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Adjusting the fuel pressure with the stock FPR

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  • Adjusting the fuel pressure with the stock FPR

    i was wondering what i should set my fuel pressure at when i purchase an adj. FPR valve in order to push the injectors to their SAFE potential? of course while i purchase this adj. FPR i will be installing a FMIC, so i'm hoping to push 12 psi with a higher fuel pressure setting, and a front mount. thanks for the help.
    1984 2+2 Conv. to Turbo
    Stock Motor w/T3 @ 9.5 psi of boost, raised fuel pressure 7 psi over stock, a tiny bit of timing advancement on the distributor and shorty intake and exhaust.


  • #2
    It's the fuel pump that will max out first; LONG before the fuel injectors will have issues from the raised pressure. With the walbro you don't want the total fuel pressure to exceed ~80-85PSI or you may experience issuesfrom the pressure bypass valve in the pump. To manage 12PSI intercooled on the stock turbo SAFELY you probably wont have to raise the fuel pressure nearly that much. Probably 6-8PSI over stock.

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    • #3
      will that 6-8 psi in fuel pressure difference support the 12 psi without an intercooler, as the intercooler will come after the adjustable FPR? or should i possibly look at buying a TT300ZX fuel pump, and adj. FPR to safely push 12-14 psi?
      1984 2+2 Conv. to Turbo
      Stock Motor w/T3 @ 9.5 psi of boost, raised fuel pressure 7 psi over stock, a tiny bit of timing advancement on the distributor and shorty intake and exhaust.

      Comment


      • #4
        umm.. what makes you feel that you need more fuel pressure for just 12psi?

        I've been running about 13psi non-intercooled with 93octane and the timing backed off about 3 degrees for awhile now. I hear no pings, knocks and feel no hesitation or stummble under boost from detonation.
        I also know a couple people who have been pushing 10+ non-intercooled for a much longer time than me!

        Of course we're probably just lucky nothings blown up so far. :|

        My point is that "in my opinion". 12 psi is just fine on the stock equipment if everything is in good condition. The only things I'd worry about are freeing up the intake and exhaust to get the most from raising the boost.

        Comment


        • #5
          well seeing as how right now i really don't feel like blowing up my car, i'll say i'm playin' things safe for now.
          1984 2+2 Conv. to Turbo
          Stock Motor w/T3 @ 9.5 psi of boost, raised fuel pressure 7 psi over stock, a tiny bit of timing advancement on the distributor and shorty intake and exhaust.

          Comment


          • #6
            im currently running 12 psi with nothing but a cone filter and half an exhaust with no problems in the florida heat.

            Comment


            • #7
              im currently running 12 psi with nothing but a cone filter and half an exhaust with no problems in the florida heat.
              well not everyone's motor is in the same shape, and i honestly don't feel like 'causing damage. i think i'll hold off for the adj. FPR, and FMIC. :wink:
              1984 2+2 Conv. to Turbo
              Stock Motor w/T3 @ 9.5 psi of boost, raised fuel pressure 7 psi over stock, a tiny bit of timing advancement on the distributor and shorty intake and exhaust.

              Comment


              • #8
                when i first got my z the engine wasnt in great shape, but after repairing some basic stuff and tune up, etc. I ran 12-13 psi all day on high octane with no issues at all. all the mods at the time was an open exhaust, 3 inch downpipe and k&n cone filter.
                1984 300zx Ae Turbo(under repair...)
                1989 240sx rb20(daily driver)

                Comment


                • #9
                  well i've had a lot of bad luck with random shit breaking in my NA motors, so i'm really playing it safe with a turbo motor and trying to keep the heat down to a minimum. i wanted to get an adj. FPR anyways for the future, and the FMIC just always is a good idea...especially in this Texas heat. :wink:
                  1984 2+2 Conv. to Turbo
                  Stock Motor w/T3 @ 9.5 psi of boost, raised fuel pressure 7 psi over stock, a tiny bit of timing advancement on the distributor and shorty intake and exhaust.

                  Comment


                  • #10
                    are you just planning on running the 12 psi or higher boost levels than that? Jason said if you get a walbro you can crank that sucker up to 80psi. however, keep in mind that ANY fuel pump you get, the more you crank the psi the less the pump will flow.

                    The walbro gss342 will flow 70gph at 40psi with a draw of 7.5 amps.
                    however at 80 psi it will only flow about 51-52 gph with a draw of 11.1 amps. these figures are at 13.5 volts.

                    You can get a walbro cheaper than a tt pump 99% of the time and the walbro is new and tried a and true. It is MORE than capable of handling 12 psi on a stock T-3
                    Attached Files
                    85 Z31 6.0 LSX turbo 766whp/792wtq
                    04 GTO, LS6, big cam, porting, N20... underway for summertime daily driver.

                    Comment


                    • #11
                      well i really want to shoot for getting close to 450-500 whp, from around 22-26 PSI of boost, and other modifications to my heads, cams, etc.
                      1984 2+2 Conv. to Turbo
                      Stock Motor w/T3 @ 9.5 psi of boost, raised fuel pressure 7 psi over stock, a tiny bit of timing advancement on the distributor and shorty intake and exhaust.

                      Comment


                      • #12
                        Morgenstern wrote: well i really want to shoot for getting close to 450-500 whp, from around 22-26 PSI of boost, and other modifications to my heads, cams, etc.
                        so you are most likley looking at a 60-1 or a 62-1 . In which case a walbro would be pulling about 9.7 amps flowing about 56 gph with total pressure with boost of about 66psi assuming you run a base pressure of 40psi. thats pushing it but one walbro may be able to do it. the walbro could do it easier if you ran a larger turbo and a lower psi. then the fuel pump wouldnt have to work as hard. but then you obviously have to worry about more lag and yadda yadda.
                        85 Z31 6.0 LSX turbo 766whp/792wtq
                        04 GTO, LS6, big cam, porting, N20... underway for summertime daily driver.

                        Comment


                        • #13
                          well i deffinatly plan on upgrading to a T04E/T3, or something in that ballpark. so 22-26 psi is something i want to achieve with that turbo, or maybe lower...who knows.
                          1984 2+2 Conv. to Turbo
                          Stock Motor w/T3 @ 9.5 psi of boost, raised fuel pressure 7 psi over stock, a tiny bit of timing advancement on the distributor and shorty intake and exhaust.

                          Comment


                          • #14
                            cheezmonta wrote: umm.. what makes you feel that you need more fuel pressure for just 12psi?

                            I've been running about 13psi non-intercooled with 93octane and the timing backed off about 3 degrees for awhile now. I hear no pings, knocks and feel no hesitation or stummble under boost from detonation.
                            I also know a couple people who have been pushing 10+ non-intercooled for a much longer time than me!

                            Of course we're probably just lucky nothings blown up so far. :|

                            My point is that "in my opinion
                            ". 12 psi is just fine on the stock equipment if everything is in good condition. The only things I'd worry about are freeing up the intake and exhaust to get the most from raising the boost.
                            Just remember: 12PSI intercooled is quite a bit more air than 13PSI non-intercooled. 12PSI intercooled on a 10 degree day would be even more air; something around 17PSI non-intercooled in terms of airflow? You can't relate pressures to airflow very well if air density is completely different, even given the same exact compressor.

                            Comment


                            • #15
                              right, i'm trying to figure out what i would need to do to start the boosting process (i.e turning up the boost) safely, and i thought that an adj. FPR, TT300ZX Fuel pump, and FMIC would start the basis for getting 300 whp. maybe?
                              1984 2+2 Conv. to Turbo
                              Stock Motor w/T3 @ 9.5 psi of boost, raised fuel pressure 7 psi over stock, a tiny bit of timing advancement on the distributor and shorty intake and exhaust.

                              Comment

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