Fuel tank questions

[Rich A]

A newbie question.
Does both halfs of the tanks have a feed and a return line?
Is there only one fuel gauge on the dash?
Who manufacture the fuel sender?

I've read though the archives and noticed that you have to switch between tanks to keep the fuel balanced in the tanks.

Is there a need for a system that would balance the fuel between both tanks and read off of one gauge?

[DaveWharran]

Speaking for my ERA only....

Does both halfs of the tanks have a feed and a return line?
Yes. I'm using AN-8 supply and AN-6 return lines.

Is there only one fuel gauge on the dash?
No, there are two gauges, one for each tank.

Who manufacture the fuel sender?
Centroid.
See them HERE and HERE

I've read though the archives and noticed that you have to switch between tanks to keep the fuel balanced in the tanks.
I don't necessarily keep fuel "balanced". I normally use out of the left tank first to offset driver weight (a lot of that!), then the right tank. Each tank is completely separate from the other. Fuel taken from one does not return to the other. Tank selection (pump that runs and return valve setting) are selected via two toggles on the dash. All are electrically interlocked so that only 1 pump can run at one time and so that fuel returns to the tank that it is being taken out of.

Is there a need for a system that would balance the fuel between both tanks and read off of one gauge?
Could probably be done but I prefer the look and function of the original that ERA built into thier car.

[Rich A]

Thanks Dave for the quick responce.
So is it safe to presume that the other manufactures use two gauges.

[scott]

I'm sure I'm being completely stupid in thinking that a small, simple communication bewteen the bottoms of the two tanks would passively balance them? There must be somethng I am missing.

[Ron Earp]

I don't think so (meaning I don't think you are on the wrong track). The original deal, to my knowledge, allowed drainage of both tanks for balance. But, I fly and have never really understood why in some aircraft tanks are separate. Just doesn't make since and it has killed many a pilot when they did not switch tanks - check the FAA records - 100s of folks have gone down with fuel in the right tank and not in the left while reporting engine problems that were later to be found fuel starvation.

R

[Eric]

I know I am not the most observant guy in the world, but I am sure that I remember the gulf cars with only 1 fuel filler lid, I'm not sure if that means 1 fuel guage, 1 fuel pump, etc, etc. , or how they transfer fuel from side to side, I know I have seen it mentioned here before, not sure if it was answered 100%.

[BenL]

[ QUOTE ]
I'm sure I'm being completely stupid in thinking that a small, simple communication bewteen the bottoms of the two tanks would passively balance them?

[/ QUOTE ]
Some of the original cars had a tube running from one tank to the other in the footwell to keep them balanced.

[Dave Bilyk]

My Dax has totally independant tanks with one (switched) fuel gauge.
Just a thought, with a balance line between the two tanks, a single fuel pump could be used for carburreted engines. Non original, and no redundancy I suppose.

Ron, thats an interesting point. Intuitively, I found myself thinking that tanks should be seperate so that a leak in one will not drain the other. But in this case it seems that practical experience suggests otherwise.

[David Morton]

On the larger aeroplanes its all about wing load relief and where you can store the fuel.
ie Boeing 747.400 the fuel pump switching sequence is draining sequence is Stabiliser, then Centre wing, then Inner Wing down until all wing tanks are the same contents then all wing tanks together. About 170 tonnes useable.
On light aeroplanes (pistons) Tip tanks are invariably the killers. I always went for unbalanced switching by using main on one side while draining the opposite tip tank and vice versa until the tip tank fuel pressure reduced. You are correct Ron. Many went that way and I suppose it was distraction or thumb up bumb.
I use the principle of the 'real GT40' system on my radar trailers which have twin 60 liter tanks and a common line between them to balance but on my GTD it would be nice to have but I didn't do it while I was building and wish I had. I suppose the real cars at Le Mans was so that they could be refuelled only on the right hand side.

[Veek]

Rich,
On a CAV the two tanks are totally separate. The dash switch activates the respective tank fuel pump and sender. The units we have are Bosch and are pretty neat enclosed floats. When you switch fuel pumps with the dash switch, you are in effect checking that respective fuel cell level as well.
Hope that helps.

[Howard Jones]

I like to leave my house with both tanks full and drive until one goes dry, switch tanks, refill 1st tank and so on. This way I always have enough fuel to get to gas station.

This is just my way to not running out of gas. But then I'm Italian.

By the way I'm getting about 100 miles on a tank. My tanks on my GTD seam to only hold 6-7 gals each. Is this correct? How does your car do on gas. How much do your tanks hold. Milage? I'm getting about 15-16 if I drive legal speeds.

I like two tanks/systems/gages looks cool and keeps me from running out of gas.

[brianstewart]

I seem to recall reading somewhere that the MKIs had separate tanks and the MKIIs had a balance tube between tanks. The fact that pictures of MKIIs show only one filler cap would support this perhaps?

Cheers, brian.

[Bob Putnam]

We don't use a balance tube for safety reasons. A balance tube would have to be tapped from the bottom of the tank, and thus would be under pressure all the time. Since our tanks are plastic, they would require metal adapters and gaskets. Not a design that I'm comfortable with. Any failure would result in a total loss of fuel.

If you look at any production tank, the fittings are always at the top, above the normal fuel level. I suspect that the MK2 had a dry-break system built into the crossover.

[Mike Dozier]

Rich

My Lola has twin tanks with only one filler.
They are cross vented from the top, and
I'll be using a large crossover, located
in the engine bay, plumbed into a single fuel pump.
Time will tell whether seperate fuel pickup/pumps
are needed...I hope not.

I haven't decided whether to use two gages or a single
gage with toggle switch....of course both tanks have
sendors...VDO mounted on the top of each.

MikeD

[Bill Musarra]

Mike,
When hard cornering, the inside tank line could be exposed to air which would go to the pump and do damage or at worse cause a vapor lock condition. It seems there has to be a suge tank or similar somewhere for the fuel pickup. Or am I not seeing it correctly. Where are you plumbing your return line? If the connecting line iis big enough, they probably equal out, so it shouldn't matter??
Bill

[DON S.]

[ QUOTE ]
I seem to recall reading somewhere that the MKIs had separate tanks and the MKIIs had a balance tube between tanks. The fact that pictures of MKIIs show only one filler cap would support this perhaps?

Cheers, brian.

[/ QUOTE ]

Most original Mk I GT40s had two separate fuel fillers, one for each bladder, and a rotary tank selector switch mounted on the engine compartment bulkhead behind the driver's right shoulder. Prior to 1966 Le Mans, six Mk I race coupes including my #1040 that were de facto factory cars but entered in the race by private teams were modified at FAV to make refueling during that long race more time efficient (I guess). The fuel bladders and interior side of the sponsons were revised to allow a crossover hose connecting the bladders to be installed in the interior of the car just in front of the seats. With the fuel bladders now connected, the rotary tank selector switch and hardware inside the bladders were fiddled to provide a "Reserve" position on the switch, and one of the external fuel fillers by the windshield was blanked off as unneeded. I don't know if the Mk IIs had this crossover system or not, or the Gulf team Mk Is, but it certainly offers the potential for danger in a severe crash with a farily substantial hose (I think the one in my car has around a one-inch ID) filled with fuel, and cutouts through the interior side of the sponsons, that could dump fuel into the interior of the car if the bladders leaked or burst. I don't think this actually happened to any car, but the potential was there. #1029, another of the six Mk Is modified with the crossover, had a pretty severe shunt at '66 Le Mans, but I don't recall any fire. I don't know if my #1040 still had the crossover system when it crashed at Monza '67. It did catch on fire, but that wasn't related to any fuel crossover system as far as I know. If the Mk IIs had a crossover, then the severe crash of #1011 at '66 Le Mans trials and the multiple rolls of #1012 at testing at Daytona would seem to have put it to the ultimate test. Authenticity aside, when my car is restored, I think I would opt out of the crossover for safety reasons.

[Richard Ibrahim]

I thought I read somewhere that the single filler was a Le Mans regulation - knowing the ACO back in the 60s, they probably informed the teams the night before the race !
Regarding the system, the tanks on my GTD were taken straight of the previously mentioned Boeing 747.Apparantly the guy who originally commisioned the build, wanted to tour Europe without stopping !They run the entire sill length and completely fill the pontoons. I've only once tried to fill both tanks, but gave up after the pump read £102!Even then the gauges showed only 3/4 full(and the VDO senders are vertically mounted at the max height position). As for getting 15/16 mpg at legal speeds - I consider it a triumph if I get 8/9 mpg (at admittedly rather illegal speeds). I generally run with both pumps on (piped in parallel and one-way valves, of course).One pump invariably pumps slightly faster than the other - but there are no ill effects and no need to keep switching pumps.

[Mike Dozier]

Bill

My car is 99% street oriented, so simplicity (and cost)
were high on the list. The crossover is big enough to
provide fuel for any momentary G-forces, and since my engine
is carbureted with street fuel pump, there is no return line. KISS principle...

MikeD

[Fred/Belgium]

Dave,
I want to order the centroid fuel senders for my car.
I assume for a GTD40 it is the 3" to 12" depth one?
Tx
Fred

[Howard Jones]

When I say legal speeds I mean as if a cop is in sight.