i've been trying to resist this post but i can't stand it anymore, i have to share. i've been working on a solution to the fuel pick-up problems many of you experience with your 3rd gens. the kit i'm putting together will use a two prong approach to solve this issue...1) a baffle/cover for the stock resevoir and 2) a small resevoir that installs just above the stock unit that takes returned fuel and holds it in wait, dumping it in the stock resevoir as needed. i'm hoping to have kits available just after the first for ~$150 retail. the installation will consist of removing the fuel pump/sending unit...snapping in the new parts...replumbing the return line in the tank and putting it back together. probably an hour to 1.5 start to finish. anyway, just wanted to gauge interest and let you know help is on the way. p.s. i,ve got the prototype installed in my car but it developed other issues and is hampering proper testing(the weather hasn't cooperated either).

 

I'm very interested. I'd really like to see some pics...

 

i need to get the parts back out of the tank and snap some pics...probably later this week. i'm also working on a 1.8t powered rabbit track car that is consuming most of my spare time. hang in there, i've been working on this a long time and really feel i've got a proper solution...well worth the wait.

 

If it's a good solution I'm interested. I'm getting nasty fuel starvation anytime I powerslide with less than exactly 1/2 tank of gas....

 

My $5 mod (without the fuel pump and AN lines, that is). Be prepard for some some pretty bloody mitts. No slosh till < 2 gallons.

Scroll down:

http://www.mantissaconsulting.com/et...uel_system.htm


Gene

 

I'd be interested also but want some more info and pictures.
Crispy

 

BTW, I'm interested as well. There's got to be a better solution than the blood and guts approach I took.

Gene

 

I was just thinking about this the other day.
I am sure eurautodave probably has a lot more elaborate solution, and I was thinking about Genes solution also, but couldn’t we simply make a top for the fuel box, and install a one way pivoting door in the intake channel of the box? It would effectively stop most of the fuel from escaping once entering the box.

There is a thread floating around I just saw that is trying to find a good retrofit solution to a built in internal sump pump that pulls fuel into a small container then draws from that.



Genes idea is very similar but uses check valves. http://www.mantissaconsulting.com/et...uel_system.htm

Do you find this not to be sufficient Gene?
Does slosh inside the box still come into play?

 

from the oil slosh thread by Kevink2 https://www.rx7club.com/showthread.p...38#post3816438

 

Seems like the best way to stop slosh if you could attach the feed tube to the low point in the tank

 

Good idea, but one door will not let enough fuel back in the covered baffle (channel is too small), particuarly given the physics/dynamics of running about on a track. Probably okay on the street, though. For example, with one door in the "channel inlet", you would not re-fill the surge when taking, say, a double apex left hander. The trap doors (http://www.hrpworld.com/index.cfm?fo...roduct_picture) actually flow a lot more than the check valves, but would be a bitch to install given the restricted access to the baffle (you'd have to get a jigsaw or similar in there to cut squares out of the plastic baffle).

Internal or external sump/catch can is probably the best solution short of a fuel cell. A "second best" approach would be to completely cover the baffle and use an 90 degree AL tube that would pass through the cover and lie at the lowest point of the surge. The other side would mount to a filter -> pump _> and so on. I might try this next simply because I fear that the -6 90 AN connection and fuel pump sock may be a limiting factor in my setup (with the Bosch pump).

Similar setup as the image, but the hardware would be mounted above the baffle.

[img] http://www.rickshotrodshop.com/stealth/P1000408.jpg [/img]


Gene

 

it's nice to see some interest in this topic. i've battled this problem so long on my car that i've given up taking it to the track. i also can't slide my car around with less than half a tank. my approach to this uses the same cover over the stock resevoir as mentioned(and pictured) above, but goes a step further, using the return line to refill a small (~1 pint) tank that sits above the baffle and drains into the resevoir when needed. the tank is actually a bmw part( that completely fixes fuel starvation issues on e46 models) that i have adapted to the application. the beauty of this modification is it's simplicity...yeah a champ car fuel system would be nice but i just want to run the car the way it was meant to be...not reengineer the whole freakin drivetrain...see jimlab's posts for that.

 

So, exactly how would you have gone about getting the right differential gear ratio for a V8 swap while improving the strength of pretty much every component involved?

 

My baffle system doesn't look anything like yours, Gene, and I've heard that the baffle in newer tanks solved the problem. Jeff Hoskinson got a '99+ tank for one of his restoration jobs and I believe it had the same baffle in it that I have.

 

The tank is effectively flat on the bottom so it would be difficult to add a hose going to the low spot..

Actually it is the 96+ tank I believe. The guy at Mazdaspeed was a little confused as to if the change was actually done in 95 since I think it was showing the same p/n but a different one for 93 gas tank.

I know Mazda changed the plastic baffle/fuel cup to accept the cover for the metal "cover" sometime for the mid-1994 year but did not add the cover. I don't know if they added the metal cover in 95 or 96.

 

Not completely solved, but better (and perhaps more elegant than my hack job). The 96+ tank/baffle cover inhibits starvation down to about .25 tank or so. Mine is custom and does better than that. The only potential issue I have is a flow problem going into the pump. I lost some fuel pressure (comparing boost vs. fuel pressure) on the dyno a few weeks ago and this may be a factor. Of course it could be the pump, wiring, grounding, or something else

Gene

 

That is my experience as well. I'm good down to just about exactly 1/4 tank (on the super accurate stock gauge) before starvation on an auto-x course.

Much better than the 5/8 tank min I used to need.

 

Dave,

I'd be a bit concerned about the size of the refill tank should the baffle/surge tank temporatily run dry. That should not happen, but is a possibility if the baffle doesn't refill properly (why I'm using check valves). For example, my car at 15 PSI can consume roughly 197 LPH which is 403 pints. That means that a one pint tank could be emptied in about 10 seconds. That's a pretty long turn, but a not out of the range of possibilities. That also assumes that the reservoir tank refills the baffle at the same rate or better than what the pump is using and there are no losses at the pump pickup.

BTW, if I recall correctly, the volume of the baffle is roughly 7.5 pints or 3.6 L.

Just food for thought.

Gene

 

From my website:

The newly created surge tank (stock baffle with a cover) measures roughly 9.5" x 6.5" x 3-4". The depth of the tank varies as it slopes upward and has an additional amount of volume on the driver's side. This is roughly equal to 210 cubic inches or 3.5 liters. Assuming I'm running the pump at max capacity for my desired goal this equals about 192 LPH of fuel consumption. Thus, the tank would be pumped completely dry (assuming no fuel flow back in to the tank) in 65 seconds. Of course, there will be some fuel loss due to sloshing out of the top of the cover. Let's [conservatively] assume that 1/2 of the tank was emptied due to slosh out of teh top. This would still require 32.5 seconds to pump dry at full boost. I feel that this is more than adequate as I cannot imagine turning left under steady state conditions and at full boost for that amount of time.

Gene

 

Thanks for the link Gene. Nice, informative page!

Starvation's a frustrating problem. I had looked another solution earlier, which added another pump and remote reservoir, but I'm really just not wanting to get too involved with this. At this point it's just an inconveniece since it's not THAT big of a deal to keep more than 1/2 tank. On the other hand I go through half a tank in 100 miles on the street, MUCH less on the track......

 

Why not try a sumping the tank, and an external pump. I know people usually think of a sumped tank for drag racing but I have mine sumped and it works perfect on the road course! You can run your tank below 1/4 without having any fuel pressure drop. I wish I had pics but if you want to see the setup pm me and I will snap some.

 

Most people's cars serve double-duty as street cars if they go to the track at all, so they don't want to listen to the noise of an external pump when they're cruising on the street. They don't want to have to modify their fuel tank either, or at least to the extent that welding a sump into bottom of the tank entails.

 

I'd like to see some pics.

My imagination says a sump welded into the bottom of the stock tank is very dangerous at best.

The bottom of the tank is low and could be damaged in any off-road event. If the sump hit something I could imagine it would rip right off and leave up to 16 gal of has spilling out in a wreck.

In a rear end collision any tank flexing could break welds on a sump...

 

I am not a professional at welding but from what I know of welding, you are actually joining to pieces of molten metal while using an adding material. I think the first problem is the Fd tank setup. Have you ever had the tank out of the car, if you notice the tank actually slopes 15 to 20 degrees to the front of the car where your stock pickup point is(pump). My understanding is under acceleration that angle is not enough to keep the fuel from running twards the back of the Tank, that is your pickup problem. Therefore adding on the sump would be the logical choice for reliability.

 

I'm not so worried about the welds themselves failing. Welding on a sump is going to make that area of the tank more rigid where the walls of the sump are joined to the tank. This leaves the walls of the tank around the sump much more inclined to tear near the sump whereas without a sump the tank would just crush.

Because the original tank material is so thin and easily distorted if you reinforce only one area of it by adding a sump it seems much more likely to tear or rupture the tank rather than just crush it.