mikellucci

iTrader: (56)

Hi guys, I need to confirm real world fuel pressures around the 2urgse. FSM states low pressure is 400 kPa or 58psi. High pressure varies 4-13 MPa or 580-1885psi.

I need to know; are these pressures at the high/low FPR's and injectors only? Are the fuel lines ever seeing near 1885psi?! Specifically trying to narrow down what the fuel delivery and return hard lines from the rear fuel pump/sender are going to max out at in terms of pressure.

Lines 77252A, 77255D and 77251J in the diagram. Thanks!

mikellucci

iTrader: (56)

Before anyone bad mouths me I'm doing this to allow flexibility/additional fuel needs in the near future and also to clean up atop the engine where my roots supercharger will soon reside. Havent ruled out nitrous either so it could be an added variable.

I'll be using ptfe -6an lines to replace the hardlines beneath the car that I referenced above. Working PSI varies by brand/price but the highest end hoses are rated at 2500psi. I guess I'll just go with those instead of the more cost effective 1500psi rated ones. I also assume the fuel return line is low pressure so anything up to 500psi should suffice?

The fittings I'll use are "RUSSELL PUSH-ON EFI FITTINGS" (for oem hardlines)
-6 AN male to 5/16" SAE quick-disconnect female (black not blue)

lobuxracer

iTrader: (2)

I know you won't like to hear this, but if it were mine, I'd be making hard lines. I've worked on enough aircraft to know braided stainless steel lines should only be used where their ability to flex is needed. The do wear out over time and they fail catastrophically when the braid starts to break and pierce the teflon. Aircraft have routine inspections on every braided line to determine if the number of broken wires per inch exceeds the standard, and they are replaced when they do. They are great for what they do, but they're not a good solution when a hard line is lighter, stronger, and more reliable.

mikellucci

iTrader: (56)

As usual, thank you for replying with insightful information! I agree with you in that a braided SS line isn't ideal for this application. I have seen my fair share of frayed lines from nothing more than a harsh routing angle and or contact/rubbing point on the subframe. I recall your input around SS brake lines as well.

I have used P.T.F.E. coated line in the past with success. The outer coating seems to be the difference maker in keeping the braids shielded from elements and contact points. I will continue to research race and aeronautics solutions to see what else will provide hard line protection while offering installation flexibility.

Back to the pressures, there's no way the hard lines are seeing extremely high psi associated with direct injection, correct? I would have to assume those plastic push-on hard line to rubber connectors would leak like a sleeve under that much psi.

Just trying to confirm for piece of mind if and when I change out the lines. Thanks!

mikellucci

iTrader: (56)

Lance, you sent me the answer before I typed that last RE.

Taken from the NCF:

The fuel delivered to the high-pressure fuel system is pressurized by the high-pressure fuel pumps and injected from the fuel injector assemblies (for direct injection) to the combustion chambers.

The low-pressure fuel pump is located in the fuel tank. This pump pressurizes fuel to 400 kPa in order to send the fuel from the fuel tank to the high- and low-pressure fuel systems.

So it would seem the hard lines carry fuel to/from the tank to the engine FPRs at or below 400kPa...which is exactly what I needed to know! Once it hits the high press. Fpr it gets rocket launched up to near 2000psi.

lobuxracer

iTrader: (2)

Pretty hard to beat the Toyota NCF. I discovered it with my Supra. Everyone at the MkIV email list back in the 90's wondered how I knew so much about the car...I just read the book, cover to cover.