Gone are the days of “burning a chip” for engine computers. Modern Engine Control Modules (ECM’s) can now be monitored real-time and then modified based on readings done after driving down the road. Pretty cool stuff indeed but it adds a whole new dimension to engine performance adjustments.
The factory install of the Ecotec in a Pontiac Solstice at its core consists of the engine, wiring harness, ECM and the Body Control Module (BCM). The ECM reads and controls engine signals while the BCM controls such things as gauges, door locks, lights, etc. In addition, the BCM supplies data used in the information center on the instrument panel showing fuel consumption, engine temp, outside temp, etc. Furthermore, the ECM and BCM talk to each other via a digital high-speed bus integrated into the factory wiring harness.
So, one of the challenges in getting the Ecotec to run in bowtie6 was making all this work outside of the factory install. After doing a ton of research and reading the Factory Service Manuals, we were able to figure out what wires actually control engine sensors and what goes to the BCM. This enabled us to change the factory harness to fit our needs. Since we did not run the factory instrument panel and did not need to control lights and such, we did not use the BCM.
A disadvantage of this approach is the lack of cruise control. In the Ecotec the throttle body is electronically activated – there is no cable in the traditional sense. Instead, the electronic “gas pedal” inside the car sends a signal to the ECM via a small wiring harness. This gets accomplished by coarse and fine potentiometer readings of the throttle pedal position (Click here for my Drive by Wire article). There is also no Idle Air Control (IAC); instead idle is now controlled by the ECM cracking the butterfly angle as needed. This is very amazing stuff. As a side note, it is interesting to pay close attention when turning the ignition to the “on” position: there is a very short “click” heard from under the hood. It is the throttle body going through its pre-check. But I digress… Bottom line: my goal is to be able to integrate the BCM into bowtie6‘s wiring and by doing so, have a fully operational fly-by-wire cruise control.
Among the wires going to and from the ECM is a group that end up in a special plug called an ALDL connector. This special connector is normally found in production GM cars under the dash on the driver’s side. It is by the ALDL that the GM TECII scanner/programmer gets connected to the car’s ECM. In my case I use my laptop along with an interface made by HPTuners to read and change the ECM’s settings.
HPTuners is a commercially available ECM tuning package. It consists of a Windows-based software running on a laptop and an interface with a USB connector on one side and a matching ALDL connector on the other. This software package is quite remarkable in what it does; equally remarkable is the lack of documentation. Sure it has online help but it is very lacking in detail and content. In the hands of a newbie it can spell disaster to the engine; in the hands of an expert it makes an already great engine even more remarkable.
HPTuners has two main software components: the VCM Scanner and VCM Editor. The Scanner is the means by which the engine’s parameters get monitored real-time. There are a number of different ways to display data: charts, a gauge panel and tables. Scanning is accomplished by connecting the laptop to the ALDL connector via the interface, starting the engine and pressing the “Scan” button on the Scanner. Then you drive down the road and start logging data – the more, the better. This data can then be saved to a log file for further analysis. Another feature of the Scanner is to load a log file and play it back – this is very helpful in determining what to change.
The tool used to re-flash the ECM is the VCM Editor. The process is quite simple: read the ECM, make adjustments and re-flash. The hard part though, is figuring out what to change and in what order. It has been my experience so far this is a bit of a black science. Information on the interweb is vast about tuning. However, discerning truth from fiction is the true challenge. There are several books on the subject and then there are tuning courses available, however they are pricey. HPTuners is the tool but what to do with and how to use it, is a very time-consuming task!
In the next installment I’ll go into more details about HPTuners…