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Thread: Need to Clear My Conscience About This.

  1. #201
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    are you maintaining lift pump pressure? or is it tanking?
    The most hated, make the most power.
    93 Ranger. 5.3 D1X. 1069hp.

  2. #202
    Senior Tuner Higgs Boson's Avatar
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    lift pump as in HPFP? that's what I mean by rail pressure, it is tanking and the injectors are working overtime to compensate. i do let off as soon as this happens so i never really run it leaner than 13 or so but still.....that's at 3500-4000 or so the high pressure goes from 12 (commanded 12) at maybe 65% throttle and .85-.9 g/cyl and nosedives to 3-5 MPa as soon as I romp it.

    If I floor it at 2000, it will be ok until I get up to that RPM range and then tank. it does hold commanded AFR of 12-12.25 until injectors hit 49% DC. it doesn't matter if I command 8 or 15 degrees of timing or 12 or 12.5 AFR.

    something is jacked with my torque model, probably, as well.

    on a side note, i DO have a breakout harness for the Baro and IAT sensors.....I do have the tune set to NA - MAP, TIAP......I need to either change it to NA - MAP, Baro or should I just remove the harness? This might be my issue, it seems to be the wild card vs everyone else.
    Last edited by Higgs Boson; 09-17-2015 at 04:37 PM.

  3. #203
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    the feed pump in the tank is referred to as the lift pump.

    Typically if the fuel pressure drops in the mid range it is the hpfp. if it tanks up top, it is the feed pump. Your timing issue is following the lack of fuel pressure as a safety behind it to save itself. fix the fuel, the timing will follow.

    any and all tables labeled "predicted" are tables that are dealing with controls via TB thus they need several cycles for the PID loop to catch up. any and all tables labeled "immediate" are spark control based. These ecms will not run true SD as they are not coded to.
    The most hated, make the most power.
    93 Ranger. 5.3 D1X. 1069hp.

  4. #204
    Senior Tuner Higgs Boson's Avatar
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    fix the fuel.....isn't that the key phrase. are you saying it's mechanical? or is there anything you know of in the tune that can cause the lack of midrange high pressure fuel pressure? i guess what I am asking is, when you see a midrange hpfp pressure issue, what is normally the cause?

    i am maintaining lift pump pressure (50-70 psi depending). the breakout harness had no impact on the fuel pressure.

  5. #205
    Senior Tuner cobaltssoverbooster's Avatar
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    if you get 50-70 without any dips then you need to check your hpfp. the high pressure regulation devices are all internal to the pump so its a complete unit.
    Last edited by cobaltssoverbooster; 09-18-2015 at 11:28 PM.
    2000 Ford Mustang - Top Sportsman

  6. #206
    Senior Tuner Higgs Boson's Avatar
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    Quote Originally Posted by cobaltssoverbooster View Post
    if you get 50-70 without any dips then you need to check your hpfp. the high pressure regulation devices are all internal to the pump so its a complete unit.
    it's a brand new Z06 HPFP with a matter of a few hundred miles on it. I guess it could have failed already....?

    What have you guys seen cause HPFP failures? Production defects or could it fail from a voltage issue due to tuning?

    When I copied the Z06 pump data over, one table, the Peak Pulse table (RPM vs Voltage), caused it to run at .2 MPa. I put the stock C7 Peak Pulse table back in and it ran fine again, idles around 3 MPa. Maybe I killed it when i did that....?

    Anyways, new one is going in next week, going to use Z06 fuel rails also, why not!

  7. #207
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    Quote Originally Posted by Higgs Boson View Post
    it's a brand new Z06 HPFP with a matter of a few hundred miles on it. I guess it could have failed already....?

    What have you guys seen cause HPFP failures? Production defects or could it fail from a voltage issue due to tuning?

    When I copied the Z06 pump data over, one table, the Peak Pulse table (RPM vs Voltage), caused it to run at .2 MPa. I put the stock C7 Peak Pulse table back in and it ran fine again, idles around 3 MPa. Maybe I killed it when i did that....?

    Anyways, new one is going in next week, going to use Z06 fuel rails also, why not!
    anything is possible. i have actually never seen the hpfp on the lnf fail when i have been tinkering with them. You can tell when the springs get weak however ad the static pressure starts to drop. I have run out of volume in the midrange due to stock cam lobes, but outside of this i just lower the boost till it stabilizes, or vice versa. Without proper scaling of the pump itself, you're going to have to fudge some tables on the main side of it to get it to do what you want.

    The problem most people are going to run into is what you see of the surface is not always the same in the background. Not all of the ltX tables are there to view and tweak. HPT can only release so much before Gm slaps their hand. Either due to patent, or trade secrets. So keep this in mind, when comparing the lt1 vs lt4 files, you're only getting a glimpse of the party through a key hole.
    The most hated, make the most power.
    93 Ranger. 5.3 D1X. 1069hp.

  8. #208
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    Sorry to revive this thread but y'all obviously know more than I do at this point. I'm probably going to change to a cat-less exhaust on my 07 GXP, it has a K&N CAI and GMPP stage 1 tune currently otherwise stock. What needs to be changed to disable the converter tests and fuel dumps to heat and cool the converter? I see the obvious things like the MIL codes but im sure there is more to it than that and I dont want to miss anything important.

    Thanks