Useable Gas
- Thread starter Hoota Caroota
- Start date
Seymour Snerd
Lifetime Supporter
Somewhere among these....
http://www.gt40s.com/forum/gt40-tec...g/36292-smiths-fuel-sender-unit-problems.html
http://www.gt40s.com/forum/superformance-gt40s/32832-fuel-smell-garage.html
http://www.gt40s.com/forum/superformance-gt40s/34109-notes-fuel-level-sender-calibration.html
The upshot is that the fuel is drawn from the tanks through ports that are not "at the bottom" so a lot is left behind (unless you drive only uphill). Also the fuel sender is probably grossly inaccurate which can contribute to the perception. The first problem requires surgery on the fuel tanks to fix. The latter is relatively easy.
Robert S.
GT40s Supporter
Thanks for the info Alan. Do you know with any certainty that Superformance has corrected this issue? More importantly, will vehicles produced in 2012 be devoid of such issues?
Thanks, Robert
Seymour Snerd
Lifetime Supporter
I have no reason to believe they've done anything about it whatsoever. But then I've never heard them say anything about any running changes. One of my not-so-pet peeves with that vendor; but I've thoroughly beaten that dead horse already.
BTW one good fix to the sender problem is simply to replace it with a solid-state sender like from these guys: CENTROID PRODUCTS - Computerized Tank Display - Electronic Senders - capacitive fuel gauges
All in all about the same amount of work as screwing around with the existing mechanical sender.
Robert,
I don't know much about the SPFs tanks, but you might consider coming up with something along the lines of what I did with my DRB tanks.Look down to post 92.
http://www.gt40s.com/forum/gt40-build-logs/13742-drb-5-a-5.html
I am planning to eventually do both tanks this way and add a pickup to the second tank. Then fuel will be drawn and returned to both tanks. The cross over line will take care of any inequalities in flows to or from the tanks. The return line to the primary tank dumps into the pick up area, so it would be rare to suck air.
I also have the centroid sender. What I like about it is that it has an electrical take off that goes to a warning lite to tell me when the level is getting low. With the setup of lines like I have them now, when it tells me I am low, I can turn it off and the guage goes back up to just under a quarter of a tank. Thats why I am going to change the lines around.
Bill
I don't know much about the SPFs tanks, but you might consider coming up with something along the lines of what I did with my DRB tanks.Look down to post 92.
http://www.gt40s.com/forum/gt40-build-logs/13742-drb-5-a-5.html
I am planning to eventually do both tanks this way and add a pickup to the second tank. Then fuel will be drawn and returned to both tanks. The cross over line will take care of any inequalities in flows to or from the tanks. The return line to the primary tank dumps into the pick up area, so it would be rare to suck air.
I also have the centroid sender. What I like about it is that it has an electrical take off that goes to a warning lite to tell me when the level is getting low. With the setup of lines like I have them now, when it tells me I am low, I can turn it off and the guage goes back up to just under a quarter of a tank. Thats why I am going to change the lines around.
Bill
Robert S.
GT40s Supporter
Two For One — Useable Gas
Thanks Alan, you do expend a lot of energy to help others, and that is a commendable trait, and I personally appreciate all your efforts.
Thanks Bill, and my above message to Alan, applies to you as well.
Regards Gentlemen, Robert :thumbsup:
Thanks Alan, you do expend a lot of energy to help others, and that is a commendable trait, and I personally appreciate all your efforts.
Thanks Bill, and my above message to Alan, applies to you as well.
Regards Gentlemen, Robert :thumbsup:
Seymour Snerd
Lifetime Supporter
In SPF's defense they couldn't do what the "originals" did which was rubber bladders that are not suitable for street use. So they supply stainless steel tanks that slide into the "sponsons" with an outlet on the rear of the LHS tank. So far so good.
But they also have to cross-connect the tanks. Since the bottom of the tank is curved, either the outlet or the cross-connect is going to be higher. Thus fuel gets left behind no matter what you do.
Unless....
If you were starting over and wanted to make sure this problem did not exist you would provide only the existing outlet port on the LHS tank and then "tee" off of that to supply the fuel pump and the opposite tank where you would also connect only at the bottom (inside) of the tank. Problem solved, but with a little more hardware (i.e. the tee).
However, I suspect the reason the crossover ports are "up" on the outside is to ease the bend radius of the 3/4" armored hose as it turns to go through the bottom of the engine mount. Of course if the crossover were made of metal tubing or used a hard eblow it could have any bend radius it wanted, so that issue would go away. But as it is they are about 1" higher, which is about 10% of the tank capacity. At that point the optimistic designer might think that with some spirited up and down and left and right the fuel would all get sucked up, but obviously it doesn't.
What I did, and I don't recommend this to anyone, is to add a second outlet port at the bottom of the front of the RHS tank, and draw from that with a second fuel pump. So now I'm drawing from the bottom of both tanks, and thus get all the fuel and don't get any fuel starvation when going up or down hill with low fuel level.
In fact the latter issue was the nominal reason for all that work. But I now have a vastly more complex and expensive fuel plumbing situation than what SPF supplies. And frankly, the whole exercise was kind of silly because a) the last gallon or two of fuel doesn't really hurt anything and b) just keeping the tanks mostly full prevents the hill starvation. But others have put in swirl tanks for the same reason.
And then of course I made an elaborate crossover tube from 3/4" stainless tubing neatly tucked away where nothing can damage it and then relocated the crossover port on the RHS tank to the inside/bottom.
This whole pile of irritating fuel system issues was kind of my Mt. Everest (or windmill to be tilted). It was there so I "had" to climb it. But it's also why my car still isn't running.... So you choose your battles and sometimes lose the war.
New license plate idea: "PHYRRUS" or "QUIXOTE"
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Seymour Snerd
Lifetime Supporter
Good question.
(several minutes later).
OK what if you really wanted to fix this without all the lunacy I went through?
Cap/plug the LHS crossover spigot. Tee off the outlet 12AN fitting with the usual AN fittings and elbows and tees.
Only problem left is the RHS crossover spigot being "too high". Cut a 12" long piece of stainless tubing with OD slightly smaller than the spigot's ID. Bend it gently into an arc such that when you slip it into the spigot it bends over to the inside and down to the deepest part of the tank. Epoxy it in place. Will epoxy immersed in gasoline last? I don't know, but there is probably *some* adhesive that will (JB Weld claims to). Install a second fuel pump for the RHS.
Or, if you have the facilities, skill and nerve, pull the tank, stand it up and fill it with water and solder a 12AN male to the low side of the tank and thus have the RHS tank the same as the left. Now plug the unused crossover spigot, put the tank back, and with suitable AN fittings and adaptors reconnect the crossover hose. No second fuel pump needed.
PS: an extension of either idea is to slip a ~4' (tank length) long tube into the spigot (or the new AN fitting) thus drawing from the front of the RHS tank. Now you've solved the uphill-downhill-starvation problem but you have to have a second fuel pump for that to work. That long tube is going to rattle unless you can fasten it down through the filler neck at the front somehow, but that's "an exercise left to the reader."
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