Ok...its a new day and i just now have had time to get back and see what has become of my post....anycrap.....it seems some of you have a problem with supplying enough juice to make 980 cfm work............well i dabble in car audio to at my job and here is some numbers to look at.

The blower i want to use that pushes 980 runs off a 115 current (what you find in your house or close to it) to produce 980 cfm it pulls 6.80 amps and requires 455 watts. Ok it dosent take a genius to know a car is 12 volt dc.....so we need a dc to ac inverter......I have one with numbers to match what i need. 1000 watts constant, 2000 surge.............it puts out 8.25amps. Now all that is needed is an upgraded alt. but for testing just a couple of times...... one is not needed.
Especially if all that is going to be pulled is 455 watts and I'm using the thing only when i need it and it wont be engaged untill then........anyway........giving it power is something i'm not worried about. ............and the price for all this including making my own intake pipe?............max.....$375................(this does not include an upgraded alt.) something which i'm not sure i'll really need....yet........I will have to relocate my batt. though to fit the blower.................Now.....Let the "thats a bunch of bullsh@#" begin.

 

Til I see dyno #'s....it seems like a far fetched idea. But then again, prove us wrong.

 

The blower i want to use that pushes 980 runs off a 115 current (what you find in your house or close to it) to produce 980 cfm it pulls 6.80 amps and requires 455 watts. Ok it dosent take a genius to know a car is 12 volt dc.....so we need a dc to ac inverter......I have one with numbers to match what i need. 1000 watts constant, 2000 surge.............it puts out 8.25amps. Now all that is needed is an upgraded alt. but for testing just a couple of times...... one is not needed.
Especially if all that is going to be pulled is 455 watts and I'm using the thing only when i need it and it wont be engaged untill then........anyway........giving it power is something i'm not worried about. ............and the price for all this including making my own intake pipe?............max.....$375................(this does not include an upgraded alt.) something which i'm not sure i'll really need....yet........I will have to relocate my batt. though to fit the blower.................Now.....Let the "thats a bunch of bullsh@#" begin.[/QUOTE]
Some basic errors.
115 volts multiplied by 6.8 amps yields 782 watts about 1 horsepower (746 watts)
Now 782 watts divided by 12 volts yields 65 Amps needed on the 12 volt side.
Even at the 455 watts that you list, still need about 38 amps on the DC side.
Some minor assumptions are overlooked here comparing AC to DC, but they are minor. More than compenstaing for that is the loss of efficiency in the inverter itself.
Like everyone else, I'm not real certain what the result will be in WHP, but hard to believe that 1 HP electrical will yield much in the way of physical HP, especially considering that the 1HP electrical isn't free either, more losses to drive the alternator, etc.

 

Typically the problem with these blower/inverter combos isn't even electrical - it's mechanical. The blower can push 980 CFM... into open air. Now put 1 psi backpressure on it... that 980 may drop to 100 CFM. 2 psi backpressure and it could be 50 CFM. Don't expect to ever see more than 1 psi of positive manifold pressure if you put a boost gauge on. The people that design those blowers aren't stupid; they understand that the design of a blower for velocity and one for pressure are totally different. Those run large diameter, high backsweep fans turning at relatively low speeds to move a large volume of air. The speeds they run aren't generally high enough to support much pressure across the fan - it's easier for the air to flow back through the fan blades than to go into your engine under pressure.

Now don't get me wrong, garage experimenting is great - even if you don't solve all the problems of the world, you learn a lot messing with this stuff yourself. Do your thing and keep us posted, OK?

 

to add to dbmans comments..

not only will the flow diminish with increased pressure on the fans, but the AC current required to maintain flow will probably rise very quickly with increased pressure. expect to provide 3x the amount of power and current at 0psi than when trying to pressurize the intake - to be safe.

dont forget about the losses from converting DC to AC. Making a square wave out of DC doesnt come cheap, even though there have been some significant advances in the design over inverter systems over the last few years.

oh yeah..and here is a dumb question... 6.80A * 115V = 782 Watts. Where did u get 455W?

 

The factory specs on the blower is where i got 6.8 amps with 455 watts and 115 v
Also the specs on cfm with 5 lbs of back pressure is still 730 cfm. And the rise in watts and amps needed as pressure builds is something to address. But do you really think its going to be a big deal when you burp it for only 15-30 secs at a time? (ok....shoot me down now)

 

I'd be really interested where they come up with that 730 CFM at 5 psi backpressure number. Want to know why?

Assuming 100% efficient compressor

730 CFM
5 psi rise (14.6 psi atmospheric)

This would take just over 15 HP or 11,195 W

At 115 AC, that's 97 Amps
At 12 DC, that would be 933 Amps

Your battery is supposed to be able to turn a 300A starter motor for 30 seconds... want to guess how long it can crank out 11,000 watts?

Realistically I have to say that a 12V vehicle electrical system is just about tapped out pushing around 80 CFM at 5 psi. Heavy duty alternator could get you up to 100 CFM maybe. But no way that blower can flow 730@5psi whether it's plugged into a car battery, a wall socket, or a nuclear reactor.

 

I still can't make myself believe that there will be a gain. That 65 amps that you need is not free, for that period of time (15-30 secs.) it will have to come from somewhere. Assuming that the alternator is the source, my version of common sense tells me that any gains that you might see will be negated by the alternator load during that time.

I haven't done the calculations, but it seems that it would take a lot of capacitance assuming that you will use these to offset some of the current. It's one thing to add some to an audio system to handle the bass peaks, but another to supply a majority of the 65 amps for 15 to 30 seconds at a time.

I next envision a test where you hook the blower to 110 volts in your garage, duct tape it to your air inlet turn the thing on while your car is running and hear the RPM of the motor increase and decide, yeah I was right. When instead your ECU is reacting to the increased air flow by widening the injector pulses, in essence the same thing that would happen if you open the throttle on the car.

Better test might be to do the same, rev to the RPM that you anticipate you would use the boost, turn the blower on and monitor the injector pulse width and Oxygen sensor voltage. The change should be seen there. If you do get a positive change, repeat the test, this time while driving the car and see what happens. Not to mention that you should be able to feel the kick in the pants if it is really there. Seems pretty simple to check your idea if you have a source of AC that will fit inside your car for the road test part.

If you get positive results with the above can then wire your inverter into the car and see what happens when the motor has to provide the power for the blower. Really tough to see the blower overcoming the electrical inefficiencies at a time when you are asking for peak power from the motor, flow rate on the motor down at that critical RPM and asking the motor to provide even more power to spin the alternator.

Keep an eye on the O2, wouldn't want it to get too lean and damage something!



[Modified by yleecoyote, 7:35 PM 4/10/2002]

 

sounds like a decent plan.
What is likely to happen is one of two things:
one) the motor will not be able to create enough pressure, and will bog down, you will get very little power and your motor will die relatively quickly.
two) it works great, but you will get a lot of power down low, tapering off towards redine. the thing here is taht while this "electric supercharger" pushed 980cfm all the time, a "real" supercharger moves more air at higher RPM to give a more even power gain.

Despite what others say, the hteory is sound. i think the problem you will run into is that the motor you have, while it moves a lot of air, does not have the torque to pressureize the air, it just spins faster to move more air.

Please, let us know how it turns out.

 

If you stick with that logic, then you would also have to assume that the energy it takes to drive a turbocharger or supercharger offsets any potential gain it produces and therefore all of us making a hundred or more HP over stock are actually just imagining things. I know in the turbo case it's partially offset by the fact that you're reclaiming lost exhaust energy, but superchargers DO work - it doesn't take 100 hp of crank power to produce 100 hp gain.

 

Quote
[If you stick with that logic, then you would also have to assume that the energy it takes to drive a turbocharger or supercharger offsets any potential gain it produces and therefore all of us making a hundred or more HP over stock are actually just imagining things. I know in the turbo case it's partially offset by the fact that you're reclaiming lost exhaust energy, but superchargers DO work - it doesn't take 100 hp of crank power to produce 100 hp gain.]

Just making the point that if some gains are found using an external source of AC, they would need to be significant enough to offset the HP needed to power this rascal from the alternator. Same applies to Turbos and Blowers on the mechanical side.

 

I always felt the downfall of all these products is that, once all the inefficiencies are subtracted, you're left with nothing. Belt losses, alternator losses, wire losses, battery losses, fan losses....

OTOH, even if the overall efficiency does suck more power from the battery/alternator than what it produces, the car can recharge the batter during "off time". Sure overall efficiency is less, but during the brief moment, I "suppose" it could offer some improved performance.

What was said before is still true though, that whatever CFM claims are made, they are into an unimpeded load.

My guess it that it will work, but the gains will be so small you won't think it's worth it.

 

So in everyones opinion........ if i want to build something such as a supercharger from scratch.....would it just be better to put the time and effort into making it run off the engine instead, and not mess with all this electrical crap?

 

Depends what you want - if you're looking to be significantly faster than you are now, you should consider a turbo or supercharger.

If you want to do something genuinely different, don't mind the risk of failure, and want to use lots of duct tape, try the electric idea. But don't expect to be running down Corvettes at stop lights (unless you have 220V AC and a quarter-mile long extension cord).

 

If you can build one that doesn't require a MR. Fusion, i'll take two of them.