RE return to fuel tank

[Roy Alan Oxlade]

Hi all

Been reading this thread and can say that several european auto
manufacturers are working on a returnless fuel system, where the fuel
pump is controlled by the ECU using PW modulation so that only enough
fuel is pumped into the fuel rail to meet the engines needs.

The biggest reason behind this is emissions, passing warm fuel back to
the tank causes fuel vapour to build up & pressurise the tank.  It
cannot just be dumped to atmosphere anymore so the vapour is passed
through a charcoal filter to sepperate any fuel before venting to
atmosphere through a valve controlled by the ECU.

To achieve this they fit a pressure sensor in the fuel line and by
knowing pressure and injector duty cycle the pump duty cycle is
calculated.

>From experience on dynos I can say that for power you want hot fuel in
the fuel rail and cold air because of its increased density.

                 From R Oxlade.