I don't disagree that there is much to learn before really attempting the project. But I think I do understand enough that what I was saying was reasonable. And I probably shouldn't have gotten my hackles up, I'll apologize for getting uptight.
Your earlier guess was correct, I'm thinking of an electrically powered centrifugal compressor. Done right, this would have less drain on the engine than either a turbo or a belt supercharger, therefore yielding more gains per PSI of boost. But electric motor choice being what it is, it will have to be limited to low boost. Parts might be not much more than $1000. This doesn't count all the overhead that comes from dealing with other engine issues that have to be looked at, but it's still likely to be cheaper than other FI setups (other than those made of used parts).
Another advantage is that since the boost pressure would be regulated electronically (ouch, a motor controller is one of the most expensive parts), there is no dependency whatever on engine speed. The boost can ramp up while you're pushing the pedal down.
A system like this would be most ideal for a hybrid-electric car, which already has a beefed up higher voltage electrical system. Such a car would get even better mileage than it does now, if it used an exhaust turbine to power its generator. Then you'd have an electrically decoupled turbocharger, with mileage better than anything in existence today, yet lots of power on demand.
