Slosh tank...

[RUNWME]

I am making a slosh tank for my STV 2.5 EFI.

Gas tank pickup is in center (from top ) of 24 gallon tank. From there it will go to 1 gallon slosh tank. From bottom of slosh tank to EFI fuel pump. Return line will goto slosh tank also. Slosh tank will not be vented but main fuel tank will be.

This way I dont need a auxillary pump and can keep fuel pump supplied with fuel.

Will this work? My voltage output on my drag engine is minimal, and don't want to supply 2 fuel pumps.

Thanks
David

[Liqui-Fly]

That's a lot of work., A holley red pump only draws about 2 amps but yours sould work. I think that's how the one Jay Smith builds works. If you can run the return line down into the tank with a line so it doesn't aerate the fuel when it splashes back into the fuel.

David

[B.Leonard]

What is the purpose of a "slosh" tank? Why can't you feed from the main tank?

On my Sterling I moved the feed to the bottom of the tank in the back to ensure it is never uncovered and to make it easier for the pump (Holley red). High flow inline filter before the pump, canister water/sep after.

-BL

[Balzy]

I have not installed it yet. I was gonna do what you are describing, but what happens if you get air in the surge tank when you run low on fuel in the main tank and suck air through the pump? How does the air ever get out of the surge tank without venting it at the top of the surge tank to the main tank? I had mine set up similar but was using a water seperator/filter before the pump and had my return running into it. When I got air in the system it just kept circulating around. I could hear air going through the pump. Changed it to dump the return into the tank and took out the water seperator/filter and no more air.

[Liqui-Fly]

Hrere is how I rigged mine. There is faulkt in just about every system. You should burp Jay's I suppose.

My system (which I have only circulted in the driveway).

Main tank to fuel/water separator, seperator to Holley red pump. Holley red to slosh tank (bottom sump). Other bottom sump to the bosch pump. Return from motor to slosh tank (anti-aeration tube) vent from slosh tank back to return on main tank.

Bruce if your fitting is all the way in the back what happens when you get off the gas and the tank is low. Also the coast guard does not want pick ups on the bottom of tanks....main tanks especially.

David

[B.Leonard]

I'm never off the gas ;) :)

Seriously, the stock pickup was at the back but at the top. The problem then was running 3-5 gal of fuel in a 22 gal tank would cause the pump to loose it's draw due to the pickup being uncovered from the boat bouncing and having to go straight up 12" made it even tougher.

I never noticed the problem with the stock motor cause I always had the tank full or near full. With the mod motor using race gas I dump in 5 gal at a time. That is when I noticed the pump running out on long runs at WOT. I also had it vapor/bubble lock on me at the dock once and had to perform CPR on the tank to clear it :rolleyes:

Is this what the slosh tank is for? Or is it nec for the bosch efi pump?

-BL

[Liqui-Fly]

I ran without one but with the new fuel tank position (pick up not optimal) and the desire to modify I don't want the motor ever getting dry shots. It's certainly a Best Pratice to put one in.

David

[Techno]

The slosh tank is to provide uninterupted fuel to the engine. Even with a bottom mounted tube you could suck air where the slosh tank is always full. It's a tiny version of the main tank with it always being filled at the gas station, never low- in affect.

If you suck through a slosh tank I think it won't be a slosh tank anymore. I thought on this and whenever the pickup sucks air it will place that air into the slosh tank (it would also need to be filled and purged on first use!). The air pockets at the top and the fuel being sucked at the bottom. Everytime you suck air more is captured and you now have a tiny version of the main tank. It will suck air now and defeat the whole purpose of having one- in fact is worse than none since it will remain in this situation of being an empty tank.
If you run a return from the slosh to main tank it would have to go under the fuel, some kind of fitting added since there isn't a 2nd one.This will only work if the return line is pressurizing the tank, but it's under vacuum to suck gas from the main????? The boshe supplies 6 ozs and returns 2, thats a negative.
If it's above fuel it will suck air instead of fuel. I don't see anyway of getting the benefits of a slosh tank without running a supply pump to keep it filled. Even running a pipe from main to slosh- off the bottom could suck in air.

B.Leonard I think a better solution for your situation is to install a 6 gallon portable tank and use it for the good stuff. This tank would be good to a couple gallons at least without a slosh tank and even better with one. If your huge tank is suppling fuel when 1/4 empty imagine a tank 1/4 the size.:rolleyes:

[B.Leonard]

Yeah thought about a new smaller tank. Figured I try the bottom pickup/fitting first.

With the fitting only 3/4" above the bottom it should work with as little as 2-3 gal I would think. Unless turning sharply and accelerating at the same time (on the gas).

-BL

[RUNWME]

Techno
I agree with you about the slosh tank trapping air if you are sucking through it. I am going to give it a try and see how big an issue it will be.

I put together a pull through slosh tank. Basically it is a 1 gallon fuel jug (1.98 at local hardware store) and I tapped the cap with a barb fitting for 1/2 fuel line fitting. I drilled the fitting and drove a brake line through it where it will pick up fuel 1/2 in from bottom of the tank. I connected this fitting to my weldon pump. Also on the top of the slosh tank, I tapped installed a bulkhead fuel fitting to allow fuel from the main tank to fill.

I turned on the weldon pump and very quickly it emptied the air from the slosh tank and started pumping. (I turned it on one side to completely allow purging)

I still have my return line going to the main tank.

I am going to try it this this weekend and see how it is working. If it doesn't maintain at least 1/2 full, then I will realize little to no benefit. If that is the case, I will add 1 more fitting to the top of the tank (vent back to main tank) and install a supply pump to keep slosh tank filled.

My total investment right now including tank,fittings and pipe is aprox 13.00

[Raceman]

BL, I'm with you. I've never run one and never seen the need. I can understand it on a roundy round boat, or MAYBE a drag boat where somebody's trying to run minimum fuel levels and make sure they can get it all. I sho' can't see it on a lake toy.

[Liqui-Fly]

When I'm out there hammering across 2 footer with a 1'4 and my fuel pressure light continually goes off I know I have a problem. So I guess it depnds.

David

[RUNWME]

Raceman
The reason for me having to install it is this. My STV has a 22 gallon tank. The fuel pickup comes from the top (no sump style) and goes down into the center of the tank. My tank is long.
With my carb motor, never had a problem. With my efi engine, I was running along in rough conditions and fuel pressure gauge was reading erractic as its picking up air. Engine even died one time due to fuel starvation with approx 10 gallons of fuel left in the tank :(

I don't want to add a slosh tank, but its either that or not run my fuel below 1/2 tank in choppy conditions. When it is smooth, no problems until tank is really low (less then 3 gallons of fuel onboard)

I could move my fuel tank pickup to back and bottom of the tank (sump style) to resolve the problem as well, I was just worried that with my long tank, it would starve for fuel when coming to a stop on low tank.

[B.Leonard]

Center pick up on a long tank is definite problem unless the tank has some baffles. Even then, a pickup that goes straight up a tube for 10-12" is not the best setup for pumps that don't like restrictions on the suction side. Prone to bubble/vapor lock at low fuel levels.

Sounds like a bottom feed/sump tank w/ baffles is all that is needed. If you want better than that an accumulator might be better than a smaller secondary tank w/ two pumps.

I've seen accumulators for oiling systems in the automotive world, I wonder if somone makes one for fuel?

Raceman - I agree a red holley can keep up with some big motor applications, but I'm finding out that in the marine world (outboards) carbs, fittings, hoses etc. tend to have much smaller openings (needle seats, fuel manifolds, filters, fittings etc.) and might complicate the issue. This might be why some people have found a Red Holley to "not be enough". The pressure might be just a tad too low too keep up with all those restrictions. For example, on my Xflow carbs the fuel inlets that lead to the needle seat are only approx 1/8" diam!! And the needle seat is even smaller! Whereas on an automotive setup you never see anything that small (v8 stuff). That would make the application very sensitive to pressure variations.

-BL

[Liqui-Fly]

It is not a solution. Not to mention losing the ability to disconnect a fuel line without fighting back all the pressure created in the tank.

David

[B.Leonard]

That's absurd. When was the time Mr. Green Jeans commented on your fuel system setup? :D

What do all the race boats (drag, buoy, offshore etc.) use? I never looked that close till I had this problem :rolleyes:

You could put a valve on the bottom of the tank if it was a problem. I just plug it when removing the tank. Plug is a chunk of hose with a bolt jammed in it. You loose a little fuel while swapping the plug with your hoes or vise versa but nothing a rag can't catch.

If this setup works, I'm replacing everything with AN/stainless braid so it will be safe and durable.

-BL

[Liqui-Fly]

I would guess the Seebolds have this figured out. You tell me what you see in their parts list and you decide.

http://www.seebold.com/html/parts3.htm

[Balzy]

You are right, Seebold has it figured out. Item#343 (#8 FLAPPER CHECK VALVE) is the secret that makes the system work. I have talked to the Seebold's about it. Also notice the (4) ports in the tank? One is an overflow back to the main tank. That's the only to expel any air that might get into the surge tank. I still have my Jay Smith tank and haven't sold it because I still plan on installing it someday but have to have a 4th port put in it and get the Flapper Check Valve. Then you will have a true surge tank that doesn't trap any air and won't starve your motor until you run your main tank dry.

[Liqui-Fly]

I bought this from JEGS. It's called a nitrous enrichment tank. Have the motor return to this tank which flows down a tube to the bottom. This prevents aeration. The other fitting on the top goes back to the main tank.

[Raceman]

I believe the Seebolds live in a little different enviroment than most of us. Only time my boats would ever pull 4 or 5 g's in a turn was if I tripped it and was on my way through the side of the boat.

As far as the tanks with the fittings at the bottom in a sump being illegal.............by who????? My yellow boat is rigged that way through a Jazz fuel cell and I don't see a problem. As a matter of fact I think the design, along with the foam probably solves several potential ones, but have run it so little it's hard to say except for a guess.

BL, I don't know how we swung back to Holley pumps, but I still believe that they're adequated to supply any outboard we're likely to have. The 6 one barrel Tillotsens I had on an early V6 created the thirstiest outboard I've ever seen and it was sufficient there with a 4 PSI regulator. I've also got one on my Pachanga with a 540/575 HP Mercruiser (1150 Dominator Carb)and it's super thirsty too. The fuel pressure guage on the dash remains constant at WOT.

[Liqui-Fly]

A sump type tank, which is obviously the better choice, were legal then why in the World do 0.00 manufacturers produce such a tank in the marine industry?

David

[BarryStrawn]

Slosh or vapor tanks have been around motorsports a long time. Many people consider them necessary on fuel injected engines to make absolutely certain the high pressure pump is fed nothing but fuel, no air or air/fuel emulsion. The Kinsler tech manuals do a nice job of explaining how to plumb one. Not required for a carb engine since a momentary burp in the fuel pressure isn't going to cook the engine.

ATL makes a little box to go inside a fuel cell. It contains the high pressure pump and has a set of trap doors to let fuel in. This is the neatest way I have seen to do it. Kind of expensive unless you need to buy the whole system anyway.

The Coast Guard doesn't like any downhill fuel flow since a leak could siphon or drain into the bilge. So the outlet is supposed to come out the top of the tank and always stay above that level.

[Techno]

The entire fuel system is supposed to be designed in a fail safe method. If anything fails it's in a safe mode. Glass fuel bowls aren't fail safe and neither is any method that will allow a fuel tank to dump all it's fuel if a part of the system fails. Locating the fuel system below the tank can siphon the fuel if the lines or fittings fail.
I personaly don't see how a fitting at the bottom of the tank and a pick up tube at the same location will supply fuel to a pump any differently. The suction is still located in the same spot. This is for bottom fitted tanks and not RUNWME tank mod.
Another opinion is after all the SS hosing and all the other armor stuff you could just put in a slosh tank and have a safer fuel system. Guessing cost would be the same?
An observation is the seeming need to place the pump as low as possible, if the thing is mounted on the engines for some whats the diff? these things seem to be capable of pretty far suction lengths. A foot suction is just about nothing. It is better to reduce the suction lengths and restrictions but don't see the need for extremes that then place it under a safety concern, which is usually considered less important.

Illegal is incorrect. They don't like it and I think they don't allow a manufactorer to build a boat this way. There are many things you can do to your boat that the manufactorer can't. Install an over sized engine for one.

[Reese]

fuel cell is really a slick setup...the tank uses a slosh tank inside the fuel cell which incorporates an intank fuel pump. This is probably the most bullet proof setup available...but not cheap.

[Liqui-Fly]

Adding this JAZ tank with fittings, pump, relays, ect was around $400.

David

[RUNWME]

I tried out my inexpensive (approx 20 dollars with fittings) slosh tank this weekend and it worked perfectly. I went through choppy conditions, several 8500 rpm pulls and 1 high speed run at 9300 rpm with no bobbles or fluctuations in fuel pressure. I never ran the main tank low, so will post on how this system performs in those conditions ( I am geussing not great) but it is a VAST improvement over last weekend when the fuel pressure gauge fluctuated in rough water.

[B.Leonard]

That's good to hear.

The bottom feed setup solved my problem. I could run with about 2 gal in the tank.

Fly - The chopper works great after the tune up. It bites no matter where you put the plate now or trim. I was amazed, although you can feel a slight more solid pull if you keep it buried at the start. It is much smoother idling in gear in the no wake zones also. It had a bad wobble before that went away as soon as you spun up. Now, I'd swear there was a 19" 4 blade thru hub on the motor if I didn't know better :D I never thought a chopper could be made to work like that. (had the weed cutters taken off and some leading-edge roll put in near the hub only)

-BL

[Liqui-Fly]

BL you keep your trap shut or else you'll drive up the price on the old cheap inline wheels.

My new slosh tank set up kicks ass. Ran the snot out of her this weekend.