So I'll ask this question. How much HP can the stock feed line support?
I'm going to say at least 600 to the rear tires..
A good pump will push the fuel thru the smaller line but it will pull a lot more current and the motor will get hotter which is not good for overall expected life span.
For the return side, the bigger pump will push a lot more fuel to the injectors than the engine can consume at low rpm so the return line then offers enough restriction that the pressure in the rail is raised beyond what the chip expects and the engine runs too rich. Makes it hard to get smooth fueling. A bigger return line allows the excess to be bled off stabilizing the pressure in the rail.
Dan was using twin nozzles on his alky system as I recall. I forget what percentage of fueling the alky provides with twin nozzles, but he may have gotten 20-25% of his fuel from the alky which allowed his single walbro to keep up
Your response is essentially the same response I just gave Brad, regarding the effects of adding a volt booster to a car and the resulting increased fuel flow from the fuel pump.
If the return line and fuel pressure regulator are free-flowing and have little-to-no restriction through them, then the engine should theoretically not have a fatter AFR. If the fuel regulator or the return line is not able to freely move the volume of flow provided by the pump, that fuel is now restricted in its' movement, and begins to "back up" as it experiences a flow restriction. The fuel becomes stuck in the fuel rail and needs a place to go. The more it is stuck in the fuel rail and increases the backpressure/flow restriction, the more pressure builds in the fuel rail.
High pressure fluid
always wants to move to a low pressure environment, so when an injector opens up, providing a low pressure cavity/space for fuel to move through, the fuel that is backed up in the fuel rail tries its' best to make its' way into the injector and into the now low pressure space. Basically the fuel tries to force itself into the injector because it sees it as an available space to move to that has lower pressure and is not restrictive (unlike the fuel rail the fuel is currently in).
This reason is why I
always suggest people upgrade their fuel rails.
NOT because aftermarket fuel rails can flow anymore fuel than the stock fuel rail, but because the aftermarket fuel rails allow you to use much larger fuel pressure regulators, which can flow way more fuel through them! A new high-volume fuel pressure regulator and a new high flow return line will help prevent any backpressure / flow restrictions in the fuel system, which also will aid in the longevity of the fuel pump and help to provide a more accurate fuel system as a whole.
