Engine/Transmission (1998.5 - 2002) How much fuel can an AN-6 line 10 feet long handle before it starts creating psi?

[rweis]

I am trying to figure out how much fuel can be pushed through an AN-6 line 10 feet long before it starts generating pressure. And same question before the pressure goes over say 10 psi.



The reason I am doing this is I have a mechanical fuel pump (RASP). If I replace the RASP with some other gear type of mechanical fuel pump I need to know what the fuel return line can handle to properly size the new pump.



My VP44 return line (the one integral to the VP44) has its own return line so that is not a factor in this question.



The line I am trying to figuer out is a fuel bypass line that is right at the input to the VP44 that returns all the fuel the VP44 does not take in of the fuel available from the fuel pump I am trying to size.



The question is what can an AN-6 line 10 feet long handle in GPH with an open end at the tank before it starts generating pressure in the line?, and if the psi in the return line goes as high as 10 psi what is that GPH?



Thanks,



Bob Weis

 

[wlowe]

I am trying to figure out how much fuel can be pushed through an AN-6 line 10 feet long before it starts generating pressure. And same question before the pressure goes over say 10 psi.



The reason I am doing this is I have a mechanical fuel pump (RASP). If I replace the RASP with some other gear type of mechanical fuel pump I need to know what the fuel return line can handle to properly size the new pump.



My VP44 return line (the one integral to the VP44) has its own return line so that is not a factor in this question.



The line I am trying to figuer out is a fuel bypass line that is right at the input to the VP44 that returns all the fuel the VP44 does not take in of the fuel available from the fuel pump I am trying to size.



The question is what can an AN-6 line 10 feet long handle in GPH with an open end at the tank before it starts generating pressure in the line?, and if the psi in the return line goes as high as 10 psi what is that GPH?



Thanks,



Bob Weis

Bob, the link below goes to the install instructions for the Aeromotive 13301 fuel pressure regulator that I recently installed. In it there is a chart showing the recommended return line hose sizes based on length and GPH. According to the chart a 10 foot piece of 3/8 (-6 AN) line is good for up to 60 GPH (regulated at 3-20 psi).



On my system I figure I'm running 100 GPH with 12 feet of 3/8 return line and have no problem regulating it down to 14 psi. Your system may be a little different since your not running the same type of bypass return as I am but the chart should give you a general idea of what you need.



Bill



http://www.aeromotiveinc.com/pdf/13301.pdf

 

[rweis]

Thanks Bill -



That tells me the "choke point" for feeding a mechanical pump is the fuel filter.



I have a 90 GPH RACOR, the VP44 at high rpm takes 45 GPH, leaving 45 GPH to go back through the return line that is prior to the fuel going into the VP44.



The VP44 has its own return line and it returns up to 70% of the 45 GPH as cooling fuel which gives 31. 5 GPH going back to the tank as cooling fuel in a seperate AN-6 line (I am glad I ran the VP44 body bypass valve return in its own seperate AN-6 line since the VP44 return of 31. 5 AND the mechanical pump return of 45 GPM (total 76. 5 GPM) might have been a little tight.



So I will pick a alternate mechanical pump that does not draw / pump more than 90 GPH at the engine rpms I run at (generally less than 3000 rpm).



That works,



Appreciate the reply,



Bob Weis