Everyone who tunes probably has their own ideas about the right way and the wrong way to tune an ECM. This page outlines how I tuned my turbo engine and some other minor adjustments I've made to other cars. This is all theoritical iformation, and you should not alter the contents of yor ECM memory unles you are sure about what you are doing. You can, with the click of a mouse, destroy your engine. Also, setting certain ECM parameters outside their factory values may violate anti-pollution laws.
The software and hardware explained on this page has worked well for me, but I haven't used any other and therefore I can't offer comparisons.
All of my tuning projects have been with older ECM's using socketed EPROM's. These are not FLASH memory OBDII ECM's.
Real-Time Tuning
First step in the process is to copy the original calibration to the notebook computer. This is accomplished by removing the chip (EPROM) from the ECM and using an EPROM burner (Transtronics Pocket Programmer 2) to read the contents of the chip. With the original calibration on the computer, I can view and edit the settings with Cats' RT Tuner program. Here is an example of the ECM calibration open in Cats RT.
Now the emulator (Transtronics Pocket ROMulator II) is plugged into the empty EPROM socket on the ECM, and the notebook computer is plugged into the emulator. At this time the ECM calibration (which was saved earlier) is flashed into the emulator. The engine will crank up and run, with the ECM operating the engine on the calibration stored in the emulator. Only difference is; by clicking on the controls in Cats RT Tuner, the ECM parameters are changed and the engine receives the changed fuel and timing settings. With this setup, you can change the settings on the notebook computer and see the effect immediately.
Once the ECM is calibrated and all the parameters are adjusted to make the engine perform as desired, the finished calibration is saved to the notebook computer. The old EPROM can be erased and placed back into the EPROM burner, then re-loaded with the new calibration file. It is now permanent and can be placed back into the ECM and used.
Data-Logging
While the real-time tuning hardware is pretty straightforward, the process of creating a good tune is not. There are numerous parameters in even these old, simple ECMs. It's best to start with a factory calibration which is for a similar engine so many of the parameters will be OK without modification. After roughing-in the main constants so the engine will run, it's time to do some datalogging and table-tweaking!
Many ECM's have built-in data streaming features, but the sample rate can be painfully slow. I opted for a stand-alone datalogging system that will share sensor signals with the ECM, and monitor the fuel/ air ratio with a Wideband O2 sensor. The program creates a file on the notebook computer which can then be looked over and used to edit the ECM calibration to eliminate lean spots, rich spots, or detonation.
My datalogging setup reads Air/Fuel Ratio, Manifold Pressure (boost and vacuum), Throttle %, Fuel Pressure, and Knock Sensor voltage. By sorting the data in Excel, the exact cells in the ECM which are responsible for faulty readings can be adjusted. By making moderate changes and repeating the datalogs, a very good tune can be developed.
Simple Adjustments
Some other things that can be fixed by chip editing are cold startup problems; idle sound/ quality/ speed; engine fan temps; speed limits; RPM limits, etc. Warning codes and the Check Engine Light can be disabled for certain sensors. Useful for when you transplant an engine to an application with no provisions for certain sensors. Such as putting an engine in a boat without any vehicle speed sensor or oxygen sensor.