Posted: Thu May 18, 2006 4:04 pm
bluetrepidation,
Chances are that the fuel pressure was controlled by PWM on the fuel pump. Since the ECU knows the intake pressure, it can set the PWM to compensate without additional sensors or pressure regulators (presumably from a look-up table, but possibly from a fuel pressure sensor).
Some cars have a 'semi-returnless' system in which the fuel presuure regulator is located near the fuel tank, these typically have a long vacuum line to the intake manfold.
Apparently the main reasons for goigng to returnless sytems was to avoid returning heated fuel (from passing near the engine) to the fuel tank, which causes evaporative emissions concerns. It also has fewer components, so it may be slightly cheaper.
Lance.
Chances are that the fuel pressure was controlled by PWM on the fuel pump. Since the ECU knows the intake pressure, it can set the PWM to compensate without additional sensors or pressure regulators (presumably from a look-up table, but possibly from a fuel pressure sensor).
Some cars have a 'semi-returnless' system in which the fuel presuure regulator is located near the fuel tank, these typically have a long vacuum line to the intake manfold.
Apparently the main reasons for goigng to returnless sytems was to avoid returning heated fuel (from passing near the engine) to the fuel tank, which causes evaporative emissions concerns. It also has fewer components, so it may be slightly cheaper.
Lance.