What does a closed fuel loop mean on a 1996 Nissan maximum?

I own a Nissan 350z and a closed fuel loop means you have no return line from the fuel injector rail back to your fuel tank. a lot of high performance cars use a return system so you can pump more fuel into the injectors and all the excess fuel that isn't used by the motor is sent back to the fuel tank. In the newer nissans the computer controls the fuel so ideally the engine receives the exact amount of fuel required. I hope this helps with your question