The stock 2g fuel tank stinks from a performance standpoint. The tank does not work well under high acceleration due to sloshing of the fuel and losing suction from the pump. You can alleviate this issue by running a full fuel cell, but that requires typically running a tank in the trunk which takes up a ton of space, requires you to have a new firewall made, and is just plain annoying to fill. What a surge tank does is act as an accumulator from which to draw fuel from. The system starts with a walbro 255lph in the tank pumping into this tank which will be mounted in the engine bay where the battery used to be. This tank is filled with zero pressure as there is a overflow port on the very top of it which simply allows all excess fuel to gravity feed back into the main fuel tank using a return line similar to the factory return line. The dual 044 bosch pumps on the side of this tank then pump the fuel from this tank through the normal fuel rail and regulator system under high pressure. Since this tank is very vertical in nature it provides the perfect method for maintaining fuel over the pumps' pickups. The return from your AFPR simply returns back into this tank, so in essence you have a loop of fuel continuously taking place solely in the engine bay. Since this tank holds ideally zero pressure the walbro 255lph in the main fuel tank has almost no resistance and therefore flows almost double of what a normal walbro would under full boost fuel pressure.
Assume you had 1600cc injectors, that were at 100% duty ALL the time, not just at the very peak upper rpm levels, but rather continuously. That would mean you are requiring 6400cc/min of fuel flow from this tank which is 3800cc total in volume. That by itself would mean that this tank would maintain volume for 35 seconds continuously, without any additional filling. Of course though you have a walbro 255lph flowing into it at 0 pressure, at say 230lph, or 3800cc/min, which would further increase that time to 52.5 seconds before the tank empties. There aren't too many places that I would dare keep my foot in the throttle for any more than 50 seconds
