Securing Baffles In A Plastic Fuel Tank

Hello All,

I'd like to see who has experience securing baffles into a plastic fuel tank. For reference, here is my tank/cell in question:

This setup has fuel cell foam in it, and has worked quite well with a mechanical fuel pump located on the engine.

I am currently working on a hanger to allow me to use an in-tank electric fuel pump for my upcoming efi conversion. As I understand it, baffling will be much more important with the high pressure pump/ efi. After doing a bit of research, I've learned that oil jugs are made from the same material as fuel jugs (high density polyethylene). So the plan is to cut up an oil jug into an appropriate shape, secure it in the tank, and hang the pump in this baffle. 

So, the question: Does anyone have experience using neodymium magnets to hold a baffle like this in place? 

I'd rather not drill through the bottom of the tank, and I'd rather not hang the baffle from the filler plate flange. This leaves securing the baffle with a magnet on the bottom of the tank, and one in the fuel tank. However, I'm not sure if the cheap magnets from the online retailers will be strong enough, or if they will be too strong and damage the tank wall. I'm also thinking that if the magnets get too close to the pump, they may cause problems. Thoughts?

Alternatively... Is there a nice low profile, self contained unit from a newer car that I can get cheaply? The thing stopping me from this path, is the 255lph pump I have on the shelf.

I'd be more worried about the magnetic attachment damaging the bottom of the tank or slipping out of place than I would be about whatever might go wrong from attaching the baffle using the flange bolts at the top...I say bolt it in using the flange bolts. If you make it a tight fit vertically in the tank that should minimize any potential for deflection.

I built mine out of aluminum. I did a pretty extensive write up in the tommy boy thread a few pages back.

Edit: halfway down page 32

Barring that, this is where the OEMs have gone to fuel pump modules.  They don't baffle the tank, they have the fuel pump sitting in ~1l of fuel as part of a self contained unit.

Thanks all, 

Duster I'll take a look for sure. My reason for using a plastic baffle is to avoid introducing things into the tank that could pierce it in a crash. I haven't had a chance to look at your design yet though.

Pete, that is what I am leaning towards, I haven't decided how to proceed yet.

A half way solution is to use the oil container as the sump for the pump and locate it with the fuel cell foam. Also make sure the return port goes straight to the sump. Some applications wind up with a small low preesure pump to feed the sump from the main tank.

Or you could build or buy a surge tank... Current tank/pump supplies and returns from surge tank, pump from surge tank feeds motor, fuel rail return (if applicable) feed back to surge tank.

I made my 3quart system from an old coffee maker tank, a 300LPH Quantum pump and a bunch of AN tube, hose and fittings.

If you go with a surge tank just be sure that any safety regs you have to meet allow them, some don't.

I'm using wiffle balls. If it works for monster jam, it'll work for me.

Ranger50 said:

I'm using wiffle balls. If it works for monster jam, it'll work for me.

Just be sure to test them for fuel safety first, it seems that the quality name-brand wiffle balls survive being submerged in gas but some cheaper ones have been found to dissolve...and again be sure that your safety regs don't require a specific foam in the fuel tank, some very stringent rulesets for classes where fuel cells are required do.

Also - Holley Hydramat is the shiznit.

In reply to Kendall_Jones :

That was my first thought. This is exactly what it's for.

We built a surge tank for our Westfield, it solved the starvation problem quite nicely. But it sure adds a lot of potential points of failure to a fuel system.

I built a surge tank of sorts for the MG that lived inside the tank. The trick is to dump the fuel return line into the sump. We were able to get a Miata to the point where it wouldn't fuel starve in T1 at Thunderhill until it had less fuel than it needed to complete the rest of the lap, and the key was the in-tank fuel return routing. This could potentially lead to fuel heating, but I don't think that's really a concern until you're low enough that you're only pulling out of the sump - which is beyond the point when the unmodified car would still be running.

In reply to Keith Tanner :

Keith,

Do you have a link to your setup somewhere? My idea with the plastic tub held in place with magnets at the bottom of the tank is to dump the return in, and just have a couple small holes in the tub to allow circulation. After chatting with an electrical engineer I know, he didn't have a concern about the magnets near the fuel pump. I may just focus on this solution for now. 

I would love to use Hydramat, but it costs more than the rest of the system combined at this point. 

Using the foam is a good point, that is what ATL recommends for their sump. I have some foam in the tank, but not enough currently, and I'm not sure I have confidence that the home brew sump will stay in the bottom of the tank. It's tempting to just get a cheap 2002 Camaro replacement pump assembly and use the sump/ full assembly from that. Although that would require a larger hole in the cell and rerouting the fuel lines.

A surge tank is a good idea, but beyond the current scope. This is a naturally aspirated, under stressed engine, running around on 225 tires.

From what I'm seeing available for off-the-shelf solutions, the sump will not need to be very big, the bottom half of a quart bottle of oil may do the trick.

My MG solution involved cutting the tank in half and using some weird stuff I found in there. Not something you want to emulate :)

In your case, I'd build a sump that attached to the pump. More like what Dusterbd13-michael did. You said you didn't want to hang it from the flange, but that's a good option. Especially since the flange appears to be in the steel cover. If you size it right, the sump will sit on the bottom of the tank. You'll want some way for fuel to get into it - on some oil pans, we used hinged flaps for maximum effectiveness, but just some holes will work.

Some prior art to look at.

A surge tank is easy. You just need a low pressure fuel pump that can flow as much as the engine needs and a cylindrical tank. We built ours pretty quickly, and since it doesn't need to be high capacity it'll fit in all sorts of nooks and crannies. But there is that points of failure problem.

GameboyRMH said:

Ranger50 said:

I'm using wiffle balls. If it works for monster jam, it'll work for me.

Just be sure to test them for fuel safety first, it seems that the quality name-brand wiffle balls survive being submerged in gas but some cheaper ones have been found to dissolve...and again be sure that your safety regs don't require a specific foam in the fuel tank, some very stringent rulesets for classes where fuel cells are required do.

Where I race, nobody cares.

Lots of good suggestions here. Thanks all. Just a reminder I am trying to avoid putting another metal assembly into the tank to keep items that could cause a puncture to a minimum. For now I have the cheapest 2001 Camaro pump assembly and some magnets on the way. One way or another there will be a solution.

Ah, hadn't considered you might try to crush the tank. You're thinking of the plastic tank as sort of a bladder for the steel housing. Got it.

I'm wondering about building a # shaped set of walls out of polyethylene that you could feed in through the pump access hole. Scallops along the bottom allow fuel to move, but you put the return in the center one. They lock together and are self-supporting and located by the walls of the tank, but can collapse if the tank changes shape. Make them half the height of the tank so you can assemble them.

Example drawing, not to scale.

These Pinto  guys sure are sensitive about their fuel tanks rupturing...Kieth nailed it though. Will work for sure and cheap.

Great idea Keith!

Edit:

Guilty as charged Turner hahaha

So, the cheapo fuel pump assembly came in... 

Its hard to contain how stoked I am that we can get this level of hardware for $50.

For those as curious as I am, here is the breakdown:

2001 Camaro 5.7L Fuel Pump Amazon Special:

Mass production is a wonderful thing. 

The cool part is that the pump inlet looks like it prioritizes fuel outside the basket, until the outside filter goes dry, then starts pulling from the basket reserve. While the Walboro looks like it could fit in the molded sleeve, it has a different inlet geometry so I don't think it will work with the inlet valves.

As you can see, I got excited and broke the level sender resistor, no worries for me as this is a Chevy part, and I already have a Ford sender.

Another cool part about this pump is the fuel pressure regulator on the return line. It also returns into the basket. Here is the regulator removed:

I'll be using the stock ford regulator at the fuel rail. While I could gut this regulator, I think I'll turn up a little dummy plug to keep the return flowing into the basket. 

The real value proposition here is the electrical plug. The pump comes with a wiring pigtail, and the hat already has a bulkhead, which could cost as much as the assembly to diy. 

Hopefully the cheapo parts don't bite me!

The regulator should be 58psi.  If you are running a Ford regulator below that pressure, it won't hurt to leave it in place.

I am surprised that the sending unit did not come with a wiring pigtail.  They usually do, the pins burn up and that is maybe 50% of the reason to replace the unit.

In reply to Pete. (l33t FS) :

Pete, it did come with a pigtail, I just didn't include it in the pictures. That's part of why it seems like a great deal to me. Any tips to avoid burning the pins up?