Why is forced induction always mechanical?
 

The only popular forms of FI are superchargers and turbochargers. Why (besides some crappy bogus stuff on ebay) aren't there any electric compressors that run off the battery (or some other electrical supply)?

With an electric compressor you're not tied to engine RPM or exhust flow / turbine size. Also it doesn't put extra load on the engine (powering the super or reducing exhust flow).

If you're eating from the battery, then it'll cause the alternator to kick into overdrive, but there are other ways to get power (ie. charge battery over time with regeneritive brakeing / exhust turbine like a turbo, rather than alternator).

Seems to me that getting variable level of boost on demand (without the worry over overboost) would make an electric forced induction system popular... so why aren't there any? There must be an electric compressor out there that has enoguh airflow / pressure for the cost of a good turbo/super.

It's simply a matter of the power requirement to run an electric SC at anything like the boost you would need to compete with a turbo or SC . You would need either a huge alternator or a big ass battery (or both)- just not practical .
I do think there would be a place for an electric SC that can flow enough to boost low end to mid range torque on the Renesis - but it would do nothing at the top end which is where most of us want the extra.

I did a little more looking around at the electric super-charger scams (some im prepared for some flames)... and yes... they're shit... but i dont see why someone couldnt make a GOOD one.

It wouldnt work if you were constantly at full boost, but considering that you usually aren't... you store up energy in the battery gradually as you drive, and you use all that energy in bursts when you run the compressor.

you can assist the alternator with regeneritive breaking (or if you're worried because there probably aren't any performance brakes that have regen braking out there), put a small turbine in the exust, like a turbo, that generates electricity. That way you dont need some monster alternator. regeneritive breaking especially.

just curious, at sealevel with no boost, how much airflow does the renesis need?

There was a local company here in San Antonio that had a Electric Supercharged Civic and it was fairly fast but their kit was like $10,000 estimated and sort of unreliable and added a ton of weight to the car. It ended up being a one off thing and the idea failed. I tried to search for it right now could not find any info on it.

It's called NAAAWZ

Thats exactly what I was thinking as soon as I read the topic.

For electric boost they go from mechanical to electrical and back to mechanical...
It involves two losses so it can't match the efficiency of the direct mechanical link.
Maybe once we can directly move air using electricity we'll get a non mechanical FI... with no moving parts ;)
The big advantage of electric boost would be the decoupling of the boost pressure from the engine RPM...

Its all about the losses associated with converting energy. Both superchargers and turbos us energy already created by the engine to spin a turbine or blower. With an electric solution you would have to convert that energy to electricity, store it, then convert it back to a physical motion to turn a turbine. Everytime you convert it you lose energy and as such lose effeciency.

And then there is weight. To store that energy would require a battery(s). Also a supercharger uses a fair amount of HP to get turning. An electric motor capable of producing the 30-60hp needed to spin a gearbox and turbine would be heavy as hell!

I would like to see a hydraulically powered supercharger. Either have exhaust gas or an electric motor turn the hydraulic pump. Draw from a small reservoir of oil which supplies oil through oil lines that in turn power a small hydraulic motor that turns the compressor wheel. I think it would eliminate some packaging restraints. It's all a fluid power link. The only thing is hydraulic pumps don't like variable speed so an electric motor would be more conducive to turning the hydraulic pump unless you have the electric motor cut-out once a certain RPM is reached once appropriate exhaust pressure builds. But that might make an overly complex system as compared to a plain ol' turbo charger.

i dont know . its not necessarily less efficient. the electric assisted steering is more efficient than the regular power steering AND it saves weight.

This is true, you will lose energy that way.
However, if you're using regeneritive breaking... you're using energy that would have been lost anyways. And if you're using a turbine in the exhust, and it is variable geometry, you can make it spin at the most efficient speed, rather than the speed that will produce the most boost.

but the biggest thing is, you're building potential energy in the battery over time, to be used quickly in bursts. Sure, its a bit less efficient... but because you're using stored energy you're going to have more than enough. over-all you'll get worse gas milage, but the inefficiency isn't going to hurt performance (which is what matters here).

I didn't realize it took so much. I find it hard to believe that a turbocharger can generate 30-60HP to run a compressor, but i guess it could happen.

You're right, it would be heavy... but people who run nitrous don't seem to mind a big-ass tank in their car, so i didn't think it'd make that much of a diff. I don't think it'd be hundreds of pounds worth of heavy.

Too bad no one picked up the last two sentences...

running an alternator needed to power such a device would be just as parasitic as a supercharger

Remember, You need energy to create energy!

Like i've said before. the alternator is constantly generating energy to recharge the battery. You aren't constantly at full boost. You store energy over time, and then use it in bursts with the compressor.

You aren't running the compressor directly off the alternator.

Sure, in the grand scheme, you lose a bit of gas milage... but since when do people who mod for power really care about that?
With an electric compressor, you'll get boost that isn't tied to exhust flow, turbo size or engine RMP, and you'll get it immediatly, whenever you want.

is this really not do-able? I can't believe that an electric engine couldn't drive a turbo's compressor. How much power does it take to drive one of em, and how much airflow does the renesis need?

There are good electrical superchargers out there. The Thomas Knight company is one of them. The best way to find them is to google and look for the review articles. There are just too many of the bogus ebay type ones out there.

you have to take into effect the bigger (read: more parasitic) alternator you will have to run and you will run more of it, you would be suprised how much more amps you would be pulling with an electric compressor

its not like turbos or superchargers are always at full boost either, most super kits have a bypass while the engine is in vacuum.

say you want to turn on your compressor at low rpm's for a kick in the pants, you are going to drain your battery and overstress your alternator at low engine speeds, so you would need a bigger one. Im not sure you understand the limits of electrical storage and how much stress your stock alternator is under with just your headlights, a/c, and stereo on.

is it doable? absolutely, is it going to work like you want it to? kinda. will it give mechanical FI a run for its money? in your dreams

the problem with electric compressors(legitimate ones) is that you cant generally run them for more than a few seconds at a time. Essentially you'll spend 2-3 times the money to end up with the same result as a much cheaper and less intrusive NOS setup

Would that be much of a problem, given what you say just after?


As you drive, you store energy in your battery, using the alternator (or regeneritive breaking / other means). Then you boost when you need it. it sucks out part of your battery... but you're not doing full boost for long.

You're not powering the compressor directly from the alternator, so the alternator doesn't have to be powerful enoguh to run the compressor.

Pair it up with regeneritive breaking (which is powerful and has the added benefit never locking your breaks), and i think you'd probably take much of the load off the alternator. Not that i've ever heard of regen braking kits for cars lol.

of course, there are variable geometry turbos that also reduce lag and are better across a wide RPM range, but those dont seem popular either. Or atleast aren't advertized as such. but thats a whole other topic :p

It would make the RX-8 sound like 2 hairdryer instead of 1.

wrong, that is exactly what you are doing. It is not two separate systems, the battery and alternator are linked at all times. as soon as you start drawing juice from the battery the alternator kicks in to replace what you are taking, and I just dont think you realize the size of a battery and alternator that you would need. you can only crank the rx-8 engine over about 15-20 seconds before your battery is gone, how many seconds you think you can spin your compressor with that little juice? especially at the speeds you need to make positive boost. using brakes to charge your battery can top a system off, but you wont be using the brakes and compressor at the same time, and short of a huge, heavy, expensive battery, you will drain your 12v before you can go through 2 gears

the main argument I am boiling down to here is that the alternator you would need to run, would suck up more horsepower at a constant speed, than any benefit you would get from on demand FI; however it seems to me that you refuse to listen to anyone on this board trying to describe logic in automotive and electrical engineering, and are more interested in arguing any point with the same old sentence about store power in a battery and use brakes to charge it.

What's in a (user)name?

you need at least something around 50kw just to run a supercharger. do you think your small battery and alternator can do that? can you imagine how thick the wire is gonna be just to handle 30kw at 12V? 2500 freaking amps, you need metal rods to handle that current. :bowdown::bowdown:

You'd have to be running the system at hundreds of volts to be practical

I think one of the biggest problems that hasn't been addressed is the rechargeability of the battery. You can't just keep dumping in charge and pulling it back out as that'll massively shorten the lifespan of the battery. You'd need a special kind of battery (meaning expensive) to deal with memory issues and to hold enough charge. Perhaps a bank of the Tesla or Tango ones?

That said, if an electric-driven supercharger could be made to work, it would be pretty neat, as you could easily switch the blower on and off at your leisure. Picture your RX-8 whirring down the road when some schmuck in a 350Z or Mustang tries to race you. You reach up, flip a switch Speed Racer-style, and leave him eating your dust.

That is more of what I see as how a electric supercharger would work. It wouldn't power up until you put your foot to the floor. Kinda like using nitrous or the supercharger in the Mad Max/The Road Warrior movie.

thats called a clutched supercharger, Mercedes did this in the slk kompressor. it only turned on at WOT. I put one of these in my ford probe, still switched. so I flip a switch and get instant boost, recently a protege adapted the kit too. it doesn't make gobbs of power but the idea has been done before....2.0 I4 160whp, @ 4.5psi. stock is 110whp....

any of you naysayers or yeahsayers actually run the numbers? its possible that running the SC electrical is actually less parasitic than running it off a belt. until someone runs the numbers you are all talking out of your ass.

its like the fuel cell at your home arguement. people say "oh its non sense to reform the NG into H2 to run through a fuel cell. you could just burn the NG for electricity. reforming it is 2 conversions so its more loss yadddyadda yadda"

well every study actually done now shows that its actually more efficient to reform it ,use the waste heat to heat your water and use the resultant electricity for fueling your electric car etc. than it is to burn the gas for heating the water and making electricity.


so somebody run the numbers

ill give you a hint though- thomas knight esuperchargers run off of separate batteries http://www.boosthead.com/product.php#

well im am interested in arguing, you're right... I like to argue, its fun.
but i use the same old sentence because nobody has explained why it is wrong... people keep on saying it wont work... so i have to assume that they didn't read that sentence or i didn't explain it right.
The whole reason I made this thread is because i'm curious and I wan't to understand... So i'm going to keep asking until I do.


yes the alternator is on the same system as the compressor would be, but because the compressor isnt always running, it doesnt have to produce enough electricity to keep the compressor running indefinatly. maybe you'd need to replace your alternator, but the new alternator you'd use wouldnt need to put as much drain on the engine as a stock alternator + supercharger because it isn't always running the compressor.

its like a well. it fills up very slowly, but thats ok because you only take water out periodically.

Draining the battery after a few seconds is a problem, though. How much does a battery that holds more charge cost? What are the available car battery technologies?


Thats what i imagine too. I have a dream where amount of boost is tied to throttle position rather than engine rpm.


Hahaha, that could be a problem for safety :p


It just baffles my mind that a little turbine sitting in your exhust can generate enough power to run the compressor (and still allow enough flow), but you need an enormus electric motor that drains your battery to run it electrically.

That little turbine is spinning at 100,000 rpm and needs anywhere between 5-10hp to drive it.

I see reading this thread so much frustration with reality. However, the universe and its rules are rather unbending. Now consider how frustrated those engineers that are trying to develop useful and practical electric electric/hybrid vehicles must be...because they know the difficulties involved!

Gasoline (aka dead dinosours and ancient swamp ferns) has so much energy stored in it it really is unbelievably amazing. Even sucking just a little bit of that energy to power a vehicle provides power beyond most any fuel available, plus....in the form of gasoline's poop (exhaust gas) we can reaps loads more energy and more than enough to power turbos, for example!

On the other hand transporting and /or transfering the raw form of energy (electricity or really moving electrons) takes massive everything...batteries, heavy wires, then there's real problems switching and controlling them little electron devils traveling around inside everything. Perhaps a plasma drive has possibilities, if we could only contain it one day, but until we come up with a cheaper and more long lasting way to store the stuff (like some form of hugely effiecient large capacity super-capacitors - they don't wear out with repeated charge cycles like chemical storage) the purely electric anything is going to remain a engineering paradox for long distance transportation - or for powering superchargers, turbos, or anything else.

I say take the car and turbo or supercharge it. Then make the body of the car a 100% solar pannel. Have a seperate computer, fuel system and electrocharger that you can use like NAAAWWWZZZ when you're racing or showing off. I'm assuming that my personal design would allow the renisis to go from 345 rwhp turbo to 1333 rwhp with the turbo/electrocharger both engauged. Just a thought.

yea, but then your car will be dangerous driving in the rain with hundreds of volts under the hood.

the problem with electricity is that its not mechanic, to get it working you need wires. its not like a belt or highpresure exhaust gas.

I think the Prius Fanbois are using some sort of electrical forced induction...or maybe it's conduction...anyway, they're claiming soemthing like 500 whp, but they have to run Optima Yellow Tops..everything has a tradeoff.

6 according to the thomas knight folk

i did, a long time ago. thus my previous comment

you typically cant run such a contraption for more than a few seconds, this is from Thomas Knight website:
thats a a pretty penny in batteries, and an ass-ton of weight to fill your trunk with. no better than NOS, except that you get to be different.(by different, i mean alone when it comes to troubleshooting)

yeah but its way cheaper to refill those batteries than it is to refill the NOS

lol, it looks like the tomas knight system is like the nitrous that you find in video games that recharges when you go fast for a while :p.

How fast it is spinning doesn't really make a difference unless its acting like a flywheel, would it? If it is only drawing 5-10 hp from the engine, then it has at most 5-10 hp worth of power. Thats if it wasn't wasting any of the energy. so why can 5hp in a turbo power a compressor, but it'd take 50hp if it was electric?

who said it would take 50hp ? It would take a lot more than 5hp though due to mechanical gearing losses......

I threw out the 30-60hp number to drive a supercharger. It depends on the type of blower, but typically it takes 15-20% of your engines power to actually drive the supercharger. This would obviously vary depending ont he gear ratio and engine airflow needs.
I remember with the procharger on the LS1 application and P1SC its something like 50hp to spin the impeller up to the 65k rpm with the resistance of average boost pressure.

hi
 

This is completely irrelevant to your post but I'm a new member and I joined because I had a few questions regarding my rx8. Embarrassing as is it to say, I don't know how to start a post to ask a question. I would really appreciate it if someone can help me by just pointing me into the right direction. Thanks a lot. :)

Go to the forum that best fits your question and click on the 'new thread' button at the upper left had corner .
Make sure you use the search button in the tool bar and see if your question has already been asked before you start a new thread .

Not that I'm a really hands-on kind of guy, but it doesn't take a genius to figure out simple laws of physics. If you're converting from mechanical to electrical there is always a loss ( no conversion is 100% efficient). Now converting back is the same thing would be even more lossy. There is simply no way that you can make it more efficient than mechanical. Not to contradict anyone here, but you don't have to run numbers to prove a fundamental concept.
Also, I guess I have to take a look at the Mercedes thing someone mentioned here, because I can't possible imagine a turbine spinning up to even 50k from 0 with any reasonable kind of lag, the motor would have to be immense. Ever see a electric go-kart engine that lies around 10hp or so? Would you stack that on top of your existing engine?

I was thinking the same thing during a fit of insomnia last night. Paul, the alternator load would have to at least equal if not exceed mechanical losses from a turbo or S/C, not to mention the alternator would have to be beefed up from stock considerably.

Years ago I was struck by the "electric supercharger" idea until I realized that stick a fan in the middle of the intake, no matter how fast it turned, presented an obstruction. It might provide some increased intake at idle, but once intake velocity speeds up I don't know of any 3" fan than can move enough air to pressurize the intake. As has been mentioned, turbos spin in excess of 150000 rpm. To get this from an electrical system would require a drive ration increase off the motor and a large enough motor to spool it up fast enough. Could probably be done, but it has to suffer more loss than a mechanically driven system.

Mawnee mentioned it, but i also got it from looking up the thomas knight system. He tried various motors up to 90hp (apperently).

I'm not looking to make it more efficient. I know that won't happen. But because you'd be using stored energy, being less efficient wouldn't be a performance hit. Your overall gas milage would be worse, but there'd be other advantages... it it could be made to work :p. Doesn't seem to be possible, but I still cant wrap my head around why a turbo could power a compressor but you'd need a big-ass electric motor to do the same thing.

does the compressor in a turbo also spin at 150000 rmp or has it been geared down? You dont need that kind of speed in a supercharger, so i cant imagine that the speed is the key. Rather than have a supercharger driven from the engine, you could have it driven from an electric motor. Why wouldn't that be able to provide enough air?

Like, i get the idea that this just wouldn't work. but i still dont get what makes it so un-doable.

(from howstuff works)

A gallon of gasoline contains about 132x106 joules of energy, which is equivalent to 125,000 BTU or 36,650 watt-hours, so...

•If you took a 1,500-watt space heater and left it on full blast for a full 24-hour day, that's about how much heat (electrical energy) is in a gallon of gas.

....

Think how much battery mass to even get a fraction of that power stored! That's the problem with battery energy - it's impossible yet to store enough to do much useful for any length of time. What is needed is superior storage technology that doesn't yet exist.

bingo. congratulations, you've won a heaping serving of common sense! now share some with the other boys and girls since they obviously need it and you dont

oh and a brand new car:rolleyes:

^ I won a car ??? :anger: just don't make it a damn electric anything please :rofl:

aw:tear:

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