First, on the flow question, I guess the best way to describe it, is volumetric efficiency flow losses; the engine is sucking air in, not just letting it flow in, hence a less than atmospheric pressure reading on an NA intake manifold. Granted, not a major deal (its the whole system that makes this not feasible, not just this) but still some percentage loss on the total.
Let's revisit the math, since you are so keen on that.
First we will start with the actual equaiton for determining the power required for continuous compression (note you still weren't that far off on this one, but enough)
Pt= Theoretical power required to compress the air continuously.
Ps= Shaft power required due to adiabatic efficiency losses in the compressor.
k= ratio of specific heat at const. pressure and const. volume, assumed to = 1.4 for air.
Q= air flow rate
p1=equivalent NA pressure at intake valve(s)
p2=desired boost pressure at intake valve(s)
Pt= (k/(k-1))*Q*p1*[((p2/p1)^((k-1)/k)-1]
For the Zetec, I've used the following specs.
Bore = 84.8mm
Stroke = 88.0mm
peak rpm = 6000
Ambient air temp = 20* C
Vol. Eff. = 85%
Stock power = 93kW = 125hp
and boost, first I used 35kPa (~5psi) and later I used 70kPa (~10psi) and no intercooler, because of Paul's apparent disdain for them.
Typical turbocharger sizing calculations come up with the following:
Flow @ 35kPa = ~0.101m^3/s but output is only ~122kW or 165hp (at the engine, not the wheels)
Flow @ 70kPa = ~0.116m^3/s with output ~140kW ~188hp
Note that the eqautions I've used for this stuff are notable optimistic as far as power output #'s. You can find calculators that use the same equations at Ray Hall's website:
http://www.turbofast.com.au/ if you wish to check for yourself.
Now, to get back to the power equation. The only caveat here, is that rather than use the std. atmospheric pressure of 100kPa, I multiply that by the volumetric efficiency we have assumed for the engine (which at 85% is pretty optimistic for high rpm) and get 85kPa.
So, for Paul's assumed 35kPa boost pressure we get the following.
Pt = 5.00kW
Now, typical centrifugal compressor efficiency is something like 65% so:
Ps = 5kW/.65 = 7.69 kW at the electric motor shaft. This is roughly 10.3 hp required from the motor.
Now, assuming your 12V system, this is roughly 650Amps running ANY TIME you wish to have boost, assuming of course, the motor is 100% efficient, though, as you all know, there aren't any of those around . . . Note also, this is only to make ~165 hp at the flywheel, or what is actually slightly less than a stock duratec. Even on a 24V system, it is still ~325Amps.
Now, Paul was looking for ~200hp w/ his 5psi, and that ain't gonna happen, so let's see what happens when we double the boost pressure to 70kPa. We know from above that the power is much closer (188hp) so this should be a reasonable amount.
Now, checking for required power:
Pt = 7.57kW
Ps = 7.57kW/.65 = 11.65kW ~ 15.6hp from the electric motor.
Again, at 12V, this would require in excess of 970 Amps, even assuming a perfectly efficient motor. and even at 24V would require ~485 Amps minimum.
I don't know about you guys, but this seems to me like its requiring a DAMN BIG electrical system, even for very short bursts on a very low duty cycle. This is even aside from finding a suitable motor, and finding a place to put it. Oh, I also failed to mention, that your typical centrifugal compressor will be spinning well over 100k rpm to meet these flow requirements, and whatever magical wonder motor paul chooses to run will need to be even bigger to account for the additional losses due to the required gearing to run the compressor at the appropriate speed.
Paul,
its not like this is a new idea. Every freshman engineering student in every school across the nation (and even world) has jumped on this at one time or another, only to find it isn't feasible (or at least worthwhile) with present technology. You have been whining about the cost of an intercooler becuase you want to do your project cheaply, but really, do you think even a version of this that doesn't even work well is going to be cheap? An intercooler, even a new one from spearco, will be a drop in the bucket compared to the cost of the required componentry for this sort of a setup. High current motors, custom compressors and gearing, much larger alternator, 2nd battery, high current electrical distribution and control components, most all needing to be custom made. All for the same amount of hp that could be had in the
other motor offered in the car stock, and all the time, not just for extremely short bursts of time. And to top it all off, you still wouldn't be legal to drive the car in california. Though, you could anyway, and really piss off all your neighbors over in Berkeley.
On Edit - I can't spell . . .
!!!!! 
