Ok, the BBK, aeromotive and all these. How exactly do they work? If the computer monitors how much excess oxygen is in the exhaust via O2 sensors and adds the proper amount of fuel then what is the need for a fuel pressure regulator when the computer compensates for A/F anyway? how exactly do they work.

 

Fine tuning. The a/f ratios of most oem cars aren't perfect.

 

vacuum

 

is the fuel pressure less at idle than it is at WOT, is that what your sayin...

 

yes....

 

i see how it is... thanks

 

the fuel pressure regulator holds the relative fuel pressure constant so that the only thing affecting overall fuel delivery is the injector open time. "the relative fuel pressure is the difference between fuel pressure pushing fuel out of the tip of the injector and the manifold pressue pushing back at the tip." when the relative pressure is held constant, then the ECU can vary the injector open time to control the air/fuel ratio properly.
when you go from naturally aspirated to force induction, you must have an adjustable fuel pressure regulator in order to compensate for the higher manifold pressure versus the vacuum (lower than atmospheric) pressure in the intake manifold.

 

rdman...that not always true, on my supercharged car AS i USE A NON VACUUM FUEL PRESSURE REG FROM ACCEL ...now when I got rid of the FMU I went to a kirban reg..... but all the other stuff I agree*L*