Fuel Cell Limit on a 318i - ITB

I need to pick some of your guys brains about a peculiar rule involving 318i cars. I plan on running some enduros in the near future, and I noticed that there is a note in the GCR stating that you can run a fuel cell, not not larger than stock size. The majority of the BMW's in IT are listed this way. My main question is why? That's a pretty big disadvantage to all the cars in those classes. Is it a carry over from long ago or a circumstance that I can't see from where I'm sitting?

Any ideas out there how this came to be?

I forgot to mention...it's a 1984 318i ITB

Where did you read the fuel cell size requirement?
The GCR 9.3.26. FUEL CELL SPECIFICATIONS states that the capacity is free unless specified elsewhere. The IT prep rules refer to the above rule when talking about fuel cells. The only general requirement I see is the cell must be located within 12 inches of original location.

It is at the end of the Improved Touring Section of the GCR, notes made in the appoved car list.

On the 84-86 BMW 318i, Under ITB, it states, "Trunk mounted fuel cell may be used but shall be no larger than stock". Stock for a that model BMW is about 14-15 gallons.

Gnapier
The GCR states that a "trunk mounted fuel cell may be used but shall be no larger than stock".
Meaning that you may have a fuel cell but it can not have a capacity greater than the stock tank. Which to me says that if you want the advantage of quick fueling with a dry break connector, the fuel cell is the way to go. Not to mention that the fuel cell properly mounted is safer than a stock tank.
Keep in mind that there is more to this type of setup than buying just the fuel cell.
cheers
Dave Paker
WDCR HP#97
2007 MARRS HP Champion

I tried to edit my post when I realized where you were reading the rule. What is the capacity of the stock gas tank? What size cell would you install if you could choose? You can always contact the [email protected] and ask for a rule change. I'd be leary of putting in a cell much larger than 15 gallons for a small race car. That would be about 90 pounds of changing weight mounted behind the rear axle.

To answer the original question - I was under the impression the note concerning the trunk-mounted cell was an allowance to the "12 inch rule" for the BMW's, that is otherwise in effect for other IT cars. Isn't it true that if the cell is trunk mounted in the 318, it will not be within 12" of the stock tank location?

So... it was my understanding that this allows the cell to be further than a foot from the original tank, but it limits the size of the cell to minimize the weight distribution shift (to the rear) that it facilitates. BTW, this would be true on some other IT-classified cars as well. But no one has apparently noticed the discrepancies, or the cars are classified but not being raced. Or they are being raced with stock tanks. :D

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Originally Posted by Gary L

...it was my understanding that this allows the cell to be further than a foot from the original tank, but it limits the size of the cell to minimize the weight distribution shift (to the rear) that it facilitates.

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Winner!

This was an allowance to those cars specifically. If memory serves, there was something about not having enough space back there to install a cell within 12" of the original. So, to toss a bone at the car, they could mount it way in the back but could not unduly take advantage of that for performance/ballast reasons.

Can't have it both ways, mang... :)

GA

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Originally Posted by dave parker

Gnapier
The GCR states that a "trunk mounted fuel cell may be used but shall be no larger than stock". ...

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You had me scared there for a second, Dave...

From the ITCS

...b. The stock fuel tank may be replaced with a fuel cell. The fuel cell shall be located within twelve (12) inches of the original fuel tank location. Additional reinforcement may be added to support the fuel cell, but such reinforcement shall not attach to the roll cage. Floor pan may be modified for installation. See GCR Section 9.3.26., for requirements.

General GCR Req's

9.3.26. FUEL CELL SPECIFICATIONS
All cars must be equipped with a safety fuel cell complying with these specifications, except for Showroom Stock, Touring, Spec Miata, and Improved Touring. All safety fuel cells shall be constructed and certified in accordance with the FIA FT-3 or higher (FT-3.5, FT-5, etc.) specifications. All safety fuel cells shall consist of a foam-filled fuel bladder enclosed in a metal container at minimum.
There is no restriction of fuel cell capacity or dimensions of the fuel cell, except where otherwise specified.

Kirk

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Originally Posted by Greg Amy

...Can't have it both ways, mang... :)
[/size]
GA

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So he can have it EITHER way, right?

Trunk mounted fuel cell may be used but shall be no larger than stock.

This means that any cell can be mounted within the 12" limitation, but NOT that this is the ONLY allowed fuel cell solution? That makes sense, upon reflection.

Kirk (who thinks that 25 gallons of fuel is always an interesting packaging challenge)

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Originally Posted by Knestis

So he can have it EITHER way, right?

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Sure. The line allowance is just that: "...trunk-mounted cell may be used but shall be..."

Find a way to put it within 12 inches and go to town on the capacity...

If I remember these cars correctly they have a stock fuel tank that is shaped like a set of saddlebags to allow the propeller shaft clearance. That would make mounting an "off the shelf" fuel cell quite difficult within the GCR specifications. These cars and the cars (like mine) that the owner did not want to cut the floor are why ATL created the "well cell" fuel cell that fits into the spare tire well in the trunk.
I am glad that I can still scare Kirk unintentionally. :happy204:

Or maybe it was the MARRS Championship in my signature that got him. :)

cheers
Dave Parker
MARRS HP#97
2007 MARRS HP Champion

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Originally Posted by dave parker

That would make mounting an "off the shelf" fuel cell quite difficult within the GCR specifications. These cars and the cars (like mine) that the owner did not want to cut the floor are why ATL created the "well cell" fuel cell that fits into the spare tire well in the trunk.

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Not that difficult... put the cell (as big as you want) inside the passenger compartment, mounted on top of the floor pan, then cover it up with a metal bulkhead. 9.3.26.1 very clearly allows this, and I see nothing in the ITCS that prohibits it... I don't own one of these cars, but seems to me this would still put you within 12" of the original tank(s).

Hey guys, just wanted to say thanks for all the insight and help. I appreciate it.

Quote:

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Originally Posted by Gary L

Not that difficult... put the cell (as big as you want) inside the passenger compartment, mounted on top of the floor pan, then cover it up with a metal bulkhead. 9.3.26.1 very clearly allows this, and I see nothing in the ITCS that prohibits it... I don't own one of these cars, but seems to me this would still put you within 12" of the original tank(s).

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Absolutely legal. I know a Rabbit that runs a cell on the passenger side floor. Actually works very well - low and protected, as well as good offset to driver weight.