Results 1 to 3 of 3

Thread: VCM/HPTuner: STFT spikes - SS/TC with K&N SRI and tuning

  1. #1
    Senior Tuner metroplex's Avatar
    Join Date
    Apr 2013
    Location
    Detroit, MI
    Posts
    1,077

    VCM/HPTuner: STFT spikes - SS/TC with K&N SRI and tuning

    So I've been working on the MAF Correction table and MAF Frequency table in VCM. I started off multiplying the full % twice so far, and have now been using 1/2 % to fine tune. The LTFT now fluctuates between -0.8 to +0.8 or up to +1.6 depending on the weather conditions. I feel it is good enough for Government work as-is, but a few people pointed out that I need to work only on the MAF correction table and by 1/2 a % only.

    Here's the latest datalog:


    The positive STFT spikes early on are from light throttle tip-in. I noticed in several instances around 1200-1700 RPM at 20% load, that a light throttle application (5% ETC) may result in a very short STFT spike up to about 11%. Or when decelerating with a closed throttle to get the +10% STFT.

    The negative STFT spikes are usually from engine braking while decelerating with closed throttle: 20% load, at 4000 RPM, 4520 RPM, 5000 RPM.

    Doing a 0-60 MPH launch, and going WOT in 3rd, 4th, and 5th gear on the freeway showed my Lambda was very close to the commanded lambda, and the STFT looked very good in those situations.

    Is this something to work on? If so, any pointers on what to correct?

  2. #2
    Senior Tuner Iam Broke's Avatar
    Join Date
    Jul 2009
    Posts
    2,305
    Looks like you have it dialed in pretty well. The ltft tends to sit at +0.8 when the stft is spot on. I think the stft swings are about normal for that intake but I never had it.

  3. #3
    Senior Tuner metroplex's Avatar
    Join Date
    Apr 2013
    Location
    Detroit, MI
    Posts
    1,077


    Latest iteration, the first couple of spikes are when the car is cold. I still notice these occasional spikes and I think it is due to the K&N SRI intake. Other than that, LTFT actually read 0 when fully warmed up. This is a morning datalog, it usually goes a bit leaner in the afternoon when it is warmer. It also didn't help today was a really cold May morning (35F on the DIC display).