there are some serious electric vacuum motors out there. with an inverter you could easily deliver 20 amps max peak power to an industrial motor vacuum compressor. I have never heard of anyone trying it. I've been contemplating it. As much as I value you younger racing people. Trying to find the maximum outputs of our favorite mills!!!! I am also getting older and looking for practicality. Wouldn't be nice to run down the interstate in a normal tame gas saving EFI mode till you hit "the pass"and then with a flip of your finger turn on the boost! rock out the obstacle and resume a miserly fuel profile. So you could choose between badasss and cheap at the mere flip of a switch. I'm new here and probably posted too much tonight. But I'm pretty stoked at what and whom I'm seeing. There is a lot of different abilities and capacities here. I'm hoping some of us could come together to develop some new ways we can all use. maybe we could even do six in a row!!!
electric induction
- Thread starter sabre694
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While there are some serious vacuum compressors out there (sort of an oxymoron)... I think you underestimate the flow of your average internal combustion engine.
Are the electric pumps/compressors that can supply this flow? Yes. Will they fit in your engine comparment and draw a reasonble amount of current?
Not likely.
Find yourself a compressor that can supply 400 CFM @ 10 PSI, and see how much HP it takes to run it...
A couple of HP is a BIG electric motor.
Are the electric pumps/compressors that can supply this flow? Yes. Will they fit in your engine comparment and draw a reasonble amount of current?
Not likely.
Find yourself a compressor that can supply 400 CFM @ 10 PSI, and see how much HP it takes to run it...
A couple of HP is a BIG electric motor.
I have heard of lots of people asking about it and others saying it can't be done but I have never read about anyone trying it or doing any serious research. I dont see it as something that is going to work for any length of time and still be practical but it may work as a fairly short term 'turbo boost' sort of thing. Heck if you can do it with a shop vac or other surplus junk maybe you just replace the whole 'blower' every time it blows up?? A big cost is going to be the inverter and then you are going to have to go to something like a Megasquirt computer to keep the fuel under and ignition under control during the boost. I could see it getting expensive enough to not make it worth the trouble but without doing the research and crunching the numbers you will never know. Dont forget to take into account the chance of blowing up your motor and or car in the process.
My guess is nitrous may be a better fit for what you are looking for.
But then who knows, you could become the 'father or the shop vac turbo' system because you found a way to do what they say could not be done.
My guess is nitrous may be a better fit for what you are looking for.
But then who knows, you could become the 'father or the shop vac turbo' system because you found a way to do what they say could not be done.
Here's the deal -
You could certainly take something like a centrifugal supercharger and, instead of running it with a belt, run it w/ an electric motor.
And, if your electric motor was sufficiently powerful (and alternator suited to match) it would work just as well. It could potentially work even better because you could control blower speed independent of engine speed (full boost off idle!!)
BUT.
I reiterate that you would be a HUGE freaking electric motor & support equipment. Just for reference, a 1/4 hp motor (which is enough to support 4 CFM @ 10 psi) weights ~35 lbs! If you assume the relationship is linear. (Which I am not sure that it is) That means you need about 25 HP to deliver 400 CFM @ 10 psi...
So go look for 25 HP motors and tell me what you find...
A lot heavier and more complex than a bracket and some pulleys
You could certainly take something like a centrifugal supercharger and, instead of running it with a belt, run it w/ an electric motor.
And, if your electric motor was sufficiently powerful (and alternator suited to match) it would work just as well. It could potentially work even better because you could control blower speed independent of engine speed (full boost off idle!!)
BUT.
I reiterate that you would be a HUGE freaking electric motor & support equipment. Just for reference, a 1/4 hp motor (which is enough to support 4 CFM @ 10 psi) weights ~35 lbs! If you assume the relationship is linear. (Which I am not sure that it is) That means you need about 25 HP to deliver 400 CFM @ 10 psi...
So go look for 25 HP motors and tell me what you find...
A lot heavier and more complex than a bracket and some pulleys
http://www.fremontindustrialsupply.com/ ... dor/Detail
Ignore the fact that it is 3phase & 230 V for a second...
And just look at the size! The thing probably weights in excess of 70 lbs...
Ignore the fact that it is 3phase & 230 V for a second...
And just look at the size! The thing probably weights in excess of 70 lbs...
I've only heard of one electric supercharger that does anything at all. Thomas Knight makes them, and they need three deep cycle batteries in the car, can only be used for 10-15 seconds at the time, and cost upwards of $2000 bucks.
Anything else is a scam. You look at the CFM rating of blowers and fans and think they'll work...but the rating is a no load rating. Any resistance behind them lowers the output to nothing.
Look elsewhere for your performance adders.
Anything else is a scam. You look at the CFM rating of blowers and fans and think they'll work...but the rating is a no load rating. Any resistance behind them lowers the output to nothing.
Look elsewhere for your performance adders.
Not insisting this is possible but thinking outside the box. 48volt dc deisel starter motor rewound for constant duty of course a gearbox attached to a twin screw compressor/ need to find some actual specs/ maybe I'm convincing myself how simple a belt driven supercharger is LOL. Thanks for input.
Superchargers just take too much hp to be electric powered.
It's the extreme example, but it takes more hp to run the blower on a Top Fuel Hemi than a new street Hemi will ever make.
IIRC, the supercharger on the Buick 3800 takes about 20-35hp to make 5psi.
It's the extreme example, but it takes more hp to run the blower on a Top Fuel Hemi than a new street Hemi will ever make.
IIRC, the supercharger on the Buick 3800 takes about 20-35hp to make 5psi.
sabre694":2ezshr85 said:
Thinking outside the box is fine, but try to restrain yourself to inside reality.
These things are not mysteries... they are physical facts. I am a mechanical engineer and I worked a lot with electric motors at my last job. I could sit down and figure the whole thing out for you, but I don't want to take the time to derive a pump equation for air.
Point is, it takes a large amount of power to drive a supercharger (or turbo, for that matter)
This power is a finite resource, and the law of conservation of energy tells us it has to come from somewhere. The best you can hope to do is increase efficiencies, but you can never exceed 100%. Because of that, there is a finite limit on how small your electric motor can be, and how much current it will require to spin the supercharger.
From my experience, I am telling you that this limit is larger than is practical/possible for an automotive application. If you really want to convince yourself, do the math. To generate 25 HP w/ a 100% efficient motor @ 12v, you need 1500 amps! Good luck with that. Even @ 100 volts, thats still 190 amps... and 100V 190A is not something to be playing around with. Forget it w/ your 48V motor... thats over 400 amps...
The truth is, there is a reason that superchargers are mechanical. Mechanical means are a fairly simple and well understood method of transferring large amounts of power. Electrical runs into some real problems once the power levels start to climb.
Thank you Ian I am not an engineer but a service tech in hvac and other electromechanical fields as well as a plumber. I was getting ready to start looking at data related to this line of thought. I will trust your opinion and save myself the time. As silly and wasteful as this type of thinking may seem to some people. I have had it pay off many times. My best example was a friend who asked me to help him damn a spring and build a water wheel to make some power. After looking at his site and doing the math I convinced him to spend his concrete budget on a ditchwitch and a lot of two inch polypipe. we ended up with over a 120 feet of fall and amazing amounts of head pressure. we were able to supply 3 2 inch lines. we keep adding pelton wheel generators as he can afford them and as of this date He receives a check from pacific power that is larger than his paycheck every month. without the dreaming and questioning he would have only tiny amounts of power not worth the equipment to make it saleable. the value of this kind of forum is that there are so many people here with different relevant experience and knowledge. please know I appreciate all input
A
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Hi Sabra694,
I am assuming that the vacuum pumps you refer to are some variation of radial-flow vaned device similar to a home vacuum cleaner, a turbocharger "compressor" or a Paxton-style supercharger. IIRC some of the industrial vacuums actually have used stage axial turbines similar to modern jet engines. If it is the latter ignore everything I am about to write.
I'm going to weigh in with the point that radial-flow turbines are velocity devices, accelerating air to high velocities, and not strictly pressure devices. Think high speed, not high torque.
By virtue of the air being accelerated and the momentum imparted to the air, pressure builds up at restrictions. In the case of a radial-flow supercharging, this restriction is hopefully only the finite piston/cylinder volume. As the pressure builds up the compressor may no longer be able to induce flow and the compressor stalls. Heat, noise, and wasted energy results. To achieve high momentum, high turbine speed is required. Without high speed, only low pressure ratios would be achieve.
BTW, My understanding is that the difficulty getting high boost pressures out of mechanically-driven centrifugal superchargers are the loads put on the supercharger's internal high step-up gearing when quick changes in engine RPM whip at the fast turning compressor wheel.
Several good turbocharger books are out there. H.P. Books published a couple of editions of Hugh MacInnes's "How to Select and Install Turbochargers". These have been my Bible for more than 20 years now (yes, I have three editions). These books can explain this concept with pretty-graphs-and-pictures-worth-more-than-a-thousand-of-my-words.
Larry P.
I am assuming that the vacuum pumps you refer to are some variation of radial-flow vaned device similar to a home vacuum cleaner, a turbocharger "compressor" or a Paxton-style supercharger. IIRC some of the industrial vacuums actually have used stage axial turbines similar to modern jet engines. If it is the latter ignore everything I am about to write.
I'm going to weigh in with the point that radial-flow turbines are velocity devices, accelerating air to high velocities, and not strictly pressure devices. Think high speed, not high torque.
By virtue of the air being accelerated and the momentum imparted to the air, pressure builds up at restrictions. In the case of a radial-flow supercharging, this restriction is hopefully only the finite piston/cylinder volume. As the pressure builds up the compressor may no longer be able to induce flow and the compressor stalls. Heat, noise, and wasted energy results. To achieve high momentum, high turbine speed is required. Without high speed, only low pressure ratios would be achieve.
BTW, My understanding is that the difficulty getting high boost pressures out of mechanically-driven centrifugal superchargers are the loads put on the supercharger's internal high step-up gearing when quick changes in engine RPM whip at the fast turning compressor wheel.
Several good turbocharger books are out there. H.P. Books published a couple of editions of Hugh MacInnes's "How to Select and Install Turbochargers". These have been my Bible for more than 20 years now (yes, I have three editions). These books can explain this concept with pretty-graphs-and-pictures-worth-more-than-a-thousand-of-my-words.
Larry P.
lpardee":1zztzu1e said:
I figured the problem was that the output builds pretty much exponentially with RPM. To stay within sane flow levels on the top end, the starting point is necessarily low. A two-speed gearbox (maybe a torque converter?) would be ideal, but has proven problematic.
Plenty of people run high boost levels with centrifugal superchargers...Paxton has sold a lot of F-2 and bigger models to customers that can play with 1000+ hp.
Lots of high-boost centrifugal superchargers out there, but mostly for racing-type one-acceleration run at a time. Not many on true street engines, because of the speed-up/slow-down/speed-up/slow-down/speed-up/slow-down as you go up and down the gears tooling around town. At least, I think that's what he's getting at regarding them.
Back in the day (1977 to 1987) we used supers with a clutch similar to an ac unit but with more mass spun up. So you would drive in a normal configuration most times and hit the switch for boost. I never owned one myself but was allowed to drive other peoples cars because I had good reaction time and they wanted their car to win. It was really fun to leave it off till the other guy thought he had you then hit the boost and roast him. Also would leave it engaged on the highway especially in the mountains
It was really fun to leave it off till the other guy thought he had you then hit the boost and roast him. Also would leave it engaged on the highway especially in the mountainssabre694":26i413r8 said:
Yup. That's right good engineering
Daimler-Benz built the DB-605 series aircraft engines using some sort of hydraulic variable speed drive to operate the supercharger. I have never seen a drawing but it apparently worked well, plus it was automatically controlled so the pilot didn't have to worry about it as altitude changed (think Eric Hartmann in his Bf-109).
We use rotary screw air compressors in the sawmill business that are physically about the size of a 6-71 Jimmy supercharger. We drive them with a 150 hp 3ø 480 volt electric motor. It takes serious horsepower to move air.
Joe
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