Results 1 to 3 of 3

Thread: LHU - Novice Tuning Strategy Question

  1. #1
    Tuner in Training
    Join Date
    Aug 2013
    Posts
    17

    LHU - Novice Tuning Strategy Question

    OK, so we got the new LHU into the Cobalt and the car is running absolutely great. Right now we have the stock tune in the car with the exception that we have made the minor changes as we are running the 3-bar MAP sensors. The car also has a Hahn Cold Air Intake and it is Cat-less and with a 3" all the way back. We did some initial datalogging to take a look at a/f's, etc. A/Fs are generally very good.... .92 .93 Lambda which I gusess this DI motor likes. The boost is peaking at 15psi but overall is pretty level at 12-13. The knock table is OK but does have some 1 and 2's in it in a few spots. (Blame crappy California gas.) We haven't collected a good sample but the MAF table is off - I would presume because of both the intake and the free-er (catless) exhaust.

    OK, so we want to begin some modest tuning and therefore the "strategy" question. My inclination after having read and watched what a lot of the more experienced tuners have posted here is to first make some smoothing attempts at the MAF table. My rationale is that as a conservative, stock-like, tune this one is a "keeper" with the exception of the MAF being a little out of whack. So, can you experienced tuners confirm or critique the following as a reasonable approach;

    1. Collect data and iterative adjust the MAF table to get it to be "good"
    2. With a good MAF table, revisit the knock table and make small adjustments to eliminate corrective values.
    3. Save this tune as a baseline, OEM-like tune.


    Another approach would be to go make the requisite Boost (DALS and WGDC), A/F and Timing table changes to reach our target objective of ~20-21psi of boost and then focus on smoothing the MAF. (We are building this as a road course car and it will pretty much always have 100+ octane in it while on the track but I don't want to run more than 20-21 psi because of heat and to maximize engine longevity.) I prefer the first approach of "fixing" the MAF table first as it gives us a good (albeit conservative) "keeper tune" but more importantly is sets a good foundation for us to start making the normal changes to produce more power.

    Opinions welcome.

  2. #2
    Advanced Tuner
    Join Date
    Feb 2010
    Location
    The Desert
    Posts
    480
    I definitely agree to first making adjustments to the MAF Frequency table (MAF location has been moved and pipe diameter has been changed) and then fine tuning with the MAF Correction table before doing anything else. I would suggest following CSSOB's or BYT's fuel trim tuning guide so that you can get your histograms and PIDs setup to properly calibrate things.

    Obviously fueling will change when you begin to dial in your targeted boost/timing/lambda but they will be minor in comparison to what will need to take place to dial in that HAHN intake.

    Once you've got the MAF pretty well dialed in, I would agree that you would want that to be your base map. The KR you're experiencing is most definitely related to terrible cali gas but also because of your ST trims being off. Once things are dialed in, the random KR will pretty much go away. I would also suggest massaging your injection timing table (HOM Single Low, can be found under Engine - Fuel - General) up in the lower RPM ranges, across all loads.

    Good luck man.
    09 RY Cobalt SS Coupe - 19K miles - Bolt ons + 7163 ZFR, HP tuned on ethanol

    Sold - 09 SRTC Cobalt SS Sedan
    Totaled - 09 VR Cobalt SS Sedan
    Sold - 09 RY Cobalt SS Sedan

  3. #3
    Senior Tuner cobaltssoverbooster's Avatar
    Join Date
    Dec 2008
    Location
    Nevada
    Posts
    4,452
    you fix cali gas kr with injection timing. you will have to experiment.
    2000 Ford Mustang - Top Sportsman