Cheap Supercharger!

[Ahmed]

Guys look what I found at http://www.ebay.com/itm/0-6-CFM-GAS.../270916918523?pt=BI_Pumps&hash=item3f13e81cfb.

I found it on eBay, it runs at 3450 rpm supplying 0.6 CFM of air at 15 PSI. Running it at a low speed can provide more CFM. And it's only $30 before shipping. What do you guys make of it?

 

[Doc Sprocket]

.6 CFM?

I just ran a 400cc engine at 3600 RPM thru a carb calculator, and got 21-25CFM. A far cry from 0.6.

Where's the fault?

Plus, by the time you enlarge that weenie little port up to around an inch ID, you'd lose a ton of velocity, methinks.

 

[fowler]

Must be an RC car super charger

 

[Ahmed]

No, if you reduce RPM you get less pressure and more CFM, probably 5 PSI boost?

 

[fowler]

Other way round isn't it

More rpm means u move more air

Less rpm but more power means it can make more pressure

That's for posative displacement pumps but I never messed with supercharges

Surely turning the pump slower thereby reducing the speed air passes though cant increase flow

 

[Ahmed]

But the vane type pump concept is simple and can be home crafted. Like this.

It consists of spring-loaded sliding vanes.

 

[exenos]

Try a smog pump off of a large v8. Much more suitable for this.

 

[Doc Sprocket]

No, if you reduce RPM you get less pressure and more CFM, probably 5 PSI boost?

What about that little volume problem? Doesn't matter how fast you run that pump- 0.6CFM is miles away from 21-25CFM.

Either way- I think it was a neat thought, but not feasible.

You might want to look into "Smog Pump Superchargers". Cheap, attainable, suitable- according to a member of another forum who's using one on a lawn tractor, anyway...

EDIT- Dangit- Exenos beat me to the punch on the smog pump... LOL

 

[B.M.800]

Try a smog pump off of a large v8. Much more suitable for this.

.

EDIT- Dangit- Exenos beat me to the punch on the smog pump... LOL

Has anyone ever done this here?
A smog pump also be used as a turbo aswell?

 

[exenos]

Well not as a turbo but as a supercharger, no exhaust gasses here.
I don't think that any one on this site has used a smog pump as a supercharger yet, although I do plan on doing this with my opposed twin once I get the kart up and running. Looking to do about 10 lbs of boost and maybe 25+ hp.

 

[Doc Sprocket]

Has anyone ever done this here?
A smog pump also be used as a turbo aswell?

The difference between a "turbocharger" and a "supercharger" is what drives the compressor. A turbo is driven by exhaust gasses. The pump basically consists of two fans- the exhaust blows past one fan which drves another fan that pumps air into the intake. A supercharger is mechanically driven.

 

[mckutzy]

Im probably a little late into the game here and just wondering about a few things...let say this is attached to a 6.5hp clone, (like most of us have) Im sure it will do something , but a little past that the motor is still going to need more fuel. Like any forced induction systems fuel and air are needed in greater supply.
Is the little gravity feed carb able to keep up with supplying fuel or is it going to need a pump. Id reckon the latter.
Then(as I understand) there is a point not much farther from starting this that it is only going to get so much out of the motor before a mere motor upgrade will solve all the power requirements, IE bigger displacement.

Now obviously If someone for the hell of it decided to do this, hey cool, but there is a point where I think it just no point. (I faintly remember someone wanted to build/built a turbo charged fuel injected clone engine??)

 

[exenos]

I agree, I'd never do forced induction with any engine under 300cc. 14psi of boost would only net you a 13hp engine in perfect world (which this one isn't. Sigh) if your using a gx200.

 

[machinist@large]

Sorry, try again!!!

Nice idea; won't work with this equipment. It's right there in the ad description; its a VACUUM PUMP. It might be useful to power a vacuum chuck on a small machine, but that's about it. The only way you could increase it's volumetric output would be to make bigger; a LOT bigger.

The seller has a stash of obscure units with a narrow range of suitable applications. They may work just fine, but to try to hop one up/ mod it as a supercharger? If it turns you on to try it, knock yourself out; just be aware that the internal tolerances are quite high. The OP's reference to hydraulic pumps was fairly as a comparison was a good one, the tolerances are similar. And also like a hyd. pump, everything has to be perfect, or it will not work.

Just thought you folks might like the info.....

Edit: Just looked at it again; it only has 1/8" NPT ports. Save your money.....

 

[Doc Sprocket]

Nice idea; won't work with this equipment. It's right there in the ad description

To be entirely fair, what goes up must come down- or in this case, what goes in must come out. Basically, you could indeed push air (instead of suck) with it, even though it's entirely inappropriate to the task.

Edit: Just looked at it again; it only has 1/8" NPT ports. Save your money.....

I think I made mention of that earlier...

AND AGAIN- Can somebody who has more theory than me, PLEASE verify whether this 0.6CFM is anywhere near appropriate, or if such an engine would actually need about 25CFM as I was postulating???

 

[machinist@large]

Some tentative #'s

To be entirely fair, what goes up must come down- or in this case, what goes in must come out. Basically, you could indeed push air (instead of suck) with it, even though it's entirely inappropriate to the task.

Many vane type vacuum pumps use similar sealing designs to hyd. pumps for the sides of the vanes; in a hydraulic pump, they have moveable side/ sealing plates that are pressurised by the pump itself as it starts to push the seal plates against the rotor & vanes. In a vacuum setup, the negative pressure being generated inside the rotor cavity causes atmospheric pressure to force the seal plates against the rotor/ vane assembly. Trying to use it to generate more than ~3 to 5 PSI of pressure will compromise/ defeat the design of the system. The 15 PSIG of negative pressure listed for the pump in question is basically the stall limit if it was pumping against a totally sealed system with ZERO leaks. The higher the vacuum gets, the better the sealing system works. Negative 15 PSIG (PSI Gage) is just this side of a total vacuum; think outer space.

AND AGAIN- Can somebody who has more theory than me, PLEASE verify whether this 0.6CFM is anywhere near appropriate, or if such an engine would actually need about 25CFM as I was postulating???

Your figure of 25 CFM is most likely right on target. Another way to look at it, is the port sizing; if memory serves me correctly (if I'm incorrect, I apologize) when you go up a size in pipe dia., i.e. 1/8" to 1/4", 1/4" to 3/8" etc, you aren't doubling your flow rate, you are increasing it by a factor of 4. That's theoretical max; actual will most likely be lower. These loose figures also only apply for fractional pipe sizes under the 1" size (inch fractional pipe sizes don't directly correspond to the actual inside dia.) Another factor is that most small engine carbs have a venturi that is quite small compared to the inlet size to help maximize the pressure drop to help aid atomization of the fuel.

Ball park, I wouldn't look for any type of air pump (industrial or automotive) that wouldn't give you at least 50~75 CFM at at least 5~10 PSI for a start if you were looking for a match for your ~25 CFM engine.....

 

[Doc Sprocket]

Many vane type vacuum pumps use similar sealing designs to hyd. pumps for the sides of the vanes; in a hydraulic pump, they have moveable side/ sealing plates that are pressurised by the pump itself as it starts to push the seal plates against the rotor & vanes. In a vacuum setup, the negative pressure being generated inside the rotor cavity causes atmospheric pressure to force the seal plates against the rotor/ vane assembly. Trying to use it to generate more than ~3 to 5 PSI of pressure will compromise/ defeat the design of the system. The 15 PSIG of negative pressure listed for the pump in question is basically the stall limit if it was pumping against a totally sealed system with ZERO leaks. The higher the vacuum gets, the better the sealing system works. Negative 15 PSIG (PSI Gage) is just this side of a total vacuum; think outer space.

Gotcha. From simplistic angles, I was simply referring to the fact that the pump had an outlet port- from which air would theoretically pass as the inlet port applies a vacuum.

if memory serves me correctly (if I'm incorrect, I apologize) when you go up a size in pipe dia., i.e. 1/8" to 1/4", 1/4" to 3/8" etc, you aren't doubling your flow rate, you are increasing it by a factor of 4. That's theoretical max; actual will most likely be lower. These loose figures also only apply for fractional pipe sizes under the 1" size (inch fractional pipe sizes don't directly correspond to the actual inside dia.)

I believe you are correct on the flow rate increases- sounds very familiar to me. However- all these things apply to ALL pipe sizes. Pipe is sized by "nominal I.D.", and always measures well above that nominal I.D., even when you get into sizes well above 1". (I did some gas piping apprentice-type work several years ago.

 

[machinist@large]

Gotcha. From simplistic angles, I was simply referring to the fact that the pump had an outlet port- from which air would theoretically pass as the inlet port applies a vacuum.

Totally understandable. If the only types of pumps you've dealt with moved motor oil or water, then you probably wouldn't have to learn/ deal with some of the more bizarre units out there.....

I believe you are correct on the flow rate increases- sounds very familiar to me. However- all these things apply to ALL pipe sizes. Pipe is sized by "nominal I.D.", and always measures well above that nominal I.D., even when you get into sizes well above 1". (I did some gas piping apprentice-type work several years ago.

Glad to hear it; maybe I;ve still got some gray matter left, after all.....

 

[B.M.800]

(I faintly remember someone wanted to build/built a turbo charged fuel injected clone engine??)

There is an engine show here in PA, a guy has some sort honda/clone he has been modifying something fierce. I dont remember it it had a turbo or supercharger, but i believe it was fuel injected.

I think he has it on a little dyno stand aswell.

Practical? No way, but it is pretty neat.

 

[devino246]

AND AGAIN- Can somebody who has more theory than me, PLEASE verify whether this 0.6CFM is anywhere near appropriate, or if such an engine would actually need about 25CFM as I was postulating???

Well...

212cc converts to 12.9370337 cubic inches...which converts to 0.00748671 cubic feet

Multiply 0.00748671 by 1800, you get 13.476078

So, best case scenario (like you'd ever actually achieve atmospheric pressure in a ICE combustion chamber ), you're moving 13.476078 CFM of air and fuel through the combustion chamber.