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Discussion Starter #1
I'm looking at having a custom fuel cell made for my MKIV that fits in the stock spare tire well of the car. If anyone know if such a product already exists please let me know, i didn't find much when googling.

Why am i doing this you might ask. Here in Norway we don't have E85 on pump, so the plan is to have a secondary fuel tank dedicated to ethanol and stock race E85 at home. Sweden and other countries close by have E85 at the pump so that's also an option when traveling with the car (Sweden is a 2 hour drive for me).

The fuel system would work like this:
Two fuel rails, FPR's etc. Car will run on the "stock" fuel system at idle and low boost, when boost goes over a set threshold the second fuel system comes online and blends in E85, when reaching a second boost threshold the "stock" fuel system shuts off and only E85 is supplied. This way you can run big injectors for E85 with no idle issues, flawless cold starts and most important for me, not use up any precious E85 when you don't need it. Perfect for people with a limited supply of E85 close by. You could also have a switch in the car to have a "track mode" for example and have the car run only on E85 when enabled. This is at least how i want my system to run, the possibilities here are only limited by you and your tuner's imagination, and your engine management system of course.

This kind of setup has been done before, but i haven't seen many of them. Here is a video of a guy in Sweden who runs a fuel system like this which is briefly talked about in this video. He runs it on a Vipec V88 ECU, so I'm pretty sure the majority of modern ECU's will be capable of managing a system like this

If you don't want to watch from the start fast forward to ~4:50 where he talks about the fuel system.

The fuel cell i was looking at in the first place is the spare tire fuel cell from Radium engineering shown below. But since i don't want to cut my rear floor, and want to retain my stock fuel tank, i need to have one custom made with a step up in the middle to clear the spare tire mount. You could fit the tank shown below, but you would have to make a solid plate for it to sit on top of, so the tank would sit very high in the car, and probably not go clear of the rear windshield.

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The fuel cell will be made to suit the Radium integrated surge tank (the one fitted in the picture above), but most types of integrated surge tank solutions will probably fit (depending on dimensions of the surge tank, hangers etc) if they have the industry standard 6"x10" 24-bolt flange.


The Radium integrated surge tank is a very nice piece in my opinion and ships from Radium with pumps etc fitted. It can be configured with 1 lift pump and up to 3 pressure pumps of your choosing, limited to the pumps that Radium stocks if you want everything assembled by them. The surge tank assembly has a dedicated fuel level sensor flange and a built in collector with check valves for running staged pumps along with a bunch of other neat features. They make a fuel level sensor that is bolt on.

Link to the surge tank assembly: FCST, Fuel Cell Surge Tank
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I will most likely make a demo model out of hard cardboard or something else suitable, and have it drawn in CAD. The company i will contact for making the fuel cell will be Fuel Safe (the same company that makes the Radium cell shown above), and it will be based on their Enduro lineup for 100% compatibility with ethanol. I estimate the cell to hold between 8 and 12 gallon of fuel (including surge tank volume)

The finished product will look similar to this:
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I will look at mounting options once i start making a demo model.

Here is a picture that shows the problem with fitting a regular flat bottom spare tire well fuel cell. You could cut this piece off, but you would have to remove your stock fuel tank because the mounting point of the stock fuel pump hanger comes up inside there as well. This picture is a random picture i borrowed off google and not of my car.
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For you targa guys (yes, I'm a hardtop snob now ;) ) I'm not sure if you could still fit the targa roof in the back with this setup, but i could try and borrow a targa roof to test fit if this is a big concern for others who might want to get in on this setup.

I don't expect this to be cheap, so i would be ready to fork out at least 1500 USD for the cell alone if anyone else is interested.

If anyone else has limited access to ethanol fuels or want this setup for other reasons feel free to subscribe to this thread as i will update here when progress is made. If enough people want to buy this maybe we can get a very good price.

If anyone have any input, let it rip :)
 

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Same, flexfuel sounds like the better solution. Two fuel systems is overly complicated. Buy a 55 gallon drum of fuel, and drain the car's system if needed. Is a cell a racing requirment?
 

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Discussion Starter #4
Why not just get a flexfuel sensor?
Same, flexfuel sounds like the better solution. Two fuel systems is overly complicated. Buy a 55 gallon drum of fuel, and drain the car's system if needed. Is a cell a racing requirment?
The upside to this solution is that the car runs on regular gas on low boost and idle. Lets say you have 10gallon of E85 and you want to drive to the track and have some fun. With only 1 tank you would run out of E85 before you even reached the track. With a separate ethanol tank you can drive to the track on regular gas, then spend you whole 10gallons of E85 on the track, then drive back home on regular gas.

Plus, my inner engineer really want to build this system.
 

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Discussion Starter #6
Do tracks in Norway not have their own fuel stations?
No, not inside the track area at least, but there have been stations very close on the tracks i have been to. We don't have E85 on pump at all though, so need to stock at home. The thought behind it is, if i want to do a day trip to the track and drive for a couple of hours, i can just drive my supra there with a full tank of E85 to use when i reach the track. If i don't have the separate E85 tank, i will need someone else to bring barrels of E85 for me. I don't want to be dependent on other people. Same on the street, you can run on regular gas all day, and if someone wants to race or you want to show off for a passenger, just flick the switch and you are now on E85 with a full tank ready to go.
 

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The upside to this solution is that the car runs on regular gas on low boost and idle. Lets say you have 10gallon of E85 and you want to drive to the track and have some fun. With only 1 tank you would run out of E85 before you even reached the track. With a separate ethanol tank you can drive to the track on regular gas, then spend you whole 10gallons of E85 on the track, then drive back home on regular gas.

Plus, my inner engineer really want to build this system.
You drive to the track on regular 98 and your 10 gallons in the trunk, top it up with E85 and let the flexfuel blend tables do the rest when you get there.
If you going with a separate fuel cell in the spare wheel well you also need a firewall over it, last place you want fuel leak is inside the cabin.
 

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Discussion Starter #8
You drive to the track on regular 98 and your 10 gallons in the trunk, top it up with E85 and let the flexfuel blend tables do the rest when you get there.
If you going with a separate fuel cell in the spare wheel well you also need a firewall over it, last place you want fuel leak is inside the cabin.
I won't have space for fuel cans in the back. I don't understand your logic though, its safer to have plastic cans with fuel in the back of your car rather than a FIA approved fuel cell?
 

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I won't have space for fuel cans in the back. I don't understand your logic though, its safer to have plastic cans with fuel in the back of your car rather than a FIA approved fuel cell?
You bring a can with E85 to the track and fill up your tank when you get there. You don't want any of the fuel system inside the cabin, at least i don't.
 

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Discussion Starter #10
You bring a can with E85 to the track and fill up your tank when you get there. You don't want any of the fuel system inside the cabin, at least i don't.
Yes, i get that, but if you have fuel cans in the trunk thats less safe than having a fuel cell there in my opinion. You are just as likely to get rear ended on your way to the track as on the track.
 
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