on a 03 protege would an electric supercharger at 5psi be worth it??

 

I rather doubt such a supercharger would be able to feed your engine at MSL+5 at much beyond idle, and if it could, I rather doubt the electrical system on your Protege could handle the load. Long story short, if you want to boost your engine, do it the old fashioned way, use a mechanical supercharger or a turbocharger.

Edit: After reviewing the "Electric Supercharger" data, I can tell you there is a 100% probability that this device will never approach 1 PSI much less 5, even at idle. Said another way, you might as well crawl under your car and tear up three one-hundred dollar bills, that will get you as much of a performance gain as this device.

FWIW, assuming you have the 130 hp 2.0 liter engine in your car, and assuming you did come up with a way to boost it by 5 PSI (i.e. mechanical supercharger or turbocharger), your power output would jump from 130 to 174.

 

the question isn't psi, it is cfm. the way that they get to advertise 5 psi is that the charger can pressurize and maintain 5 psi under certain conditions (ie; possibly a plastic bag or something of similar build with zero extra atmospheric pressure). an engine creates a vacuum that the charger would have to overcome in order to make pressure. that is where cubic feet per minute come into play.

a stock turbo on the average car runs at about 45 cfm @ 5 psi. for comparison, that would be enough cfm and almost enough psi to operate a high volume, low pressure paint system. that would mean that two of these things would have to produce enough flow and pressure to paint a car without losing any pressure at any point. having done all types of finishes, i seriously doubt that is possible. my tank-less HVLP system is about the size and shape of a squirrel-cage fan and it will even bog down if i run it somewhere kind of stuffy and stale. that thing will be operating under the hood of the car. think about it.

 

This "thing" has been talked about on every car forum I have ever been on, including this one.
I have only one thing to say about it: If it sounds too good to be true, it probably is. It's a wet-dream for racing video junkies caught out in the real world for once.

Stay away from plastic junk claiming HP/MPG increases that only cost $35... the last price I saw these at... and that was down from well over $200.

Even suckers catch on quickly. Don't be one of them. Learn before you are taken for your money.

 

Those "superchargers" are not usually recommended for Mazdas, but I wouldn't recommend them for any car that I wanted to keep reliable and be able to use.
There's a reason the price of these have come down so much and so fast. Take the hint.

As far as "honing your intake" is concerned, I am all for port, polishing and matching the head if it needs to be removed anyway, but this seems to only be a good financial decision if you are racing it and trying to extract the last little bit of power from the engine.
Again, I don't buy the "improved fuel mileage" hype or that it would make that much of a difference in a DD. 'Sounds a lot like sales hype to me.

 

What you apparently don't understand is that at any throttle setting above idle, the electric supercharger is more likely to reduce manifold pressure than anything else. Said another way, I wouldn't put it on my car even if they paid me that $350 (or even $3,500 for that matter).

 

... And it only works @ WOT!! The manual switch is installed under the accelerator pedal and is only active when the throttle is fully depressed.
Every one I have ever talked to about these things says the same thing, Stay Away!! They don't work... at least not on modern ETB cars.