Bladders & Foam

[JohnB_SPY8808053]

No - I'm not talking about beer. ;)

I was just wondering - has anyone replced their tanks with fuel cells or modified their tanks by adding a bladder or foam?

Thanks,

John B.

[tony soper]

I had an FIA FT3 ATL 60 litre cell in the Corse S that I raced in British GT's (now owned by Graham Scott)

Fitted just in front of the gearbox (alfa v6)

Either ATL or Premier can make one, the ATL cost about £1300 plus vat and that was in 1996

Hope that helps

[JohnB_SPY8808053]

Hmm - What about adding a liner/bladder to the existing tanks?

Any thoughts?

John B.

[rutthenut]

I fitted safety foam into my tanks when they were first made. Needed an 'access hatch' to get it in there, but that was easy on new tanks.

[roger001]

ATL sell baffle foam, but it will mean opening up the existing tank, but it is on my to do list.

http://www.atlltd.com/bafflefoam.htm

[JohnB_SPY8808053]

That's good to hear - I was wondering if anyone else had cut the top of the tank.

My idea was to take that a step farther and add a rubber liner:

http://www.jcwhitney.com/webapp/wcs/stores/servlet/ProductDisplay?catalogId=10101&storeId=10101&langId=-1&productId=265843&mediaCode=ZX&appId=384851

Then to put a short length of clear hose on the bottom port and seal the open end so I could see if any fuel leaked through the bladder.

Next I would fill the tank with foam, leaving space for a pick-up line from the top. I'm not sure a surge tank is needed as the bottom is pretty small to begin with.

Last I would seal the top with a thick alloy plate slighly larger than the opening that had bolts threaded trough it around the edges. This piece would go just INSIDE the tank with the bolts protruding through holes drilled around the edge of the opening. When tightened down, the rubber liner should form a seal between the 2 plates. The fill-pipe, pick-up and testing port would all be part of this plate.

I'm probably missing something but it seems like an easy way to make a decent fuel cell without spending $2000. Anybody have any ideas or opinions?

John B.


(accidentally posted the message before it was complete)

[chris.richard]

Just what size of hole are we talking to fill the standard Hawk tank? Is it impossible or just difficult through the sender unit or filler hole?

[roger001]

ATL metions "cut to size" baffle foam, so I guess it means cutting the top off a hawk tank, putting the foam in and re welding the tank.

better than the car going BOOM!

[JohnB_SPY8808053]

We're talking about the flat piece that the fill-pipe attaches to. I was thinking that the hole should be almost as wide (front to back of car) and about half as tall (side to side of car). Of course you need to leave room around the edges for the flange and bolts.

The foam pieces are much larger than the fuel-pipe and some of the them will have to be cut to fit. I think it would be impossible to get the foam in the tank properly without a larger hole to work through.

John B.

[colin artus]

My tanks are foam filled: the tank was cut in half and the bottom filled with ATL foam, then a horizontal baffle was fitted above the foam which a) keeps the foam in place and b) prevents the fuel from sloshing up the sides of the tank. The two halves were the joined together. I intended to run both tanks half full for racing as this would give enough fuel for the sort of sprint races we do here in the UK.

Colin

[chris.richard]

Has anybody actually handled the foam to be able to comment on compressability and re-expansion?

[SUSIT]

Cant recommend highly enougth that you all do this if you are keeping the tanks in the rear. Just spent an hour or so on the strat here's how the tank looks.
Stephen

[chris.richard]

Is this a caption competition?

[SUSIT]

Opps:D :D

[rutthenut]

Originally posted by roger001
I guess it means cutting the top off a hawk tank, putting the foam in and re welding the tank.

On my tanks, I had a removable panel on the top surface. This is about 7" x 5" and has the fuel filler neck welded on to it. A rubber (neoprene?) seal is used as a gasket between this and the tank itself, with metal plate below that which is threaded to accept small bolts (M5 / M6) every inch and a half or so. That clamps down nicely and is better than needing to weld the aluminium tank, although it would be more work in the first place.

No photos I'm afraid, my car is kept elsewhere at the moment.

The 'fuel cell foam' is actually more of a 'mesh' than you might expect for something of this description - a bit more like a nylon brillo pad with a very high ratio of space to material. It does therefore compress very easily, and seems to return to size just fine. Even though you could fit this in strips through the filler neck, you would also have to get your hand and arm in there to position it. If large pockets were left in the tank, this would reduce the effectiveness of the foam somewhat.

Also, if you are modifying the standard type tanks at all, I would strongly suggest that you fit some sort of baffle to reduce the tendency for fuel to run up the tank sides. I can get fuel starvation on longer, high speed, bends if run at less than quarter full. Although the tank is tall in profile, the outer wall does slope outwards and the cornering force does make fuel flow up and away from the fuel outlet. A simple downward-angled plate against the outer wall would probably solve that, although more baffling can only improve matters. Just make sure the fuel can easily flow back down to the fuel outlet too.

One final comment on my experience of using foam of this sort, is that I have found a tendency for some grades of fuel to 'bubble up' when filling then from the pump (fuel station pump, that is). You can see this easily when looking down the filler neck, as the fuel swirls hits the tank foam and gets somewhat aerated (sp?). Not a problem when filling the tank, although it can shut off the pump and require a bit more manual effort to fill it prooperly. But I think the same sort of thing can happen as the fuel circulates around the system when running.

Entering the tank from the fuel return line, it travels through the tank foam on its way to the outlet, fuel pump/filter, injectors and around again. This can lead to air bubbles appearing in the fuel, which can be ascertained by the fuel gauge reading high, which will return to normal if left to settle with the engine off. This can also mean that the engine will be running lean, but this only seems to occur if there is not much fuel left in the tank. With enough remaining fuel, the bottom of the tank will not contain aerated fuel and there should be no problem.

One prevention for this is to ensure that the route from fuel return line to fuel pickup is not too long and does not have to travel through too much fuel foam. Another prevention, or cure, may be to fit a swirl tank into the fuel system. To my mind, that is just overkill, but this sort of problem can arise - depending on the routing of your fuel lines into and out of the tank. Without foam in the tank, this is unlikely to show up as a problem.