Originally Posted by bud-weis
yeah but an injector will only supply an amount of fuel dependant upon injector open time and the pressure within the rail, which is controlled by the reg, so if the car runs fine on standard pump with reg set to 3.0bar, then it will run the same with no adjustments to the regulator but with 044 pump ??
Not if due to the amount of petrol leaking out of the system via the injectors being open the fuel pressure is acutally dropping slightly lower than 3.0 bar becaues you have maxed out the flow on the pump, therefore when mapping it you end up with the injectors needing to be open longer to get the same amount of fuel in.
Then you fit the new pump which now maintains the pressure like the old one should have done and bingo you end up running richer.
Pretty unlikely set of circumstances really, but just saying its possible, the regulator doesnt have complete control over the pressure, as all it can do is limit the fuel returned, if the pump flow has been used by the injectors, there is no fuel to return anyway!