Fuel Cell Location Rule?

[Off Camber]

Help Rules Guys.
Fuel cell location rule.

"must be within 12 inch of original location"??

does this mean center of old tank to center of new location or from outer edge of old tank to outer edge of new location.

I am trying to move the tank as far back as possible to help distribute weight better but do not want to put it in wrong location.


Thanks for the advice.
Cheers SteveP

[charrbq]

Your best bet is to call Topeka and get a firm opinion on that question. The rules are sorta vague on that. I've seen cells run in the front passenger area before that were considered to be legal. I wouldn't want it there, but it has its advantages. If you get a solid answer for Topeka, let me know 'cause I've never got one.

[shwah]

It means what it says.

Within 12" of original location. The front and back edges of the tank are part of the original location. If you are within 12" of any edge of the original tank you meet the rule.

If they want it to mean something different, they will put different words in the book.

Personally I would concentrate more on lowering the rotational moment of inertia than getting more weight in the back of a fwd car.

[joeg]

I agree with Chris--12 inches (or less) from the perimeter of the stock tank to put the edge of your fuel cell (side to side, fore or aft).

Cheers.

[lateapex911]

Bingo..it's edge to edge. Thats a lot of latitiude. Jinx Jordan has his mounted nearly in his passenger seat in his CRX.

[ddewhurst]

***I am trying to move the tank as far back as possible to help distribute weight better***

Steve, think about a pendulum before you make your final decision. Think in terms of the fuel cell being just in front of your rear axle vrs the fuel cell being as far rearward as you can place the cell.

[charrbq]

***I am trying to move the tank as far back as possible to help distribute weight better***

Steve, think about a pendulum before you make your final decision. Think in terms of the fuel cell being just in front of your rear axle vrs the fuel cell being as far rearward as you can place the cell.
[/b]
Yep, it's a trap a lot of guys fall into. Idea is to better balance the weight of the car by offsetting the weight of the engine by putting the fuel cell to the rear. When you change direction, as in a turn, the back end wants to stay in the same direction as before the turn. I'm sure there's a law of physics with someone's name attached to it, but manly means that the backend starts driving the car in a turn. Imagine what that translates to in terms of getting a little loose in a turn. The closer to the center of the car, the better. Of course, the lower, the better.

[lateapex911]

It's called a "High polar moment of inertia", and I think that weight placed further from the CG has a greater effect, pound for pound.

[charrbq]

That's the name! The rule about Mrs. Inertia Polar's movement, as told by her husband, High! :wacko:

[Motor City Hamilton]

Speaking as another Waterford racer and a guy who was just a step too far behind you trying to buy that fuel cell, I'd mount that cell close to the stock location. You're in a front drive car, probably needing more front bite anyway. I would center it side to side, mount it as low as would be safe and move it to the front of the old tank well. Keeping the fuel load toward the center of the car will give you less of a change in handling as the fuel load changes. That's my $.02

[ddewhurst]

***Mrs. Inertia Polar's movement, as told by her husband, High!***

Chris, is Mrs. Inertia Polar's movement the same as high ungulation ? :blink: :119:

[Bildon]

The latest "The Consultant" column in RaceCarEngineering has a bit on this very question.
There is no "right answer" it's a "this depends on that" deal.

About the front bite comment. Realtime did some research long ago about F/R weight ratios in FWD.
50/50 is undriveable, snap changes in handling being a bad thing ;-)
55f/45r I think would up being optimum given their cars (Acura Integra, gen. 1)

Since most FWD cars are closer to 70f/30 or 65/45 you do still want to move the weight rearward when making a race car out f it...While bite is important so is reducing the weight up front to reduce understeer and excessive tire load/heat/wt. transfer etc.

The location of the original fuel cell is often a good indication of a good place to put 100+ lbs of fuel dont you think?

As always YMMV....

[charrbq]

Exactly right, Bill. The problem I've seen in VW's and Hondas is the location of the stock tank is perfect...in the middle of the car and down low. Problem I've seen is that, after including all the necessary bulkhead to protect all concerned, it moves the fuel cell up to a higher roll center. Not really the optimum location, either. Maybe I just haven't seen someone do it properly, but moving it to the rear doesn't look too great either.

Opinion? In production cars, etc. the fuel tank is removed, flooring cut, and the cell is suspended in the area where the tank used to be. This lowers all that weight down to a livable height. All the IT cars I've seen, remove the tank and use the floor for the cell, raising the CG. Would it be safe/legal to remove the tank, cut out the floor, and mount the cell to the depth of the old fuel tank, as long as the original location was used?

[ddewhurst]

Chris, many cars that I have viewed have the floor cut out & the cell at the lowest possible height. Then they fab a horizontal trap door firewall.

[charrbq]

That's what I wondered. All I've seen have the dang thing sitting on the tub, putting the whole mess up about the middle of the seat back. Not the best idea, in my thinking.

[shwah]

The location of the original fuel cell is often a good indication of a good place to put 100+ lbs of fuel dont you think?

[/b]

I guess it also depends on how much fuel you carry.

In Mathis' GP Rabbit the fuel cell is in passenger seat area. Provides a nice offset to Chuck's lithe figure on the driver side, is lower than we could put it if it were 'outside' the car, and helps reduce polar moment of inertia. Of course in that car there are so many other things we were able to do to pull weight off the front tires it is a whole different animal than our IT world. Of course this did necessitate the fabrication of a firewall between the cell and the rest of the driver compartment, but what's one more fabrication project...

For my IT car I would place a cell in front of the rear axle, as low as legally allowed. Seems like as safe a place as I can come up with, and should help rotate a little better. However, the factory tank is serving me just fine right now.

[ddewhurst]

***Mathis' GP Rabbit ***

Chris, this is one dam fast cotton tail. Saw his race at the June Sprints. Kent Prather, here comes serious competition at the Runoffs. :o

[shwah]

Thanks for the nice comments. The Sprints were a pain in the ass until the last 6 or 8 minutes of qualifying on Saturday. Buy hey last year that car never finished higher (or lower) than second. We just started calling it 'Chuck's 2nd car'.

Something tells me Kent will have something for all comers come October. There is a reason he has all of those trophys.

[RKramden]

I'm sure there's a law of physics with someone's name attached to it
[/b]

"An object at rest tends to stay at rest and an object in motion tends to stay in motion with the same speed and in the same direction unless acted upon by an unbalanced force."

This is the NEWTON

Might it be Newton's First Law? :)