Fuel Tank Baffles - Modifications
 

Let me start off by saying that I have been doing HDE's in my FD for the past 8+ years. In the beginning fuel slosh was never an issue. I could run my tank down to 1/4 tank without a problem. Over the years I have gone with stickier tires and the baffles began to break loose, one after the other. As long as I kept my tank level to 1/2 it was never really an issue. This past race season the final baffle broke loose and now fuel slosh is a serious issue. One other thing to note is that I've been using Hyperion's tank cover for the last couple of years. In my experience it works well as long as there are factory tank baffles in place to slow down fuel movement inside the tank.

I've done a lot of searches on this forum and elsewhere to figure out the best way to resolve this fuel issue. Here are the options and associated costs.

1. New Tank - $600
2. Install Sump - $500+ - inlcludes sump, pump, filter, lines and fittings
3. Install Surge Tank - $600+ - inlcudes pump, tank, lines and fittings
4. Install Custom Tank Baffles - $200 - includes materials and check valves

The new tank was my first idea but then realized that it was just a matter of time before they broke off and I would find myself in the same position.

The sump was my next option but I didn't necessarily like the idea of running an external pump with external lines running around the tank. I didn't like the surge tank for the same reasons. I want to keep the tank simple, avoid excessive lines and keep all parts of the fuel system away from the interior of the car. Most setups I've seen involve running tanks and lines inside the hatch area. I've seen setup that place the surge tank behind the rear diff but this is not an option for me since this is where my tranny cooler is going.

These leaves me with modifying my existing fuel tank baffles. My uncle is a welder and he agreed to help me out so I can do this mod with just my time, effort and materials. I read a thread where Gene Felber did some mods to the factory surge compartment. First he plugged up the factory inlet channel. Then he installed one way ball check valves on three sides of the surge compartment. After looking at the compartment closely I like the idea of installing ball check valves, but I'm not sure I see the need to plug up the factory inlet channel since the factory baffles seem to direct fuel to this opening. As of right now I don't have any baffles in my tank but was thinking of building baffles that resemble the stock baffling system but greatly reinforced to prevent them from breaking off. After all, I feel the factory baffling with the surge tank cover worked pretty well when it was all in place.

To those who may have some knowledge of fuel tanks or have build tanks in the past... Would it be smart to mock the stock baffling or should I abandon that whole idea and just build a couple of walls (with holes) inside the tank to slow down fuel movement and not really direct the fuel in any particular manner. I could also build some walls that are angled in such a way that would channel fuel in the general direction of the surge compartment. In this case, maybe the factory inlet would be not as beneficial and should be blocked off and I would just be relying on the check valves to allow fuel to enter at the left, right and rear sides of the compartment. I've done some searches on tank baffling but I'm not really finding anything that is helping me all that much. Most custom tanks involve channeling fuel to a sump, not a factory type fuel pickup system.

There is a surge compartments available from pegasus racing but it doesn't appear to be all that different from Mazda's factory surge compartment with check valves installed so I think it would be a waste of money.

There are a lot of good pics of the factory fuel tank baffling here:

https://www.rx7club.com/showthread.p...+tank+pictures

Thanks for the pics Luigi. I will be referencing these when to construct my own custom baffling.

Please share any thoughts or ideas. Thanks.

Josh

never mind

Not sure why you wouldn't just stick w/ the Hyperion fuel cover?

I ran it down to less than 1/8th last weekend at VIR, running 285 Hoosiers.

The fuel cover doesn't work well if there are no other baffles in the tank. The stock baffling is needed to slow down the movement of fuel and to channel the fuel into the surge compartment.

I'd pick up a used '94 tank with the baffles in place, and reinstall the cover.

If I could find one with baffles in tact for a reasonable, I would do that.

Have you tried asking Fritz if he has something laying around?

Mazda Motorsports price was ~$450 last year. I believe that is what I paid for it. No idea how that compares price wise to a fuel safe.

I don't have Mazda Comp membership. They are $600 from Malloy. Fritz does not have any.

I'm pretty much set on constructing baffles for my existing tank. I was looking for suggestions from anyone who has ideas or experience with this sort of thing. I will most likely be copying Mazda"s basic design with a few minor changes. I will also be using slightly heavier guage steel and I'll be tig welding them in place. I'll keep the surge tank cover and add ball check valves to the surge tank.