The timing chain and the camshaft seems really inefficient; I'm looking forward to when camless designs become more mainstream. Koenigsegg (among others, I assume) has been working on this tech [0][1].
It is really inefficient. A lot of energy is wasted compressing the valve springs to open the valves. This is a problem if you try to make a high-revving engine, for instance, in order to get better fuel efficiency at low speeds and good power at high rpms: to allow high-rpm operation, you need stiffer valve springs, but this significantly affects your fuel economy.
They've been working on camless valve actuation for decades. I read an article about a prototype system back in 1992. The article then said that the power requirements of the solenoids was a big problem. I'm not sure what the problem is these days. As you noted, Koenigsegg has a working prototype in an actual car (not on a test stand, connected to mains power, like the one in the article in 1992), and it seems to work fine. There's probably some kind of problems with reliability.
> It is really inefficient. A lot of energy is wasted compressing the valve springs to open the valves.
This isn't as bad as you might think, because of the nature of springs. When the valve closes again, most of the energy spent compressing the spring is returned to the engine!
Yeah, and they're the only ones using it. As your link notes, there are significant disadvantages to that system (as well as advantages), namely complexity, greater moving valvetrain mass (you need two cam lobes per valve), and inability to use hydraulic valve lash adjusters (which means you have to periodically adjust them; not a problem on a racing or high-performance motorcycle, but definitely a problem for a passenger car where these days you want to be able to go 100k miles without any service other than oil changes and tire rotations).
This is a problem if you try to make a high-revving engine, for instance, in order to get better fuel efficiency at low speeds and good power at high rpms: to allow high-rpm operation, you need stiffer valve springs, but this significantly affects your fuel economy.
The alternative is to just not design for high RPM; the most efficient internal combustion engines are huge low-speed two-stroke diesels used for ships and stationary generators.
Large marine diesels have very low RPM. Some of them red-line at 102 RPM, and normally operate much less than that. A typical passenger cars idles at 1200RPM and redlines around 6-7K RPM.
Then again a single piston in the marine engine weighs 2x of an entire car so they can easily do things that one wouldn't bother to do on a smaller engine.
Huge engines aren't feasible in cars. More mass to carry around means lower fuel efficiency. Stationary plants don't care much about mass, and with ships it doesn't have that much of an effect.
Well, power electronics have really come a long way since 1992, and that might make a big difference. For instance back in 1992, DC-DC converters were shit, most power supplies were still linear instead of switching, and the electronics needed for, for instance, driving a 3-phase brushless motor were big and expensive. These days, that stuff has gotten much smaller and cheaper. We now have power MOSFETs able to handle huge currents with ridiculously low losses, in rather tiny packages. A chip the size of your fingernail can handle over 100A with losses in the single milliohms, and the main problem becomes handling the waste heat (with 100 amps, even 4 milliohms means 40W!); usually these things are used for high-frequency switched applications, so the total on-time isn't that much.
Back in 1992, making an electric car like the Tesla probably wouldn't have worked out too well. Instead of an electronically driven induction motor (or a 3-phase brushless motor as some other vehicles probably use, also electronically commutated), they would have had to use a brushed DC motor which isn't so great for longevity or efficiency, because the electronics needed for the better motors would have been too expensive, bulky, and inefficient. Now, DC brushed motors are all but obsolete except for small, cheap applications like <$50 power tools.
The same might have been an issue with those camless valves: actuating those solenoids precisely probably required some serious power electronics capable of supplying and switching high currents at very high speeds. Modern power electronics are good at that now.
I wonder if one problem isn't control of the valve speed. If the solenoid is moving too fast, that'll wear the valve seat much faster (in a regular cam engine, the valves don't shut that quickly at low rpms because the valve profile prevents it). In a cam-less engine, the solenoids would effectively be going full speed all the time, meaning more valve seat wear from slamming shut so hard. This makes tuning engines easier perhaps (more digital-like operation: on/off), but increased wear is bad for something you want to last for hundreds of thousands of miles with no service. So they might be looking for a way to control the actuation speed of the valves, and vary it with engine speed as cams do now. That means even more complex power electronics.
0: http://blog.caranddriver.com/koenigseggs-camshaft-less-engin...
1: https://youtu.be/Bch5B23_pu0