I am leaving next Saturday to pick up my SPF Mark I. I have heard conflicting information regarding fueling the car. I know there is a crossover pipe/line between the two fuel tanks, but is it large enough to equalize the level of gas between the two tanks while filling from a single fill nozzle? Or does the fuel flow in faster than the tanks equalize, in which case I could be spewing gas all over everything while one tank is only partially full?
Fueling an SPF Mark I
- Thread starter DB Clutch
- Start date
Hi!
I understand your concern as I have it every time I fuel my SPF MKII. I have found that there is a considerable lag between tanks, and what I recommend doing is opening both fuel caps and SLOWLY adding fuel---feather the hose nozzel, occasionally stop, look down and over to see/hear that fuel is not spilling out or gurgling to the rim, then feather again and don't worry about topping things off, since you don't need to as a practical matter. Get comfortable with how the whole arrangement works. For example, I often just add about five to seven gallons or so based upon the distance I have traveled and not the fuel gauge. This gives peace of mind and minimizes chances of a spill and gets you far enough to the next stop. One observation about these cars is that you generally have to "re-jigger" your thinking when operating them. Don't worry---take things slowly until you adapt to the car and get to know it a bit better. Is your car a new build?
/s/ Chris Kennedy
San Diego
Chris,
Thanks for the information. I don’t know if it’s a straight shot down from the fuel cap to the tank, but I was thinking of making a marked stick to check the level of the tank opposite of the one being filled. That way I would know the difference between the tank being filled and the opposite tank. I realize that they will equalize, I just don’t know how long that takes.
Yes, this is a new build. Ordered in December 2021, arrived
December 14, 2022. Shipped to Scottsdale, Arizona where it is being finished by Airpark Motorsports.
Thanks for the information. I don’t know if it’s a straight shot down from the fuel cap to the tank, but I was thinking of making a marked stick to check the level of the tank opposite of the one being filled. That way I would know the difference between the tank being filled and the opposite tank. I realize that they will equalize, I just don’t know how long that takes.
Yes, this is a new build. Ordered in December 2021, arrived
December 14, 2022. Shipped to Scottsdale, Arizona where it is being finished by Airpark Motorsports.
I open both caps and fill from one side and have no issues. Only consideration is that the opposite side cap when open if on a decline can spill over before the side being filled tops out. I listen for the gurgling of fuel on the opposite side as the warning to slow down flow rate.
You can see this as training for future ways of transport.... electric vehicles : you dont drive very long distance and takes time to fill...
Yes, the crossover tube will not equalize as fast as you can fill with a standard hose nozzle. If you open the opposite fuel lid and cap it speeds the process. If not, it is an additional 2-40 minutes that you will be at the pump regardless answering the questions "is this a Lamborghini, how much does this cost, how fast does this go, how much does this cost, my cousin's neighbor had one with a Chevy motor like they had, how much does this cost, etc."
Rick, what size is the crossover tube on your cars ? Also would you happen to have a picture.
Thanks for any and all information.
Regards Brian
Thanks for any and all information.
Regards Brian
Offhand gonna say 1". I may have pictures,
All we have ever seen have the same key for both caps.
but am not home for a couple weeks and have limited access to my pix/records.
Thanks Rick !!
Regards Brian
Regards Brian
Whatever you do park away from those pesky metal bars around the pumps!
I have to ask, have any of you noticed the fuel from one tank seems to not travel to the other tank very well when driving the car? the cross over tube just isn't large enough. We just recently removed my passenger tank because the fuel went bad in it. the friction in that cross over tube is so great that a much larger tube would be needed to work properly. I know this because I recorded the levels of both tanks after fill up and after driving with a camera. I run one pump that pulls from the drivers side tank and found the fuel just does not want to flow. The new aluminum tanks I fitted are great, but the pinch point is the welded AN fitting on the tanks. it appears they pinch the flow too much. I'm concluding that maybe a cross over tube of 1-1/2"-2" and an AN fitting with that size opening would only be the way it would work properly.
I’m not surprised that the fuel transfer is very slow. You need a difference in height of the two reservoirs. I suspect that the fuel transfer would need a much larger pipe (as you suggest) and sufficient ventilation of the tanks.
I had been planning on developing a transfer pump system for my GT, but never got to that point in its development.
You don't need a difference in height, you just need a pipe of sufficient diameter. Eventually the two tanks will level off, you either need patience or a diameter larger pipe.
The Lotus Europa has a pair of fuel tanks, one on each side of the car, located behind the seats. Each tank has a standard diameter fuel line that joins at a T that acts as both a transfer pipe and a feed the fuel pump. It takes a while for them to level off if you fill just one said. If the hose at the fuel pump is long enough it's faster to fill both sides.
Europa parts manual: https://www.rdent.com/manuals/europa/tcparts/fuel_system/la.htm
Or you get a pair of fuel pumps with switches, one for each tank (you don't want to run dry in one tank and push air into the fuel line). Alternately, some of the original Mk I cars had a mechanical valve to switch between the two fuel tanks.
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I had 2 50 gallon rain barrels (A & B) collecting downspout water 10’ apart. There was a shed between them. They were connected with a 1” PVC pipe at the bottom. Barrel B had a spigot at the bottom connected to a garden hose that ran down a slight hill to my wife’s garden. I was not getting more than a trickle through the pipe and the water in A would actually overflow while B was almost empty. That’s when I realized that with A & B on the same horizontal plane that there was not enough head pressure to cause the water to transfer from A to B and raise the level of B to be equal. I didn’t want to run a larger pipe nor go through the trouble to implement a transfer pump on something that should have been simple and without ongoing troubles or expense.
I lifted A up 3’ as an experiment (using a hose). Finally I got A to raise the level of B to the point where it would slowly overflow. She was happy and so was I. I left it that way until we moved about 5 years later.
—
understanding that gasoline weighs more than water, but the remaining physics should be close to analogous to a pair of fuel tanks.
excuse the poor illustration…
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