There is a possibility that I have discovered a design flaw in the Maxima fuel system. I finished my fuel system upgrade yesterday and finally got my gauge pod installed today with the fuel pressure gauge. The gauge shows 52psi fuel pressure at idle but under WOT the pressure slowly begins to drop all the way down to 38psi at redline. I don't have enough data at this point to know if it is supposed to do that or not. I may have even caused the problem when I added the inline pump that isn't being used under normal conditions. The car does not drive, feel or sound any different than it normally would since I finished the project. However it does sound different when I power the booster pump and set the regulator to 50psi. The engine sounds so much smoother than it used to like it isn't starving for something at 6600 RPM anymore. The butt dyno doesn't say anything different with the booster pump on so the only way I am going to know is when I get my Stochiometric gauge plugged up and take the car to the dyno. I'll add more to this when I aquire more data but does anyone out there have any contacts with Nissan engineers? I would like to know if the ECU is mapped for this kind of pressure drop or is the fuel system supposed to maintain 50+ psi under WOT at redline. Are we being shafted with crappie fuel pumps or did I cause this problem? Actually I don't see how I would have caused any choke points since all the lines and fittings I used are 3/8" and the factory lines are 5/16".

 

Can you clarify? You seem to say conflicting things. Are you saying the fuel system shows 52 psi at IDLE and 38 psi at WOT/redline? Not visa-versa?

Fuel pressure has nothing to do with the ECU. It's all maintained by the fuel pump and mechanical pressure regulator. The regulator has a vacuum "relief", wherein whenever there is vacuum in the intake manifold (idle, low throttle), it drops fuel pressure by 5 psi. On the 4th gens, the car is supposed to run at 38 psi at idle/low throttle and 43 psi at higher rpms (such as WOT/redline).

 

Clarify what? I said exactly what is goin on. In the '02 Maxima the fuel regulator is in the fuel tank. The system has no return line, only a feed line going into the fuel rail. At idle the system is at 52 psi. At WOT the pressure slowly drops all the way down to 38psi when it reaches redline. There is NO vacum operated pressure regulator because the regulator is in the fuel tank. Thats the reason I had to add the booster pump and external regulator in the first place. So now I can install the EFI dry NOS kit.
The reason I asked about the ECU is because in order for the engine to run correctly the ECU would need to be mapped to run at 52psi idle and 38psi WOT at 6600 RPM. If it isn't mapped for that the engine will lean out under those conditions.

 

You went to a smaller fuel line? 3/8" = 6/16"

 

My bad, the stock is 5/16 not 7/16