be nice to get away from the periodic checking/adjusting, I wouldn't trade the simplicity or reliability for more electronics.
I understand the use-case of replacing the carburetor with fuel-injection, and computer-controlled fuel injection allows you to optimize the performance of the engine for a variety of cases that are only measurable with electronic (i.e. computer) sensors. But what's the use-case for replacing the camshaft. It's got a monkey-stupid job, lifting and dropping poppet valves. It performs that job perfectly because it's dead-simple. It's directly connected to the crankshaft, so it operates for as long as the engine is turning. It's got a dead-easy task, of lifting and dropping lightweight valves, so it contributes virtually no parasitic drag to the engine, and because of the simplicity of the design, (it's a rod with bumps on it) it lasts FOREVER. Whoever heard of replacing a camshaft? The reason why nobody's moved to electronic valve control is that the camshaft is in the Dieter Rams design hall of fame. It's great design: It's not part of the problem, so don't change it.
The engine is just a constant-load, constant temperature (once it warms up) generator to top up the battery. Any adaptation to power demand should be handled by the electric drivetrain.
Nullius in verba
Lots of discussion about what happens with a mistimed valve in an interference engine. It's a valid concern, but as has already been pointed out, happens a lot in regular camshaft engines also. The most trivial example is a broken timing belt.
Someone mentioned that electric valve actuators could be less forceful than a mechanical valve train, so that the piston slamming against an open valve would be bad but not catastrophic. But valve springs tend to be pretty strong, so it'd take lots of force to open a valve, so maybe the impact would be catastrophic after all.
To me the advantage of digitally actuated valves is the elimination of not only the camshaft but also the springs. As Ducati discovered awhile back, if your valve train pushes the valve open and then pushes the valve closed without springs, you can maintain much higher RPMs without danger of valve "float", where the spring isn't able to push the valve closed in time. This same type of arrangement should be possible in digital systems also, where the valve is electronically opened and also electronically closed. Then if the system goes dead (electoronic version of a timing belt snap) the valves are under no pressure and the impact force with the piston is much lessened.
A mistiming might still be difficult, but there should be a way to design the system to survive it.
I don't see the primary benefit to be one of efficiency. I see this as a way to get wickedly high RPMs. Think of a motorcycle engine that redlines at 3000 RPM or more.
Oliver's law of assumed responsibility: If you're seen fixing it, you will be blamed for breaking it.
Go buy the solenoids with the required lifetime specs. What do you figure, 10,000 operating hours per year, 100000 rotations per hour, a valve opening every other rotation?
That's 10M actuations per year. An engine is good for about 10 years, 100M actuations. 16V per engine (or so), so you need on average 1 failure or less per 16V per 100M actuations.
Now go price that out and I think you'll find the reason why we don't do it this way to be obvious.
Or just ask anyone who has had a fuel injector replaced and remember that an engine usually as 4x as many valves as fuel injectors.
http://lkml.org/lkml/2005/8/20/95
why are we still burning fossil fuels for transportation anyway?
One more MAJOR advantage of a camless design (if not the single greatest advantage) would be the ability to have extremely canted valve angles. Retrofitting an existing cylinder head design with camless engine technology is only scratching the surface. The biggest benefits would be gained by designing the cylinder head ports around the capabilities of the valve actuators. With cylinder head differences like this, we're literally talking about the difference between NASCAR horsepower levels and streetcar horsepower because cylinder head designs are the undisputed most important factor in making horsepower.
With traditional cylinder heads (on OHV engines), valve angles are limited by the rocker arms. Rocker arm rotation about one axis is trivial, but when the valve is canted it makes the valvetrain design exponentially more complex and prone to wear due to lateral loads as the angle is increased. A camless engine design wouldn't have this limitation. That being said, the camless designs have their own challenges, namely soft valve seat landings due to a nearly perfect square-wave lift profile.
All the same arguments could be used against your car if compared to a horse-drawn carriage about a century ago.
With rocker arms, it's possible to change the pivot point, which allows changing duration and lift.
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I hope your link gets the attention of the moderators because that was really cool.
BS. I've taken long trips in my Tesla, no problem. And "payback" played no role in my decision to buy. Even with gas less than $2/gal, I laugh at the suckers when I drive by a gas station. I have 235 miles in my tank every morning. Free, too, with my solar panels. (I'm not interested in whines about solar cost, either. All infrastructure is paid for somehow.)
Opposed Piston Opposed Cylinder engines have two pairs of pistons facing one another, each in a cylinder on opposite sides of the crankshaft. There is no cylinder head, just a ring of ports for intake and exhaust in the cylinder walls near where the pistons bottom out. With a slight timing offset, the exhaust ports will open before the intake ports. It is a fascinating design, simple and elegant, with very few moving parts and a high power density. The engine is completely balanced, and all of the linear forces cancel, leaving little load on the bearings, just torque. There are other interesting concepts out there, but this one is actually being mass produced today.
Electric cars are certainly attractive, but the reality is that hydrocarbon fuels are going nowhere. The energy density and flexibility are simply too great, and we have an immense amount of infrastructure and equipment that make use of them. The fastest way to a greener world isn't through electric cars, but rather synthetic carbon-neutral fuels, which can be efficiently produced using heat from nuclear reactors. Nuclear Ammonia is particularly interesting, because the feedstocks are readily available from air and water. Other replacement fuels can also be synthesized, but extracting carbon from air or water will add to the cost.
Good points.
But not dynamically. Once the engine is assembled, the duration is fixed.
Read that as "camelless". Oh good we can have cars without camels?
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It's not about being more reliable.
It's about being more flexible. Maybe faster.
Bound to be a way to make the circuit fail closed.
deleting the extra space after periods so i can stay relevant, yeah.
https://www.youtube.com/watch?v=f4p-55a3WV8
Koenigsegg has had at least one car driving around with air/hydraulicly operated valves for a few years now. It's got tens of thousands of miles on the setup.
Now.. someone just needs to get the system to market.
You would have to be crazy to be sane in this world. -Nero
I designed some spacecraft. We were limited on what we could use for a microprocessor because we needed something with history. We almost used an 8051 variant. Same goes for engines, lets say you invent an awesome engine, it even makes you toast in the morning amongst other great things like saving you fuel. You take it to one of the manufacturers, and they love it, because it saves their customers fuel and it give them more incentive to buy their products. Then they tell you, we have these things called warranty's that we offer on all of our vehicles can you tell us the MBTF? Most of the parts are new so you go back to your lab and run it for 5-10 years.
2) The valves landed harshly leading to valve seat wear. The SAE paper suggested using a method for softer valve landings.
I am just a computer nerd, but perhaps they need to rethink the valve all together to achieve a cam-less engine. Maybe an electronic trap door that slides open and closed really fast would work better. It wouldn't need a rod to push it along the Z-axis and there's no longer a valve seat to even worry about!
Now, if you'll excuse me, I have backups to corrupt.
I try to read slash-dot every day... Never posted before. :)
If I understand your post? I would say electromagnets coupled to the valves would be the answer.
It's possible to digitally controlled electromagnets instead of a camshaft.
P.S. let me know what you think?
Koenigsegg have a Saab car running with camless technology as a study model for their own hyper cars. There's a few videos on the t00b.
with the cam only being responsible for opening
The trailing profile on a cam is there to slow down the valve as it closes, to prevent it slamming too hard on the valve seat - if that wasn't needed then cams could be asymmetrical and look more like a comma than an egg.
They sentenced me to twenty years of boredom
Well I did say close as fast as the cam allows but yes it might not have been clear.
When you come home, you open your mechanical door by pushing. Why not have sensors and motors? Will it improve the experience significantly. I think that is the crux. Unless the technology significantly improves something, like electronic fuel injection, electronic fuel pumps etc., did, there is no point.
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Notwithstanding the OP observation concerning the rate of development of the internal combustion engine (and at the risk of starting a flame war, which is not the intent) why not move away from *all* the sins of reciprocating engines and go with something like a Wankel rotary? Yes, I appreciate that the biggest single failing of the rotary is often rotor wear, but the rate of development of materials science has been so incredible over the last 10-15 years that it is pretty much certain that a clean-sheet design started today would be a quantum leap forward from anything we have seen thus far. I've never personally driven, let alone owned, a rotary engine, but maybe starting with a problem statement of "How do we get rid of mechanically operated valves?" is setting our sights a bit low?
I drive a Tesla model S and sold my gasoline car since I drove it so rarely. For most of my driving I spend 5 seconds every night plugging it in and 5 seconds in the morning unplugging it. It doesn't even matter if I forget a day or two. When I do take it on long trips the waits haven't been that big a deal in most cases. I drove from the Bay Area up to Seattle and it took two days (and no, I don't feel like driving 14 hours straight). Most of the stops had plenty of stuff around to do and more often than not the car was ready to continue before I was. One stop had a nice brew pub across the street. Another was at a nice upscale outlet mall. Most had good places to eat or do other activities within easy walking distance.
Total cost to drive to Seattle, not including food: $0 (I stayed with friends near the halfway point). Even if I stayed in a hotel it's only $60 each way, far less than I'd spend on gas.
It gets easier and easier to travel as more and more charging stations are built along more and more routes.
I never had to stop for over an hour. The longest I had to stop was around 40 minutes.
It gave me a chance to stretch my legs and get something to eat. The only drawback is I had to stop more often than my car did for bathroom breaks.
People tend to make a big deal over the charging time, but unless you're regularly going on these long drives where you drive non-stop it really is no big deal. I spend far less time charging than most people spend filling up their cars at gas stations. As I said, it takes me 5 seconds to plug in in my garage every night. Take 2 steps back, grab the cord, press a button on the connector (which opens the charging door) and plug it in. I don't have to get out of my car and stand in the cold filling my car up. Every morning I start out with my car 80% full. I drive around 1000 miles/month on average and my monthly electricity bill for the car (using PG&E, not one of the cheaper utilities) is $50. I don't take it easy either when driving. I don't miss gas stations.
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Tesla actually offers this, however few people take them up on it. They contacted me about doing it but it's at Harris Ranch. I replied that I would rather take the money spent on a battery swap and buy a nice steak dinner there and that seems to be the common thread. Not a lot of people take advantage of it. If Tesla put it someplace else then I might use it, but not there.
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While the pros for a technology change like this would be interesting especially for motor tuning and efficiency, I assume the cons are pretty big ... for one, the rise and lowering of the valves isn't a binary on/off setting, but requires specific speeds (otherwise you may mess up the valve springs etc.). Also, with the current cam shaft technology, destroying a motor is more or less dependent (at least as valves and cam shaft go) on failure of the timing belt or chain (which is why there are specific recommendations in which intervals they should be replaced). With more sophisticated actuators, any failure in controlling them correctly could lead to bent valves or worse ...
They call it a "Digital Cam" because when you graph valve lift vs time it literally looks like a square wave.
I doubt that - if you drop the valve too quickly it's going to bounce, so no square off-the-cliff graph for the valve closing bit.
I'm not saying that they cannot do it, I'm saying that it's stupid to do so. Open the valve as fast as you want to, but closing it needs to be done gradually, which is why the closing surface of the cam lobe is gradual and not simply cut off.
If you cut a notch in the cam after the stationary point you too can have a square fall-off-a-cliff valve closing profile. However that still gives you valve bounce.
I'm a minority race. Save your vitriol for white people.
So awesome, you can gain %2 efficiency at the end of the power band in automobiles ... and it'll break 1,000,000 times more often because the existing design is a single solid chunk of metal that sits in the second hottest most stressful part of the engine ... and you want to replace with a bunch of moving bits and magnets.
Industry is full of electro-mechanically continuously unloading compressors controlling such valves with orders of magnitude more run time than your crappy little car.
I'm going to call bullshit on your sensational "break 1,000,000 times more" statement.
The answer is that there is no benefit in the majority of cases.
Just because you can digitize something doesn't you must.
The cam shaft is extremely simple and extremely unlikely to fail. It just works. It only has two failure modes, one internal one external.
Internal: structural failure, which for those up to speed on their material properties, is extremely unlikely. Any structural failure root cause is more likely to be the result of a bad batch of material than anything else.
External: rotation failure. This isn't a failure of the shaft, but a failure of another component of the engine that is failing to drive it's rotation.
It is because of this simple reliability that there has been little reason to reengineer or replace the camshaft.
By contrast digital timers have much more complexity and points of failure. Now I do believe that reliability is ultimately an engineering problem, and one that will be solved in time. And there may come a point when the pros of digital cam replacement carry a net benefit. But that time is not now. The primary scenarios I can envision (currently) where the digital replacement would be preferable would be things like extremely vibration sensitivity, or where physical space requirements are too tight to allow a cam shaft, or possibly where the reduced need for lubrication (though if you have a need to avoid lubrication you probably want to avoid internal combustion and its myriad moving parts entirely).
The guy who said the election was rigged won the presidency with the second-most votes.
Here's a rotary engine with no valves: Liquid Piston
I am just a computer nerd, but perhaps they need to rethink the valve all together to achieve a cam-less engine. Maybe an electronic trap door that slides open and closed really fast would work better. It wouldn't need a rod to push it along the Z-axis and there's no longer a valve seat to even worry about!
The beauty of the poppet valve is that it seals tighter the higher the pressure is across it. Other valve designs have been tried, but there are always sealing and friction problems.
One of our competitors trademarked the term "hypothesis". From now on, we will call them "boneheaded ideas".
I am wondering if there is a full analysis of cost / benefit with regard to emissions and efficiencies. I would love to see an the emissions per mile ratio added into the mix so we can see exactly what the lower emissions / lower mileage cars could do, if we cared less about emissions and cared more about mileage (fuel economy).
Agent K: A *person* is smart. People are dumb, stupid, panicky animals, and you know it.
All the same arguments could be used against your car if compared to a horse-drawn carriage about a century ago.
Not exactly... There are definite advantages to automobiles over horse drawn conveyances which drove the conversion. Gasoline was faster, more convenient , could carry more and carry it further than what it eventually replaced. Internal combustion engines eventually ended up cheaper than the horses they replaced, power for power None of this applies to battery powered cars... They are more expensive, carry less, carry it shorter distances and are less convenient to operate/charge than their predecessors. The *only* possible advantage to electrics is their environmental impact *might* be less (not that it actually is) when operated using specific power sources but they rarely make financial sense, much less environmental sense.
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
At the beginning there wasn't gas stations everywhere and people surely had "range anxiety" too.
Take a look at the FIAT MultAir engines - https://en.wikipedia.org/wiki/...
Yea, so? They invented the Jerry Can to fix that and allow you to strap extra fuel to the running boards. That was easy... The electric car's "Range Anxiety" problem isn't going away even if you had quick chargers every 100 miles. Even an 80% charge takes 45 min for modern batteries, that's a long time to get you another 150 miles down the road. Strapping extra batteries on the running boards just isn't an option here and the charge time is largely a physical limitation of the battery and not easily overcome. Like I said before, we will see incremental improvements, but there will be no revolutionary changes in electric cars.
"File to fit, pound to insert, paint to match" - Aircraft Maintenance 101
Changes in momentum are what cost energy. Having a bunch of pieces of metal constantly reversing direction inside the cylinders seems pretty 1920s.
--- wad
Suppose the autos still equipped with 5 speed manuals or automatics got finer control over valve lift and dwell at all RPMs and conditions? There'd be significant improvements, no doubt about it. BUT suppose an engine and CVT were carefully designed to work together for maximum efficiency. I seriously doubt that there's that much to be gained over computer-controlled mechanical/hydraulic variable valve timing and lift. Notice that most Subaru models are now available with CVTs and many manufacturers are touting 8 and 9 speed transmissions.
I can imagine having both a camshaft and individual actuators where the cam opens the valve the minimum amount of time and duration and the electric or hydraulic actuator supercedes it much of the time. Then if the actuators failed there'd still me a limp-home mode. What about interference? Don't do it. There are plenty of efficient engine designs that don't have it. It's already bad news when mixed with timing belts.
I think I'll wait for the digital crankshaft.
"The biggest change that can be made to the valve system is to move away from springs and to a manual close system"
This has been around almost forever (desmodronics was developed back in 1896) but adds a _lot_ of mechanical complexity when done with cams - there's a reason that only Ducati have stuck with it.
"That being said, the camless designs have their own challenges, namely soft valve seat landings due to a nearly perfect square-wave lift profile."
I suspect that problem (mostly caused by the need for incredibly stiff springs) is vastly overstated when the valve doesn't have a camshaft pushing it.
There have been (and are) designs which move the rocker pivot points dynamically.
However - "mechanical complexity" rears its head. The more mechanically complex a device is, the harder it is to maintain and the easier it is to break - particularly in automotive engines when a lot of "mechanics" should be wearing striped aprons, not blue overalls.
"The trailing profile on a cam is there to slow down the valve as it closes"
See previous comments about the springs....
"Gasoline was faster, more convenient , could carry more and carry it further than what it eventually replaced. "
Electric cars were around first and there were more of them (as were steam cars). Gasoline came later and was regarded as far inferior - the advantage was that you could carry much more fuel (range) with you on a longer trip and buy 2 gallon bottles of gasoline at most drugstores(*), whereas electricity was limited in availability.
(*) It was sold as cleaning fluid.
Yeah I mentioned Ducatis in another post. Reading back it wasn't obvious but I meant manually closing the valves in conjunction with an electric system. I've worked on ducati engines before and trying to get the shims and loaded vs unloaded gap right sucks.
Or just use a relatively small air control valve and solenoid. Pneumatics then open the valve. And a hefty spring to close it. If you're being clever, I bet the vented bypass air from the pneumatics could be injected into the cylinder during intake along with the fuel.
That's the whole point of solenoid systems. If you're using a solenoid to open the valve and fighting against spring-closure then it's not worth moving away from camshafts.
A workable solenoid system has to be able to open _and close_ the valves.
This is what Fiat have achieved in their multiair systems, using cam-actuated pneumatics to open/close the inlet valves (no return springs. Pneumatics move the valve in both directions) where the activation is electronically augmented to achieve late opening, early closure, multiple openings per stroke (or no opening at all) in order to eliminate the throttle.
Technically there's no reason why they need a camshaft at this point. Whilst Multiair still uses it to directly operate the exhaust valves (there are few advantages in playing with exhaust valve opening lift/duration/etc and has a fallback position of "limp home" operation if the electronics fail, the electronics has proven extremely reliable and the fact that the timing is already well under control is seen in the electronic enhancement of the pnuematics.
Even if solenoids can't _directly_ drive valves at the moment, they can be used to control pneumatic openers/closers at sufficient speed and accuracy that the cam is already obsolete. A large part of why you don't see camless Fiats (yet) is manufacturer conservatism. Taking them out is a big step and consumers may resist.
"Through variable Camshaft Gears modern engines already control the in- and outlet timing for maximum efficiency today"
When you show me a purely mechanical cam which can dynamically double pop the inlet valve or do late opening/early closure under lightly loaded conditions like Fiat's Multiair cam augmenttation system does in order to eliminate the throttle system, I'll agree with you.
Otto engines are only efficient at max load/wide open throttle. At all other loads they're rotten and most of that comes back to the fact that a throttle is needed.
Conventional variable cams can only adjust opening duration over specific RPM and/or load ranges. All valvetrain cam operation is a compromise in a automotive engine, given the near infinite range of power and rpm demands placed upon it.
On the other hand if you can run one at fixed speed and power load, you don't need any of the complexity (and weight) associated with a variable valvetrain and can tune for best power output. This is the guiding principle behind a series hybrid - even then, being able to eliminate the mass of the cam system is a winner for automotive use.
"Theoretically, with enough fine control over the valves and a good computer to control it, you could do away with the throttle altogether and use the valve duration, lift, and timing as the throttle."
It's not a theory. Fiat have already done it.