BIG JIM 54

I mean REAL BOOST. Not the toy fans on EBay.

These things you see on EBay are wimps! They will probably decrease air flow due to their own restriction.

900 cfm won't do you anything either.

Since I never plan to sell this device I made, I don't mind telling you all about it.

First, these people who say you can't make significant boost electrically in a Chevy V8 are mistaken I believe. I say, "believe" because I actually haven't finished the project yet but all the numbers come together.

Second, why does everyone believe you have to drive an electric motor with only 12 volts just because that's what the car is wired with?

Third, Roots and centrifugal type superchargers use about 45 HP to make say, 150 HP in a car engine. No electric motor you can put in your car is going to produce 45 HP, agreed. So that is out of the question. But turbo compressors can make a lot of boost. They require RPM to make boost because the exhaust of a car doesn't have a lot of pressure behind it.

However, to offset turbo lag, it's advisable to use 1 or 2 small turbos that spoolup quickly. One large turbo is felt to be counter-productive since the spoolup time would be so slow. But it does push a lot of air at a lower RPM ultimately. Just not practical for the street.

Now to my project. I have found a very large turbocharger compressor off a big Detroit Diesel. As it was made, it weights over 50 pounds and has an 11 inch impeller to make boost with. Cutting off the exhaust side, it now weights 19 pounds. Do you all get where I'm going with this?

Yep, I found a 3.8HP 24 volt electric motor (over 2800 watts). It's only 4"x7". This motor has so much torque it will pull your arm out of its socket. This is going to be hooked up to the compressor side of the turbo impeller shaft with a Kevlar belt arrangement with various size pulleys that I can put on to vary impeller RPM. Impeller RPM would determine boost levels.

That 3.8HP electric motor only runs at 5000 RPM. But here's how the calculations come out. I can over-drive the motor at 1:4 or 1:5 or more so that big turbo compressor spins at 20-25,000 RPM. At that RPM, that size compressor will make 5-6 pounds of boost in a Chevy 350 at 5000 RPM. I don't know exactly how far I can go with the ratio but I figure maybe 1:10 overdriven. 0 to 20,000 RPM comes in 0.8 seconds so no lag ever.

Still so far, I know you're thinking probably that it's impossible. I'm not done yet. 2 small motorcycle batteries in the engine compartment hooked up in series to supply the 24 volts will power the motor. They will be charged in parallel by the car's alternator. They do nothing but turn on the motor at WOT only. The engine's throttle body will have mounted a small push button off-on switch wired into 2 Ford 60A starter relays that will send power to the electric motor running the turbo impeller when I put my foot in it. Even with 24 volts, it will require 118 amps for a motor to make 3.8HP. That's why the 2 60A relays. I don't think that electric motor will need all of its 3.8HP to make my target boost level.

I have all the necessary parts except waste gate, plumbing and other stuff I'm sure I'll discover I still need. But it will make for one quick '87 Corvette. And like I said, the numbers are there. I still have to figure injector and fuel pump/regulator size.

I am reasonably sure I can spin that compressor to make 10 pounds of boost by altering the ratio of pulleys. But I'm going to start slow so as not to run into detonation and/or engine destruction. The engine is fresh however.

But just with 6 pounds of boost at 5000 RPM into my slightly modified Chevy L98 TPI engine, I'll be making 550-600 HP! And it will be virtually instant!
No power loses from just driving the forced-induction pump like with a supercharger and no "turbo lag" from an exhaust-driven pump. Best of everything.

My question. Why hasn't someone done this before and why do all the "experts" tell me it can't be done? Am I going to make history?

BIG JIM

lead foot 85 vet

24 volts/2800 watts =116.6 amps....how long is that battery going to last...the fun of forced induction is that its there all the time...you can get what your taking about with NOS for short bursts......make a system with out pulling power from the alternater and working all the time and then were taking. :cheers:

honas

Dude, Congratulations on just thinking about it. There will be alot of people who will tell you to forget it. Make it work for under a grand and I will try it! BH

MrSpeedyBob

A few things jump out at me.

1) 3.8 hp x 768 watts per hp = 2918.4 watts. It's not goin to be 100% efficient so you'd better figure on suplying 3.2 or 3.3 kw at least.

2) a 350 at 5000 rpm and 85% VE will eat 743750 cubic inches of air per minute. Think of that as about 62000 linier ft/min through 1 square inch hole. suppose you push it through with one pound of force, that means 62000 ft*lb per minute = 1.9 hp per pound of boost. So, strictly from a "laws of physics" standpoint 3.8 hp will not produce more then 2 pounds of boost on a 350 at 5000 rpm. At lower rpm you will be able to make more boost. You might have a real torque monster off idle.

jfb

It will take a lot more than 3.8 Hp to turn that blower to provide the boost you claim!!! Also, I doubt a motorcycle battery can deliver 100 amps and even if it could, I calculate it will be discharged in 40 seconds. Good luck.

xs650

rkessel, your numbers look pretty good, but on top of the that turbo blower section has it's own ineffieincies. With the airflow he will be able to get with that amount of power, it will be operating at way off it's optimum point. It will be doing good to deliver 60% efficiency from the impeller alone. So multiply your results by .6 to get an optimistic view of what might result :cry

Albertgofaster

Interesting project here, Well I am going to follow this close It sounds really possible however please consider the below. ALso I would like to see some pics when you finish this historical event please keep us posted I am very interested on this.


Well I agree you will exhaust your power supply well before you can really get any significant boost from the blower. Maybe a more suitable power supply will be needed.


:troll :lurk: :troll

85 Dave

3.8 hp is not enough. It may feel strong, but electric motors make their maximum torque a 0 rpm. A belt driven blower uses 45 hp to drive the blower because that's how much power you need to pump that much air. Doesn't matter if the hp comes from a crank driven belt, waste heat from the exhaust, or an electric motor. 45 hp is 45 hp. Your electric motor won't be strong enough to turn the compressor at the needed rpm.

Caboboy

Big Jim, props to you for having the idea, and thinking it thru as logically as you have :cheers: I should mention you've got great sack for bringing it out to share before you've even started the project too..... :eek:

This being said, I've got to agree with the others.........the physics just aren't there. I think you'll hit fairly good at low RPMs initially, and be out of steam less than half a minute later...........it would be really cool if I'm wrong though :D Best of luck on your project, this is going to be cool to watch :thumbs:

SBNova

I remember reading a while back in a magazine that it takes something like 40 hp to drive whatever supercharger they were testing with an electric motor. Then theres the fact that you will lose horsepower to generate the electricity to power the motor, and those batteries will provide 24v in series- but for a mere seconds at that amperage load.

cdnguyred88

:cool: either way good luck, sounds like a lot of work.
:cheers:

SPEED750

I'm dieing to see how this works out.But I have some concerns. First thing is a turbo spins close to 100,000 rpm.It needs that kind of rpm to make boost, I don't think you can make any boost off 25,000 rpm.Thats why they're so hard on bearing.Have you seen the turbo timers, It's a device that keeps your car running for 5 minutes after you shut it off and leave.This way it has plenty of time to cool off the bearings.You won't be spining that fast so it really doesn't matter.As far as no lag, don't count on it.I have a lot of experience with electric remote control cars.They make some badazz electric motors that spin 50,000+ rpm.With no load they snap to max rpm, but pushing a load it takes a few seconds.All electric motors have max torque at 0 rpm and you put juice to it.Can you imagine your ceiling fan going from 0 to 300 rpm in .8 seconds.What are you going to use to supplement the fuel side?A lean condition will kill your motor.
Please understand I'm not trying to flame on you.Just trying to point out some downsides.I love it when somebody is motivated with a new idea. :cheers:

BIG JIM 54

Thanks for the response from all of you!

Remember, I said the target was 20-25,000 impeller RPM but that I could go a lot more. I believe 50,000 RPM is possible which even if 20-25,000 wouldn't make significant boost, 50K would. And who says I have to stop at 24 volts. I'm sure I could get away with 36 or even 48 volts going to this motor for short periods. That's the beauty of electric power. 48 volts will double the motor's power output to 7.6 HP. I'd bet my reputation on that being enough power to turn that compressor at any speed I need to make the boost I want.
Also, not all turbos spin at 100,000 RPM. Small ones do because they have to to make boost and they have to be small to spoolup quickly. Large pumps spin slower and this sucker is BIG!

We are getting 100A from 6 sub-C size, 3300mah Ni-MH batteries in electric r/c cars so why is it hard to get 120A from two unspecified size motorcycle batteries? Hell, I'll put two DieHards under the hood if it will get the power I need so that comment is really non sequitur. Also remember it's only going to work at WOT and how many seconds do you run on the street at wide-open throttle?

Also, why is it that some of you think it would take more than 3.8 HP to turn what is basically a high-output fan running between two ball-bearings? I mean, how much pressure to you think is coming out of an exhaust pipe? You can put your feet over the exhaust outlets and stall an engine. Turbo type compressors make boost by RPM, not torque but I am converting the torque of the eclectic motor into RPM with the overdrive belt. To me, it doesn't seem like a difficult concept to comprehend.

But as I implied from the topic of my post, I have heard it all before about how it can't be done. But neither could the speed of sound be exceeded or bottled water ever become a marketable commodity. Somebody had to do it first. I'm just doing it for fun and not as a business venture. That's all.

I may be in for a rude awakening and I'm not saying that's not a possibility. But to add more background info about myself, my full name is BIG JIM Greenemeyer. If any of you out there are into racing high-end radio-controlled electric cars, you probably have heard the name. I hope this doesn't sound pretentious but I am considered by many as the #1 authority in world on the electric motors that power these cars. I make my living now as a motor consultant to the big companies like Associated Electrics, Team Orion and Trinity Products. I've been building and designing toy car motors for 39 years and have a published book on the subject, BIG JIM'S R/C Motor Black Book" sold by Trafford Publishing. Just type "BIG JIM" in any search browser and my website will come up.

I don't say the above just to toot my own horn but to let you all know that I am probably more aware of the power and versatility that can be achieved from a properly designed and applied electric motor than most people.

BTW, I believe it's the heat from the exhaust that does most of the "heating-up" of a turbocharger and necessitates "cool-down" cycles and intercoolers. Obviously I won't have that problem but I am aware of the heat caused from compressing air. But if it doesn't work, there won't be any heat. If it makes significant boost and if their is a large amount of heat, then I'll deal with it and will be the least of my problems when running 600HP on the street.

I also said I haven't worked with the fuel side of the numbers yet. But turning the cold-start injector into a fuel suppliment injector only under full throttle has crossed my mind. We don't need that stuff in CA anyway.

And yes I realize I'll have to have different ducting when the compressor is running and when it's not, even for the few seconds at a time it will be running.

1 Electric Horsepower = 746 Watts. And I'm not an engineer.

Thanks again for all your comments and suggestions.

BIG JIM Greenemeyer http://www.bigjimracing.com
Motor Forum at: http://www.rccars.com





[Modified by BIG JIM 54, 2:42 AM 11/16/2003]

Mr Mojo

Jim, I wish you luck, I'd like to see you do it, and when you do, make sure youpost all the details, sounds like an interesting project.

BTW, I have an old school Tamiya Blackfoot that I clocked at 25 mph, I acquired a better motor for it and the thing flies now, I just need a new controller.

SonnyinVA

good luck!
sounds like you'll have fun trying it, whether it works or not.
i can only imagine how many BUGS will show up during the install/tuning... :eek:

is there some way to bench test it?

SPEED750

"Also, why is it that some of you think it would take more than 3.8 HP to turn what is basically a high-output fan running between two ball-bearings? I mean, how much pressure to you think is coming out of an exhaust pipe? You can put your feet over the exhaust outlets and stall an engine. Turbo type compressors make boost by RPM, not torque but I am converting the torque of the eclectic motor into RPM with the overdrive belt. To me, it doesn't seem like a difficult concept to comprehend."


"Contrary to popular belief, turbochargers do not make free horsepower.To develop boost on the street, you will see about 2.5 lbs of backpressure for every pound of boost.At 6 psi of boost , the back pressure would be 15 psi.
The turbocharger does not provide free horsepower, but it does manage to overcome it's own drive losses." TURBO PERFORMANCE HANDBOOK

A turbo is not a fan, it is a compressor.A fan doesn't have to deal with backpressure, a compressor does. It does take torque to spin under a load.If you overdrive the electric motor you will lose torque.
I'm not saying it can't be done, but it will take some serious HP if you want to overdrive a motor to spin 25,000 rpm pushing a load.
Good luck, and keep us posted!
[Modified by BIG JIM 54, 2:42 AM 11/16/2003][/QUOTE] :cheers:

BTW Big Jim, I make my living selling bottled water. :D

ukchevybuilder

I'm not going to say whether it will work or not but I do think that there three problems `1) getting a powerful enough motor to run for more than a few seconds 2) getting a drive that will reliably turn a centrifugal compressor fast and 3) the electrical drain load

1) depends on how good a motor and how much it can be overloaded for short periods. That is actually how a starter motor succeeds ( thanks to Charkes Kettering who was a very smart guy).

2) I doubt you can drive a turbo charger compressor externally at design rpm as the bearing design and balancing is very esoteric. However that isnt to say it cant be done as the old Paxman centrifugal superchargers DID work and they had only a belt drive. I would suggest looking up anything you can find on Paxman blowers as they have already done a lot of the R+D in the long distant past.

3) the electrical drain is an issue but have you thought of capacitors. They can store a lot of potential but only give a short dicharge but maybe this is all you need. As a "by the way" BMW recently did a cute stunt on electric cars by putting some VERY BIG capacitors into an electric X5 SUV and showing it doing a wheelspin start with electric power . So capacitors big enough can work

There is another example of "slow build, quick boost actually . Long, long ago GM research invented a really neat passing manouver "supercharging" system by applying lateral thinking ( yes GM R+D are actually inventive) . They used a small air compressor off the front drive belt to charge up a large air tank , bit like truck or train air brake applications. Then they discharged the high pressure air into a venturi which dragged in a lot of extra air at moderate boost purely through areodynamic design. The result was a quick passing surge of power without a continuous power drain.

The BMW or GM slow build up of potential energy and quick release ( into your electric motor and compressor) might be a way of getting round the basic power conflicts involved.

Just an idea

COMPVET

Oh, Oh
Problem here,
Deteoit used roots style blowers. They are a positive displacement type of compressor which means if you are not turning it no air gets past it. In other words if it is not turning your motor can not run. Second problem lies with the positive displacement again. If you can power it up at all you would end up with tons, and I mean tons of boost at idle and it would taper of to zero at some point in the RPM rage and a minus figure if you tried to RPM higher than that.
Pete

CentralCoaster

:withstupid: Especially with a 10:1 mechanical disadvantage.

red L98

hey , I wish you luck keep doing what you been doing and itll workout :thumbs: :hurray: