So, I decided to put a new fuel tank into my 2007 Exige. There was absolutely nothing at all wrong with the stock 10 gallon tank. (Nothing except I can still recall the days when I drove a tiny P-car, the '76 912E, that had a 21 gallon tank would do better than 30mpg hwy. )
I'd had done some reading, much of it here at Lotus Talk, and learned about the possibility of fuel starvation in sustained left hand corners, and saw photos of what that could do to a superchared 2zz. I read about swirl pots and such fuel system additions. In the end, I chose to simply go with a larger capacity tank. One with good anti-surge protection built in. When I saw that many of the choices in this catagory weighed less than the stock tank, I was sold. (Even though such things are not cheap.)
Here is the tank I purchased: the aluminum 60L (15.85 gallon) tank offered by Elise-Shop. It looks to be as big as you can go without getting into the bag-tanks. (Which were also very interesting to read about. Great PDF with install instructions here: http://myelise.fr/entretien/entreten...reservoire.pdf
So, with a garage full of metric tools from my 914 days, no real experince working on a Lotus, and my wife's iPad as a shop manual substitute, I dove in. I originally estimated it should take about 4 good hours to preform the swap. (And, at a qualified shop, it might.) My friends had warned me about the 'british car rule', where things always take 3 time longer than you expect... And the warning proved accurate. Working at a relaxed pace, it took about 12 hours over two days to complete.
Step one was raising the car up. I don't have a lift, but I do have two sets of the big plasic ramps, and a good floor jack, so that got my car off the ground.
Step two involved removing much of the interior. Pulling the seats out is not too bad (Although the passenger side is not much fun to put back in.) The most annoying part is the seat belt cross bar. Once I had the rear speaker enclosures out, I found there is enough room to get a 1/4" socket wrench in there, it just takes a long time to remove the bolts.
Once that was out, I pulled out and cleaned the rear plastic. I also took out the center console, but that turned out to be unnessecary. Then I had to unbolt the driver's side seat belt reel to get clear access to the fuel pump firewall cover.
Then I could disconnect the fuel line, and the sensor and power connectors. Some minor blood loss was experienced due to all the sharp aluminum edges, but that was expected.
The filler tube can be disconnected from the engine compartment, with just a minor amount of contorntionism and swearing.
Next, I had to remove most of the underside aerodynamics and covers. On my car, step one is to take of the CF side skirts. Then the diffuser and engine undertray. Last, the shear panel, which isn't hard, it just has an awful lot of bolts holding it in place.
After that, I disconnected the emergency brake and shifter cables. Both are easy to disconnect, but the shifter cables are hard to see under all the tubes and hoses in the engine compartment. The two big "C" clips I could reach from above once I'd removed the oil cacther pots, but the "R" pins were tough. I was able to move enough of the hoses out of the way to pull one from above, and the second was easier to pull from below the car reaching up.
Getting serious now- I used my floor lack to support the tank while I removed the tank brackets. Then used it to lower the tank to the floor. (It was, of course, full when I did this!) I could then slide it out from uner the car, spilling almost no gas!
Here are some comparison photos of the stock tank and the 60L tank.
I weighed them both to confirm the numbers I'd found online. On my (super accurate!) bathroom scale, dry, and without the pump assembly installed, the new tank was just over 12 lbs, and the original was more than 26 lbs. This seems like a pretty sneaky way to remove mass and gain capacity!
Here is what the room the tank occupies looks like:
Those hard closed cell foam spacers have to come out. That is where the larger tank gains it's volume.
I transfered the stock pump assembly into the new tank. I had no problems pulling it out of the old tank, and, as advertised, it dropped right into the new tank. The only real issue I found with the new tank is that the fill tube is larger diameter than the stock. This could be a benefit for those who also install a larger and faster fill assembly, but it does mean you have to make some sort of adapter to keep the original fill neck. So, I did that, at least for now.
Putting the new tank in was easier than taking the old one out. (Especially since it was empty!) You have to angle it to get it to 'go around the corner' in the frame, but that was not hard. Then I just did all of the above, in reverse!
I drove it around the neighborhood a bit after finishing, and it all looks good. I'm off to Buttonwillow this Friday to give it a proper running in. (As I drive really slowly on track- I'm a complete novice- If you see the burgundy stripes on white, go easy on me!)
I hope this article is useful for someone!