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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: 2, Interesting) by NovelUserName on Friday February 28 2014, @10:36PM
Its interesting to me because they selected pneumatics rather than hydraulics. I had always understood that the compressibility of air made pneumatic actuators problematic for high precision or high speed applications. At the speeds you need to actuate valves for normal ICE operation (~=6KHz) I would have told you that the problem of modeling how the air flows around your valve as it opens and shuts would make your control problem nightmarish- especially if you want to have your valve open and close on a specific profile rather than just popping open and shut as fast as possible. This implies either some very dedicated testing or a quite clever control system.
On to my main point:
I'm skeptical of the claims of a 50% efficiency gain. The camshaft generates nowhere near that much drag, and you still need to power the pneumatic system, which the old motor doesn't. Most of this putative gain then has to come from being able to adjust the valve timing and lift dynamically.
I can only assume the following: A conventional engine could match (or nearly match) the power output of the demonstrated pneumatic system. A conventional engine could match the efficiency. But the same engine could not do both. By picking some arbitrary middle point for the conventional engine performance you appear to have simultaneously wildly improved power and efficiency, when really an ICE that's well designed for it's use case will be competitive with the pneumatic system in either power or economy.
The other point is that small cam-actuated engines are making HUGE gains in efficiency and power output lately. Ford for instance has a 1L motor that puts out 300HP, and ( in a racing car anyway [youtube.com]) will do 100MPG. I very much doubt that simply dropping this pneumatic system on top of that motor will result in 390HP and 150MPG from the same motor.
(Score: 1) by demonbug on Friday February 28 2014, @11:47PM
First, valves generally only switch twice per full cycle - intake valves open and close on the intake stroke, and remain closed for the remaining three strokes (in a 4-stroke). With two strokes per rotation (so two rotations per full cycle), you're only looking at 3,000 cycles per minute at 6,000 RPM, or ~50Hz (rather than 6KHz you stated).
As for the efficiency gain, it is less about drag and more about timing. Depending on throttle position, engine speed, intake pressure (boost), and probably an assortment of other variables, the valve lift and timing are going to vary widely for maximum power and/or efficiency. With variable timing from using different cam lobes (or sculpted lobes to allow more gradations) there is some variability available to engines, but nowhere near the same range as this would offer - there just isn't a practical way to program all that into an analog camshaft. Plus, on the efficiency end, you would be able to just seal off whatever cylinders you don't need at the moment - and you could even vary rotation by rotation which cylinder is shut down to spread wear evenly and improve balance.
That said, their 50% number does seem pretty high; but maybe they are comparing to an ICE with fixed valve timing and port fuel injection. Combine the infinitely variable valve timing and lift with direct fuel injection, and I can easily see that 50% increase in efficiency.
(Score: 1) by NovelUserName on Sunday March 02 2014, @03:03AM
Well, that's embarrassing- On top of forgetting that the valves don't actuate each cycle, I made the elementary mistake of forgetting that minutes aren't seconds when converting RPM to Hz.
Thanks for pointing that out!
(Score: 1) by mrkaos on Saturday March 01 2014, @02:30AM
and to me because they chose those over electromagnetic.
I'm not, though this is not a criticism of your point, just that ICE are so damn inefficient that improving them is a matter of picking what you want. The induction of the system is a big place to do this and it's not a matter of drag but one of *volumetric efficiency* or VE.
A cam is only efficient in a very narrow band of RPM and timing the opening and closing of valves dictates the VE of the engine. So with a cam your valves are open for the same relative duration or RD (in percentage terms to the length of the stroke) at any RPM. What this mean is that engines with a cam has a great power range for a limited RPM.
However, you need the opposite characteristics to have the power band cover the entire rev range. At low RPM the valves short be open for a shorter RD and for higher RPMs a higher RD. There are also post-combustion things you can do so more air is available for the next combustion cycle. This, in a nutshell is why it's possible to start to attain better efficiency in an engine with a system like this.
Also you are able to shut down cylinders that you don't need during cruise, so you use less fuel. Ahhh we do that now with engine management systems - which is true except that what they don't do is shut down the 'compression' cycle and power is lost there.
Many of the efficiencies won't be *ahem* driven into ICE designs without radical new EMS, but apart from being disappointed that my own design will probably never see the light of day, this is a great step forward.
My ism, it's full of beliefs.