Fuel tank connections
Discussion
Just about to start running in my fuel lines.
Using the standard factory config. pipes go from tank to pump, non-return valve, tee piece, filter, carb.
Other pipes go tank to tank both at the top and bottom.
Question, When you fill tank 1, tank 2 will also start to fill but will it fill very quickley or do you still have to go round the other side and fill tank 2?
Steve
Using the standard factory config. pipes go from tank to pump, non-return valve, tee piece, filter, carb.
Other pipes go tank to tank both at the top and bottom.
Question, When you fill tank 1, tank 2 will also start to fill but will it fill very quickley or do you still have to go round the other side and fill tank 2?
Steve
The two tanks are essentially indepedent. The balance pipe is just to provide somewhere for the fuel to go if it all goes wrong and a valve fails or the tank gets over filled. You'll have to fill each tank in turn. This amuses my mate with a Landrover no end... At least we don't have to lift up the seat to get at the filler cap!
If you want both tanks to behave as one then you need to have bigger fittings welded onto the tank at the bottom and much larger diameter hose for the balance pipe. I'm sure I've heard of folk on here who have done it. They had to use at least -10 hose I think. The diameter has to roughly match the hose on the petrol pump if you think about it.
If you want both tanks to behave as one then you need to have bigger fittings welded onto the tank at the bottom and much larger diameter hose for the balance pipe. I'm sure I've heard of folk on here who have done it. They had to use at least -10 hose I think. The diameter has to roughly match the hose on the petrol pump if you think about it.
You will still have to go round the other side and fill it there as well. My fuel lines have been modified but the factory dash 6 balance pipe is still intact. I wish I could have changed it to a dash 12 like Andycanam has done. This would allow you to fill both tanks from either side immediately. If the tank I am filling is full, I can literally watch the fuel drain down the neck as it balances out very slowly. It was allowing me to put in about 16 pence at a time when it got to the top of the neck.
It does depend on what you require from the system as a primary design point - some may prefer having two seperate tanks, but I prefer being able to fill fuel from any pump in the garage, and would like to keep both tanks at the same level to aid weight distribution. Having two comletely independent systems does provide you with redundancy, however, should a fuelpump fail.
It does depend on what you require from the system as a primary design point - some may prefer having two seperate tanks, but I prefer being able to fill fuel from any pump in the garage, and would like to keep both tanks at the same level to aid weight distribution. Having two comletely independent systems does provide you with redundancy, however, should a fuelpump fail.
I put a -12 fitting about 3/4 of the way up the top of the tank. The idea was to allow filling from either side and not have large amounts of fuel sloshing back and forth in the corners. The remainder of the fuel system is standard. I plan to run both pumps at the same time during hard cornering to prevent the pickup from running dry and not have to plumb a swirl pot. I will deminately have a regulator close to the carb.
ken
ken
We were able to install a -10 interconnect pipe without welding in a new bung.
This was accomplished by carefully drilling out the supplied fitting with the correct size drill for a 1/2" pipe thread. We then carefully tapped the hole checking with the new fitting many times during the cutting as there's not a lot of material left. Use a vaccuum while you're cutting to help avoid chips getting into the tank. Grease on the cutting tools can also be used to grab the chips.
http://home.comcast.net/~rosenracing2/wsb/html/view.cgi-photo.html--SiteID-574465.html
In the photo we were using an old press-on fitting for checking the depth of the thread. The final installation had screw on fittings for the hose.
I've not done the math, but the -10 has to have at least 4 times the flow rate of the -6. I have no problem filling the 2 tanks from one side.
If I remember correctly, I cut off the protruding portion of the -6 fitting on the tank before I started to drill.
This mod worked very well for me, but this should only be attempted by someone who is familiar with performing this procedure.
Jack
This was accomplished by carefully drilling out the supplied fitting with the correct size drill for a 1/2" pipe thread. We then carefully tapped the hole checking with the new fitting many times during the cutting as there's not a lot of material left. Use a vaccuum while you're cutting to help avoid chips getting into the tank. Grease on the cutting tools can also be used to grab the chips.
http://home.comcast.net/~rosenracing2/wsb/html/view.cgi-photo.html--SiteID-574465.html
In the photo we were using an old press-on fitting for checking the depth of the thread. The final installation had screw on fittings for the hose.
I've not done the math, but the -10 has to have at least 4 times the flow rate of the -6. I have no problem filling the 2 tanks from one side.
If I remember correctly, I cut off the protruding portion of the -6 fitting on the tank before I started to drill.
This mod worked very well for me, but this should only be attempted by someone who is familiar with performing this procedure.
Jack
Running a larger balance pipe between the two tanks introduces fuel surge on hard cornering and could detonate engines.
I'll stick with the proper recommended Ultima set-up.
Filling the Ultima at the petrol station is a serious pose and the nozzle can easily reach both tanks without a need to move the car so you can fill up at any of the pumps.
I'll stick with the proper recommended Ultima set-up.
Filling the Ultima at the petrol station is a serious pose and the nozzle can easily reach both tanks without a need to move the car so you can fill up at any of the pumps.
If you replace the upper pipe with a larger one (as already described), you won't have any problems with fuel flowing between tanks on high G corners. However, it will allow you to fill both tanks from one side. I think it's the best solution suggested so far.
If you are intending doing a lot of high G cornering, you should really be fitting a swirl pot, to prevent any fuel surge problems anyway.
James
If you are intending doing a lot of high G cornering, you should really be fitting a swirl pot, to prevent any fuel surge problems anyway.
James
kzrd said:
Running a larger balance pipe between the two tanks introduces fuel surge on hard cornering and could detonate engines.
I'll stick with the proper recommended Ultima set-up.
Filling the Ultima at the petrol station is a serious pose and the nozzle can easily reach both tanks without a need to move the car so you can fill up at any of the pumps.
How do you know this !! have you experience with it or are you just specualting.. but please remember that when you have less the 10 litres or so the pickups are at the front and you do experence hard excelleration fuel loss.
PS the balance pipe can only be fitted above the chassis rails therefore will be at least 2" of tank below the pipe at minimium, not a problem with cornering, Ask Andy..
PS James is right swirl-pot with in tank fuel pumps feeding it is best solution for hard driving.
>> Edited by gtrclive on Friday 22 August 12:06
If you ran a single pump from each tank and switch between them AND had a large balance pipe then you would be at risk of surge and thus detonation.
BUT what you obviously don't know about our cars is that we run a system that collects fuel from both tanks simutainiously... effectivelly having one tank with two pick ups so that one is always covered....... Also there is about 8litres in each tank that can not be 'surged' to the other. Along with the fact that the carbs hold a considerable amount of fuel and that the pumps flow like taps and draw fuel down two 6- (or bigger) lines.
So Obviously I disagree with that statement...
If your worried about surge fit a swirl pot.
Andy
PS
Before people start thinking there is a problem or start overreacting, Ultima fill the tanks with anti surge foam as standard and have carefully positioned the fuel pick-up to prevent surge.
BUT what you obviously don't know about our cars is that we run a system that collects fuel from both tanks simutainiously... effectivelly having one tank with two pick ups so that one is always covered....... Also there is about 8litres in each tank that can not be 'surged' to the other. Along with the fact that the carbs hold a considerable amount of fuel and that the pumps flow like taps and draw fuel down two 6- (or bigger) lines.
So Obviously I disagree with that statement...
If your worried about surge fit a swirl pot.
Andy
PS
Before people start thinking there is a problem or start overreacting, Ultima fill the tanks with anti surge foam as standard and have carefully positioned the fuel pick-up to prevent surge.
I'm not worried about surge in the slightest or anything else with my factory Ultima twin fuel pump system. I think you will find if you speak to the factory about fuel systems that they tried your set-up briefly many years ago along with several others and then discarded it in favour of their current set-up.
Well neither me Jeff or Brad have tried them briefly... but have collectivelly done a huge amount of track, strip and hard road use and none of us have had a problem!
The current factory set up clearly works, but that doesn't mean other set up's don't as you suggest....
I personelly hated the idea of having to fill up both sides at a filling station, and having had the car on the road for over a year I glad I don't... but I suppose it's down to personnel taste!
The current factory set up clearly works, but that doesn't mean other set up's don't as you suggest....
I personelly hated the idea of having to fill up both sides at a filling station, and having had the car on the road for over a year I glad I don't... but I suppose it's down to personnel taste!
I have just one large (100 litre) tank that goes across the whole width of the passenger compartment. It has 2 fuel pumps and 2 pickups (one in each side). If the surge problem actually occurred, I would get it worse than anybody, as I've basically got a -10,000 connection between the 2 sides 
Despite doing many racing miles in my car, fuel starvation has never been a problem.
It was designed by Ultima, and built for them by ATL. I bought it when I was converting the car for endurance races.
James
Despite doing many racing miles in my car, fuel starvation has never been a problem. It was designed by Ultima, and built for them by ATL. I bought it when I was converting the car for endurance races.
James
I'm not worried about fuel surge; I'll let a good fuel regulator stop/limit flow to the carb if there is a sudden abundance. More worrisome is the possibility of running lean if the tank pickup is uncovered by a high G maneuver. There seem to be multiple ways to cope with this possibility. Swirl pot, altered tank shape and multiple pickup/fuel pumps that remain on at all times. Lastly keeping the fuel level as high as possible would be effective.
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