Trunk modifications

team-gpracing

team-gpracing

Well-known member
So, I have seen that most people seem to cut a hole in their trunk/remove the spare tire well in order to mount the fuel cell at a lower point in the vehicle. I'm not seeing anywhere that expressly permits this modification. Can someone clarify?

1. The body, unibody, frame and their components can be
lightened, provided that structural rigidity is not compromised
to the point of requiring additional support. No nonstock
openings can be created in the bodywork. The lightening
of the cars structure can not create any openings
into the cockpit, or from the wheel well to the engine/trunk
compartments. Existing seams in the unibody and frame can
be welded

The reason I am asking is I am considering making this modification, or removing the spare tire well to allow for more exhaust room. If the latter, can I remove the well in order to make room for a muffler?

l. Exhaust System
1. The exhaust header and exhaust system is unrestricted.
Floor pans can be altered only to recess mufflers. No modifications
can be made to the bodywork to fit any other part
of the exhaust system.
 
From 9.3.27.
FUEL CELL SPECIFICATIONS (Page 102 of June 2015 GCR) which can be found here:

http://cdn.growassets.net/user_files/sc ... 1432744934

1.
Installation
Internal body panels may be modified to accommodate the installation of
fuel cells as long as modifications serve no other purpose. If installation
includes encroachment into the driver’s compartment, a metal bulkhead
must prevent exposure of the driver to the fuel cell. The fuel cell must
not be installed any closer to the ground than 6 inches, unless enclosed
within the bodywork or OEM floor pan.

There's more there, but this answers your basic question.
If this modification also happens to create more space for exhaust, that's just good luck.
 
Bill Underwood":25t3stpq said:
From 9.3.27.

1.
Installation
Internal body panels may be modified to accommodate the installation of
fuel cells as long as modifications serve no other purpose. If installation
includes encroachment into the driver’s compartment, a metal bulkhead
must prevent exposure of the driver to the fuel cell. The fuel cell must
not be installed any closer to the ground than 6 inches, unless enclosed
within the bodywork or OEM floor pan.

There's more there, but this answers your basic question.
If this modification also happens to create more space for exhaust, that's just good luck.
Click to expand...


It certainly seems to me that the two statements highlighted are mutually exclusive. It looks to me like the rule says that you can cut out the bodywork exactly the size of the fuel cel can (+ 1/4" I'll call it, for ease of fitment). Not that you can "accidentally" remove an additional 10" to accommodate exhaust.

By the way, I have no dog in this fight. I actually think a rule clarification to allow exhaust to fit under the car would be a good thing. I just don't think that is what the cited rule states.
 
So I cut the hole, drop my cell down into it an inch (theoretically), and use the rest of the space for whatever I want. Yes?

There is a rule clarification about exhaust. You can modify the underbody to accommodate mufflers only.
 
Internal body panels may be modified to accommodate the installation of
fuel cells as long as modifications serve no other purpose.
Click to expand...

Body – All parts of the car licked by the air stream and situated above the
belly / floor with exception of the roll bar or cage.
Click to expand...

So, the floorpan is considered an internal body panel. Cut up the floorpan any way you want, throw in your cell.

Here's the exhaust rule:
Exhaust System
1. The exhaust header and exhaust system is unrestricted.
Floor pans can be altered only to recess mufflers. No modifications
can be made to the bodywork to fit any other part
of the exhaust system.
Click to expand...

From above, the floorpan is not considered body work - so as long as you don't modify doors, bumpers, rockers, etc - you're safe there.

The second sentence, and the word "only," would lead me to believe you can't move stuff around for the exhaust pipe, but you can do whatever you want to the floorpan for the muffler.

The exhaust pipe has to connect to the muffler, somehow, so I think as long as you make it clear the modifications were for the muffler and inlet and outlet, and not for just the piping away from the muffler, you'd be good.

Were it me, I would ask for a clarification. But I like causing trouble.
 
Please read all of 9.3.27

As to location- 9.3.27.1.b
b. Fuel cells must be located within 12 inches of the standard
tank. The 12 inch measurement is taken from the perimeter of
the stock and alternative fuel cell. Fuel filler location is unrestricted
with installation of a safety fuel cell.
 
Wouldn't the spare tire well be considered part of the floorpan and thus eligible for modification to fit the muffler? Might depend on the car, but in my VW the well is part of the floor pan IMO.
 
Sometimes we are obligated to use the GCR glossary. Normally use as a supporting platform for seats, physically separate the interior (cockpit) area from the underside of the car.

This item has been discussed in the past, IIRC don't believe it's an open book for anything other than muffler. Try site search engine.
 
David is right. Don't look elsewhere for an excuse to recess an exhaust.

1.2.3. Interpreting and Applying the GCR
A. Interpreting the GCR shall not be strained or tortured and applying
the GCR shall be logical, remembering that the GCR cannot specifically
cover all possible situations. Words such as “shall” or “shall
not”, “will” or “will not”, “can not”, “may not”, “are” or “must” are
mandatory; and words such as “may” and “should” are permissive.
9.1.5/D. Interpretation
1. An addition, modification, substitution or removal, must not be
made unless specifically authorized.
2. An authorized addition, modification, substitution or removal can
not perform a prohibited function. An authorized addition, modification,
substitution or removal of one component does not permit the
addition, modification, substitution or removal of any other component
unless the addition, modification, substitution or removal is
specifically authorized.
 
I would remove the spare tire well, mount the fuel cell from below the trunk floor. You may find you now have enough space to close off the open trunk floor area created by removing the spare tire tire well with a single panel of flat metal. Weld or rivet it in place. Seal it for protection from flames from below.

Place a small acces door in the new flat trunk floor to allow you to remove the gas cap and fuel the car from within the trunk. Secure it with some dzus pins or other positive retention means. The opening that was created by removing the spare tire well is now sealed for fire protection, and the cell bottom should be over the minimum 6" ground clearance below the cell. And there is only one small secured acces panel in the trunk. With a flat in the trunk.

Depending on the width of your fuel cell and the width between the rear frame rails, you may have enough room, between the frame rails, and/or under the right frame rail, to mount the muffler to the passenger side of the fuel cell.
 
John just spelled out the 1st Gen RX7 formula.

The fuel door on my car is retained by what looks like a window latch from a residential window. you can probably pick them up at hardware store for about a buck, and is extremely easy to open and close.
 
I may have misspoke in my earlier post. I'm not looking to recess exhaust, just maybe some more room for muffler. I think dropping the cell down will still allow more space. Thanks to all.
 
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