how does the air get separated from fuel?

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fnschlaud4620

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I was just wondering if anyone could explain how this picture works in more detail. I am mostly interested in how the air is separated, does the filter do all of it or is it something special in the housing of the unit?

From this picture it appears fuel enters the filter, and "airless fuel" comes up through the center of the filter to the injection pump. The "airfuel" mix is pushed out of the top filter head opposite of where incoming fuel enters. I would think the pressure relief valve would be on the "airfuel" port returning back to the tank.

Am I correct or am I missing something?

21c3_1.GIF
 
Give Charlie @ AirDog a call. He will more than happy to explain the whole process to you
 
Being that pic is from FASS ask DieselDan , he would be more than happy to explain it.
 
The air bubbles hold on to the fuel molecules with their little hands. When you turn on the FASS, it makes so much noise that the air bubbles have to let go of the fuel molecules and cover their ears causing them to rise to the top .
 
RonA said:
The air bubbles hold on to the fuel molecules with their little hands. When you turn on the FASS, it makes so much noise that the air bubbles have to let go of the fuel molecules and cover their ears causing them to rise to the top .
Click to expand...

And that is why I have NO air bubbles in my fuel. LOL LOL
 
I just don't think the big name big dollar pumps are worth the money, I want to run an A1000 aeromotive pump, which seems to be king of the pumps as far as reliability. I just think a normal filter head can be modified to return fuel to the tank with a pressure relief valve, to eliminate air bubbles.

For the same cost I can have larger filters and the a1000 pump. Yes it is more hassle with plumbing, but the benefit of the a1000 with air separation is what I am after.
 
I figured that by the time you give 350 for the pump, 75-100 for a filter base and filter, Either a draw straw or a hellman sump, plus the time to get all the right hoses and AN fittings plus trips to the hose store, i would be way over the 499$ price of the AD150 so it doesnt even matter to me if it seperates air or not really, as long as it supplies the fuel and has a lifetime warranty. Tim
 
I believe the ideas are structured around the concept that water is heavier than diesel, and air is lighter. The pump draws from the top of the WS. The filter has a tube that runs down it and only fuel from the bottom is pumped to the engine, the return bleeds off from the top of the filter.

That's just my theory though


Its that compact package of the FASS/AD systems that makes them appealing. I'd much rather have someone mill a filter base to bolt on an A1000 and get the best of both worlds.
 
RonA said:
The air bubbles hold on to the fuel molecules with their little hands. When you turn on the FASS, it makes so much noise that the air bubbles have to let go of the fuel molecules and cover their ears causing them to rise to the top .
Click to expand...

Cocaine is a helluva drug!
 
I've never been convinced that the "separate air from the fuel" schtick is any more logical than magnets that clamp over your fuel lines to align fuel molecules...

They're good pumps, but I think that's just because they're good pumps.
 
Begle1 said:
I've never been convinced that the "separate air from the fuel" schtick is any more logical than magnets that clamp over your fuel lines to align fuel molecules...

They're good pumps, but I think that's just because they're good pumps.
Click to expand...

Air separation does work at a low flow volume...however I am not convinced the air and fuel are properly separated when the engine is under full load and demanding high flow volume
 
RonA said:
The air bubbles hold on to the fuel molecules with their little hands. When you turn on the FASS, it makes so much noise that the air bubbles have to let go of the fuel molecules and cover their ears causing them to rise to the top .
Click to expand...

Close Ron, but it's actually the #2's hydrocarbon chains that entrain the air molecules, so the noise makes the fuel molecules cover their ears (think of a caterpillar going belly-up...) :hehe:
 
The best method, that i've witnessed, to make air separate from a liquid is to pull it under a vacuum. When a liquid is in a vacuum, the air bubbles expand and rise more quickly than they do when under pressure.

Last time my fuel system had a vacuum was when my lift pump died and my VP had to pull fuel from the tank and through the dead lift pump. Engine ran really poorly until it shut down!
 
I never believed in that air separator theory, but I like the extra water separator and 3 micron filtration.
James
 
Well, If the process works the way I think it does I can not see the air being separated from the fuel when the pressure drops under high fuel need situation.

When the pressure drops because of demand the pressure relief valve returning fuel back to the tank should close, sending all fuel to the injection pump. The best I could see is having a line full of airless fuel for the pump but once that is all used (like in a pulling situation) then I think fuel demand would take priority to air separation.

Unless I am missing something.....

It would be nice if a representative from one of the major companies could explain it here for me. I wonder if there is any data that compares a non air separation system to an air separation system that measures the amount of air coming to the injection pump, not just before/after HP figures.
 
if you look at a properly built race car it will have a return style fuel system - always

and the regulator is never inside the fuel pump - sorry

when i build a fuel system i put the reg as close to the motor as possible

thats not for looks - i do it for a reason

the less distance there is from the outlet of the reg to the inlet of the injection (or carb) the less of a pressure drop there will be

it also helps get the air out of the fuel

the older fass pumps (stand alone) have a internal reg (like a holley blue pump has). they return the excessive pressure (fuel) to the inlet side of the pump. that type of system works, but barely. they actually create air in the fuel by design. the pump is almost constantly cavatating, and sounds like it too. thats where this whole 'airdog fuel preparator removing all the air outta ur fuel' crap comes from. and the 'quieter operation'. they do have a bypass style regulator - but its built into the pump not up front where its supposed to be

fass no longer sells the stand alone unit but the same thing is avail from (cant remember company name right now). best way to go imnsho is to get one of them and build your own system (or pay me to do it). put a bypass reg up by the motor and use a large i.d. return so that the pressure cant not creap. build a system like that and not only will your supply pressure be rock steady but the fuel will be more dense (like airdog is claiming)

hope that helps

don

*ps - best way to get air out of fuel is to start off with it that way. a bed mounted tank with a sump on the bottom of it

and a pump mounted below the tank

(fuel is being shoved into the pump instead of the pump having to suck it out of the tank)
 
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frtbummperandfasspumpmods003.jpg


frtbummperandfasspumpmods009.jpg


frtbummperandfasspumpmods016.jpg

(sharp edge of pressure side has not been deburred yet in pic) (that is how fass ships em tho)

get the idea?
 
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