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.
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.