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Thread: Vvt generic questions

  1. #1
    Senior Tuner TheMechanic's Avatar
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    Vvt generic questions

    So on my basic daily beater 2008 2.4 Malibu chicken I have done some modest mods for longevity of trans and fuel mileage.
    Kind of want to start messing with the cam timing. Interesting driving is this has a very modest two stroke like acceleration. Seems like it hits a higher rpm (2800 or so) sweet spot and it takes off like a 100 horsepower fire breather dragon (lizard).
    Anyways wanted to see if anyone had any tips on cam timing for this. I figures a lot of the mid throttle/load would be fake EGR to reduce NOx but not to sure where to start. I don't really care about driveability. Little hiccups and such don't bother me. I've got time to experiment.
    Tune.
    2008 Malibu 24 liter factory file P0128 TRANS AND SPARK MOD.hpt

    Cam screenshots.
    Screenshot 2023-11-13 161111.png

    Screenshot 2023-11-13 161148.png

    Screenshot 2023-11-13 161216.png

    Screenshot 2023-11-13 161243.png

    Screenshot 2023-11-13 161308.png

    Screenshot 2023-11-13 161328.png

  2. #2
    You'll probably only need to use one set of tables (low, med or high), depending on what your baro/atmosheric air pressure is; the setpoints to determine when a table is used are also adjustable - for example, high tables are used when at 95 kPa and above. You'll also need to know how the tables relate to the cam movement; based on the pics I'm guessing they function similarly to the E39A (LFX) where a higher number in the intake tables means more advance (so 0 is home position and you can only advance the cam) and a higher number in the exhaust tables means more retard (0 is home, can only retard the cam); I'd also venture to guess you have 25 degrees of movement in both cams.

    Apart from this, unless you have a dyno you'll just have to do some steady state driving and WOT pulls to see where you get the best air flow (MAF) and/or see what settings make the car accelerate the fastest. In general, you'll start the intake cam more advanced (lower RPMs) and advance it less as RPMs increase; likewise the exhaust cam will start off more advanced and you'll retard as RPMs increase (so both cams start off more advanced and become more retarded at higher RPMs). If these are factory cams I suspect there won't be signicant changes to the tables, at least at the higher load areas; believe the mid range/load areas are for EGR so you could flatten these if so desired, if they improve air flow/fuel economy while cruising.

    Or at least this is how I went about it when playing with my aftermarket cams.

  3. #3
    Senior Tuner TheMechanic's Avatar
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    Yeah that is what I figured. Just wanted to see if anyone had a direction to go. Oh and the reason for six tables is one set of three is for intake and the other set of three is exhaust cam.