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Thread: Tuning with air conditioning on

  1. #1
    Tuner in Training
    Join Date
    Jun 2011
    Location
    USA
    Posts
    48

    Tuning with air conditioning on

    How does one accomplish this? I have been multiplying the Engine>Torque Management>Engine>AC Torque vs. AC Pressure table but I really have no reference on what I'm doing.

    Before I started my STIT would go to like 30+ when the AC turned on, so I kept adding to the table so now its close to 0 STIT. But its not consistent, It seems to start off positive STIT but after a while it will end up negative STIT even with the same logged AC voltage.

    Also does anyone know what AC sensor voltage = what pressure? I can log voltage but that doesn't help if I don't know what pressure that equals. I have seen a chart that showed a liner 1volt=100lbs but it wasn't LS specific.

    Thanks,

    Dave
    2001 Pontiac Trans Am M6 "cam only"
    228/232 110 cam, 10° overlap @.050" lift
    Edelbrock stepped headers, ORY, hooker catback

  2. #2
    Senior Tuner
    Join Date
    Nov 2002
    Location
    Central Florida
    Posts
    2,503
    The actual drag torque of the compressor has not changed.

    Therefore the table you mention, has no reason to change.
    It is only the most obvious, not the most appropriate. The
    problem really lies with an inaccuracy in the VE tables at
    lower RPM and higher MAP. Untouched, across cam swap
    and such, the table becomes unrealistic and says you are
    pulling more air than you really are. Idle airflow commands
    air mass which is worked through, roundabout, from VE
    table and the IAC g/sec vs position.

    Look at the MAP with A/C on, vs A/C off. Should be a
    significantly higher value. Work on the VE cells abutting
    real MAP, real RPM, get fueling to be slightly lean and
    see what the result is.

    IAT plays a significant role in both the mixture, and the
    indexing of this drag-torque-vs-A/C-pressure table. If
    you make the IAT see outside air, like what is cooling
    the condenser, that will make the head-pressure (thus
    drag torque) prediction more reasonable.

  3. #3
    Advanced Tuner blownbluez06's Avatar
    Join Date
    Jan 2008
    Location
    Forney, TX
    Posts
    982
    I work the table, get it close, turn the A/C-on LTIT's back on and let it remember. the resolution on the table isn't such that you'll ever get it "perfect"
    Hsquared racing engines RHS 427, Procharger F2, Moran Billet Atomizer injectors, Alky Control,Mast LS7 heads, Nitrous outlet kit,Tilton quad disc clutch, DSS shaft, RKT56 ZR1 trans, RPM Quaife diff. Built and tuned by yours truly.