Although small in size collectors are one of the most important performance upgrades to any fuel cell. Located inside the fuel cell, these units utilize several small check valves that allow fuel in but not out; the result is much more consistent fuel delivery to the engine even at low fuel levels. For street racers, the result is consistent fuel delivery through even the tightest turns; for off-roaders this means a constant supply of fuel no matter how rough or steep the terrain; and for boat builders and captains the harshest seas. Although not a necessity for some, collectors are a must for anyone looking to push their vehicle to the limit.
What are they?
Collectors are, essentially, internal surge tanks. They're placed inside of the fuel cell and consist of several check valves that allow fuel in but not out, a pickup, and are made of the same nylon cloth-resin material as the bladder
How do they work?
Every time you step on the gas, brake, or turn fuel sloshes in the tank. The job of the collector is to take advantage of that and "collect" the fuel as the vehicle moves. when the vehicle moves side to side or front to back, fuel is forced through the check valves and into the collector. The weight of the fuel then pushes the balls inside the valves closed. Every time the vehicle changes direction the collector is recharged; the result is a consistent supply of fuel to the engine. even at low fuel levels the inertia of the moving fuel drives it into the collector, keeping it full even as fuel levels in the rest of the cell may be well below the top of the collector.
Are they necessary?
The necessity of the collector will always boil down to 1) the design of the fuel cell; and 2) the vehicle application. A typical example would be a sloped-bottom design. The design itself is meant to collect fuel at the lowest point of the cell, thus reducing fuel slosh; but as the size of the cell increases so too does its "footprint", or bottom. The larger the footprint the more extreme the fuel slosh can be with consequences ranging from vapor lock to engine starvation. Thus, even though designed to direct fuel to a specific location, as the footprint (and the cell) increases so too does the need for a collector. Additionally, the intended application of the vehicle (i.e. racing) will also dictate the need for a collector. For a weekend warrior looking to stay safe while having fun, the need for a collector will vary with the size and design of the cell; however for a dedicated racer a collector is usually recommended for both increasing performance and protecting your system from starvation.