Demand Delivery System - Returnless Fuel Delivery

Returnless fuel delivery systems are being developed to assist the vehicle OEM to meet lower emissions requirements for evaporative hydrocarbons from the vehicle. Because the fuel return line contributes to much of this vapor formation, its elimination is desirable. Existing returnless delivery techniques are considered including mechanical and electronic means for pressure regulation. A unique returnless system, called Demand Delivery System (DDS) incorporates desirable attributes of the existing techniques and provides additional functions of a rail mounted micro-size demand regulator. This DDS system eliminates the return line and its cost, providing significant reduction of vapor generation in the fuel tank. The Demand regulator provides rail pulsation damping, the ability to manifold vacuum reference, an accumulator function during hot soak, accommodation of dynamic line and filtration losses, and superior transient response to dynamic engine demands.