Jim,
For 2009 stock is required. So make sure you are stock for Nationals. For 2010 it is open for discussion.

Now one point to consider is that we do occasionaly run enduros. No restrictor will allow faster fuel flow and allow for faster pit stops. Remember last year at Miller when we ran 2 hours, but were required to add 5 gallons of gas. In that case your 21 gallon tank made no difference vs my 17 gal, but a large filler neck would have made your fuel stop to add 5 much faster. Plus from a safety perspective the stock neck is a proven unit. Once you start modifing to to flow more what risk of fuel leakage might you introduce in wreck? Who knows maybe none, but that is something that needs to determined.

So again.. it is valid topic for 2010, but as always unless there is valid reason why a change is good I will err on the side of no changes. Rule stability is good as well as dealing with know issues vs possibly introducing ones that are not understood.

Removing the flapper door was allow since a fuel jug can tip can catch on the fapper door getting stuck when trying to remove it. This can cause problems during refueling that can be dangeriuous in the fuel may spill. I have never had that happen, but I can clearly see how it could.

BTW.. fuel cells are very tough install in a 944 in the first place. Custom fit cells are very very expensive and standard box shaped cells have a hard time fitting and need alot of fabrication to get right. 90% of the time a fuel cell is alot more hassle that what it is worth.

Joe, just out of curiosity, are you saying you guys knowingly put in a rule allowing fuel cells with the intent that it wouldn't change the requirement for the stock filler neck to be retained? I also wonder if a car with a fuel cell would be compliant if the stock filler neck was retained but not connected to the fuel cell or used to fuel the car. I really don't see anything in the rules that would prohibit that.

We'd have to fabricate a bulkhead to enclose the filler and vent tubes, like this:
www.jrmock.com/image-folder/fuel-cell/Final-Plumbing-1.jpg
(I hope these folks don't mind linking their How-to page.)

While this is a nice job, first I'd be concerned about the more points of failure it creates in order to adapt to the stock filler(rubber hose adapters, clamps, welding, etc) and about how the filler tube dips before dumping into the tank causing gas to pool there. It just seems like it defeats some of the purpose of having a cell.

I just wanted to simplify install by using no filler neck, just a flat cap on top of the cell, covered by a latched metal filler door accessed through the rear hatch and just vent externally instead of back into the filler neck. It seems like this would be safer than stock, especially in a rollover since there are check valves to keep fuel contained. But it sounds like that would not meet the CCR requirement of a "solid metal bulkhead"

I think it may be hard to improve on the safety of the stock tank on a 944. I have seen a 944 flattened to the C-pillars without leaking fuel (fatal accident for the driver of the car that hit the 944). I have also seen a few cars with fuel cells have fires d/t improper installation of the fuel cell/lines. Granted this was installer error, but is easy to do. The 944's have safe tank designs, and are hard to put fuel cells in without compromising their OEM steel bulkhead between the tank & driver. I'm sure it can be done, but much more easily screwed up than done better.

spec944#74 wrote:


Steve this installation uses the stock filler neck.


If the stock filler neck is just a dummy part then it does not follow the rules as it is being by passed.

The stock tank on a 944 is quite well protected and has a roll over check valve ball that will seal the fuel in the tank. There's no need for a fuel cell in a 944. That rule was introduced by Brian Cohn? at NASA National a few years ago.
I was against it.
Flat bottom fuel cells that fit in a 944 are tough to plumb correctly so that the pump doesn't starve. Our stock tanks are shaped like inverted pyramids, which is a great design. STOCK is good.
The unleaded restrictor or filler neck trap door keep things even in endurance racing among 944's. You can have a whiz-bang fueling system or a plastic 5 gallon jug and the fuel still has to go through that small trap door. It's the great equalizer. It can put us at a disadvantage compared to other car types in the E2 enduro class during refueling.