It also greatly annoys me that they refer to it as a turbocharger, when it absolutely is not. Probably a marketing thing...
Another thing though, turbochargers aren't just run off free, waste energy. This idea also annoys me. Yes, a great amount of waste energy escapes via the engine exhaust, but this isn't all magically recovered by the turbocharger's turbine. The turbine is a restriction in the exhaust system, it creates back-pressure which makes it more difficult for the pistons to expel exhaust gases on the exhaust stroke. Think about it this way, a well set up turbo has a ~1:1 drive pressure to boost ratio. So for a good system, for every PSI of boost you make, you increase exhaust back-pressure a directly proportionate amount. I doubt people would argue that restricting the exhaust on a naturally aspirated engine would have no effect on engine power output.
Just because it isn't directly coupled to the crankshaft does not mean it isn't sapping energy from it.
I'm not saying it isn't one of the more efficient ways to extract that work. For an electric supercharger, you're converting mechanical energy to electric at ~90% efficiency, then electric back to mechanical at ~90% efficiency. This is absolutely less efficient than a supercharger coupled to the crank via a belt. The efficiency gain over a standard supercharger likely comes from being able to completely decouple it when not needed. The performance probably comes from being able to have it build boost in direct relation to the pedal position, not engine speed.
I feel I'd rather a positive displacement blower such as a roots or screw type that can be decoupled via a clutched drive pulley though. Hell, I don't think it even needs to be decoupled. Most roots style blowers today have an internal bypass, and sap less than 1 HP when not using it and just cruising along. Being positive displacement blowers, these give instant boost.
Back in the day, I had two Mercury Cougars. One was a base LS, with the N/A 3.8 V6, the other was an XR7 with the supercharged 3.8 V6. It used an M90 roots style blower. It made full boost from when I pushed the pedal to when I hit redline, and the supercharged one got 2 MPG better than the N/A car. Loved the sound of that whine too, lol.
