You have to give credit where it is due. In previous years, we’d have to wait months after a new car came out before tuning software was offered at all, and even then it was just a Beta version at first. Well the good folks at HP Tuners weren’t messing around. The VCM Suite 2.24 software, which can be downloaded from their website right now, offers full control (spark, fuel and even transmission) of the E92 ECM in the 2014 Chevrolet Silverado, GMC Sierra, and Corvette Stingray. In fact, check out the screen shots below, which are actual read files from running and driving C7s.
As many tuners may be aware, the new E92 ECM uses an advanced, torque-based control structure (see the sidebar for more info). While this may be quite a bit different than the Gen III/IV computers, HP Tuners has been working with these schemes for some time on the E78 and E39 computers used in GM’s other direct-injection engines, such as the LFX V-6 in the Camaro. However, the E92 is even more complicated than these computers. There are literally hundreds of parameters defined in the software – 56 just for idle, 72 for the fuel injectors, and 61 for the fuel pump and system. And there are even tabs for turbocharger (48 parameters) and supercharger (22 parameters) applications. But fear not – HP Tuners software is designed specifically to allow calibrators the ability to not only change these parameters, but also to understand them, too, by providing definitions for each one. Despite the tight timeline, HP Tuners was adamant about offering a quality product with the depth that professional calibrators and racers have to appreciate.
VCM Suite 2.24 not only tunes the E92 ECM, but it also offers extended support for a number of Gen IV engines with 289 new GM ECM/TCM files (including the 2014 Camaro SS and ZL1). New parameters were added for the E67 and E38 to control idle, spark, fuel, and ETC. It even provides support to Chevrolet Performance crate engines, 1.4L Cruze and Sonic, and custom operating systems – perfect for boost applications that require higher MAF ranges and a real VE table scalable to 2.5 bar. For more info check out HP Tuners website.
What is a torque-based control structure? And why is it used?
In the early days of EFI, the computer had only a hand full of inputs and the only thing that affected its output was your right foot. And then came traction control, stability control, and the list went on. Now there are even more sensors and systems that influence how the car will react to the demands of your right foot. As the result, GM (as well as Ford and Chrysler) has switched to this torque-based control structure, which will integrate all of the various systems and streamline the control process.
When controlling the engine there are two types of actuators: predicted (slow) and immediate (fast). The predicted actuators are all airflow based such as throttle, boost or the camshaft phasing, which can increase or decrease torque in a slower fashion. The immediate actuators pertain to spark and fuel, and its only value is in decreasing torque very quickly. An RPM Limiter is one example, which would retard timing and/or cut fuel as it approaches the limit by making an Immediate Engine Torque request. Another approach would be a Predicted Engine Torque request to limit the throttle (and boost), which is obviously not nearly as aggressive. When combining both approaches, you have a limiter that is fast and effective yet smooth.
How does it affect tuning?
The Driver Demand table is now a crucial part of the calibrators’ lexicon. The ECM uses Desired Throttle Torque to calculate the Desired MAP, which in turn uses Throttle Inlet Absolute Pressure sensor to determine how much to open the throttle blade to achieve the Desired MAP. This is crucial to understand because in a turbo application, you could crank up the boost and make the same power because the throttle closes to compensate. Now the Driver Demand tables are what command engine power based on vehicle speed and position of the gas pedal. From there it is converted into Driver Demand Axle Torque, where it is calculated by a number of things including Axle Torque Limits, Maximum and Brake Torque Limits. And in a turbo application there are many ways that the ECM can control boost to prevent over-boost (to protect the engine) and over-spinning the turbo.