why don't electric superchargers work?

[strongboy2005]

I have heard it time and again: electric superchargers don't work. However, I have never fully grasped the reasons why it doesn't work. Conceptually, it seems that an electric motor-driven fan forcing air down the intake at a greater-than-stock speed is at least going to make SOME power. I don't understand why it wouldn't work.

[eRic 02sc2]

read http://www.electricsupercharger.com/

[quiksc2]

Originally Posted by eRic 02sc2

read http://www.electricsupercharger.com/

That didn't really explain why it doesn't work.

[xupthree60]

it restricts the air flow more than it boosts it. since its always on it cant boost too much or u will be way too lean at low rpms, so when u are up at high rpms it actualy restrics air flow cuz the fan can turn fast enough. also it does feel like u get a boost when u turn it on, but this is cuz it is very restricting to the airflow when not in use.

[fdryer]

Originally Posted by strongboy2005

I have heard it time and again: electric superchargers don't work. However, I have never fully grasped the reasons why it doesn't work. Conceptually, it seems that an electric motor-driven fan forcing air down the intake at a greater-than-stock speed is at least going to make SOME power. I don't understand why it wouldn't work.

Simply put, fans cannot compress air to the pressures necessary for generating large amounts of horsepower, the reason why superchargers and turbochargers are robustly built. A rough calculation has fans able to output less than 0.5 psi while the real stuff can boost pressures over 30 psi and more. Another way to look at this is that a fan is designed to move a volume of air without any appreciable amount of pressure behind it while the turbos and superchargers do both. Lastly no one has seriously done the R & D to develop an electric supercharger as this will be just as expensive as the others. Happy holidays ! ! !

[KCW]

what FDryer said ^ + power

these electric blowers are designed to be cheap bolt on performance boosters

the problem is, you cant get enough power from a cheap (small) electric motor to push a real blower or turbo with enough power (horse power) to blow enough air into the intake.

Someone could do the math and figure out the HP on the shaft of a real turbo, or a supercharger, and then figure out how large of an electric motor you would need to get the same output

the motor would be huge! These electric blowers are basement inventor products designed by people who dont understand engines, physics, and they cant do the math to design a system that would actully be better than nothing.

[sl_don]

you could spin a supercharger with a engine starter motor and get acceptible boost pressure but the starter motor draws like 30 to 60 amps so any power made using this device will go into making the electricity to run it + the extra weight would likely result in lower performance than with out it.

[bobc455]

They can. Just a few "real world" problems to overcome.

Fist, you would need a huge electric motor to do it- figure about 20HP (just to establish a "ballpark"). And 20HP would put a hell of a draw on the electrical system, not to mention be very heavy and probably wouldn't fit under your hood while in the company of your engine.

20 HP is about 15,000 watts, which would equate to 1,250 amps at 12V (assuming 100% efficiency which isn't correct). That's one heck of an alternator. Oh yeah, and don't forget that alternators are very inefficient, I think about 40% (someone can confirm). So you'd need a 3500 amp alternator to keep up. Or if you run it intermittently, you'd need a bank of 3-4 automotive batteries that would take a while to recharge (adding about 100 lbs and taking up more space).

Realistically, you would want to maintain a constant pressure increase as the RPM changes- that means you'd need a variable speed motor controller as well, figure another 10-20 pounds for that. And more efficiency losses. And another thousand dollars or so (provided you could find one to work at 12V).

Frequently you see fans rated at, for example, 800 CFM- however that is only in a free-air situation (~0 delta-P). In order to be useful, the blower has to generate a significant pressure increase at the given airflow- that is what takes the oomph. So when you see an electric supercharger on ebay, be sure to note both the CFM *and* the pressure increase (i.e. boost)- this is where they fall on their face.

-Bob Cunningham

[KCW]

Originally Posted by sl_don

you could spin a supercharger with a engine starter motor and get acceptible boost pressure ....

I dont think you could get the needed speed from something the size of a starter motor. What does a starter spin at? 1000 rpm? 3000?

doesnt a spooled up turbo spin around 20 to 40,000 RPM?

[Darcane]

Originally Posted by quiksc2

That didn't really explain why it doesn't work.

I think that's because he was trying to show one that does work. I've never tried or even seen an e-Ram, but I can see that it might work. There was another company (I think they were called ACTurbo) making an electric supercharger that should work, but they have since gone out of business. The one I was thinking off used a large elctric motor to power a compressor like you would find on a turbocharger or centrifugal supercharger. It could produce some significant boost, but drew a lot of power from the batteries (yes, plural; the kit came with an additional battery IIRC).

Here's video of an unusual supercharger at work:
http://videos.streetfire.net/video/a...ad23ca9564.htm

OK, yes it's obviously not practical for using on the street, but it shows that an electric SC could work. I think that one is gas, but you can get electric leaf blowers of similar specs. I'm guessing (since I don't know the model using in the video) that one that size will probably push about 400cfm at slightly elevated pressures and requires about 1.3HP (about 970W) to do it. This is similar to what the e-Ram is rated at.

Now look at the bilge fans for sale on eBay. These are the "electric superchargers" that do not work. Most can move up to 200cfm in free air and run on less than 50W. A stock Saturn DOHC 1.9L needs about this much CFM anyways, so the fan at full power is just keeping up, it's not adding a thing. These fans are simply not powerful enough to do anything for your engine.

Mike

[00satSC1]

Originally Posted by KCW

I dont think you could get the needed speed from something the size of a starter motor. What does a starter spin at? 1000 rpm? 3000?

doesnt a spooled up turbo spin around 20 to 40,000 RPM?

If I remember correctly (which I probably don't) starter motors are capable of very high rpms they're just not built to withstand running at these rpms for a long period of time.

[Primenal]

Well, don't buy one off Ebay. I tryed it myself. I got it though, hooked it up, and it seemed to run better at the time. My car was having a couple of problems though before I got it on, that was since fixed (like a clogged cat). So, I guess I was thinking it ran well because it never ran for **** with the clogged cat, and something else was wrong...Can't remember.
So, I turn it on, and THOUGHT I was getting more of a boost. After a while though didn't seem to have the same amount of power. I put my old filter back on (without the charger), and the freaking thing ran like a BEAST compared to with the charger!
Also, the ones on Ebay are cheaply made. I was very happy with the intake pipe they gave me, and the K&N filter. The charger was made of crappy plastic though, and I ended up overtightening the clamp....Cracked the plastic. It's hard to tell what is overtightening to...Cuz you want it to be snug enough to be air tight, but I think that's somewhere around when the plastic bends down!
Overall, I didn't pay a real great amount for it. $ I could have put somewhere else, but I consider it as a lesson to not do again. Go with real modifications that you KNOW will work.

[westwind999]

Well they could work but the problem as others have said is power. Most of the ones everyone sees for sale have only a few watts of power. Your alternator doesn't have enough output to power anything very large. I saw some video of someone with a leaf blower blowing in the intake on a dino and it showed some significant difference. You just can't power a leafblower size motor off of your alternator. Of course if you make something bigger it needs to be designed properly with pressure relief and a reasonable control system.

[Gerry Proctor]

Oh great! It's groundhog day...again!

Nissan actually explored an electric supercharger to assist in a turbo lag issue, but abandoned it due to unsatisfactory results. They were using a motor to help spin up the compressor.

Fans move air. They do not compress it. Airflow with fans falls rapidly with resistance and completely stalls at total resistance. You can do a somewhat unclean experiement with a simple circular fan by just taping a fabricated tube over the output side. Flows a lot of air unrestriced. Move it closer to an obsticle, like a wall, and you'll notice that airflow falls dramatically and it doesn't make very much pressure. Put it completely against the wall, and airflow stalls and pressure goes to zero (remember, fans can not compress air). Do not be fooled by the design of the fan. There are many types of fans and some even look similar to the compressor wheel of a turbocharger but there are significant differences once you start picking out the details.

Now, anyone who ponders that these things can make a difference and we're just Doubting Thomas', please do not let any of us stand in your way of making this purchase. Perhaps you could have the family pony up as a memorable Christmas present.

[sl_don]

Originally Posted by KCW

I dont think you could get the needed speed from something the size of a starter motor. What does a starter spin at? 1000 rpm? 3000?

doesnt a spooled up turbo spin around 20 to 40,000 RPM?

like a super charger you need gear multiplication. a centrifigul supercharger is driven by the motor if it was 1:1 you'd get a peak rpm of whatever your engine can do (less than 8K RPM) so it gets a small pully then ir has an internal gear reduction to get the final impeller speed)

so you would have to do the same with said starter motor. now the problem is the gearing required to get the right impeller speed is very hard to turn. that is why a starter motor is required. they make lots of torq. now doing this will require electricity. remember when you start your car all power is diverted to the starter so imagine you electric super charger putting that kind of load on your electrical system when you are trying to go fast.

[eljefino]

If anyone's driven a stick shift car and accidentally, or purposefully, moved it with the starter cranking... that's how much power the car's electrical system can supply the wheels. Period. It doesn't matter if it's physically turning the crank or indirectly blowing air in to turn the crank. Actually more efficient using a starter, I think, than turning circular motion into pumping air that gets converted back into circular motion. That 1/2 mile per hour draws a couple hundred amps and is not sustainable by the 100 amp peak alternator.

If one wants electric boost, buy a honda insight.

It's possible some electric supercharger users are thrilled with the increased airflow by a mostly closed throttle when they're driving around town. But as other posters said, once airflow gets serious the electric bilge fan (marine app rebadged) runs out of steam. These are the same maroons who like grossly oversized throttle bodies... tons of airflow at 1/10 accellerator position.