Nissan 370Z Forum - View Single Post - *****Fast Intentions "Twin Turbo Kit" is here*****

phunk · 02-20-2013, 09:15 PM

There are 2 options for working around a fuel pressure drop in the system in a scenario such as this, and you can optionally take both steps.

Option 1, increase the plumbing size to reduce pressure drops. This can get expensive depending on how far you take it... because a duration of the conservative sized plumbing is physically built into the inlets of the factory fuel rails. The fuel rails themselves are massive and do not need upgraded... however to cut off the ends and weld on different inlets isnt an option for customers who need bolt on solutions, and welding fuel rails is often prone to pinhole leaks. It just makes more sense to move to billet fuel rails so that its simple to add larger plumbing. Well, this gets expensive now.

Option 2: convert to a return fuel system. For one simple reason, to regulate fuel pressure as close as you can to the rails. How does this help you may ask?

Lets say you have a walbro 255, and you are running out of fuel on top. You might say to yourself... oh, I am running out of pump, so i need to put in a larger pump so that pressure doesnt drop anymore. Well, thats old school thinking... thats what it USED to mean when cars had return lines and regulators in the engine bay.

Because pressure drop. While you might be losing pressure in the engine bay with your 255... you might NOT be losing pressure all the way back up the pump. If you arent, then upgrading the pump isnt going to do a dang thing, because the regulator is still going to be holding open at the same pressure in the back. BUT... if your regulator is in the engine bay, and you still have a pressure drop... a larger pump can actually fight the restrictions by flowing greater at higher pressure. Your regulator in the engine bay can hold pressure where its supposed to, and you just let pressure skyrocket at the pump to keep up, compensating fuel pressure drop across the lines.

Basically all I am saying here, is that nobody can argue unless they have *more than one* fuel pressure gauge in their 370z. You might be surprised if you knew how much fuel pressure can drop from one end of a fuel rail to the other, let alone across an entire car.

02-20-2013, 09:15 PM	#535 (permalink)
phunk A True Z Fanatic Join Date: Mar 2009 Location: Chicago Posts: 3,657 Drives: 370 Rep Power: 947878	There are 2 options for working around a fuel pressure drop in the system in a scenario such as this, and you can optionally take both steps. Option 1, increase the plumbing size to reduce pressure drops. This can get expensive depending on how far you take it... because a duration of the conservative sized plumbing is physically built into the inlets of the factory fuel rails. The fuel rails themselves are massive and do not need upgraded... however to cut off the ends and weld on different inlets isnt an option for customers who need bolt on solutions, and welding fuel rails is often prone to pinhole leaks. It just makes more sense to move to billet fuel rails so that its simple to add larger plumbing. Well, this gets expensive now. Option 2: convert to a return fuel system. For one simple reason, to regulate fuel pressure as close as you can to the rails. How does this help you may ask? Lets say you have a walbro 255, and you are running out of fuel on top. You might say to yourself... oh, I am running out of pump, so i need to put in a larger pump so that pressure doesnt drop anymore. Well, thats old school thinking... thats what it USED to mean when cars had return lines and regulators in the engine bay. Because pressure drop. While you might be losing pressure in the engine bay with your 255... you might NOT be losing pressure all the way back up the pump. If you arent, then upgrading the pump isnt going to do a dang thing, because the regulator is still going to be holding open at the same pressure in the back. BUT... if your regulator is in the engine bay, and you still have a pressure drop... a larger pump can actually fight the restrictions by flowing greater at higher pressure. Your regulator in the engine bay can hold pressure where its supposed to, and you just let pressure skyrocket at the pump to keep up, compensating fuel pressure drop across the lines. Basically all I am saying here, is that nobody can argue unless they have more than one fuel pressure gauge in their 370z. You might be surprised if you knew how much fuel pressure can drop from one end of a fuel rail to the other, let alone across an entire car. __________________ Charles @ CJ Motorsports : Website \| Facebook \| Instagram \| YouTube Home of the 9 second, stock longblock, stock drivetrain 6MT 370z. 9.91 @ 142mph Last edited by phunk; 02-20-2013 at 10:09 PM.