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Thread: 21 XPT tune revision/suggestions for upcoming drag races

  1. #1
    Potential Tuner
    Join Date
    Jan 2023
    Southwest PA

    21 XPT tune revision/suggestions for upcoming drag races

    hey guys ive got a decent base map on my 21 xpt but was looking for suggestions/revision/fine tuning of details on it to get it running the best it can on stock bottom end. its running a big turbo, BC stg 2 cams, id 1700 injectors on pump E-85. its obviously got all the supporting mods like 3'' turbo back, charge/intake pipes, and head studs. A few local fairs are having sxs drag races coming up in the next 2 weeks so im trying to get this running as best i can(especially initial take off). its not running poorly by any means but just looking for some fine tuning suggestions to help with any spots that can be improved. ive attached my current tune and a data log of launchs. thanks for any revisions or tips guys!!!!e85 big turbo 1700injectors.hptyard runnn.hpl

  2. #2
    Advanced Tuner
    Join Date
    Mar 2009
    Andover, MN
    I seen this just out of curiosity of polaris tuning, why so rich? .69 lambda? What is it, a two stroke lol.

  3. #3
    Tuner in Training
    Join Date
    Mar 2022
    Quote Originally Posted by ns158sl View Post
    I seen this just out of curiosity of Polaris tuning, why so rich? .69 lambda? What is it, a two stroke lol.
    I didnt look at his tune but if you have boost values pushing past the 4000 decimal range for raw value similar to 40.00psi-key on baro (13.9 for me)=relative boost limit of 26.1 psi better safe than sorry! also pending total timing advance under boost (which should prob be near 25-30*?).

    Safety more than optimal fueling as you wont cost yourself all much power at higher rpms. sometimes I get e 85 that's 71% based off my sensor. sometimes its 88% winter it's down to 45-50 range and it blows!

    lower the E ratio (pending fuel) the richer lambda target is going to get. so that can help there by giving a safe ratio for e/gas blend ratio vs targeting leaner. ideally max power AT LOWEST MANIFOLD EGT should be found around .76L no concern for EGT set it to .8 but EGT temps climb FAST to me, the gains from doing so don't really outweigh overheating the piston or binding a ring and listing the piston land and scuffing the cyl walls from high expansion rate of the piston.

    he could prob go .73-.74 and still be fine. all depends on what is seen on the logs.

    Just so it dont cause issues with STFT and LTFT by needing too much fuel addition and it is holding you back to a lower tq limit due to limit of injection self correction %
    Last edited by VFORCEJOHN; 09-22-2023 at 10:28 PM.