Results 1 to 13 of 13

Thread: Adding an aux pump to an LT4 car. What should I change in the tune to take full adv

  1. #1
    Advanced Tuner
    Join Date
    Jun 2018
    Posts
    224

    Adding an aux pump to an LT4 car. What should I change in the tune to take full adv

    So we're adding a auxiliary pump to a LT4 car. What should I change in the tune to take advantage. I'm guessing I can add low side fuel pressure to keep the high side feed better. I've got a few ideas I just want to make sure I don't mess anything up.

  2. #2
    Tuner in Training
    Join Date
    Jun 2015
    Posts
    48
    you dont change anything in the tune as the aux pump isnt getting controlled by the ECU. You set your FPR and hobbs switch to whenever you want it to come on

  3. #3
    Advanced Tuner
    Join Date
    Jun 2018
    Posts
    224
    I was looking to find out if there is a certain field in the fpcm that I should be messing with.

  4. #4
    Potential Tuner
    Join Date
    Jun 2019
    Posts
    4
    Interested in this as well. I will be installing a DSX aux pump and was under the assumption some values in the FSCM would need changed. Anyone have input?

  5. #5
    need to adjust some settings in the fpcm to allow the added fuel psi that the aux pump is going to supply

  6. #6

  7. #7
    Advanced Tuner
    Join Date
    Aug 2014
    Location
    Central, LA
    Posts
    489
    I'm assuming a DSX kit here...

    The real key is table ECM 6975, make sure the hi flow areas are at least 500 kpa. Then ECM 7030 make sure it's at least 500kpa as well. If you want it to enter "hi flow" more often you would decrese numbers in ecm 17022, and to come out of hi flow easier increase 17023.

    With factory tune settings an LT4 SHOULD kick on the dsx kit when flow rates match.

  8. #8
    I'm in DSX Tuning auxiliary pump hell myself right now. I just installed one as part of a supercharger upgrade on my 2017 ZL1.

    In the logs, I've noticed a few issues.
    • When the aux pump kicks on, the in-tank pump backs off in an attempt to maintain the desired fuel pressure. However, when the aux pump suddenly turns off, the pressure dips significantly before the in-tank pump has the chance to get back up to speed. There's probably a way to tune around this, but I wish the DSX kit would just use a PWM pump and phase out slowly.
    • Sometimes, mid pull, I'll see dips in fuel pressure. It's not because the pumps can't keep up with the load because the pressure will recover on its own within the same pull. Something else is going on.


    Sevinn, do you know what happens with the values in the Maximum Desired Pressure table (6975) are exceeded? I'm wondering if my dips in fuel pressure mid-pull might be related to exceeding the limits here.

  9. #9
    Advanced Tuner
    Join Date
    Jun 2018
    Posts
    224
    I'm working on one in a 5gen Camaro and will be doing a C7 next week if all goes well. The most I can get our of DSX is you have to increase the minimum flow tables. So when the pump kicks on and adds pressure and the stock pump backs down to compensate you just don't give it the chance. By increasing the min flow tables the stock pump just can't pull enough pressure out. I haven't taken this to the genV platform yet but we'll see what happens.

  10. #10
    Advanced Tuner
    Join Date
    Aug 2014
    Location
    Central, LA
    Posts
    489
    Quote Originally Posted by travislambert View Post
    I'm in DSX Tuning auxiliary pump hell myself right now. I just installed one as part of a supercharger upgrade on my 2017 ZL1.

    In the logs, I've noticed a few issues.
    • When the aux pump kicks on, the in-tank pump backs off in an attempt to maintain the desired fuel pressure. However, when the aux pump suddenly turns off, the pressure dips significantly before the in-tank pump has the chance to get back up to speed. There's probably a way to tune around this, but I wish the DSX kit would just use a PWM pump and phase out slowly.
    • Sometimes, mid pull, I'll see dips in fuel pressure. It's not because the pumps can't keep up with the load because the pressure will recover on its own within the same pull. Something else is going on.


    Sevinn, do you know what happens with the values in the Maximum Desired Pressure table (6975) are exceeded? I'm wondering if my dips in fuel pressure mid-pull might be related to exceeding the limits here.
    How far are you exceeding them? That table I feel is a bit mislabeled as it acts more like a floor for desired pressure.

  11. #11
    Advanced Tuner
    Join Date
    Aug 2014
    Location
    Central, LA
    Posts
    489
    Quote Originally Posted by JASON11WS6 View Post
    I'm working on one in a 5gen Camaro and will be doing a C7 next week if all goes well. The most I can get our of DSX is you have to increase the minimum flow tables. So when the pump kicks on and adds pressure and the stock pump backs down to compensate you just don't give it the chance. By increasing the min flow tables the stock pump just can't pull enough pressure out. I haven't taken this to the genV platform yet but we'll see what happens.
    You can play with Open Loop DC on the in tank pump to offset it a litte, but the aux kits will always hit kind of hard.

  12. #12
    Quote Originally Posted by sevinn View Post
    How far are you exceeding them? That table I feel is a bit mislabeled as it acts more like a floor for desired pressure.

    I see spikes at around 600 kPa, but mostly I see 550 kPa where the max is set to 500 or so. I'm sure the mechanical pressure relief valve is probably opening near 600 occasionally.

    The problem is my setup is relatively mild. When the aux pump kicks on, the primary pump basically has to wind down to its minimum duty cycle and often there's still too much pressure. When the aux pump turns off, I get a momentary pressure drop because my primary pump is basically off and has to spin back up. If I bump the min DC up, then I'm back at too much pressure.

    These aux pumps sound like a good idea in theory, but when you get into the details all they do is confuse the crap out of the primary pump logic. It'd be much better if the aux pumps were variable output and pressure controlled.

    I've ordered a new aux pump with a lower flow rate in hopes that I can keep the primary pump moving more fuel without too much pressure.

    Talking to DSX, I guess I'm "patient zero" for having these issues. Apparently every other aux pump just works absolutely perfect in all scenarios. (In other words, they offered zero assistance.)

  13. #13