Aeration of fuel - is it a real problem or not.

[STINEY]

I have noticed a growing trend of people noticing problems that they are tracing back to the aeration of their fuel.

Long and short of it, the added oxygen is causing some undesirable chemical processes, deterioration of lines, pumps, etc.

My thoughts are related to fuel tank modifications, specifically return lines being added to older tanks.

IF there is any validity to the above claims, wouldn't it be a good idea to run a new return into or near the bottom of the tank, rather than the top?

Discuss please....

[JeffMcKC]

I think your mixing up Oxygenated with Aerated

[TheSilverBuick]

Ethanol is an acceptable substitute for "Oxygenate Additive" in fuel by the government as well.

Formerly tetraethyl lead, then MTBE, and now Ethanol.

[STINEY]

As far as mixing them up........ technically I understand the difference......... but the stuff I'm finding uses the terms loosely, so I tried to throw them both in there to cover all the bases.

If air is introduced into the fuel, and air has oxygen in it, and chemically the fuel absorbs some extra oxygen atoms, wouldn't that be oxygenating it?

We know ethyl alcohol will absorb water from the air, and water has oxygen in it, so it seems possible to me.


I'm just planning out where my return will go. I want to separate it from the pickup to keep the fuel temps even (crossflow the tank) and am wondering if it would be better to return IN the fuel instead of introducing a stream that is splashing down inside the tank.

Splitting hairs I know. A return down low could also double as a drain. I'm leaning that way, but most of what I see is returned to the top. Is this just because its what everybody else is doing? Just thinking out of the box...

[TheSilverBuick]

The only issue I'm aware of with aeration caused by the return line putting physical bubbles in the fuel pick and causing pressure drops in EFI systems. Carb's have a vent to the air anyways so air around the fuel shouldn't be much of an issue, and the bowl(s) let the bubbles settle out. Gasoline has had plenty of time to absorb air at the gas station, as they aren't pumping nitrogen into the tanks as they get lower. Not to mention how much aeration occurs in the gas tank even with out a return from simple acceleration, braking, and turning causing waves and sloshing. I'd say its a non-issue.

[TheSilverBuick]

I don't see why you couldn't put a return line at the bottom as long as the fuel pump has enough capacity to push against the head level of fuel in the tank, which can't be more than a couple psi. My Thunderbird's return is under gas until at least the half tank mark.

[JeffMcKC]

Oxygenated is a Molicule in the fuel, if you have it you have fuel present. Aerated is the lack of fuel, that would be a issue but not the same. Aerated fuel can be baffeled and controlled. Also air is not made up of just Oxygen

Aerated fuel bad, Oxygenated fuel good.

[JeffMcKC]

The only issue I'm aware of with aeration caused by the return line putting physical bubbles in the fuel pick and causing pressure drops in EFI systems. Carb's have a vent to the air anyways so air around the fuel shouldn't be much of an issue, and the bowl(s) let the bubbles settle out. Gasoline has had plenty of time to absorb air at the gas station, as they aren't pumping nitrogen into the tanks as they get lower. Not to mention how much aeration occurs in the gas tank even with out a return from simple acceleration, braking, and turning causing waves and sloshing. I'd say its a non-issue.

It can be a major issue in a holley carb, the bubbles can get down and be sucked into jets, you need to match the hole size in the needle to the fuel used and not try to make up for it by using higher fuel pressure. New Bottom Feed trying to control float bowl areation

example

http://blp.com/cart/index.php?main_page=product_info&cPath=65_108_268&products_id=578

http://www.facebookvideodown.com/dyno-testing-at-blp-needle-seat-r-d-with-1290hp-single-4-bbl-e-57382.html

First part is a .150 N&S at I believe around 5.5 psi, the second part is the new design and low pressure, a 6.90's pass.

http://www.youtube.com/watch?v=s-q1e...f4ko9UfKYLBMN0=

[BKBridges]

Aeration can be a problem if there are stagnation points in you fuel system allowing bubbles to collect/coalesce. Once they get big enough they can travel onward to the injectors (EFi stuff) and unless you're running a flow-through return system or have scienced out your fuel rails with bubble rejection designs (big engineering theme in early OEM rail designs) you may get a shot or two of air into your motor instead of gas. In the wimpy stuff I build and drive its not super important, but it can be a big problem on big HP race cars. Not sure how youd aerate the fuel without having a fuel leak at the same time (pump inlet side of the fuel system). Sucking air through a crack or loose fitting is usually the cause unless youve uncovered your pickup in the tank while driving, which is just basic sucking air.

[TC]

On a carb motor the biggest problem is aeration in the float bowls by running to much fuel pressure.........

[Barry Donovan]

a return at the top or bottom..I don't see what would stop aerating a leak.

that is a unique problem. if you got a pump at the tank, the whole ride is pressured..where would air be? it would have to be prior to pump.

the full return stuff is very nice, and for some a better gas station does need to happen. I found the one that uses nitrogen enriched (shell?) but that is me and my runted stuff.

[CDMBill]

This is the Aeromotive sump I am adding to my stock 20 gallon tank. The two possible outlets are om the bottom and the return is the one higher and to the right. It is intended that the return flow into a solid fuel mass but as that isn't always the case it is baffled form the outlets. The more open outlet is preferred for most applications They are separated to avoid cross siphoning. I'll use the second one for a fuel temp sensor. The tank mods are those suggested by Aeromtove and are intended to fix both drag strip and auto-x aeriation issues.

Those videos posted by Jeff are a revelation in terms of what's happneing inside a float bowl.





I'm also adding these one-way gates on each side of the sump and the tank will have dividers to force fuel flow to the gates.

[milner351]

Those clear float bowl videos sure make jet extensions look like a really good idea.

That aeromotive sump is quite a piece of hardware - it looks very deep - how far below the stock tank is that going to hang down?

Since the falcon fuel tank is new, never had fuel in it, I'm thinking now is the time for this type of modification.

[CDMBill]

This was my little home made sump when I put in a new stock style tank back in '05. It worked fine for the carbed set-up but has been an issue with the EFI as I have to keep the 20 gallon tank 2/3rds full to avoid exposing the the inlet on burnouts or braking.



That's why I'm adding the new sump. I added the dotted line on the Aerootive drawing to show where he bottom of my tank will be in relation to the sump. I also drew in the little section view to the left. The net is it will be a inch lower than the lowest part of the tank and will extend the 12" across at the very back of the tank. It won't be much different than what I have now excpet the return will come back to the sump instead of back into the full tank. On that return I have an extension line that retruns the fuel to the bottom of the tank in the middle to avoid mechanical aeriation.

[STINEY]

Now this is getting interesting.

Is the top of your old sump welded to a large cutout in the stock tank? Or is there a series of round holes cut in the stock tank to act as a baffle? It seems weird to me that you need 2/3 tank, but if the whole section is open I guess I can see how fuel would vacate the sump on decel or turns.

I'm heading your direction with EFI on a similar FOX mustang tank (although it is already a factory EFI tank), but I've heard where my setup goes lean on right turns in the factory configuration. I want make it the best scenario possible while its apart and fume-free.