Fuel pressure

[john]

What do you run for fuel pressure? I am at ~41 right now and am thinking of upping it. I am starting to hit fuel cut at 20 psi. I am thinking of raising it to 43 psi. Will higher fuel pressure and lower injector pulse widths increase timing and/or help eliminate fuel cut? What are the downfalls of running too high fuel pressure? I thought I heard John galantvr41064 is running 52 psi for fuel pressure. Is that correct?

Sorry, I am just looking for more ways to support high boost.
Thanks, John.

[Shane@DBPerformance]

Fuel cut actually has nothing to do with having enough fuel or not.

[1ViciousGSX]

set it at 43psi

[john]

I just went out and did a couple of logs at 41 psi (fuel pressure). When I was going to the spot, I was hitting 20psi (just checking what I was running). When I started logging, I was only running 17psi. WTF. My o2's were .94 all the way with no knock at all and timing around 18 spiking at 21. I need to turn the boost back up and log some more. Car felt like it was running really rich. Didn't see half as fast as before.

I thought that injectors had something to do with fuel cut. When I upped to 550's at the same boost, I didn't hit fuel cut anymore. Maybe just a coincidence. Also I notice that I hit fuel cut when my injectors go over 25 ms. I thought I heard that upping fuel pressure will lower injector ms and take me further away from fuel cut.

[JET]

Shane is just getting technical. Airflow is what causes fuel cut. If you are using a SAFC though, that will lie to the ECU and tell it that it has less airflow so you don't hit fuel cut. I run my FPR at 45psi and John is running 50 psi I believe. I have heard that over 75 psi you start to run the risk of getting too much dead time at high RPM's. The extra fuel pressure makes it harder for the injector to move.

[john]

What is dead time?

[JET]

The amount of time in between shots of fuel. At a certain time the injector will not be able to keep up with the RPM's, increasing the pressure makes it hard for it to keep up. When exactly this happens, I don't know and it would depend on the RPM's you run too.

[Shane@DBPerformance]

You could raise the fuel pressure and then inturn take some fuel out on the AFC. That will help to fool the ECU away from fuel cutting.

[Jacek]

i have a question about setting the fuel pressure. i knoticed that the manual has to different setings, one with the vacuum hose on and one off (10 psi difference) now when everyone says that the base pressure is 36 psi it shows that with the vacuum line off. does everyone who raises it up then to 45 or whatever take the vacuum line off to set it? i wouldnt think it would matter since the 10 psi difference but thought i would just check.

[Shane@DBPerformance]

Always measure base fuel pressure with the vacuum line off.