There are two types of fuel trims: LTrim or LTFT (long-term fuel trim) and STrim or STFT (short-term fuel trim). The PCM adjusts the fuel-injector pulses based on the values (fuel trims) it has learned. Your PCM's fuel system control relies on the pre-cat oxygen sensors to adjust the part-throttle air/fuel ratio to 14.7:1-15:1 for low emissions and fuel economy.
The HP software runs on a 300 MHz-and-faster laptop with at least 64 MB of RAM and a serial-port connection.Įven though we are going to tune at WOT, we need to do some part-throttle tweaking. One license can program all of the same type and year vehicles (other OBD-II programming packages can only be used on one VIN), and the HP Tuner package includes an OBD-II diagnostic scanner (that can be used on other OBD-II vehicles) that includes features such as data histo-gram displays that dramatically aid with your custom tuning.
In this article we'll focus on changing your wide-open throttle (WOT) performance to avoid any changes to the vehicle's emissions during part-throttle. HP Tuners software allows you to change the entries of your PCM's tables to improve the performance of your vehicle. The product is easy-to-use and has many powerful features consisting of three primary utilities: VCM Scanner (OBD-II diagnostic scanner), VCM Editor (PCM editor), and VCM Flash (to read and program your PCM).
HP Tuners also offers an Enhanced IO upgrade that allows you to log your own wideband oxygen sensor along with your vehicle's other OBD-II data, for example.
VCM Suite Pro is designed for the home enthusiast, as well as the professional tuner. For engine control, the PCM takes many sensor inputs (O2, TPS, RPM, MAF, MAP, etc.) and calculates the target outputs (primarily spark advance and fuel-injector-duty cycle).We'll be using HP Tuners VCM Suite Pro for our OBD-II PCM programming. If your GM car/truck is a '96-and-later, it incorporates an OBD-II-based PCM, which controls the transmission as well. The author consulted with a pro (Bryan Herter of PCM For Less) before attempting any of the programming.
If the programming is done incorrectly you can impact emissions (perhaps violating local emissions laws), do serious damage to your engine, and possibly harm yourself and bystanders. In essence, these packages provide you with the ultimate control of your vehicle's powertrain control module (PCM).Understand that you do this at your own risk. But for about the same price, you can obtain a package that enables your own custom tuning for more power and alteration of operational parameters far beyond the capabilities of the hand-held programmer.
There are several Internet articles that discuss this tuning in far more detail than can possibly be provided here.There are many aftermarket hand-held programmers that enable the installation of generic performance tuning and change some simple operating parameters (tire size, gear ratio, fan temperature, etc.). The purpose of this article is to provide some initial exposure to OBD-II tuning and the capabilities and state of the technology as it stands today.