HDP

iTrader: (2)

Click link...

https://www.rx7club.com/showpost.php...1&postcount=64

rynberg

The baffles are designed to minimize fuel slosh during cornerning. Given the already poor baffling of the 93-94 tanks, I would say that this is a significant problem....I would get a brand new gas tank that has the improved 95+ baffling. I don't think they are that expensive and you've already got the old tank out already.

HDP

iTrader: (2)

No, I did not remove the tank. I was able to remove them without dropping the tank. The baffles were already broke and had been moving around making that noise as long as I've had the car. There is still a plastic baffle intact that the fuel pump sits in, so wouldn't that be sufficient? I can't justify buying a new gas tank just to keep fuel slosh to a minimum during cornering.

7racer

Jeez! What do you have living in your gas tank that broke the baffles out like that!!!

HDP, if your tracking your car OR taking a street corner hard on a low tank of gas you MIGHT suck in some air into the gas line.

You probably could get by running as full of a tank of gas as possible.

If you are going to drop the tank, it's actually REALLY easy. Just remember to get the screws at the gas filler neck.

axr6

The baffles are really important when you do high-g cornering and slush the fuel around. If your fuel level is low enough the fuel pump will grab air and you will have an engine miss, lean fire situation. In normal driving you will not miss it since those baffles are not that great to begin with.

When I raced my FD I stuffed the fuel tank with the same foam that racing fuel cells use. This will prevent sloshing far more and better than any rigid baffle system that you may find in an FD. The foam did not seem to reduce the gas tank capacity significantly. My records indicate that the when 5 gallons of fuel was added to an empty tank the fuel gauge read 1/4 with both foam and without the foam.

Albert

HDP

iTrader: (2)

Where did you purchase the baffle material?

axr6

Sorry, I really do not remember where I purchased it way back in 94. Probably through one of the local racing shops I used to deal with.

It should be easy to find, just Google some fuel cell manufacturers or race shops which sell fuel cells. The nice thing is that you can stuff the foam in without having to remove your gas tank. You stuff it right through the fuel pump opening and just leave enough room free for the pump assembly to hang down.

I also forget the price for tha foam, it is probably not cheap. Nothing is cheap in racing but, will probably be far cheaper than replacing the tank.

Albert

HDP

iTrader: (2)

I found some in my Speedway catalog. Fuel Cell Safety Foam 16"x4"x6" $7.95 per brick/stick

HDP

iTrader: (2)

My fuel cell foam arrived today. I plan to install it along with my new fuel pump this weekend. Of course, no instructions came with it so how should I arrange them (foam bricks) in the tank?

axr6

I'm not surprised that no instructions were provided for the bricks as they have no clue what application it would be used for.

I forgot exactly how I arranged mine. Of course, I packed mine with the baffles still in place so, your packing will have to be different. The missing baffles should present no problem as the racing fuel cells came without baffles too.

Basically you should pack it tightly, slightly compressed against other pieces and the tank walls, top to bottom, all the way across and just leave a square shaped well unpacked that allows the pump assembly to operate freely. Be sure to construct the bricks tightly in such a shape and way that they will not move around.

Albert

HDP

iTrader: (2)

I'm not sure I follow you. There is the plastic baffle that the pump sits in still inside the tank. Only the metal baffles were removed. The description called for 1 brick per 4 gallons of fuel. 20 gallon tank = 5 bricks.

axr6

If you only purchased (5) 16"x4"x6" bricks, you misunderstood what I was saying when I wrote that I "stuffed my fuel tank" with the foam. "Stuffed" means, packed all the way tightly, except the plastic baffle that the pump sits in.

I do not know what description you are referring to that uses only 1 brick per 4 gallons? You need to have enough foam to stuff the whole gast tank, unless you'd be happy to simply build some kind of divider wall only that prevents major sloshing, side to side. I'm not sure how you'd construct such a wall and prevent it from shifting. I imagine that IS possible but, that is not how I did mine. If you look at a racing cell it tends to be filled nearly 100 percent with foam with maybe a tiny bore left open for a fuel measurement stick. I filled my FD tank fully with the foam except that area surrounding the plastic baffle for the fuel pump. That is why I also said that it was not a cheap solution.

Albert

HDP

iTrader: (2)

Well, I would probably only need 2 or 3 more bricks and @$7.95 per brick, I won't break the bank. I'll try the ones I have and see how well it fills the tank.

HDP

iTrader: (2)

The 5 foam bricks work fine. I probably could squeeze 1 more in there but I think what I have will be sufficient. Thanks once again.

axr6

You're welcome. I'm surprised that 5 were enough for that size tank. Looks like you got a good solution quite inexpensively.

Albert

scotty305

iTrader: (2)

How did you determine "fine"? What tests convinced you that your current setup is working better than before? Can you now take hard corners with less than 1/3 tank of fuel, without any starvation issues?


I don't mean to sound like a jerk, in fact I agree with the use of foam bricks in fuel tanks. My point is, how do you know you've solved your problem without sufficient testing?

-s-

axr6

While you addressed your question to HDP I'll take a stab at answering it. HDP had a problem that his internal tank baffles broke and had to be removed. There is NO DOUBT that the foam will greatly reduce the fuel sloshing that would happen in a tank with no internal plates.

When I raced my FD I drained the fuel tank completely and added gasoline 1 gallon at a time and recorded the fuel gauge display for each amount of gas in the tank. I tried to start each race with "just enough" gasoline in the tank to eliminate the added weight and handling problems that come from an overly full tank.

So, I kept real close records on my gas in the tank and also on how far I had to fill the tank for a 20 min, or 25 min race at various tracks. I also recorded exactly at what level the engine stumbled as the fuel sloshed under hard cornerings in the stock fuel tank. I was not happy with the amount of gas I had to load up with the stock gas tank in order to avoid the sloshing problem.

So, I installed the foam and recorded a significant improvement on the slosh problem. Now, I could start with less gas in the tank and complete the race without any hickups.

Yes, I could drop way below 1/3 of a tank and still have no fuel miss. I started most of the races with just a hair over 1/3 full tank, with 8 gallons of fuel.

Albert

dgeesaman

iTrader: (7)

HDP: my fuel tank baffles are rattling. For now I'm keeping the tank more full, but that won't cut it forever. (And a new tank is $500, so this foam seems quite attractive).

Got any tips for removing the old baffles? They look pretty sharp and nasty in the pics.

PS: by my best squinting, those foam blocks look just like the standard open cell foam I see everywhere. They are making mad money selling those things at $8/ea. I think I'll go the the arts/crafts store, buy a chunk, and if gasoline doesn't degrade it, I'll use that instead.

Dave

axr6

Dave

Just make darn certain that the foam from the arts/craft store does NOT degrade over time (as many foams have a tendency to do so) as it could hopelessly clug-up the fuel system. I "assume" that race quality foams have been long-term tested for fuel cell use as I had used fuel cells in tree different race cars, all with foam in the cells, and they showed no signs of degradation over the years.

As far as I know the fuel cell foam that I put into the tank of the FD back in 1994-1995 is still in there for the present owner and I have not heard of any problems.

Good luck,

Albert

dgeesaman

iTrader: (7)

I did some digging on that, and found:
1) you should replace that fuel cell foam after 5 years (just like a plastic fuel cell tank, the foam will be chemically attacked and embrittle, and once it gets brittle enough I imagine it will crumble to dust and jam the works quickly)
2) Polyurethane foam is the recommended choice for exposure to oil/fuel. However I'll have to dig deeper, and if I buy something I will test it. I may not be able to find a cheaper source for it anyway.

Dave

HDP

iTrader: (2)

Mine didn't say anything about replacing after 5 years...

dgeesaman

iTrader: (7)

Well I got started on it just now and my fuel tank baffle is definitely rattling loose.

But I have 2 questions:
1) I found a plastic cap type thing and a very fine wire spring laying loose in the bottom. Since my fuel level sender hasn't worked properly recently, I assume these are related. Any info on how to put this back together would help a lot.
2) The baffle is only loose at the far passenger side of the tank. The other spot welds near the fuel pump are ok. Should I try to work the welds until they break (risking a tank leak) or can I safely cut the baffle and leave the part that is well secured? I have a pair of wire cutting dikes that should do the job but I'm afraid to use them in immersed in fuel and vapor. It seems that leaving that section in and filling the rest with foam would be the best approach.

Oh, for anyone doing this, I strongly recommend a long rubber glove. I don't know where to get one (nearest animal hospital, perhaps) but bare arm in fuel is not cool.

Dave

HDP

iTrader: (2)

First I drained the tank then I used sheet metal sheers, bent back and forth till the remaining spotwelds broke loose and folded the baffles so I could pull them out the opening. I'm not sure what the parts in the tank were, but maybe someone who does can chime in.

dgeesaman

iTrader: (7)

Ah. I should have drained the tank but it's not in a suitable location for that. (I also don't have a suitable drain pan for that amount). I had planned on doing this job with a near-empty tank, but when the fuel level sensor quit working I didn't want to run out of gas. I guess it's time for a siphon pump.

Anyway, I may bend up the loose part of the baffle and shove the foam around it. The part that isn't loose seems to be quite secure. Later if I get industrious and the tank is low maybe I can cut that section off with shears (and hope I don't explode) or just leave it be.

Dave

Eggie

You already have a suitable pump in the tank! Just put a hose from the pump to a gas jug and use a jumper in the Diag box to run the pump. Remove the jumper when you need to change jugs or the pump spits.