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Discussion Starter #1
I'm using a small fuel cell, it works well but it's too small for street driving.

When I was using the OEM style tank the fuel would just rush to the back and uncover the sump causing a lean condition. I don't really want to weld an external rear sump on the OEM tank.

Has anyone added baffles or otherwise to make an OEM type tank work when cutting 1.5 second or faster 60' times?
 

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I'm using a small fuel cell, it works well but it's too small for street driving.

When I was using the OEM style tank the fuel would just rush to the back and uncover the sump causing a lean condition. I don't really want to weld an external rear sump on the OEM tank.

Has anyone added baffles or otherwise to make an OEM type tank work when cutting 1.5 second or faster 60' times?
This is kind of a cheap fix, but you could always rig up a simple switch to go between the two fuel cells. One for street driving and one for when you want to romp on it at the track. you could have it mounted just in reach of the drivers seat too.
 

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You could always run a surge (header) tank.

David
 

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+1 to what David said. Low pressure electric pump feeding a quart or so tank the mechanical pump feeds from. You can put it in the trunk or in the engine compartment.
 

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First off what you said makes absolutely NO sense.

Point 1: Fuel will fight for level as soon as possible, and attain it even in high gravity situations.

Point 2: If you were Leaning out in a 1.4 mile run with a stock tank, then you didn't have enough fuel in the tank for that run.

Point 3: If you can rush that much fuel to the back of the tank and hold it there through your run then you A: either only run you car with 2 gallons in your tank, or B" you are pulling 3 G's throughout your entire run.

What am I missing here that the other guy's don't see?
 

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Who the hell races with only 2 gallons of fuel in their tank....?
Drag racers. Every gallon of fuel is 6 pounds. Less than 17 gallons is 100 pounds and the typical door-slammer drag car will lose roughly 1/10 second per 100 pounds - that's a lot after spending $500 for a race carb or traction parts or something to get that 10th. Free speed. It only takes 1G to slosh the fuel to a 45° angle. Even 1/2 tank would expose most front-pickup systems like most of our stock tanks have, so 1G during a run will see the engine lean-out. Usually small fuel cells are used with sump pickups, or the stock tank is modified with a sump or baffles, or a header tank (like aerobatic aircraft use and known as an accumulator or surge tank to many) is used to keep fuel feeding to the pump.

A 600 hp engine only needs about 17 ounces of fuel for a 10 second run. With 6 ounces in each carb bowl but only 4 in the lines, he will only make it to the 330' mark before the float level begins to drop. Even if the 1G didn't last the whole run, the float level will still drop and give a lean-out. A surge tank or sump with over 17 ounces (actually 17 - 4 (lines) = 13) will give a full run with full bowls even if the pickup can get zero fuel during the entire run. Problem solved.

Sumps or surge tanks are generally sized for 50-100% extra fuel than necessary, so a 24 to 34 ounce volume is more than plenty. Reality is a spin-on remote fuel filter unit with a lengthened center pickup tube holds about 16 ounces (or more depending on filter choice), and has been used many times as a clean $30 fix for this common situation. Throw a cheap feeder pump (a.k.a. boost pump, lift pump, or low-pressure (almost zero pressure) pump) on to feed it and it's all good.
:tup:
David

[EDIT] PS: Low fuel is also to reduce risk in racing. 1/2 tank can make a much bigger fireball than 2 gallons.
 

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Discussion Starter #8 (Edited)
FE: Tell those that are running a string of 11.05's that there wise to make sure they have a full tank of fuel ;-)


Picture of surge tank anyone?
 

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Think rt has the easiest fix. use a switch valve thats used for switching between the 'front' and 'rear' tanks on the f series trucks. I doubt you would need the ability on the street for a full on blast...
 

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Here's a couple examples. In the 1st pic the 'kitchen' fire extinguisher is an example of what I used for my first home-made surge tank. I used a steel-body type so I could just braze the fittings on. Slick. A bit big, but it was for road racing and needed to be big for long power pulls on sweeping courses. The remote filter on the right has been simply modified with a center pickup to act as a surge tank, and will bolt anywhere there's room. Originally for UPS type trucks, I grabbed it on FeeBay for $10 new, but it's basically the same as any other remote filter. And, it's a filter.

The second pic shows a generic oil catch can found online for cheap. Remove the sight tube fittings, plug the top hole and replace the bottom fitting with a fuel line barb fitting for a bottom fuel outlet. Done. Billet, comes with a mounting bracket, and they typically run around 25 ounce (750 ml) capacity. Easy. Cheap. Perfect.

David



 

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Discussion Starter #13
PSIG,

Thanks for the pictures.

I should have mentioned I'm using a Carter mechanical street/strip pump.
 

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No difference if it's feeding a mechanical or electric pump - same setup.
:tup:
David
 

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Discussion Starter #15 (Edited)
The surge tank might fit just in front of the OEM tank. Seems like it would be best to be below the main tank.

If the surge tank was partially above the level of fuel in the main tank, would the mechanical pump fill the surge tank above the main tank level, or just to the level in the main tank?

Using the big filter as the surge tank would be an added bonus. Perhaps this one:
http://www.summitracing.com/parts/SUM-G1507/

or this one:

http://www.summitracing.com/parts/FRM-HPG1/SuggestedParts/?prefilter=1

Not sure how much fuel they hold?



surge.jpg
 

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If the surge tank was partially above the level of fuel in the main tank, would the mechanical pump fill the surge tank above the main tank level, or just to the level in the main tank?
The concept is just a little different. Because there is poor gravity feed from a stock tank, we have to help it with a little pump. If you had a huge bottom drain (sump style) instead of a pickup, then you could do a pure gravity system if the entire surge tank (accumulator) was below the bottom of the main tank. See pic below. Some carb race regulators use a return, but if your carb uses a regulator without a return or no regulator at all, then yours would be the same - except no "Return from regulator" line is needed.

We need the 3rd line (Fuel/Air return to main tank) to get the air out of the surge tank. Without it, when the pump sucks fuel up, air would get trapped in the surge tank leaving little or no room for fuel - the whole point of a surge tank. So, mu suggestion is to rig it like the pic and know you have a bulletproof fuel feed setup. The other big benefit of using the little LP feeder pump is the ability to put the components anywhere you like - not just below the tank. So some put everything in the trunk, or on a frame rail, forward of a front tire, or even in the engine compartment as others have already mentioned.
:tup:
David

This is my generic accumulator drawing for carb or EFI setups. If you have no regulator return, delete that line only. If you have a carb, the HP pump would instead be your mechanical pump or carb electric race pump. All setups should have either 3 or 4 lines:

 

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I have access to some retired alumnium O2 bottles. They have a threaded fitting on top, are about 14" tall, and 3.5" in diameter. They do have a 1/4" hole drilled near the bottom that would have to be pached or modified to accept a fitting. I could send you one for the price of shipping if you want.
 

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Discussion Starter #18
The concept is just a little different. Because there is poor gravity feed from a stock tank, we have to help it with a little pump. If you had a huge bottom drain (sump style) instead of a pickup, then you could do a pure gravity system if the entire surge tank (accumulator) was below the bottom of the main tank. See pic below. Some carb race regulators use a return, but if your carb uses a regulator without a return or no regulator at all, then yours would be the same - except no "Return from regulator" line is needed.

We need the 3rd line (Fuel/Air return to main tank) to get the air out of the surge tank. Without it, when the pump sucks fuel up, air would get trapped in the surge tank leaving little or no room for fuel - the whole point of a surge tank. So, mu suggestion is to rig it like the pic and know you have a bulletproof fuel feed setup. The other big benefit of using the little LP feeder pump is the ability to put the components anywhere you like - not just below the tank. So some put everything in the trunk, or on a frame rail, forward of a front tire, or even in the engine compartment as others have already mentioned.
:tup:
David

This is my generic accumulator drawing for carb or EFI setups. If you have no regulator return, delete that line only. If you have a carb, the HP pump would instead be your mechanical pump or carb electric race pump. All setups should have either 3 or 4 lines:

PSIG,

Suggestions for the LP pump?
 

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Suggestions for the LP pump?
In-tank or external? Any little pump made for a carb will do, as they are designed to occasionally run dry. Those are generally diaphragm, turbine (fixed vane) or centrifugal pumps - not gerotor (gear) or roller-vane pumps used in EFI as they have internal contact and need constant fuel to lubricate and cool the parts. It also can be quite small as the pump fills the surge tank when you're not using full power, which is most of the time even in drag racing. Below are some examples I've used.

David

The small and reliable Mr. Gasket 12S diaphragm pump. Enough flow to easily feed 400-600hp intermittent. Low power draw and under $40 on-line:

Any one of several generic electric carb pumps. These generally have enough flow to sustain constant high-power like racing boats, or intermittent drag and street to well over 1000hp. Higher constant amp draw for the overkill though. Everywhere for good quality units fairly cheap:

Low-pressure in-tank pumps from various European and American dual-pump EFI cars that use the system I outlined above. This one is the in-tank Ford feeder pump, makes high-flow at 5-7 psig, and can be adapted to in-line placement. $20 to $40 online:

 
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