From the many people I have talked to about them, their opinions are expressed here:
Eh, they work, kinda. Well, they add like an hp.......But not worth the money. If you REALLY wanted one just go spend the 40 bucks are a hobby supply store and build it yourself.
I did a lot of research into them myself when I first got my box. When the only 'dyno' charts I saw were for mustangs......I said screw it. There was a group of people who did affix a leaf blower to their civic and it gave a nice increase in power, but eh....Really, still not worth it.
I believe that if the price is right, and it really does work, then go for it, but don't hold your breath.
air is sucked in with fuel
mixture is compressed
with me so far? good!....so if you engine does this it needs air. the faster it runs, the more air it needs. like an air pump. a traditional supercharger or turbo causes the incoming air to be compressed, and maintain a constant state of pressure proportionate to engine need (RPM)
now these devices normally use a good portion of engine power to operate properly, because it takes a lot of power to compress air at high speed.
an electric system to compress air at a useable rate is a very high power device. there is nothing in your car (electrically speaking) that can produce enough power to keep up this type of activity. read (impossible)
i have seen one system that comes close...it uses a trunk full of stand alone batteries and capacitors to make a useable 15 second burst...approx...(been a while since i looked at the system) and it cost almost as much as a real supercharger.
the inline fans on systems like the e-ram or other things are basically bilge fans from boats. they are just used to vent compartments on boats and RV's.
even if you found one that was pretty powerful it has no compressive power to supercharge. and as RPM increases the device itself cannot keep up with air demand, and eventually it becomes an airflow obstruction and actually will starve the motor of air....
sorry to sound like a dink about this...but i wasted a few months in college trying to make this stuff work...it's a great idea...and I'm excited to see what happens when cars finally go off the 12V standard in a couple years...then maybe if ya wanna know more i have some great boring books on thermodynamics and mechanical engineering you could read...as to the leaf blower thing yes it could work...but it won't keep airflow following the RPM curve...so performance will be sketchy and unpredictable
I am in the industrial fan business myself and I know this wouldn't work unless you mounted up a monster fan that required TONS of juice.
I don't know the exact number so I'll use some rounded off example type numbers for this senario.....
An engine is basically an air pump, it sucks air in to burn fuel and pumps out exhaust. Suppose our engine at full throttle and at redline could go through 400cfm of air. You would need a fan that could pump in alot more cfm than that and at a decent amount of pressure for extended periods of time for this to work.
In my line of work we have fans that pump out well over 100,000cfm, but we make smaller, high pressure fans as well that would be perfect for this. The reason it wouldn't work is a high pressure blower that puts out enough air weighs in excess of 350lbs and runs off of a 3 hp electric motor requiring 230V.
So not only do you need to add the weight of the fan to your car, you would need to add the weight of the battery bank to power it.