X180 ESPRIT TURBO FUEL TANKS-DIY - LotusTalk - The Lotus Cars Community
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post #1 of 59 (permalink) Old 10-23-2014, 10:14 PM Thread Starter
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X180 ESPRIT TURBO FUEL TANKS-DIY

Aaaahhh, rusty tanks...

Sooner or later, it'll happen to all of us.

Petrol with ethanol attacks the "Terne" anti-corrosion plating rendering it ineffective. Ethanol reacts with led and ruins the coating. Microbial growth damage it, too.

I found re-coating 26 years old tanks not cost effective and not acceptable from the reliability stand point.

Since there are several threads describing tank removal procedure, I'll just add a few observations and focus more on tanks fabrication and modifications.

1984-1988, Esprit Turbo cars have very specific tank configuration.
RH tank has a round sump from which an external pump(s) draw fuel trough the bottom nipple. Also, RH tank has a drain at the bottom of the sump. On the top, we have: a level gauge/sender and a fuel return nipple with a pipe extending down to the sump; this design supposed to serve as a swirl pot of a kind.

Preparation:
Emotionally unpleasant & brutal period of time during which the (un) lucky owner is required to dismantle everything in the engine compartment and above the tanks. Level of deconstruction (read: "destruction") is utterly depressing.

Removal:
1. Interference with seat belt bracket. No way around it. Use 4' crow bar and brute force to bend the top tank flange inboard. Use 1/8" plate to protect the bulkhead below the bracket. Push up and support the tank with piece of 2x2 inserted into the bottom hole. Wiggle the tank and roll it over the side.

2. Pulling out the LH tank is a grand PITA.
Follow the "engine drop" method to open up the gap on the left side.
First, the engine has to be lifted to facilitate engine mount removal (both sides have to be removed!). Then, engine may be lowered to open the cam tower-to-buttress gap. The gap between cam towers and the buttress is very tight, even when with the engine "dropped".
The cross-over balance pipe at the bottom of the tank fouls the well wall side. I've simply cut it off.
If the gap is still not large enough, go ahead and jack the LH rear body lifting point to gain another 1-2mm in the opening, or remove the left engine support (three, 8mm bolts with 13mm heads), and drop the engine further down.
BTW: Check these bolts for tightness, because they have a morbid tendency to vibrate loose. I'm going to add Nord-Lock washers to both supports.

RH tank comes out easier (!) providing the upper half of the Bosch MAFM/Fuel Distributor and the plenum cover is removed.
.
Tanks are heavy and awkward to manipulate. For convenience and better grip use small vice grips locked securely over the top flange. They act as a are very nice "handles".
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post #2 of 59 (permalink) Old 10-24-2014, 06:24 AM
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If your are going to replace the tank and have no intention to refurbish it then fill the tank with some water add some fire-suppressing foam and cut it into pieces and remove it that way. A cutting wheel on a grinder goes through the tank skin like butter. We cut one into chunks and bent the tank inwards and lifted it out in about ten minutes.

Of course, kiss the old tank goodbye.....

Tom Mieczkowski
1989 Esprit Turbo
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post #3 of 59 (permalink) Old 10-24-2014, 06:40 AM
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When I removed my tanks, the right side was the PITA.

Just proves, no two Esprits are exactly alike.

++++++++++

PS, Obviously Mr D doesn't use his crowbar enough, it's awfully rusty!


Atwell Haines
'88 Esprit
Succasunna, NJ USA


"Not all angels have wings." - Turbo R
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post #4 of 59 (permalink) Old 10-24-2014, 07:06 AM Thread Starter
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Quote:
Originally Posted by carbuff View Post

Just proves, no two Esprits are exactly alike.


I AGREE!

My tanks are not identical dimensionally! There is a slight difference in length and width between LH and RH! Height is the same.

To facilitate the installation, I'm going to make new tanks 1/2" smaller fore-aft and 1/2" narrower. Bottom balance pipes are eliminated. New design makes them detachable, so they won't interfere with tank re-installation. For that purpose a small sump had to be added to the left tank (with a second drain/clean-out plug, M12x1.25mm, standard Auto-Zone part).

Note: 1" nipples are made of a SCHEDULE 80 pipe (0.150 wall). Thin wall pipe (Sch 40) has a dangerously thin wall left after cutting the thread. Safety First!
.
P.S. To lift the engine, LH engine mount heat shields have to be removed (M6 screws with 10mm heads). Check the condition of your trailing arm bushing behind the vertical shield #39.
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post #5 of 59 (permalink) Old 10-29-2014, 06:19 AM Thread Starter
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1. Tank(s) Sizing and Dimensions.
Primary consideration should be an ease of fabrication and installation. Measure each tank individually, do not assume that the left and right is a mirror image! You may be surprised what you’ll find out. Subtract ½” from the length and width. When it comes to the height, the bottom of the new tank will be where your old tank bottom flange edge is now (mine are 11.5"). The new top will be where the old top is. No flange at the top is required. Use a paint pen to mark all dimensions, datum points and notes directly on the surfaces of each tank.
Important dimensions are: grounding straps caged nut-to-floor (datum), x-pipe nipple-to tank floor [not the same LH to RH !], filler neck location and its incline.


2. Materials
There are a couple of excellent choices in corrosion-resistant materials. Primary concerns should be: formability, weldability and weight.

a) Easy-to-Weld Highly Corrosion-Resistant 5052 Aluminum, ( 0.090-0.100” thick)
Good combination of weldability and resistance to salt water. Commonly used for boats, buses, trucks, and trailers, as well as for chemical drums.

b) Highly Corrosion-Resistant 5086 Aluminum, ( 0.090-0.100” thick)
Excellent corrosion resistance with good formability. Commonly used in marine applications, such as in ships, oil rigs, tanks, and pressure vessels.

c) Super-Corrosion-Resistant 316 Stainless Steel, ( 0.048” thick ?)
Molybdenum gives 316 excellent corrosion resistance. Used in a variety of marine and chemical-processing applications.

Buying materials: Don't forget to check an eBay and Amazon also.

Tank surface: LH= 1260 sq in, RH= 1340 sq in
Baffles: LH= 345 sq in, RH= 309 sq in
Density: Aluminum = 0.098 lb/in^3
Stainless = 0.29 lb/in^3
If you choose aluminum, use 0.090”- 0.0100” thick sheet for walls and tops; 0.06” sheet for baffles
If you choose stainless, your primary consideration should be weight and “oil canning”/warping of the large flat surfaces (stiffening beads will be necessary).

One 48”x36”and one 36"x36" sheet will suffice for both tanks. Additional, smaller 0.06” sheet for baffles can be ordered at the same time.

OE tanks weigh RH=24 lbs, LH=22 lbs. Aluminum tanks: RH=15 lbs, LH=13.5 lbs

All bungs/pipes/nipples (including x-balance pipe), should have at least 0.120" wall and be made of the same corrosion resistant material as the tanks. Do NOT use any carbon steel components (ex: Time-serts, mounting bolts, etc.)


3. Tank details, modifications and improvements.

Material used: aluminum.
- Eliminate x-balance pipe extensions and instead, add a ¾”-14 NPT (thick wall) weld bung to the RH sump to accommodate a short 1”OD pipe/nipple, which will screw in after the tank installation.
- LH tank: add 2.5” ID small sump w/3/4”-14 NPT weld bung and drain plug.
- Use stainless Heli-coil or Time-sert type inserts (use stainless only! Corrosion!) at the fuel return nipple (M12x1.5mm), fuel sender ring (M5x0.7) and grounding bolt blocks (M8x1.25 upgraded to 3/8”-16 w/threaded inserts).

- Note: The fuel level gauge/sender ring has 5 holes (54mm CPD), forming an irregular pentagon with following dimensions between the holes (center to center): 30mm, 32mm, 32mm, 30mm and 35mm. The 35mm dimension faces the tank outboard wall, positively indexing the fuel sender and float orientation.
- New marine grade Neoprene or Viton gasket is required. VDO 226053 Replacement Fuel Sender Gasket•2-1/8" bolt circle (54mm).

- Replace the grounding point “cage” brackets with a solid aluminum blocks of the same geometry (6 degree incline). Heli-coiled holes are perpendicular to the 6 degree (outboard) surfaces of the "cages"/blocks.
- Replace OE foam pads: bottom one with 3/8”-1/2” closed cell poly foam cut to the OE size (Zoro tools.com). Top pad has to be thicker. Alternatively, aluminum L-shape hold downs fastened to the top board/shelf could be fabricated to add required lateral stability.
- Depending on the foam thickness used, the grounding block up/down location has to be adjusted. The easiest way to determine block location is to insert the tanks into the wells, line up the inlet tube with the filler neck end, canter the balance pipe bungs in the side wall (large) hole and project the grounding bolt hole location onto the tank side. Weld the blocks according to your markings.

Note: It is recommended that Heli-coils be installed w/red Loc-Tite. Loc-Tite de-bonds when the heat is applied, therefore do not install them until after all the welding is done.




* TO BE CONTINUED...
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post #6 of 59 (permalink) Old 11-04-2014, 10:20 AM Thread Starter
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Left tank, more progress.

Note that all joints are welded inside and outside.
Safety = Job One!
Although I'm not planning on any "Dukes of Hazard" jumps, but a couple of G-s may happen if I hit the pothole.

This tank is fully baffled, an extra horizontal half-baffle was added over the sump opening.

Make sure that your 1" x-pipe extensions and sump bungs agree w/each other. It is prudent to "chase" the x-pipe bungs with 3/4"-14 tap before "closing" the tank.
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post #7 of 59 (permalink) Old 11-04-2014, 10:29 AM
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Great work!

2012 Lotus Evora S GP Edition #14/14
1995 Lotus Esprit S4
1991 Toyota MR2
1987 Renault GTA

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post #8 of 59 (permalink) Old 11-05-2014, 09:50 AM Thread Starter
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4. Heat shields
Left tank gets a significant amount of radiant heat from the header. You may add a Thermo-Tec blanket directly to the tank walls and bottom or to the compartment wall (the shiny side always towards the header).

5. Hold down boards
Use 18mm thick, 5 ply marine grade plywood, it is an excellent and durable material. Front mounting holes and rear slots are too close to the edges of the board. To mitigate this condition a ½” should be added to the rear edge and front holes diameter should be reduced. Fuel inlet clearance windows were too wide and too close to the edges creating some weak spots. Charcoal canister nest hole was too big and had to be moved forward to prevent fouling the cold air intake pipe. To preserve the wood add a couple of coats of linseed oil. If you decide to add some colour, use oil based alkyd enamel paint.
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post #9 of 59 (permalink) Old 11-05-2014, 07:52 PM Thread Starter
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Oh, and the most important thing!

To keep the tank and the boards dry in the future – fix these gaping holes at the fuel filler door hinges.
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post #10 of 59 (permalink) Old 11-05-2014, 09:44 PM Thread Starter
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Since these 84-88 ET tanks have no strainer screens in front of the pumps and the fuel filter is plumbed in AFTER the pumps (!) (common sense is not that common, huh?), Porsche 928 strainer will be incorporated into the RH tank sump (M37x1.5mm bung).

... to be continued.
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post #11 of 59 (permalink) Old 11-06-2014, 07:54 PM Thread Starter
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Right tank swirl pot.

The photo shows the plactic MB tank swirl pot surrounding the strainer where the fuel is drawn from the tank. The fuel return line enters the swirl pot perimeter via a venturi. The venturi allows the return flow to draw fuel from the bottom of the tank into the swirl pot allowing the swirl pot to remain full and overflowing, even when the tank is almost empty. In fact, when this system functions correctly the car should continue to run until the tank is almost completely empty with only the fuel in the swirl pot remaining. A full swirl pot prevents air being drawn into the strainer.

The swirl pot performs two functions. One is as a baffle to prevent cavitation in pump suction line when levels are low and fuel could be slopping around in the tank. The second, also with low levels, is to cool hot return fuel by mixing with cooler fuel in tank to help with hot starts.

Last pic shows the OE pot/sump at the bottom of the RH tank.
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post #12 of 59 (permalink) Old 11-07-2014, 06:19 PM Thread Starter
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PART II
LAYOUT and FABRICATION

1. Primary Datums.
Tanks have to be precisely located in relation to some key components like filler necks and the cross balance pipe.
Bottom of the tank is the datum surface in “z “direction. Grounding bracket surface is the lateral datum (in y direction). Filler tube continuity/alignment and balance pipe bungs determine the tank fore-aft and up-down position. Grounding bolt location is the fore-aft datum in x direction.

2. Layout
Measure each tank individually (you may be surprised what you’ll find out), and subtract ½” from the length and the width. Do not assume that they are the same! New LH tank is 1” narrower by design to facilitate installation. Both tanks are ½” shorter to mitigate any interference with the seat belt bracket.
Left tank final dimensions: 17.5"L x 14"W x 11.5H, tolerances= +/-1/4". New tank goes easily in and out the well clearing both cam towers.

3. Welding
For safety, each joint should be TIG welded inside and outside. Top of the tank is welded last, from the outside.
There are two ways to attach walls to the top and the bottom: “over” or “to the side”. In each case, the 2x thickness of the material should be added to the respective dimensions of the tank.
Tops and bottoms tend to warp when inlet pipes are attached and when welded to the walls. Adding a few stiffening beads could remedy this problem.
Some fabricators may insist on using 1/8” sheet. It is a matter of convenience for them (easier to weld), but it means 25% weight penalty and a higher material cost for you.
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post #13 of 59 (permalink) Old 11-10-2014, 07:12 AM Thread Starter
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INSTALLATION

1. Location and set up.
Tank has to be positioned in the well in such way that:
a) balance pipe bung is at the center of the round hole (inboard wall) and
b) inlet pipe should line up with the fuel filler neck.
With the tank L=17.5” there is an ample room for fore-aft movement/adjustment. Up/down adjustment and forward tipping can be controlled by adding foam pads between the tank bottom and the floor of the well.
Grounding bolt and the bracket fastens the tank to the wall and prevents any movement. Therefore the “block” should be fabricated as a last bit. Its thickness and location is determined by a) and b).
Usually, the "block" is specific for each tank and have a different angle depending on the position of the tank (determined by foam pads underneath). My old one measured 6 degree. My new angle is 7.5 degree.
A simple MacGyver/DIY gap protractor could be built using 3 wooden strips.
Two outer pieces are joined at the tip with a piece of tape forming a "hinge". Middle piece spreads two outer pieces apart when you push on its end.
Rubber band or a piece of tape holds everything together. Insert the strip between the tank and the wall, push on the middle strip. When outer strips fully contact the walls withdraw it and measure the angle.
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post #14 of 59 (permalink) Old 11-15-2014, 09:00 AM Thread Starter
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Pressure testing before final permanent installation is necessary.
OE tanks were tested to 0.3 Kg/cm^2 (~5 psi)
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post #15 of 59 (permalink) Old 11-20-2014, 09:24 PM Thread Starter
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Right tank is a little bit more complicated than the left.
"Real" swirl pot and Porsche 928 fuel strainer have been integrated into the sump.
Fuel return line will attach to the black tipped venturi nozzle (Cejn 11-208-9953), which mixes fuel from the Distributor with cold fuel from the tanks.

.
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post #16 of 59 (permalink) Old 12-01-2014, 03:54 PM Thread Starter
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RH tank baffles and 3/8" return line (Flouroelastomer)-in place.
Added a gusset to stiffen/support the balance pipe bung.
The forward/outboard upper corner had to be modified to clear the main wiring loom.
Next, the top will be welded on.

Fuel sender mounting ring has 5 (unequally spaced) threaded holes (M5x0.8, 54mm CPD), forming an irregular pentagon with following dimensions between the holes (center to center): 30mm, 32mm, 32mm, 30mm and 35mm. The 35mm dimension faces the tank outboard wall, positively indexing the fuel sender and float orientation.

In OE design holes are trough-and-trough allowing to draw off fuel by capillary action up the threads causing fastener heads and sender base corrosion.
To seal off bottoms of the holes, design had to be changed. Mounting ring was made thicker and holes were not drilled all the way trough (blind holes). Heli-coil inserts were installed with Loctite 271.
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post #17 of 59 (permalink) Old 12-01-2014, 05:05 PM
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I made some dwgs when I had mine fab'd
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post #18 of 59 (permalink) Old 12-01-2014, 06:52 PM Thread Starter
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Very nice. Since I did not plan to make more than one pair, I've drawn directly on the metal (with Sharpie pen and carbide stylus).

Inlet pipes were the most PITA job.
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post #19 of 59 (permalink) Old 12-02-2014, 06:19 PM
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sorry, I see there are differences. I thought you might compare against your dimensions while you were fab'ing so we could evaluate my dwgs before I publish for the community. mine fit pretty well but one pair of eyes can miss something.
nice work on your tanks!
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post #20 of 59 (permalink) Old 12-08-2014, 06:43 PM Thread Starter
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Pressure tested both tanks today. No leaks!
In addition to the weight savings, (RH=15 lbs, LH=13.5 lbs. 18 lbs savings),
I got unexpected bonus - additional capacity.
Left tank holds 11.5 US gallons, right one 12.5 US gallons.

Last edited by MRDANGERUS; 12-12-2014 at 04:59 PM.
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