Fuel tanks
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Renato,
I built my setup with the tank connectors. I used 3/8" fuel lines with elbows at the tank to save space in the side pod fiberglass. I chose that size because i have the ribbed flooring and the lines are hidden or protected in their recess.
I went through several iterations before I got what I have today. That is, one set of pumps from the passengerside tank ONLY. I run fuel injection so I have a return line that only goes to the passenger side tank. The devil is in the details.
Both tanks have baffles to prevent or slow down the sloshing. The connecctor line is placed at the mid point of the tanks. The Passenger side tank has a trap door arrangement to keep fuel around the pickup which is at the back of the tank. The fuel return line empties into this area as well. This keeps the pickup submerged in fuel a majority of the time. Nothing will do it 100%. A low pressure pump will survive occasional air entry. I use the swirl pot setup so I have a low pressure pump from the fuel tank to the swirl pot. This then feeds the high pressure pump to the injecctors. What isn't regulated returns to the tank. Both tanks are vented both front and back. Both vent lines run to the front of the tanks and join the front vents that terminate on the sil plate next to the filler caps. Each line has a roll over valve that will allow air to move in or out under very low pressure(expansion of vapors as becomes heated and in, on lowering fuel levels). The vents are front and back because one or the other is exposed to air all the time and it allows them to vent any build up of pressure.
The tank sender unit is a centroid unit and is placed just outside of the trap door arrangement. If it were inside the trap door it would read full most all the time and would only show low fuel when the entire system is dry!! When both tanks get near half empty, the guage will swing with acceleration and decelleration. That serves as the first warning that the fuel level is droping.
The driver's side tank fills the role of a refiller tank. The level of the tanks will not drop so fast as to fall behind. The only inconvience if you want to call it that is when you fill up. If you do one side and then switch to the other, they will both be a little bit shy of truely full as they are trying to equalize.
Hope that answers most of your questions. If you want more info on other setups that work. let me know.
Bill
I built my setup with the tank connectors. I used 3/8" fuel lines with elbows at the tank to save space in the side pod fiberglass. I chose that size because i have the ribbed flooring and the lines are hidden or protected in their recess.
I went through several iterations before I got what I have today. That is, one set of pumps from the passengerside tank ONLY. I run fuel injection so I have a return line that only goes to the passenger side tank. The devil is in the details.
Both tanks have baffles to prevent or slow down the sloshing. The connecctor line is placed at the mid point of the tanks. The Passenger side tank has a trap door arrangement to keep fuel around the pickup which is at the back of the tank. The fuel return line empties into this area as well. This keeps the pickup submerged in fuel a majority of the time. Nothing will do it 100%. A low pressure pump will survive occasional air entry. I use the swirl pot setup so I have a low pressure pump from the fuel tank to the swirl pot. This then feeds the high pressure pump to the injecctors. What isn't regulated returns to the tank. Both tanks are vented both front and back. Both vent lines run to the front of the tanks and join the front vents that terminate on the sil plate next to the filler caps. Each line has a roll over valve that will allow air to move in or out under very low pressure(expansion of vapors as becomes heated and in, on lowering fuel levels). The vents are front and back because one or the other is exposed to air all the time and it allows them to vent any build up of pressure.
The tank sender unit is a centroid unit and is placed just outside of the trap door arrangement. If it were inside the trap door it would read full most all the time and would only show low fuel when the entire system is dry!! When both tanks get near half empty, the guage will swing with acceleration and decelleration. That serves as the first warning that the fuel level is droping.
The driver's side tank fills the role of a refiller tank. The level of the tanks will not drop so fast as to fall behind. The only inconvience if you want to call it that is when you fill up. If you do one side and then switch to the other, they will both be a little bit shy of truely full as they are trying to equalize.
Hope that answers most of your questions. If you want more info on other setups that work. let me know.
Bill
Advantage 1 fuel sender
No messy clutter of crossover valves
I haven't found any disadvantage
jim
No messy clutter of crossover valves
I haven't found any disadvantage
jim
I wanted to do something like this for my RCR, but to this point have not found a convenient way.
The RCR has a completely smooth undercarriage and the center spine runs the length of the cockpit, so running the equalizer tube inside the cockpit would only work to a point, because the tube would have to rise up and crossover the spine.
Running it across the front of the footboxes may work, but again, you have the two radiator tubes to hop over. Similar situation at the rear in the engine compartment.
Still thinking about it though...
And as Bill points out, there will be a lag from fuel being added at one side to be equalized with the other side. I would hope that lag would not be so slow as to cause one side to overflow due to return fuel from a high volume fuel pump / regulator exceeding the flow rate of the equalizer..
The RCR has a completely smooth undercarriage and the center spine runs the length of the cockpit, so running the equalizer tube inside the cockpit would only work to a point, because the tube would have to rise up and crossover the spine.
Running it across the front of the footboxes may work, but again, you have the two radiator tubes to hop over. Similar situation at the rear in the engine compartment.
Still thinking about it though...
And as Bill points out, there will be a lag from fuel being added at one side to be equalized with the other side. I would hope that lag would not be so slow as to cause one side to overflow due to return fuel from a high volume fuel pump / regulator exceeding the flow rate of the equalizer..
Randy,
There is a solution to the lag time. I have one, just never thought of adding it til just now. A one way check valve facing the passenger tank. They come in all sizes. May have to add it in now that I think of it.
Summit Racing® One-Way Check Valves - SummitRacing.com
There is another solution for you sooth bottoned guys. Place the linnes toward the front of the tanks and run them through the front bonnet area away from the cabin. Yes it will be near the water lines but the heat transfer I fell will be negligable. If it still bugs you add some closed cell insulation.
For those of you that want to fill your tanks from one filler there is a H crossover that can be done with the filler tubes. This is placed a couple of inches above the tanks and goes throuugh the front bonnet area as well.
Man, I am just full of ideas:idea:
Bill
There is a solution to the lag time. I have one, just never thought of adding it til just now. A one way check valve facing the passenger tank. They come in all sizes. May have to add it in now that I think of it.
Summit Racing® One-Way Check Valves - SummitRacing.com
There is another solution for you sooth bottoned guys. Place the linnes toward the front of the tanks and run them through the front bonnet area away from the cabin. Yes it will be near the water lines but the heat transfer I fell will be negligable. If it still bugs you add some closed cell insulation.
For those of you that want to fill your tanks from one filler there is a H crossover that can be done with the filler tubes. This is placed a couple of inches above the tanks and goes throuugh the front bonnet area as well.
Man, I am just full of ideas:idea:
Bill
I may be able to sneak an equalizer in there under the coolant tubes (not so much worried about heat transfer) as seen by this photo of an early mockup of my cooling system:
BUT
I would need to either route that bypass line through the cabin and footwell (which I would rather not do) or in the wheel well area as seen by this picture of an RCR40 chassis:
Looks like I might be better off running any sort of equalizer tube in the engine bay itself
I will get some images up of the bottom side of the RCR40 when it was up on the lift...
BUT
I would need to either route that bypass line through the cabin and footwell (which I would rather not do) or in the wheel well area as seen by this picture of an RCR40 chassis:
Looks like I might be better off running any sort of equalizer tube in the engine bay itself
I will get some images up of the bottom side of the RCR40 when it was up on the lift...
Randy,
I guess it comes down to how much room under the cooling pipes you have. The OD of the fuel line should be about 1". The cabin could be used if you shield it real good. Let,s face it. we drive these cars with 15-20 gallons of gas just mm. away from our hips, so a 3/8 line under our butts shouldn't be such a big deal. Right???
Bill
I guess it comes down to how much room under the cooling pipes you have. The OD of the fuel line should be about 1". The cabin could be used if you shield it real good. Let,s face it. we drive these cars with 15-20 gallons of gas just mm. away from our hips, so a 3/8 line under our butts shouldn't be such a big deal. Right???
Bill
The disadvantage of this type of system is that, if there is a failure in the conecting pipes, then the petrol from both tanks will be released onto the ground....That could be a lot of petrol....
It would be much safer if the pickups for the tanks were from the top, with pipes going to the bottom of the tank, a failure with this type of system would only result with the petrol in the pipes being allowed to escape, not all of the petrol from the tanks.
Even though you need 2 senders, and 2 gauges, you could still make a simple system without the need for crossover valves
It would be much safer if the pickups for the tanks were from the top, with pipes going to the bottom of the tank, a failure with this type of system would only result with the petrol in the pipes being allowed to escape, not all of the petrol from the tanks.
Even though you need 2 senders, and 2 gauges, you could still make a simple system without the need for crossover valves
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Would not contemplate it at all.
The split tank and fuel system always allows for a contingency back up, is less complicated ( if you go carbed, not rturn line is nec. and therefore no fuel switch valve if you use tow checkvalves) MY system is like this and very reliable. Also i could use two different quality fuels if i want.
Don´t see any advantage on the connected tanks which would outrun the disadvantage of complexity.
TOM
The split tank and fuel system always allows for a contingency back up, is less complicated ( if you go carbed, not rturn line is nec. and therefore no fuel switch valve if you use tow checkvalves) MY system is like this and very reliable. Also i could use two different quality fuels if i want.
Don´t see any advantage on the connected tanks which would outrun the disadvantage of complexity.
TOM
Renato
Lifetime Supporter
Thanks to all for great information.
I like the idea of one fuel sender, simplifies the electric. My guess is the only way to meter two thanks is to have a switch or two gauges (or a double needle gauge like the ones used in aviation).
My fuel system is return-less EFI and plan to use Aeromotive A1000 Bypass Regulator. Even the system is return-less the regulator puts back certain amount of fuel. Not sure what is the amount. If I use two pumps that would mean buying two pumps, two filters, two check valves and a tee to the regulator . The question would be, where does the return go, what tank? Both maybe? I would need a solenoid valve and run everything through a selector switch or a manual selector valve.
Gets complicated really quick.
I understand the idea of a redundancy in having two of everything, but in my system all comes down to the single regulator anyway.
All the chassis will have similar problems not only RCR. Do you run the pipe through the cabin or not? I don't like the thought of fuel in the cabin but it can be done safety with a bit of planning. The cooling pipes don't make it any easier.
Some of trucks (like Ford F150) with dual tanks have a switch inside cabin to switch between tanks and fuel pumps. System incorporates a selector solenoid valve with feed and return in one body. No connection between tanks. So it's been done by big guys and (I guess) it works more or less reliably. That was one of my choices if I go with dual systems.
Regards,
Renato
I like the idea of one fuel sender, simplifies the electric. My guess is the only way to meter two thanks is to have a switch or two gauges (or a double needle gauge like the ones used in aviation).
My fuel system is return-less EFI and plan to use Aeromotive A1000 Bypass Regulator. Even the system is return-less the regulator puts back certain amount of fuel. Not sure what is the amount. If I use two pumps that would mean buying two pumps, two filters, two check valves and a tee to the regulator . The question would be, where does the return go, what tank? Both maybe? I would need a solenoid valve and run everything through a selector switch or a manual selector valve.
Gets complicated really quick.
I understand the idea of a redundancy in having two of everything, but in my system all comes down to the single regulator anyway.
All the chassis will have similar problems not only RCR. Do you run the pipe through the cabin or not? I don't like the thought of fuel in the cabin but it can be done safety with a bit of planning. The cooling pipes don't make it any easier.
Some of trucks (like Ford F150) with dual tanks have a switch inside cabin to switch between tanks and fuel pumps. System incorporates a selector solenoid valve with feed and return in one body. No connection between tanks. So it's been done by big guys and (I guess) it works more or less reliably. That was one of my choices if I go with dual systems.
Regards,
Renato
For the sake o discussion, I would like to address a few of the things brought up.
Mick, I don't know of anyone that uses a pickup from the bottom. I am sure there is someone out there that does.
I don't like saying everybody, so I will say most everybody uses a hard tube or flexible hose with a sock on the end to draw the fuel to the top. Can't remember seeing a fuel cell or competition tank that didn't exit from the top.
If the draw was from the bottom you don't have any good way to filter the fuel before it enters the line. Some leaks from the lines to the pump occur from the suction that is created from a clogged line(at the tank) which might collapse the line around fittings and the like. Then the tank has to be emptied in order to fix. If on top, they might draw air.
When you say "failures" I am assuming you mean wrecks or "offs". You may have a point there as it could get torn off in such an event. The cure for that is to make sure the takeoff point is on the inside of the tank at the bottom. I didn't mean hanging down from the bottom of the tank.
My tank is a wedge shaped design with a triangulated framework around the tank. I need to add one section of framework around the middle of my tank to guard and protect the small fitting I am using, or I need to move it to the inside. I have a spacefrane that would allow that.
Tom, Maybe I am just not understanding you. Do you mean a contingency is a second set of everything?? Why get complicated(and expensive). A simple tube that connects the tanks is less expensive, no maintenance, won't wear out as soon as a pump, and is less expensive to replace when it does.
We all have to watch our guages(or why put them in), so when it says low it is time to refuel.
With the two guages(or one guage for both tanks) I am assuming there is power to both and are active at the same time. If not(or just one guage), then how do you know if there is gas in the other tank. I guess you find out when the tank you are using runs out and you switch it!! That's too much for me to remember in my old age, and too much to spend near my retirement.
I think you are the only person I know that can(could) drive to a competition with two blends of gas to choose from. I usually "run what I brung". With the price of race gas, I will trailer the car to the meet.
Bill
Mick, I don't know of anyone that uses a pickup from the bottom. I am sure there is someone out there that does.
I don't like saying everybody, so I will say most everybody uses a hard tube or flexible hose with a sock on the end to draw the fuel to the top. Can't remember seeing a fuel cell or competition tank that didn't exit from the top.
If the draw was from the bottom you don't have any good way to filter the fuel before it enters the line. Some leaks from the lines to the pump occur from the suction that is created from a clogged line(at the tank) which might collapse the line around fittings and the like. Then the tank has to be emptied in order to fix. If on top, they might draw air.
When you say "failures" I am assuming you mean wrecks or "offs". You may have a point there as it could get torn off in such an event. The cure for that is to make sure the takeoff point is on the inside of the tank at the bottom. I didn't mean hanging down from the bottom of the tank.
My tank is a wedge shaped design with a triangulated framework around the tank. I need to add one section of framework around the middle of my tank to guard and protect the small fitting I am using, or I need to move it to the inside. I have a spacefrane that would allow that.
Tom, Maybe I am just not understanding you. Do you mean a contingency is a second set of everything?? Why get complicated(and expensive). A simple tube that connects the tanks is less expensive, no maintenance, won't wear out as soon as a pump, and is less expensive to replace when it does.
We all have to watch our guages(or why put them in), so when it says low it is time to refuel.
With the two guages(or one guage for both tanks) I am assuming there is power to both and are active at the same time. If not(or just one guage), then how do you know if there is gas in the other tank. I guess you find out when the tank you are using runs out and you switch it!! That's too much for me to remember in my old age, and too much to spend near my retirement.
I think you are the only person I know that can(could) drive to a competition with two blends of gas to choose from. I usually "run what I brung". With the price of race gas, I will trailer the car to the meet.
Bill
I have a CAV with a connecting hose (8AN) between the two tanks. Works great unless you park on a slope (Left side of car higher than right side) the fuel will drain back into the right side which I don't have a pickup. I'm installing a low pressure check valve that hopefully fix the problem
Not quite the only way, I plan on using a microcontroller to account for fuel tank shape and drive one gauge off two senders. I have it working on breadboard...
See the video I took of the controller driving the gauge.
[ame=http://www.youtube.com/watch?v=tbC9ubBLYdc]Arduino controlled fuel gauge - YouTube[/ame]
Guys been following this discussion trying to decide how to run twin tanks, in a 1989 Countach anniversary they run a 2" pipe the u shape in the picture out of one tank and then back to the rear chassis rail, across the rear frame and then forward again to the other tank, I believe the early Countach' s were a pain to fill as they had no equalise pipe. I am also looking hard at a Toyota MR2 sw 20 tank as that will fit nicely down the centre console it even has curves in the side to follow seat shapes and foot space as well and still has room for the shifter on top, and of course its all under the car closed in, it also provides a little weight up front in the centre of the car, its about a 50 ltr tank and better still it will fit my car, as I have mocked one up at present in my shell, best part it has the pump, the sender, and all the venting systems that Toyota used.
Attachments
I found these on this site a few years ago.
Hi Renato
I've been thinking about fuel tanks too. At the minute, I'm leaning towards having the two tanks operate separately. Not really for any other reason than I think it'll be cool having two gauges and being able to switch between tanks. I remember having a ride in a Jag when I was a boy and was amazed it had twin fuel tanks which you had to fill up from either side!
Hi Mick - those diagrams look really helpful.
The 6 port pollak valve looks like a good solution and should take a lot of hassle out of setting a system up. Assuming they work reliably...
I've been thinking about fuel tanks too. At the minute, I'm leaning towards having the two tanks operate separately. Not really for any other reason than I think it'll be cool having two gauges and being able to switch between tanks. I remember having a ride in a Jag when I was a boy and was amazed it had twin fuel tanks which you had to fill up from either side!
Hi Mick - those diagrams look really helpful.
The 6 port pollak valve looks like a good solution and should take a lot of hassle out of setting a system up. Assuming they work reliably...
Ian Anderson
Lifetime Supporter
Pollack valves look OK
But I have had 2 fail and when they do you end up draining from 1 tank and overfilling the other.
Instead of pollack valves I suggest you go for electronic solenoid valves.
Tank - pump to non return valve to T connector swirl, return from swirk to another T to a solenoid valve to tank (Energise each solenoid with the pump drawing from that tank)
Then run your HP system Swirl HP pump, filter to fuel rail return to swirl
As you are in the UK you can find on e bay solenoid valves that they use with LPG conversions (Solenoid will run about 0.75 amp when energised.
IAn
But I have had 2 fail and when they do you end up draining from 1 tank and overfilling the other.
Instead of pollack valves I suggest you go for electronic solenoid valves.
Tank - pump to non return valve to T connector swirl, return from swirk to another T to a solenoid valve to tank (Energise each solenoid with the pump drawing from that tank)
Then run your HP system Swirl HP pump, filter to fuel rail return to swirl
As you are in the UK you can find on e bay solenoid valves that they use with LPG conversions (Solenoid will run about 0.75 amp when energised.
IAn
Do fuel flow tests on any solenoid you think of useing, we never found any to flow enough without internal modifications, even then they are very marginal. Frank
Renato
Lifetime Supporter
Hi David,
Very nice setup. Are you inputting two analog signals from sensors in to the processor and averaging the output signal to the dial?
Renato
Very nice setup. Are you inputting two analog signals from sensors in to the processor and averaging the output signal to the dial?
Renato
