| I, personally, have found no conclusive evidence that suggests the OEM fuel flow design will produce a significant and/or detrimental pressure drop as fuel moves through the fuel rails. In short, there is no reason to independently flow fuel through each of the two rails - let it enter the rear of the passenger rail, exit at the front of the passenger rail with the hose bridge into the front of the driver's rail, and then exit the rear of the driver's rail. If you really are seeking attention to detail, purchase a set of the 300-Degree fuel rails... and route the fuel the same as OEM. As for a regulator, that depends on your fuel pumping setup. Regulator Bypass Volume
Bypass volume is the quantity of fuel which is returned back to the fuel tank by way of the fuel pressure regulator. In an unloaded engine condition where the volume of fuel required by the engine is at its lowest, the volume of fuel which is returned back to the fuel tank is at its highest. In a loaded engine condition where the volume of fuel required by the engine is at its highest, the volume of fuel qhich is returned back to the fuel tank is at its lowest. Bypass Volume is only important in the unloaded condition - if the regulator is unable to bypass the quantity of fuel exiting the fuel rails, this will result in a fuel pressure higher than needed. If you are using a single OEM TT pump with the OEM fuel pump controller, the OEM regulator will work just fine. It is perfectly capable of bypassing the volume delivered by the pump when the OE pump controller is working properly. If you are using a dual pump configuration, you have a few obstacles. You cannot drive two pumps with any OE pump controller - the electrical load is too great for the controller to handle and it will result in burning up the power MOSFETs within the controller. Because of this, and with the currently available options, you have a few choices. 1) Drive one pump with the OE controller and setup the second pump with either a relay to run it at full speed when the fuel pump circuit is powered or by way of a pressure switch/relay to turn on the 2nd pump at a boost pressure within ~80% of the 1st pump's maximum output (and I would use 550RWHP as the 80% load on the 1st pump). 2) Install an additional fuel pump controller to operate the second pump. Option #1 will not require you to use anything other than the OE fuel pressure regulator. Option #2 will require that you use a fuel pressure regulator that provides greater bypass volume than the OE. I know for fact that the Aeromotive regulator will work in this setup - I dont know about any of the others. EFI systems employ O2 sensors in the exhaust tract in order to provide feedback information to the ECU. This information is used to more accurately control fuel delivery. Our ECUs are capable of working within ~+/-22% increase or decrease in fuel injection in order to produce an air/fuel mixture of 14.7:1 (stoichiometric). So, if you were to use a pump setup that were to over-run the regulator and produce a higher fuel pressure than normal, the ECU will adjust the injector pulsewidth to account for this and prevent the engine from running rich and wasting a lot of fuel... So for idle and cruising conditions, even if you were to use an under-sized regulator, the ECU will work FOR you and make the proper adjustments BUt only so long as your O2 sensors are in good shape and you have no exhaust leaks upstream of the sensors. In fact, the fuel system operating at higher pressures will improve atomization of the fuel and consequently, improve combustion efficiency. The only way for you to verify that you aren't over over running the regulator will be to use a conzult device to monitor the fuel alpha correction factor. Even though the ECU can make larger injector pulsewidth corrections, I would recommend that you accept no more than a 14% enleanment alpha on either bank while in closed-loop. Any more than this and it wont allow enough "headroom" for the ECU to make corrections later down the road, if needed. Keeping your alpha correction to no more than +/-14% when checked will ensure that the ECU will have the room necessary to make future corrections and avoid failing an emission test or impacting fuel economy. In short, the answer to your question is long. There are too many factors involved to sum it all up in just a few sentences.. :)
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