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The wiring is nothing compared to building and plumbing the surge tank. Both are well within your capabilities though, but I think a surge tank is a better bang-for-buck than reworking your tank again.
That is true once the mat is initially wetted, however if the mat is dry and you only dip one end of it into fuel I really doubt it will pick anything up at all. The only way that would work is if there is enough wicking for it to soak fuel across the entire mat starting from one end. Perhaps there is, but I don't think I would want to rely on that.
Actually you only need low pressure transfer pump coming from the main fuel tank. You vent the surge tank so it is at atmospheric. Your main pressure pump(s) lives in the surge tank. You can either have the pressure regulator return dump back to the surge tank or go all the way back to the main tank. Returning to the main tank allows the fuel to cool back there so there is always a supply of cooler fuel coming into the surge tank. Surge tank provides a favorable aspect ratio and a consistent head (amount of fluid above the pump) to maintain an air-free supply of fuel to the engine, even when the transfer pump is delivering air.
Would you really run your fuel tank low enough to have that situation? That would mean your fuel tank is almost completely empty or you're really on a steep incline (with low fuel). I would think with a decent fuel level in the tank that the mat would always be in good contact with the fuel?
How do you vent the surge tank? Is there a return that goes from the surge tank back to the main tank, and that's used as the vent?
Haha I know I'm capable of making it.. not sure why I'm being stubborn about the extra wiring.
Would you not want to have the transfer feed line enter the bottom of the nicely medium diameter & tall height tank and have the return to the main gas tank near the top, and thus keep it a closed loop surge tank and have the gas tank vented? I'm currently having venting issues with my gas tank.. I think the vented cap is stuck, but I'd like to have a filtered and check-valved vent line from the top of the gas tank to insure that it truly is open to atmosphere with no residual pressure in it at all.
This is outside of my expertise unfortunately so consider anything I said above as talking out of my @$$ as I usually do. I am confident that a surge tank is the way to go if you are still having fuel issues, but I am not 100% confident on the best method of plumbing and venting.
I do like the idea.. at the very least it moves the most-stressed part of the fuel system, the high-pressure pumps, to an easily-accessible location under the hood. And having a low pressure pump moving fluid under minimal volume should keep the gas tank temps down quite a bit. I have to disconnect the fuel lines and FPR to remove the heater blower/box on the firewall anyway. Might also be a good time to rearrange my FPR-rails setup to have the FPR after the rails instead of before it.
I think maybe in my diagram above that I should have run the return from the regulator back to the main fuel tank. My intank is a 340 lph and my inline is a 4303, but now I'm going to run the 340 all the time and have the 4303 come on under boost.
408GT do you have a build thread that I can click thru out of interest?
The more I think of it, the more I like this idea.. my current setup works almost all the time, which means my main tank baffling is more than adequate for a transfer pump so I wouldn't have to touch the tank inners or bulkhead or even pump bracket, just move the 2 high pressure pumps to the engine bay and find a suitable low pressure pump. Having a hard time finding a high volume low pressure in-tank electric pump tho, seems almost all available are high pressure EFI pumps. Having a single low pressure pump in the main tank means less fuel squishing, which means less heat in the main tank.
I like the idea of a swirlpot in the engine bay with inlet-outlet ports tangent to the OD of the tank, creating [hopefully] a less turbulent fuel flow. Make a nice heat shield for the surge tank with maybe some ducted airflow, and the tank could potentially be cooler than the main tank near the tailpipes in the back.
Here is a surge tank an online friend of mine built. Very simple and you might be able to hide something like this in the same area he did - behind the driver's side headlight. Scroll down for detail photos.
Thanks for that link Clint.. interesting read, he seems very similar to how I operate.
With the air filter (single one now, but two in the future with twins), intercooler piping, headlight wiring, and the general shortness of the Nova's tiny front overhang, I don't really think there's room to jam it behind a headlight.
I'm thinking it could go where the heater blow motor is on the passenger side of the firewall under the front fender, kind of like where a lot of dry sump tanks are put on pro touring Camaro's, except due to the smaller size have in in front of the firewall and not in a sheetmetal'd recess.
Also, you can see where my fuel hardlines and FPR currently are.. stupid huge heater box needs to go bye-bye!
Also found this, it's a rollover vent with built in float to limit the amount of gas that passes thru the vent when the vent is in the upright position (ball check valve not engaged) but fuel is sloshing around.
I think for the surge tank the feed line from the gas tank should be fairly near the top where the return line to the gas tank would be, that way when the car is parked the whole volume of the surge tank (upwards of a gallon probably) doesn't gravity drain back to the gas tank, and potentially overfill the gas tank (if it's a full tank) and run up the vent tube. I bet the above vent would work decently for quick sloshing, but wouldn't seal well against constant pressure head from an overfilled gas tank. I'd put a drain fitting on the bottom of the surge tank to drain it in the case of maintenance.
Interesting having the surge tank inside the main gas tank.. is that your setup? Unfortunately the Nova gas tank is maaaaybe 6" tall or 7" at the highest point, and given the metal labyrinth I tack welded in it and the size of the access bulkhead I made, there's just no way I'd be able to fit 2 high pressure pumps and a low pressure transfer pump as well as a fuel level sender.
Yep that's my setup. Works great. I was able to make an 11 second run with the gas gauge on "E". The chevelle tank is only about 7" high and is wide and flat. I left the stock sender in place at the front of the tank. That bucket holds about 2 liters.
Nice! I dig that. With my tank, the recess I put into the top of it for the access panel area is the minimum height needed to the 90* bulkhead fittings on the top of the panel, in order to maximize the height in the tank under the access panel. That being said, there's still only enough height to just barely fit in a pump with its intake sock below and the output hose on the barb on the top of the pump with the minimum bend radius on the hose before it kinks.
Then again, I could lay the twin hi-pressure pumps on their side thus raising the intake socks up from the very bottom to maybe 1" above since they'll be guaranteed to be submersed in fuel, and the transfer pump can be on its side as well because air intake isn't such a big deal. But in the end, I really don't want to modify the welded setup in the gas tank.
Since it would be a direct drop in, I could add a hi-pressure pump in the existing mounting bracket and used that as the transfer pump. Then move the existing TRE 300 pumps to the new surge tank. Not a single thing, including wiring, would need to change for the main gas tank. The kicker is I still have my original Aeromotive Stealth 340 pump which wasn't actually the problem when "my fuel pump died" the first time, it was the wiring and tank bulkhead that failed.. so that could literally just drop in and be good to go.
From my research, it seems a hi-pressure pump with the same body as the Walbro 255 will flow just fine in low pressure applications. I was worried that continual low pressure would mean continual high gear RPM and maybe premature wear, but then the load just be very minimal so maybe it'll all be okay in the end? Also the low load of a single pump would mean much less heat input into the main tank, so that tank would be cooler than the surge tank and possibly help keep the surge tank cooler.
Surge tank located in trunk underneath parcel tray? More protected and requires no cutting or welding mods to the gas tank. There's already a hole in the trunk floor where I was planning on running my vent/rollover high point loop, and I want to install in a trunk firewall behind the rear seat back for noise anyway..
Something along these lines. I'm thinking it's best to return the fuel from the rails/FPR to the surge tank so that the discrepancy in fuel flow rates between the low pressure and high pressure pumps doesn't drain the surge tank into the main gas tank under low load aka minimal injector duty cycle.
That's a good system, But one thing to consider. What happens if the lift pump ever fails ? I realize its a slim chance.
I made my in tank can with a flapper valve in the bottom of it, So that fuel will always be at the level of whatevers in the tank at a minimum. So If I ever had a failure of the lift pump, I wont be stranded.
That's a fair point.. maybe I add a 2nd lift pump.. I mean there'll be an unused spot in the mounting bracket and the wiring and hoses are already there.
On a side note.. I've never been happy about the operation of the stock style floating lever arm level sender, and want to change to a vertical float or impedence style tube.. does anyone have any experience or comments on this or other style of aftermarket/racing level sender?
01-12-2017, 04:25 PM
