The fuel tank is done!
Highlights: 304 stainless steel (including the weld-on bungs, baffle, trapdoor, etc).
The stainless fill and vent tubes runs to the center section of the tank, filling it from there so it wouldn't be stopped by the trap door (additional fabrication work, but worth it).
We set it up and did a test of usable capacity (how much gravity fed out of the tank when it was level, until the stream reduced to pencil size. Mike referred to this as "sitting idle" usable capacity, citing that if one where to goose the gas a little, fuel would rush back and be retained near the bank of the tank for a while thanks to the trapdoor.
We then tilted the nose up to see how much more was left in the tank. Those number will be posted later... and we are happy with them.
To recap, last year Mike used cardboard to workup a form fitting template to the tunnel in the Fiero. We wanted to use as much of the space as possible.
He then taped the template together, and had hoped a friend of his that owns an industrial overhead door company would have found the time to cut out the more uniform parts and bend them in a brake for us. That didn't happen, so Mike had to put in
considerable more time with the plasma cutter and welder to put the tank together.
I'm at about $800 in materials in the tank (the flat stainless, tubes, bungs, stainless trap door).
Onto some pictures!
The rubber filler/breather tubes in the Fiero were sonic welded together, and both were in bad shape. So replacements were sourced. Here a picture of the old filler tube.
Here is the template and top part of the tank before we bent it to follow the 'dip' in the tunnel. This is a great image to show some of the complexity that went into the tank. After the bends were introduced, it made tack welding a few spots a two man job, as there wasn't a good way to get clamps to hold things where they need to stay and still be able to weld.
Before Mike welded on the additional bottom extension I suggested (it's still not the lowest part of the car, don't worry). I took the opportunity to take some pictures of the front baffle. There is an identical notch on the opposite side. He used the baffles as internal structures to secure many of the pieces to a 'core'. The position of the baffles was picked by where the tank straps sit, insuring rigidity.
Next up is the stainless supply bung. We discussed the idea of having a "blister" of some kind, that would create an internal 'dip' for fuel to drop into, but we decided against it, as that would have become the lowest point under the car, and a higher chance of something happening that would compromise the tank. Besides, with the trap door, it should keep fuel back there without issues, negating most of the benefit.
I talked about the fuel sender alright. Mike's measurements were spot on for it, meeting their requirement for space at the bottom of the tank, and let Mike recess the mounting point of the fuel sender. Here's a picture of it during a test fit, before he welded it into place.
In the tunnel there is this pocket that we originally wanted to make use of. Unfortunately, in our first test fit we found that it would be impossible to have enough wiggle room to connect/disconnect fittings and hoses, since the nose would be wedged into the pocket and the back of the tank would have to 'swing' up and down into position. So Mike had to cut off that portion and weld it back up. Capacity lost was minor, less than a quarter of a gallon.
Here's picture of it setup for our leak and capacity testing. There is some minor distortion/waviness to the metal. Stainless steel really dislikes being TIG welded in cold weather.
We capped off everything (including small breather vent) and filled it up to the top of the larger fill tube, which is above the tank. This, and rotating the tank, allowed us to make sure all the welds were tested. We found one pinhole. Not bad for so much welding!
After that, it was "idle usable capacity" test time! Place your bets! (we did!)
We used a 5 gallon bucket, and filled it up 3 times before the stream from the tank got to be less than pencil sized in width. That's 15 gallons!!
After lifting the nose a few inches, (now emptying it into a 1 gallon jug - empty windshield wiper jug) we got to a little over the halfway mark. So overall capacity is ~15.5 gallons. Given that the later, larger stock tanks were 11.9 total capacity gallons (and most people guess it's about 10.5 - 10.75 usable capacity), I'll take our 3 gallon increase!
Next weekend will be installation and then pressurizing the fuel system to check for any leaks there. If no leaks, we will begin the idle tuning of the car!
There is a vendor that makes exact replacement tanks, and they are top quality, made out of aluminum. We wanted to see if we could make something to hold more, and we wanted it to be out of stainless. And if we ran into issues, or hit a time crunch, that was our backup plan.
