Mustang Fuel Tank - How does fuel transfer from the passenger to driver side?

[Junkyard Dog]

Has anybody cut open a fuel tank and looked inside? Do you know how it operates?

How did Ford design the transfer of fuel from the passenger side to the driver side, where the fuel pump is located?

Obviously, it cannot get over there all by itself. Just look:

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[Skye]

I'm under the impression it's nothing more than gravity.

From the track posts I've read, everyone goes out with at least 1/2 tank, to prevent starvation under Gs.

People heading to the drag strip, they might have differing requirements.

To keep the pump from running dry* on the street, I've never run less than 1/4 tank.

* People can and do run to "E" on the gauge, sometimes to the point of an additional alarm. I do not. It's generally not a good idea to run any pump to where it's sucking nothing but air; the internals of the pump overheat.

For those with home water circulation systems, same. If draining and purging the system, like when you empty the hot water heater each season, purge all the air from the lines. The water cools the pump internals. Running it dry leads to premature failure.

 

[Junkyard Dog]

I'm under the impression it's nothing more than gravity.

Look at the photograph. Gravity would never accomplish anything unless the car tipped over and came to rest on its driver side door.

 

[Ewheels]

I think there's some sort of secondary pump to move fuel from one side to the other.

I assume the S650 uses the same tank as the S550 and there are several writeups on it over at M6G. Lots of fuel starve threads on high-G turns.

 

[Junkyard Dog]

I think there's some sort of secondary pump to move fuel from one side to the other.

I assume the S650 uses the same tank as the S550 and there are several writeups on it over at M6G. Lots of fuel starve threads on high-G turns.

The S550 and S650 tanks look very similar, so there must be a similar method of operation. Moreover, this is a common fuel tank design in sporty, low cars where the driveshaft passes under the tank (the hump is to clear the driveshaft). I was reading on a BMW Z4 track forum about this fuel starvation issue, which was common, but not universal. They did not come up with why it was happening, although one of the members cured the issue in his car by using a custom bracket to mount a fuel pump to the side of his stock fuel pump canister. The sole mission in life for the additional fuel pump was to pump fuel from the side without the fuel pump to the side with the fuel pump, always keeping that side of the tank full. Seems like a sledgehammer to kill an ant, but he reported that it solved his issue. One member with a very fast, full race car capable of very high G forces did not experience this issue, and others who did admitted the they tracked for a couple of years without experiencing it, so speculation was that something would fail in the stock system and cause it. Anyway, the BMW track forum folks never figured it out.

I cannot find a good explanation anywhere for how fuel is transferred from the passenger side to the driver side in a Mustang, but it is transferred somehow, and apparently not well enough to overcome the G forces when making a sustained high G force turn.

I would be very interested in anybody sharing how this works in the Mustang fuel tank if you can find it.

Somebody has to have looked inside of one of these things.

 

[Ewheels]

The S550 and S650 tanks look very similar, so there must be a similar method of operation. Moreover, this is a common fuel tank design in sporty, low cars where the driveshaft passes under the tank (the hump is to clear the driveshaft). I was reading on a BMW Z4 track forum about this fuel starvation issue, which was common, but not universal. They did not come up with why it was happening, although one of the members cured the issue in his car by using a custom bracket to mount a fuel pump to the side of his stock fuel pump canister. The sole mission in life for the additional fuel pump was to pump fuel from the side without the fuel pump to the side with the fuel pump, always keeping that side of the tank full. Seems like a sledgehammer to kill an ant, but he reported that it solved his issue. One member with a very fast, full race car capable of very high G forces did not experience this issue, and others who did admitted the they tracked for a couple of years without experiencing it, so speculation was that something would fail in the stock system and cause it. Anyway, the BMW track forum folks never figured it out.

I cannot find a good explanation anywhere for how fuel is transferred from the passenger side to the driver side in a Mustang, but it is transferred somehow, and apparently not well enough to overcome the G forces when making a sustained high G force turn.

I would be very interested in anybody sharing how this works in the Mustang fuel tank if you can find it.

Somebody has to have looked inside of one of these things.

https://www.mustang6g.com/forums/th...hat-options-for-an-na-car.212738/post-4238187

 

[GrabThatBlue]

The outside shape is different than the inside shape.

 

[Junkyard Dog]

The outside shape is different than the inside shape.

Could you elaborate a little, please? I mean, the hump for the driveshaft has to be there internally, too, right? Or am I missing something obvious?

 

[Junkyard Dog]

https://www.mustang6g.com/forums/th...hat-options-for-an-na-car.212738/post-4238187

Ewheels, thank you for sharing that. So three pages in, they discuss that there is a 1/8" line that feeds one of the venturis, which is how the fuel is transferred from the passenger to the driver side. On page one, KPM notes: Two venturis, one pulls from each side of the tank.

So . . . the four venturi KPM system solves this issue even though the tiny little 1/8" line remains?

engineermike posted - "We did some testing and each stock venturi pump moves about 180 lph into the bucket per side. 360 lph is ok in most situations but 180 won't keep it happy for long."

 

[GrabThatBlue]

Could you elaborate a little, please? I mean, the hump for the driveshaft has to be there internally, too, right? Or am I missing something obvious?

It has a pump inside. And yes, if it can't get enough suction the gass will not get through. That's what happened in the video of Misha yesterday with his Dark Horse on the Nurburgring.

 

[Junkyard Dog]

Photo from page 3 of one of the KPM systems.

 

[Junkyard Dog]

Also from page 3, by KPM:

"The KPM fuel bucket requires 10lph for each venturi jet. 4 venturis jets = 40lph total​

Each venturi siphon draws 363lph from the tank into the bucket 4 venturi siphons = 1452 lph total​

​

1452lph - 40lph = 1412 lph bucket refill rate."​

​

and

​

We tested the standard venturi and with the aim of improving on it, we designed our own.​

As you have noted, we couldn't much improve on it. The end result is the best siphoning we could achieve.​

We then needed to increase the venturi numbers to match the KPM fuel pump output.​

 

[Junkyard Dog]

So I read the whole thing, and if I am understanding what I read correctly, the problem is not that the driver's side goes dry, while all the fuel is over on the passenger side saddle (the theory I have read here on the forum) but that there are only two venturi. When cornering hard, one venturi cannot pull the fuel from the passenger side. The remaining single venturi is not sufficient to keep the pump canister full.

In the KPM system, under hard cornering, there are still multiple venturi keeping the canister full when the venturi drawing from the passenger side are unable to over come the G forces.

Do I have it right now?

 

[Junkyard Dog]

For comparison, here is the stock pump. Four venturi and two umbrella valves in the KPM photo above v. two venturi and one umbrella valve in the stock photo below.

DS = Driver side
PS = Passenger side

 

[Junkyard Dog]

engineermike wrote, "Yes, kpm and oem have this figured out. Once the level falls below the hump, it does its best to keep all the fuel on the drivers side by way of the overflowing bucket. And with the way the venturi pump and vapor separation work, there is no concern about getting air sucked into the pump as would be the case with a pump on each side."

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