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Had to set K value low... fuel pressure wrong?

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  • Had to set K value low... fuel pressure wrong?

    Well, first i'll tell ya'll what i've done. I've removed the two resistors in the ecu plus R201 and soldered in the romulator (this is a drag car so it will be under constant adjustment anyway.) I'm running the 420cc injectors from jim wolf technology and the stock maf (will be running dual mafs soon but first lets get it running on one) So, here's my problem -- I've adjusted the latency and the ttp min according to the math and came up with a 5b and 8's and 5's for the ttp min. The bloody thing won't start with a k value of 150. I tried 120, then 90 and so on untill i got to 4c and the bloody thing ran. I'm assuming it's my fuel pressure and here are the pressures that i got --
    40 psi with ignition on after fuel pump runs.
    35 psi while starting with fpr vacuum unhooked
    35 psi with fpr hooked up
    30 psi with 20" mecury applied to fpr manually..

    If anybody out there has any suggestions as to what else it might be it would be much appreciated The other thing that crossed my mind is that perhaps i should be unplugging the fuel system everytime i upload to the romulator? Please help.. getting frustrated -- here's some pics of the project so far.

    Here's the hood work and the intercooler piping:









    Upload Photo with PicTiger
    8.5 custom arias pistons (.020 over)
    eagle rods
    t70 turbo (man was that a squeeze)
    38 mm external wastegate
    mild port/polish
    3 angle valve job
    custom intercooler piping
    twin external intakes with z32 maf
    rad moved back
    3" exhaust with only a resonator
    romulator
    420cc injectors
    custom body work, homemade oil lines and fittings..
    walbro 255lph in-line fuel pump.... and lots of headaches... lol

  • #2
    Biggest thing I can think of is that if you are still using the stock maf you do not remove those resistors. Put them back in and see what happens.

    Comment


    • #3
      Very interesting what you have done there.Thats bad ass.
      It is overkill for 420s.How about 850s or +.
      You will need to port the crap out of the heads as well.
      imagination is a virtue

      Comment


      • #4
        i don't know if i can replace r201... not sure what the electronics guy did with it.... arghhh.... i thought it just got rid of limp mode. hmmmm.. i'm going to check the afm's and see if they are both broken and ceck the fpr and see if it's screwed..... i'm pretty sure that the afms from the n/a and the turbo are the same -- maps are the same -- so maybe if i try another afm it will help... i can't believe that i misread the instructions and removed those resistors before it was necessary. oh well... stupidity hurts. god i hope he didn't throw out r201....
        8.5 custom arias pistons (.020 over)
        eagle rods
        t70 turbo (man was that a squeeze)
        38 mm external wastegate
        mild port/polish
        3 angle valve job
        custom intercooler piping
        twin external intakes with z32 maf
        rad moved back
        3" exhaust with only a resonator
        romulator
        420cc injectors
        custom body work, homemade oil lines and fittings..
        walbro 255lph in-line fuel pump.... and lots of headaches... lol

        Comment


        • #5
          You only pull the resistors if you are swapping MAF's... re-install them if you can.

          If you can't you may be able to re-scale the VQmap to get it running fairly well... or adjust the K and fuel maps. Either way will take a lot of trial and error.

          Comment


          • #6
            well well... maybe i'll just install the z32 maf... i'm going to see if i can borrow one tomorrow from a guy here in town and see if it will run. Just a quick question -- what did those resistors do anyway? It would appear to me that they drop the voltage.. I ran the car today without the maf hooked up and it ran perfectly with the k value set to 120hex up to 2000 rpm -- where it hit some sort of fuel or spark govenor. So, it would appear that the maf map is the culprit. Thank-you so much for your help.
            8.5 custom arias pistons (.020 over)
            eagle rods
            t70 turbo (man was that a squeeze)
            38 mm external wastegate
            mild port/polish
            3 angle valve job
            custom intercooler piping
            twin external intakes with z32 maf
            rad moved back
            3" exhaust with only a resonator
            romulator
            420cc injectors
            custom body work, homemade oil lines and fittings..
            walbro 255lph in-line fuel pump.... and lots of headaches... lol

            Comment


            • #7
              yeah that governor thing is there so you down mess up the mixture and go lean at high rpms , it only happens when the MAF is disconnected or broken or whatever so you are totally fine , just get those resistors back on there...

              Comment


              • #8
                R201 is a surface mount. Good luck soldering it. Generally, how those come off, is you melt the solder and it'll stick to the tip of the iron.

                Whenever I've had to fix surface mount stuff, I'll find the regular equiv of it, and solder that into place.


                You're probably better off with trying to get a z32 maf going on the car.
                vg33et -blew some chunks outta it, then gave it all away.
                2009 370z touring/nav/sports

                Comment


                • #9
                  Yeah.. i guess that's the best option -- z32 maf... Oh well -- live and learn. It's nice to have finally figured out the problem though, after 40 hours in the shop changing k values, cleaning fouled plugs, checking vacuum lines, fuel pressures etc... And i don't think my dual maf thing would have worked without changing the vq map anyway due to the fact that the voltage is not directly proportional to the air flow and therefore i would have had to plot the values on a graph, and then take the airflows and divide them by two and figure out what hex value that would be on the graph... Or at least that's what i think i'd have to do but it's too much bloody work anyhow.
                  8.5 custom arias pistons (.020 over)
                  eagle rods
                  t70 turbo (man was that a squeeze)
                  38 mm external wastegate
                  mild port/polish
                  3 angle valve job
                  custom intercooler piping
                  twin external intakes with z32 maf
                  rad moved back
                  3" exhaust with only a resonator
                  romulator
                  420cc injectors
                  custom body work, homemade oil lines and fittings..
                  walbro 255lph in-line fuel pump.... and lots of headaches... lol

                  Comment


                  • #10
                    the dual maf can be made to work, I'm sure.

                    My heads a little cloudy after 11 hours of work.

                    Is it that you work the K value
                    or do you work the TP scales?
                    both maybe?
                    My brains out of it, I wasn't really concerned about it too much..

                    I had caught something interesting the other day, about how gm or some company was converting cars from MAF to MAP after their MAF units were failing (too fragile, they'd be doing the hotwire burnoff, and if you jar it bad enough (closing hood) they'd break and fail.)

                    basically, they'd add the MAP, install a new PROM with a modified VQ table, the VOut from the MAF would be moved to the VOut of the MAP, and they'd leave the intake temp sensor in the MAF working.
                    vg33et -blew some chunks outta it, then gave it all away.
                    2009 370z touring/nav/sports

                    Comment


                    • #11
                      That's pretty neat -- that gm maf to map conversion. As for the vq map and the k value -- i think i would have to double the k value and muck with the vq too -- it looks like a quadratic map so it should be a fairly basic map to adjust for two mafs, but it would still take some time to ensure it's perfect operation. It will not be difficult to convert my dual intakes to operate with one maf. I think what i'm going to do is just plumb the two together before the maf, though i could plug off one of the intakes. Going to place a bid on e-bay right now for a z32 maf -- it would appear that the turbo and na mafs are identical in part number.. is this correct?
                      8.5 custom arias pistons (.020 over)
                      eagle rods
                      t70 turbo (man was that a squeeze)
                      38 mm external wastegate
                      mild port/polish
                      3 angle valve job
                      custom intercooler piping
                      twin external intakes with z32 maf
                      rad moved back
                      3" exhaust with only a resonator
                      romulator
                      420cc injectors
                      custom body work, homemade oil lines and fittings..
                      walbro 255lph in-line fuel pump.... and lots of headaches... lol

                      Comment


                      • #12
                        That should be right.

                        alot like the z31 maf's.
                        vg33et -blew some chunks outta it, then gave it all away.
                        2009 370z touring/nav/sports

                        Comment


                        • #13
                          excellent... i did notice that the z31 na maf vq map is identical to the turbo one, but yet the part numbers are different i think only due to the 6th wire on the maf which i do believe is the air temperature sensor wire... thanks again man!
                          8.5 custom arias pistons (.020 over)
                          eagle rods
                          t70 turbo (man was that a squeeze)
                          38 mm external wastegate
                          mild port/polish
                          3 angle valve job
                          custom intercooler piping
                          twin external intakes with z32 maf
                          rad moved back
                          3" exhaust with only a resonator
                          romulator
                          420cc injectors
                          custom body work, homemade oil lines and fittings..
                          walbro 255lph in-line fuel pump.... and lots of headaches... lol

                          Comment


                          • #14
                            if you did want to measure a new vqmap for a bypassed z31 afm, you'd have to have one afm reading normally.... you'd have a split intake before the afm, one side with a second afm installed to measure voltages, but the unmetered side would have to be smaller, I think going down to half is too low for the ecu but I may be wrong

                            if you could log both afms voltage at idle, then look in the vqmap where the lower one lines up, and shift the table, and create the missing section with guess & test

                            Comment


                            • #15
                              i think you would still have some issues with shifting the map as that still assumes certain amount of linearity... I really wish i hadn't taken out those bloody resistors because then i could play with this whole thing.I actually didn't divide the flow in two anyway... i used 3 inch for the main afm and the second afm comes into the 3" elbow with a 2.5" swedge, therefore the second afm is metering 40% and the first 60% --i did this in case i was going to run a bypass and disconnect the second afm so that the increase in airflow would be approximately proportional to the increase in injector size. It's a darn shame i won't get to play with maps at that detail level in this case but there will be many more projects with which i can play. Thanks for all the input guys... it's really nice to get some solid information on this kind of stuff, there is absolutely nobody around me that has a clue about ecu re-programming. In-fact there are only 2 shops in Calgary doing this and that's 180 miles away. This forum is a godsend...
                              8.5 custom arias pistons (.020 over)
                              eagle rods
                              t70 turbo (man was that a squeeze)
                              38 mm external wastegate
                              mild port/polish
                              3 angle valve job
                              custom intercooler piping
                              twin external intakes with z32 maf
                              rad moved back
                              3" exhaust with only a resonator
                              romulator
                              420cc injectors
                              custom body work, homemade oil lines and fittings..
                              walbro 255lph in-line fuel pump.... and lots of headaches... lol

                              Comment

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