What's the max base fuel psi ran??

[frankg]

What is the most fuel psi someone has run on an xp fuel pump without problems. I want to crank my base fuel psi up as much as possible to try and stretch my 009's a little farther. I want to try like 27-30 boost but will need more fuel. I ran 25 boost and like 50-52psi fuel on my 11.36 pass. I know this isn't the proper way and i should get bigger injectors but i just want to try it !! Any ideas? Thanks,Frank

 

[TurboDave]

Goin' to join the ranks of those searching for a new turbo block, eh?

 

[ijames]

You've got two things going against you, the bypass spring opening at some point and the drop off in delivered volume with increasing delivery pressure. I run an external Bosch 204 pump with a 120 psi bypass spring, and when I ran red stripes I went all the way up to 65 psi base pressure at 20 psi boost. However, the O2's quit rising after about 63 psi because the pump volume was now the limit. If you really want to know for your exact pump, pull the return line apart down by the frame crossover under the power steering pump, get a gallon jug, and time how long it takes to deliver a gallon as you start cranking up on the fuel pressure regulator. The volume will drop smoothly with pressure and then when the bypass opens it will drop sharply. That's a lot safer than trying to watch a pressure gauge taped to the windshield and detecting when the fuel pressure no longer rises with boost .

 

[frankg]

How much more boost or how much quicker ET's did you get out of it??? FRom changing it from like 50psi to the 65psi you ran? Thanks, Frank

 

[ijames]

Sorry, Frank, but it's been a few years. I think it was maybe .3 and 3-4 psi going from 50 to 60? I basically just kept tuning upwards until I was maxed out, and never went back down to see what the difference was.