fuel cell pickups

[benracin]

My fuel cell simple has a hose running down into the tank entering the tank at the front left then laying down as it crosses left to right towards the front of the cell. Due to this layout I'm getting fuel starve issues on long right handers. I'm sure moving hose to the left side of the tank would cause the same issues on long right handers.

I'm thinking that what I need is two corner pick ups on both sides of the tank. In order to do that do I need 2 fuel pumps that then feed into the same fuel line? Can I do it with one fuel pump or is there something I'm missing all together?

Thanks!

[lateapex911]

ben, check out some of the fuel cell sites...they make surge tanks that fit into the cel.... foam can help too. Maybe that might be a simpler solution.

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Jake Gulick
CarriageHouse Motorsports
ITA 57 RX-7
New England Region
[email protected]

[racer_tim]

Same principle as a baffled oil pan. Does you car have Fuel Injection? If so, check out the VW section on how we've overcome this problem with starvation.



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Tim Linerud
San Francisco Region SCCA
#95 GP Wabbit
http://linerud.myvnc.com/racing/index.html

[Speed Raycer]

A lot less complex, but my cell has a T at the end of the main line and then two hoses that branch off to either side of the cell. Pretty simple solution and not a whole lot of effort involved.

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Scott Rhea
It's not what you build...
it's how you build it

Izzy's Custom Cages

[JohnRW]

This is actually a FuelSafe surge tank - $130. Got these in a couple of cells...solve many problems:

http://www.hrpworld.com/index.cfm?form_pro...&action=product

[benracin]

Scott, I like your idea because of the cost, but what I'm wondering is if one tube is in air and the other is in fuel, wouldn't the air win over and get drawn into the fuel line? I guess that's why I was wondering if I need to fuel pumps.

I'm sure the surge tank would work, but I'm having to go low buck racing this year. Wait a sec, hasn't that been every year???

Oh, and this is an ITA rx7.

Thanks!

Ben.

[MMiskoe]

Get a surge box of some sort, don't mess w/ multiple pick ups into a common line, it doesn't work well (in my experience). One pump w/ two pick ups will suck air when it can, as air is easier to pull. Two pickups, two pumps w/ check valves & tee's tends to deadhead the weaker pump which causes it to cavitate, then when the stronger pump sucks air, the weaker pump has a bit of lag to overcome due to the cavitation. Net result - same hic-up & sputter with way more crap to haul around.

I have an "ATL Black Box" w/ one pick up. It will pull the cell down to less than 1 gallon.

[Eagle7]

I've got a cell with foam and a surge tank. There's a section of track at Grattan with 4 sweeping turns one after the other - R R L R. I starve on the last R if I'm down under 3-4 gallons.

It was recommended to me to not run the return line into the surge tank (which I didn't), as it is hot fuel that you don't want going back to the engine until it can cool off. Seems like the return into the surge tank would fix this - although it's not a problem for me because I need the fuel to make weight.

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Marty Doane
ITS RX-7 #13
CenDiv WMR

[racer_tim]

Marty, I'd rather have hot fuel in my surge tank than air.

My sump tank has 4 fittings in it. #1 on top from cell, #2 on bottom to stock fuel pump, #3 on top, return from motor, #4 on top, return to cell.

I would have to assume, that any hot fuel returning from the motor, has to be in MUCH less quantity than comming from the cell.

Case in point, have you ever seen the volume of fuel returning from the sump tank? I did that with a "T" as my fuel port access. I did it also to drain my cell for winter storage (But in CA, you don't really need to do that). It took me over 15 minutes to drain 4 gallons from the cell to an external jug, using this method.



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Tim Linerud
San Francisco Region SCCA
#95 GP Wabbit
http://linerud.myvnc.com/racing/index.html

[badal]

I have a hard time believing foam will make ANY difference.
The average Nextel Cup pit stop is under 15 seconds for 22 gallons of fuel. The foam in those cells does not seem stop fuel from flowing into those cells, so how could it stop it from flowing side to side?

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"Bad" Al Bell
ITC #3 Datsun 510
DC Region MARRS Series

[benracin]

I've looked at some surge tanks online and for the poor racer, over $100 is a little expensive. I'm kind of wondering if one could build one on his own.

I saw in an older post someone had suggested taking one of those large fuel filters, empty out it's guts, slap it in the fuel line and wham-o, you've got the poor mans surge tank. Sounds like it just might work to me! One question though. Do you need a pump infront of the giant filter and one behind it or just one pump on one side of the filter.

[JohnRW]

Your idea is basically an 'external surge tank'. Lots of cars with fuel injection and fuel cells have them, as the injection system takes a total crap if it sucks any air at all. Any kind of can will work - large fuel filter, empty propane torch bottle etc. You just need to suck off the bottom and dump the feeds and returns into the top, then vent any overflow back to the cell. This requires a 2nd 'feed pump' to supply the external tank.

Why not fab up something cheaper that won't require a second pump, since a 2nd pump = $ and another failure point ? Build a 8" x 8" box...you could probably use flattened coffee cans soldered together...or maybe just a plain coffee can. Wander around a plumbing dept. and find some 'ball check valves' like some sump pumps have...or maybe a boat yard and snag some 'self-bailers', or a hardware dept and find some hinges that you can use to create 'trap doors', any of which will keep the gas contained in the box. Back in my dark past, I had a VW oil pan with door hinge trap doors. If no one can see it, they can't laugh at it.

If you're creative, you can probably build something for $10-20 in parts.

[racer_tim]

Ben, I made an external sump tank from P/N SUM-3000101 at Summit Racing Products.

Picture @ http://static.summitracing.com/global/imag.../sum-300101.jpg

I moved the top fitting to the side, and added 2 others at the top. Here is it on my VW
http://linerud.myvnc.com/racing/2002/sump-tank-1.jpg

So my setup is: I have 2 pickup's in the cell, with a "t" fitting to a single facet electric pump, which feeds to 1 of the top fittings in the sump tank. The bottom fitting feeds the stock VW fuel pump, the 2nd top fitting is the return from the engine, and the 3rd top fitting is the return to the cell.

Before I built this setup, I would starve out on left hand corners with 4 gallons still in the cell. I could hear the facet pump start to "tick" when it was sucking air. A few seconds later, the car would sputter. It would recover in a few seconds, but this wasn't good, since the session wasn't over.

Since going to this setup, I still hear the facet pump sucking air (ticking) but with this quart of fuel still feeding the stock pump, I haven't had any problems.

The Summit part was around $50 and the other fittings were about $40, so for under $100 I fixed the problem.



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Tim Linerud
San Francisco Region SCCA
#95 GP Wabbit
http://linerud.myvnc.com/racing/index.html

[benracin]

Well JohnRW and Tim those are some swell ideas. I like your idea Tim but those prices are getting close to an actual surge tank. I wonder if your set up can be made with nice cheap parts although John does raise a point that it's another point of failure.

If I went with John's idea, what metal would you use to submerge in fuel? Will anything do or will some rust as soon as they sit un-submerged for a bit. I'd probably weld a little box together but I'm wondering if the fuel would eat it alive.

My other issue is that I don't want to cut an opening in the cell. So if I can create a surge tank and have it fit into the normal opening in the cell that would be awesome.

Sorry if I'm getting to low budget. I was reading the air dam post in the tech section and its really got me on a 'inventing stuff at homedepot' spree. Walking around the depot inventing race car parts is one of my favorite hobbies.

[Greg Gauper]

The surge tank from ATL is basically a fuel resistant plastic box with three check valves (one on each side) + a fuel pick-up on the fourth side. I installed mine so that the check valves are facing to the sides and rear with the pick-up towards the front. The box has an open top, fits in the cell thru the stock opening (you have to unbolt the plate and cut out a section of foam to install) and then it just sits in the cell. My fuel return line dumps back into the surge tank to help keep it full. The only thing to be careful of is don't have the return line located too close to the pick-up, or you can suck air bubbles if the return fuel becomes aerated. I had this problem when I first converted to Fuel Injection for G-Prod. I isolated the return line with a scrap of cell foam and it has worked fine since then. I have managed to run the tank down to less than 1/4" of fuel at Road America, but have a slight problem at IRP and Mid-Ohio with long left hand sweepers (I offset the tank to the left since most tracks in Cen-Div are right handers) unless I carry an extra gallon or two on board, so I end up 6-12lbs heavier due to the extra fuel...not a big deal and I can find other places to take weight off. I think this slight problem will be cured by shifting the tank over 1 or 2 inches, plus I plan to add a simple baffle/cover plate for the surge tank. What I think is happening at those tracks is that the fuel is sloshing out of the surge tank. Note: This is on a Prod car with slicks so my cornering loads are a bit higher than a car on DOT tires, so it might not be an issue for an IT car.

If you can get your hands on three check valves (check if ATL sells just the valves) you could probably build a tank your self out of aluminum and save some money. It's a pretty simple design.

I'm personally not a big fan of external surge tanks from the safety standpoint. The internal tank is contained inside the cell which is a bit safer and the installation is pretty very straight forward.

Ben, is your car carb'd or injected (I can't remember)?

If it's carb'd, before you go to the trouble of re-inventing the wheel, you might try something simple like re-routing the fuel pick up line so that it faces the rear and draws fuel from the rear of the tank. As you accelerate, the fuel sloshes towards the rear and towards the pick-up. Alternately, you can do what the Spridget guys (carb'd engines) do and run is two small pumps with pick-ups located on either side, with the outlets connected via a 'T' with check valves on each side. The outlet of the 'T' feeds the carb. This way at least one pump is always delivering fuel no matter which direction the car is turning. Carb'd cars aren't affected by air. FI cars are a different story. A well designed simple surge tank will help.


[This message has been edited by Greg Gauper (edited January 04, 2005).]

[benracin]

Thanks Greg. I do like the two pick up, two pumps idea. It's just so simple. And the car is a first gen RX7 with a wonderful carb. Marty up above mentioned that two pumps will fight each other. Do you think that would matter in my low pressured fuel system? I think my current fuel pump puts out about 6-8 lbs and I'll be adding a holley pressure regulater to bring it down to 2 1/2 lbs.

Just moving the pickup to the rear or to the left side would help at Road America in the carousel but it has me wondering about long left hand turns like turn 5 at Blackhawk.

[ddewhurst]

Dam, I knew there is a reason why I use the OEM tank. It's inexpenseve & it works.

Have Fun
David

[benracin]

Well where is the fun with that David? If it doesn't take 10 trips to Home Depot I'm not interested.

[MMiskoe]

For a cheap pick up box look around at what OEM tanks have in them. Often it is a plastic tub w/ a "devil's trap" for the fuel to get into - must go around several corners, no straight lines out and some have a little threshhold that traps a small puddle. Some of these are small enough to fit through the standard opening on a fuel cell and can be held in place w/ the foam same as the ATL black box.

For materials to use inside the cell - I'd go w/ aluminum - light & easy to work w/. If you try to get check valves be careful, the "cracking pressure" has to be near zero (ie thay can't have a big spring in them holding the ball closed). The ATL valves are like a tube w/ a ping-pong ball inside that floats back & forth, blocking flow in only one direction.

[benracin]

Can I just make this aluminum box out of bending tabs and rivets or would I actually need to weld the thing? Is there some type of adhesive I could use to seal the seems that fuel won't eat away?

Thanks so much for the help everyone. This is going to be a fun project.