85rotarypower

Well, there isn't much information about installing a fuel cell in an RX-7, so I'm going to document the install of the fuel cell I just picked up.

It will take me probably a week to finish as I haven't too much time to work on this, but its not a lot of work to install. Basic mechanical skills are required, and you have to know how to use a welder. But anyway, I'll get into the preparation for installing the fuel cell.

The fuel cell I'm going to use is a 15gal RJS economy cell with the foam removed to use a standard rod type fuel sender. The dimensions are 25 1/2" x 17 1/2" x 9 1/2". Its a fairly cheap fuel cell and just as good as an RCI or Jaz cell and comes with the foam. Only thing it doesn't have is a hole for the sending unit, but thats not a big deal as its not hard to put a hole in the top to install one.

The first thing you have to do is remove the rear carpet to expose the floor below. Chances are, you have already removed the original gas tank already, but if not, its not hard to remove. Just undo the two straps at the front side while supporting the tank with a jack, then when the straps are gone, just lower the tank. Remove the fuel level sender connector and fuel lines and get rid of the old tank.

Next, you have to find a way to take out the spare tire well. Its unfortunate, but if you want to use a fuel cell in one of these cars, you can't have the spare tire well. Anyway, I found the best way to take this out is to just use a cutting wheel on an angle grinder and cut it out. Drilling out the spot welds isn't easy and doesn't work well overall. Cutting around the tire well works best. The only obstacle is the two reinforcement rails at the front and rear.

This is as far as I have gotten so far. Its probably the hardest part of the whole deal as well as the spare tire well is a PITA to get out. Here are a couple pics of the fuel cell itself and then placed into the rear of the car, showing how well it will fit between the frame rails.

aussiesmg

iTrader: (1)

Are you going to drop mount the tank or sit it inside the trunk space, drop tanks make the weight a lot lower, lowering your center of gravity.

camocarl

iTrader: (5)

First off why are you placing the fuel cell inside the car? Why don't you cut a hole and drop in the fuel cell in were the original gas tank was, and make a frame around it? And when your remove the foam thats make it just makes it like any other gas tank. The foam is one of the most important components of a fuel cell. It is designed to reduce the slosh of the fuel and the chance of an explosion by reducing the air volume in the cell. If the cell does ignite internally, the foam absorbs the expansion and the energy of the explosion. At that point, the oxygen is used up and the flames go out. The cell must be filled with at least 80% foam to perform effectively. The foam only requires 3% of your total capacity. Why are you doing this? What are your plans for this car?

85rotarypower

Ok, I guess I should have been a little more clear. I will be drop mounting the cell to be about level with the floor for the hatch area. From there I plan to fab up a removable cover to keep the cell isolated from the interior, much like if it was mounted in a regular trunk. The picture was mearly to try to show you how wide the cell was compared to the car. If I were to just mount it in the car, I wouldn't have cut out the spare tire well.

As for removing the foam, its not really a required item, at least from what Ive been told. I really don't want to spend another $150 to get a tube type fuel sender when I can get a regular rod and float type for 1/3rd that price. The car will be mainly used on the street, but I plan to take it on the drag strip once in a while and mabey some autocross. I'm trying to think of a way to keep the foam and use the cheaper sender, but at this point in time, I see no answer. Your starting to get ahead of me with your questions. Please leave questions till the end when you see exactly how things are going to sit.

As for why I chose to use a fuel cell, my fuel system requires fuel line sizes and flow rates bigger than the stock pickup and return tubes can provide in the stock tank. Also, I have a special custom exhaust that will have a muffler on each side of the fuel cell, much like the 2nd gen dual exhaust. Having the fuel cell lets me mount it between the frame rails and gives me the clearance I need for the exhaust. What I am doing here can easily be addapted to have the cell offset for a stock style exhaust. I have thought long and hard about this and this is by far the easiest way to meet my needs. I'd rather overengineer my fuel system than leave it as being just enough. Read my sig and you'll see what I mean.

Kim

For your own safety, please mount the cell in a fully enclosed metal container.
I know you will have it sealed from the interior, but in case of an rear end accident, the exposed lower part of the plastic fuel cell will crack and spill fuel.

31rx7

Really, spend the money for the right sender, put the foam in, encase it in an enclosed metal container.

How are you planning on filling the cell with gas once it is installed?

85rotarypower

I will have to pop the hatch and remove the cover to expose the cell in order to fill it.

About the sender again, the tube sender itself is almost the same amount I spent on the fuel cell, which is totally outrageous. Either way I have to remove a little bit of foam to make room for the sender.

As for enclosing the cell, its no more vulnerable than the stock fuel tank where it is. Being so closely mounted to the back, the stock tank would most likely rip open in an accident as well, and frankly, enclosing it won't make much difference. The metal enclosing it will just crush and puncture the fuel cell, probably making things worse.

I can see now that there is going to be some controversy in the way I install this fuel cell. This is meant to be somewhat of a budget install, without sacrificing safety.

85rotarypower

Ok, time to show you the design of the basket. It didn't take long to make this, about a half hour. Anyway, its two straps that go around the bottom and from there I have a strap that goes around the tank to hold it from side to side. Here are some pics. Pretty self explanitory. The straps are 1" wide and are about 0.070" thick.





Unfortunatly, since mother nature decided to be a bitch today (got cold and snowed, while yesterday it was 55*F outside) and I've run out of steel for the straps at the moment, I can't get any more done. I plan to add a "ring" around the top of the tank, just under the tabs you see in the pics. Also, things are going to be a little slower going as I managed to crush my thumb while using tin snips to cut the straps. I guess thats what I get for not using the proper tool.

camocarl

iTrader: (5)

Id use 3/4" or 1 inch square tubing all around it. Something to give it some sort of protection. Those RJS cells arent legal in SCCA partly because it doesnt have any metal surrounding it. Something like an ATL or FUELSAFE cell has a metal case surrounding the plastic fuel cell then foam inside. If you can figure out a way to keep the foam in it would be a lot more safer!

85rotarypower

I've been thinking about it and I think I'll just bite the bullet and get a tube style sender and keep the foam. You may think differently than me, but if there is enough force in an accident to wreck the rear bumper then actually make it to the cell, I don't think anything is really going to protect it properly without making things much heavier and bulkier. As it is this fuel cell is about the same weight as a stock tank. The plastic is about 3/8" thick.

Kim

Sure its heavier but does it make a difference?
If not in a crash, then maybe road debris or some punk with a tool could screw up the cell.
Can you pass inspection with a fuel cell?, we cant overhere
Personally i would put it in a container, but ofcourse its your choice.

85rotarypower

I'm not sure if it will pass inspection over here, but the car already passed once and it doesn't need to be inspected again unless I sell the car.

As for boxing it in, I may consider using some 0.060" thick steel around it. Seems like a lot of people suggest it.

Boswoj

OK - several people have documented the installation of PROPER fuel cells in the racing section. I'm not sure of your reasons for needing a cell, becasue if I were intending to use the car on the street and not racing, I definitely wouldn't replace the stock tank. Needing higher fuel flow is simply not a good enough excuse as that can easily be accomplished using the stock tank. Every state in the union REQUIRES your fuel to be surounded by metal. If your state ever requires a vehicle inspection, or a patrolman can see your plastic cell under the car, he has a right to ticket you, in addition to towing the car and requiring you to make it safe before returning it to the road.

My cell? It's in a highly prepared race car, and is a bladder AND foam encased in a metal box, with an additional metal bulkhead installed between it and me. Even though I am wearing a nomex suit, gloves, shoes, balaclava, and helmet - I still have a strong desire NOT to burn to death. Do yourself a favor and do this install right - a poorly installed cell is less safe than the stock tank and I can't think of many more horrible ways to go than in a burning car.

(EDIT - D'OH!: OK, well last time I looked, Canada hadn't been accepted as the 51'st state! Check local laws to verify the metal container laws!)

85rotarypower

I'm going to probably encase the cell in sheetmetal, but the basket I made is going to be the main support of the cell. The cover for the cell is going to be made of angle iron and heavy sheetmetal. But anyway, I'm sure the laws require the cell be covered in metal, so thats why I decided to do it, on top of personal safety. There is plenty of reason for me to use a cell. First off, I want to be unique with the exhaust. This will provide that ability. I'm planning a 2nd gen style dual exhaust, also, I want to overengineer the fuel system so I don't have to worry about it. Also, the stock tank that I have was a piece of **** and its hard as hell to get one around here. I'll post pics of what I did tomorrow.

If there have been many documented installs of fuel cells in a 1st gen, show them. I haven't been able to find and detailed installs whatsoever.

Hyper4mance2k

iTrader: (40)

Just so you know you usually don't burn to death. You sufficate from inhailation of your burning flesh, then your body burns... Geeshe some people. LOL!!!

85rotarypower

Thanks for the graphic representation of what actually happens. It actually sounds better just saying that you get burned to death.

85rotarypower

Ok, little update here. I haven't got too much done as I'm just taking it slowly and I don't have the sheet metal I need to enclose the cell. Anyway, here are a few pics of what I have done so far.

Couple pics of how the cell fits in the car.




Pic of how high the bottom still sits. The cell is only really visible if you get right on the ground.


Filling in the open spaces from the spare wheel.

avu3

My 95 lincoln has a plastic tank OEM and no metal around it. Not sure how I feel about it, but I know lots of folks with them and they've never had an extrodinairy problem with road debris.

I'm not saying you shouldn't enclose yours. I would, its much too exposed on the back of an RX7, particularly with the ratio of suv/truck to small cars.

Scott

85rotarypower

This is exactly what I mean. I worked at a plastic sorting facility for 4 weeks about a year back. My job was to take old plastic that was piled up in the rear of the building (about a 400 foot by 400 foot pile stacked up to 50 feet high in places) and put all that into sea containers to go to china. The plastic included globs from purging the machines, plastic intake manifolds from neons, and plastic gas tanks. LOTS of plastic gas tanks. Most of them were quite big too and for the most part looked like they belonged in trucks. My fuel cell is no thinner than these plastic tanks, and these are being used in almost anything now. Hell, my dads 2005 dodge ram has a plastic tank, my 97 thunderbird has a plastic tank, and I'm pretty sure there are MANY others.

Whanrow

My 90 Jetta and 92 Golf both had plastic tanks. What could possibly be the difference is that in both cases, the tanks were under the passenger seat, rather than at the rear of the car. Lots more car between them and any potential impact....

racintang

I started on mine this week to but just saw the post. I used an air hammer sheer and cut a circle right at the top of the spare tire housing. I got a piece of sheet aluminum for 20 bucks, from my father in law (he owns a sign shop) and cut a 27 inch circle out. I then weld a cross over the hole and screwed down the aluminum with some foam sealer for a good air tight seal. I used screws to be able to remove it later. I'm going to use a 15 gallon aluminum tank also. The bracketwill be pretty much identical to your picture put have longer braces to sit lower. I'm also going to get an old chevy caprice license bracket to use on the rear of the car so I can have the full filler cap under the plate. The filler tube will run through the aluminum directly in to the cell ( just like a 60's mustang ) which means the brace on the underside may have to be moved or cut out. No big deal since it's fairly thick aluminum.

racintang

Got a little more done on mine. When you look at the prices keep in mine that I used the best parts. I used a gasless wire welder to weld the steel together. If you don't have one you can buy one from sears for $125.00. I am using 3/8 inch bolts to secure it to the frame of the car. Once I get my fittings in I will mount it and post some more pics. This is a real world price for a new fuel system so you should budget at least $1000.00

Steel Fuel Cell with Sending unit - $289.00
-8AN fuel line, stainless steel braided 1000 psi - $109.00
-8AN fuel fittings inclusing tip over valve - $100.00
Fuel filter and fuel pump - $200.00
Aluminum to patch the spare tire hole - $20.00
1x1 steel tube, 2x2 flat bar and bolts - $125.00

drozhenbane

To anyone who doesnt agree with this guys choice to go with a fuel cell:
Q- New Tanks cost how much?
A- Ummm have you found one yet??? LMAO

Q-Rust Free Tanks cost how much?
A- umm yeah, kinda hard to find eh?

Q- When *** ended with enough force to crush 2 feet of steel, what are you rates of survival?
A- WHO THE HELL CARES! WHAT ABOUT THE CAR YOU IDIOT!!!!!!

Q- 1st gen Fuel Senders cost how much?
A- Not worth it, if you manage to snag one!

Q- How much for a 10 Gallon, GM Sender Fuel Cells Readily available on EBAY?
A- $50-$150 all day long............

My solution is easy....Why waste your time, when other options are available? I am in the same boat, my sender is dead, the stock tank is rusted beyond cleaning. I couldnt care less about safety! Truth be told if I am in an accident bad enough to burn me alive, the coronary I have because my beloved toy is trashed will not even compare to any physical damage I recieve! You guys need to back down, and applaud this man. He is doing something worthwhile with his car. SO it doesnt fit your taste, or your safety prefference. Who cares? its him who has to die, not you! I say congrats to the man, who has more ambition than most of us, who shuffle our feet just to change the oil!

racintang

And for those that ask why I did it. Simply beacuse this will be for some autocross/street adn bracket racing on the oval track.

85rotarypower

I haven't been able to get much done recently, but for those of you wondering about my safety, I will be changing the whole design. I'm going to build a frame around it with 1" box steel and cover the whole thing in .060" thick steel. From there I'm going to weld up a custom filler neck to fit to the stock filler, use a GM 0-90ohm tube sender, and an aftermarket fuel gauge. All said and done, its probably going to be $400 CND, but thats still MUCH cheaper than for me to find a good used FB tank and sending unit. My tank was rusted pretty bad and the sending unit was FUBAR'd, and it didn't provide the size of fuel line I wanted. I've got the fuel lines all setup already, I've just gotta finish mounting the fuel cell and make a cover for it. I'll be covering the whole thing in POR15, since its resistant to gas spills, and makes for a very long lasting finish.

I have to agree with what drozhenbane says about the safety thing. Chances are that if I'm in an accident big enough to rupture my fuel cell, I'm likely either already dead or on my way out.

Oh ya, another thing to consider with the Jetta and Golf tanks mentioned by Whanrow, what happens if you get t-boned at 60mph in the passenger side? I've seen a car get t-boned at that speed before and it isn't pretty. Mostly the gas just leaks out of the tank when its punctured. It doesn't explode into a fireball.