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germanbird writes: "Jalopnik has an interesting article up about Koenigsegg's Prototype Camless Engine. The engine uses pneumatic actuators rather than a cam to open and close the valves in the engine. The engineers behind this claim that it can provide "30 percent more power and torque, and up to 50 percent better economy" when applied to an existing engine designs. The article and some of the comments also mention that some work has been done with electromagnetic actuators to accomplish the same task. It may be a while before this tech is mature enough for passenger vehicles, but maybe if a racing series or two picked it up, it might give some of the manufacturers the opportunity to work the bugs out?
Not sure this is on topic for SoylentNews, but the article brought me back to my introduction to engineering course in college. One of my classmates was a car nut and I remember a discussion with an EE professor one day about the potential (or actually lack thereof due to performance issues) for using electric actuators to open and close valves."
(Score: 4, Informative) by Ellis D. Tripp on Friday February 28 2014, @01:00PM
when the SAE and automakers were considering a shift to 42V electrical systems in cars. In addition to shrinking the size/cost of wiring harnesses (higher voltage = lower current = thinner cheaper wires), the higher voltage would have made it practical to runs some larger loads such as A/C compressors and power steering electrically, rather than via belts from the crankshaft. The higher voltage would also have made it possible to use solenoids to actuate the intake and exhaust valves, removing all the frictional losses in the valvetrain, and allowing for simple variable valve timing for improved performance and emissions.
Unfortunately, it was soon discovered that switching 42VDC is a lot harder than switching 12V. Switch and relay contacts quickly eroded, and power semiconductors at the time were expensive and barely up to the task. So the 42V initiative was quickly forgotten.
"Society is like stew. If you don't keep it stirred up, you end up with a lot of scum on the top!"--Edward Abbey
(Score: 3, Informative) by carguy on Friday February 28 2014, @01:59PM
Even before the unsuccessful 42V initiative (good memory Ellis!), there were various attempts at camless valve operation. We were in contact with Moog about 1990 when they contributed to the Lotus effort [wikipedia.org]. There were running engines built although they were limited to a relatively low ~3000 rpm. I believe that there were versions with both electro-hydraulic and electric actuation. One of the important uses for these test engines was as a simulator to quickly test different valve timing, without the need to machine new cams.
Programmable valve timing can also remove the need for the throttle -- just open the intake valve a tiny bit for idle. But there is something reassuring about a throttle plate that can be closed to control the engine -- throttles are missing in Diesels, which have been known to run away if the fuel control jams on...
The peak power required to move a poppet valve for a high speed engine is not trivial. A roller cam is actually fairly efficient because the energy stored in compressed springs is returned (mostly) to the cam when the valve closes.
Were any other readers involved in similar programs at other manufacturers? There are many clever people in automotive R&D and camless engines became a hot topic as soon as realtime computer control was in reach.
(Score: 3, Informative) by Grishnakh on Friday February 28 2014, @04:32PM
But there is something reassuring about a throttle plate that can be closed to control the engine -- throttles are missing in Diesels, which have been known to run away if the fuel control jams on...
That's not a problem.
The reason it was a problem on older diesels is because, back in those days, they used mechanical (engine-driven) fuel pumps. The fuel never stopped flowing until the engine stopped, or the tank ran out. On modern vehicles, this isn't a problem; if you want your engine to stop and it's "dieseling", you just turn off the electric fuel pump. It won't be instant that way, but it won't take very long because fuel pressure will drop quickly.
We were in contact with Moog about 1990 when they contributed to the Lotus effort. There were running engines built although they were limited to a relatively low ~3000 rpm.
I remember reading about a test engine like this back around 1992 in an academic magazine. They said at the time that the power required for the solenoids was really high. I never heard again of any such attempts.
(Score: 2, Informative) by drussell on Friday February 28 2014, @10:33PM
Yes, it's still a problem, and is the reason that many larger diesels (esp. stationary engines) have emergency air shutoff damper valves.
The burning of the diesel fuel (which can be halted by the electric fuel pump shutting off, some kind of mechanical fuel valve closing or even emergency hack to the fuel line with an axe) isn't the only possible cause for a runaway. It is true that if your rack hangs open or some other type of main fuel system failure causes the runaway, the regular fuel cutoff / anti-run-on device should cause the engine to stop when the key is turned off.
The more common reason for a diesel runaway, especially on turbo diesels, however, isn't fuel, it's engine oil. Whether it's pulled in due to a worn engine, overfilled crankcase, cracked block/head or most likely on a turbo, failure of a turbo shaft seal spewing engine oil into the intake side. The engine is now running on the crankcase oil instead of diesel. Shutting off the key won't help and there's many, many times more than enough oil in the crankcase to destroy the engine before it runs out.
The only surefire way to stop a runaway diesel is to block the air supply. This can be done either by covering the air intake completely with a book or block of wood or whatever, (usually only practical during service with easy access and air cleaner removed) or better yet, simply blasting the air intake area with a CO2 type fire extinguisher (NOT a dry chemical one, that would destroy the engine!) until the engine stops. Works like a charm. Most people who work on diesels know to have a CO2 type extingisher right handy in the shop, always ready for this purpose.
Personally, if I had a diesel vehicle, I'd carry one with me, just in case. (I have dry type extingushers in my vehicles, but if I had a diesel I'd have a CO2 for it also as well!)