metroplex

This should apply to other S197 Mustangs as well.

I have the Steeda Cold Air Intake, and have been using the Shelby GT MAF Transfer Function for just over 2 years without any problems. However, I decided to actually datalog the LTFT and STFT (Long and Short term fuel trims) earlier this year and wasn't too thrilled to see them being way lean, as expected with an aftermarket intake. I was hoping the OEM MAF calibration would get me close enough. I have been using SCT's Pro Racer Package (SCT Advantage software) for almost 10 years but one of the biggest challenges I faced as a DIY tuner is that tuning the MAF was always a pain since I had to sift through lines of LTFT/STFT data.

Enter HP Tuner's VCM Suite... I bought this originally to tune up my 09 Cobalt SS Turbo because I installed the K&N Short Ram Intake and caused the LTFT's to spike 10-12% lean. Since the Cobalt comes with a wideband O2 sensor and direct fuel injection, it was different to tune than a Ford but was actually easier thanks to the VCM Scanner and VCM Editor programs. VCM Editor works kind of like SCT Advantage, except VCM Editor works much much much faster even on an Atom netbook. VCM Scanner's histogram feature is probably the most awesome feature I have seen. I'm sure there is a way to program Microsoft Excel, or create some kind of MATLAB/miniTab program to do this as well, but VCM Scanner's histogram collects data points for your MAF (or any other PIDs you wish to log). Within 2-3 tries, I got the Cobalt's LTFT down to +/- 2%.

I applied that approach to the Mustang, and got similar results. I used SCT's Pro Racer Package to flash the tune, and VCM Scanner to collect the data. If LiveLink can do the same thing as VCM Scanner, I haven't figured it out and LiveLink crawls on my laptops.

I only used 2 histograms: LTFT1+STFT1 vs MAF Voltage, and LTFT2+STFT2 vs MAF Voltage. The PIDs are self-explanatory. Just driving the car around, it would collect data at each MAF voltage point and average the fuel trim data. I found that the MAF voltage never went above 3.6V even when I pushed the car hard.

I'd create an Excel worksheet that averages the data for each bank, to create a master table that is to be multiplied as a percentage in the MAF transfer function with SCT Advantage (which coincidentally works the same as VCM Editor). After 3 attempts, my fuel trims look very good. Additional fine tuning is to be done by multiplying the MAF transfer function by half percentage (1/2%) of the data obtained to prevent excessive adjustments.

Using VCM Scanner:


Using Excel worksheet:


Using SCT Advantage:


Results:


HP Tuners also supports the S197 Mustang, and I used VCM Editor to look around their rendition of the PCM calibration. It is organized differently from SCT but the meat and potatoes are the same.