1 Topic by obsolete (edited by obsolete 2011-03-11 09:57 PM)

  • From: Mini-so-ta
  • Registered: 2010-09-08
  • Posts: 1,181

Topic: Homebrew baffling in a plastic fuel tank

I was wandering around a local junkyard today and came across a very complete '90 Beretta.  Amazingly, nobody seemed to want any parts off this thing.  Examining it reinforced the fact that I was an idiot to buy an '89.  Not only did the '90 get the 3.1 MPFI instead of the 2.8, but it has a sweet plastic fuel tank.  Unlike my tank, this plastic one hadn't rusted at all...

We have an annoying fuel starvation problem below half a tank (yeah, half).  So, the gears started turning.  If I buy this plastic fuel tank for $25 (what a steal!) and add some baffling, I can simultaneously solve our fuel starvation problem and get rid of old rusty mess that's currently under the car.

So, when it came to what to use for baffling, my first thought was black ABS, as that's what the tank appeared to be made out of.  A little bit of research told me I was wrong, and that ABS is not suitable for submersion in gasoline.  Apparently the stuff to use is HDPE, specifically fluorinated HDPE.  The two best sources of this that I've been able to find are the white translucent Nalgene bottles (the kind you used in science class, not the transparent polycarbonate ones you take hiking), or just regular plastic gas cans.

So, I'm thinking about cutting up a Nalgene bottle or small plastic gas can to make a trap-door style baffle around the fuel pickup, using little brass hinges on the trap doors.  I'll glue the the baffle to the tank floor with JB-Weld.

As I'm sitting here, basking in the glow of what appears to me to be a brilliant idea, I can't help but think that like every other idea I have that appears to be brilliant at first, this plan is actually fatally flawed.  Maybe JB-Weld won't stick to the tank?  Please, let me know what you think.

It was too snowy for a lot of exploring, but I did make a "Down on the Junkyard" find of my own: this 50s Buick Century.  And the guy said "we don't have a lot of old cars" when I was asking about Beretta stuff.

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  • jrbe
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Re: Homebrew baffling in a plastic fuel tank

There are some fords that use a venturi off of fuel pressure from the pump to suck fuel from the bottom of the tank into the reservoir/pump housing.  Then the pump sends pressure partially to the venturi and the engine.  Im pretty sure the early 2000 maybe up to new fords had this style.  It was all part of the fuel pump basket/float.  If you have a large fuel pump access cap you might be able to fit one of these in there.  Maybe even convert your float to it.  This style is sensitive to the fuel pump, get one big enough to not have to worry about fuel pressure dropping off with your hp.

Chevys use the same venturi style but im not sure which models use it.  You might be able to find a direct drop in that has the venturi/reservoir setup.  A decent description here, http://www.corvetteproblems.com/general … ide-frame/

-Killer B's (as in rally) '84 4000Q 4.2V8. Audis never win?

3 Reply by jrbe (edited by jrbe 2011-03-12 05:17 AM)

  • jrbe
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Re: Homebrew baffling in a plastic fuel tank

For holding it down, a properly sized aluminum rod with rubber vacuum caps as cushioned feet that push on the bottom of the reservoir and the cap should work if theres something locating it from slipping side to side. 

Some of the venturi reservoirs have springs to help push them to the bottom of the tank.

You may be able to make a flap door reservoir like you said but it will be a pain.  Fuel slosh will distort the plastic and have the check flaps leaking.  You might be able to reinforce them with stainless pieces riveted through the plastic.

-Killer B's (as in rally) '84 4000Q 4.2V8. Audis never win?
  • From: Houston (Spring) Texas
  • Registered: 2010-02-22
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Re: Homebrew baffling in a plastic fuel tank

Dont do it.
It will fail tech

quite simply: use your existing tank, or buy the ATL fuel cell from the Lemons store (which is the best deal on the internet)

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  • From: Columbus, OH
  • Registered: 2009-05-26
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Re: Homebrew baffling in a plastic fuel tank

I'm not quite sure it would fail tech if the tank mounts in the oem location, is an oem tank, and hasn't been modified on the outside.  I do NOT think it would be a good idea to put any fasteners at all through the tank walls, though.  (ie, even stainless rivets.  don't do it!)

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  • From: Davis, Ca
  • Registered: 2009-04-30
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Re: Homebrew baffling in a plastic fuel tank

Any mods to a fuel tank will be subject to intense scrutiny...     Stock tank in stock location is OK, beyond that...  Well,  it'll be difficult to get through tech...   
   
From a purely performance point of view, I've seen most home-engineered fuel starvation tricks work out poorly..

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  • From: Van Nuys, CA
  • Registered: 2011-02-11
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Re: Homebrew baffling in a plastic fuel tank

Why not just get some fuel compatible foam and fill the bottom of the tank with it to decrease the sloshing?

http://www.summitracing.com/parts/SUM-290190

That's what its for, and being foam can be squished into a small hole, but left big enough to fill the bottom of the tank.

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  • From: Atlanta, GA
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Re: Homebrew baffling in a plastic fuel tank

Plastics like polyethylene that are very chemically resistant are also highly resistant to the chemicals that make up most adhesives.  JB weld just isn't going to hack it.

The fuel system is not the place to take shortcuts.  Leaks will get you black flagged and trailered.  Buy a new OEM tank if your's is rusted out.  The OEM rule refers to the tank that the manufacturer installed in its stock location.  I'd only consider the plastic one if it was an exact fit.

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  • From: Hayward, CA
  • Registered: 2010-03-23
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Re: Homebrew baffling in a plastic fuel tank

HDPE, nothing sticks to it.

if you make a cut in that thank you'll have a hell of a time sealing it up again.

1 quart surge tank at the front of the car, with 2 fuel pumps.

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Re: Homebrew baffling in a plastic fuel tank

mackwagon wrote:

1 quart surge tank at the front of the car, with 2 fuel pumps.

+1

Surge tank / swirl pot should cure fuel starvation issues. Just don't make a 1.5 gallon 'fuel bomb' like we did before common sense prevailed!

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  • From: Mini-so-ta
  • Registered: 2010-09-08
  • Posts: 1,181

Re: Homebrew baffling in a plastic fuel tank

Thanks for all the feedback, everyone.  The '90 tank is an exact fit, OEM plastic version of our existing tank.  I don't plan to cut or puncture it in any way, so I believe it will pass tech (of course, John has the final say).

st_rage wrote:

Plastics like polyethylene that are very chemically resistant are also highly resistant to the chemicals that make up most adhesives.  JB weld just isn't going to hack it.

This is what I was afraid of.  I did look at the foam--Summit seems to have a pretty good price on it.  It would take around 10 of those blocks to fill up our tank, and would probably screw up the fuel level sender.  Oh well.  I'll ask the rest of the team what they want to do; nobody seems to want to chip in for a fuel cell at this point, and I'm not going to finance it all myself.  Maybe we'll just leave it the way it is, and come in for fuel every hour...

Former chief proprietor and lead bad idea generator of Binford "More Power" Racing, 2010-2013: humbly self-proclaimed the best Chevy Beretta in Lemons history.
  • From: Mini-so-ta
  • Registered: 2010-09-08
  • Posts: 1,181

Re: Homebrew baffling in a plastic fuel tank

mackwagon wrote:

1 quart surge tank at the front of the car, with 2 fuel pumps.

I thought adding a surge tank was forbidden.

Former chief proprietor and lead bad idea generator of Binford "More Power" Racing, 2010-2013: humbly self-proclaimed the best Chevy Beretta in Lemons history.
  • jrbe
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Re: Homebrew baffling in a plastic fuel tank

The reservoir i was talking about was stainless reinforcements in a plastic reservoir box that slips into the stock tank through the fuel pump access.  No holes through the stock tank or messing with it, just through the added reservoir.  Sorry, i guess i didnt make that clear.  flap doors to let fuel in and keep it in.

  If you could find the right size container that slips in and make sure the doors dont get hung up on the pump or sock filter the pump might be able to hold it all down.

-Killer B's (as in rally) '84 4000Q 4.2V8. Audis never win?
  • From: Mini-so-ta
  • Registered: 2010-09-08
  • Posts: 1,181

Re: Homebrew baffling in a plastic fuel tank

jrbe--yeah, I think that would be the most practical approach.  I'll go back and check out the tank again some other time.  I think it has a decent sized access hole.

Former chief proprietor and lead bad idea generator of Binford "More Power" Racing, 2010-2013: humbly self-proclaimed the best Chevy Beretta in Lemons history.
  • JThw8
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Re: Homebrew baffling in a plastic fuel tank

jrbe wrote:

The reservoir i was talking about was stainless reinforcements in a plastic reservoir box that slips into the stock tank through the fuel pump access.  No holes through the stock tank or messing with it, just through the added reservoir.  Sorry, i guess i didnt make that clear.  flap doors to let fuel in and keep it in.

  If you could find the right size container that slips in and make sure the doors dont get hung up on the pump or sock filter the pump might be able to hold it all down.

obsolete wrote:

jrbe--yeah, I think that would be the most practical approach.  I'll go back and check out the tank again some other time.  I think it has a decent sized access hole.

We had ordered one for our fuel system and ended up not using it.  Need a pretty good sized access hole but once you know how much room you have to work with let me know, we'd probably make you a nice deal on the one we bought smile

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