In many modern vehicles, more and more systems are controlled by microprocessors. As technologically advanced sensors are able to measure various engine and driving conditions on- the-fly, the input from these sensors is collected, analyzed and submitted to a master computer. This master computer, the engine control unit (ECU) or engine control module (ECM), processes the information it receives and sends the proper output signals to the engine hardware it controls. In some cases, the signals are sent to other computer subsystems for further processing.
You could have all the right parts to make the power, but if the tuning is not optimized you’ll be down on power, suffer from poor gas mileage and you may even cause damage to your engine. There is nothing more critical to the performance of an engine than the amount of fuel delivered and the timing of when the spark plug is ignited.
Text by Richard Fong and Arnold Eugenio // Photos by DSPORT Staff
Your ECU and You
Factory engine management systems make adjustments to fuel delivery and ignition timing based on data gathered from a myriad of sensors monitoring the engine. The data is read by the system and sent to the ECU, where its data inputs are plugged into a factory-tuned matrix that defines the output controls to be sent to various hard components in the fuel delivery and ignition systems. The matrix is actually a combination of several data arrays particular to each component being controlled; fuel injector control data is pulled from one array, ignition timing control from another.
These arrays are in turn combined with other arrays containing parameters for specific conditions as read by a number of other sensors present on the engine. Generally, these sensors include; engine speed (RPM), vehicle speed sensor, oxygen sensor, manifold air pressure sensor, throttle position, and coolant and oil temperature, intake air temperature and more.
Some OBD-II devices like Hondata’s FLASHPRO not only permit reflashing of the ECU, but also feature Bluetooth wireless connectivity to access data and clear CEL codes.
ROM Chip on Your Shoulder
Some older ECUs contained memory chips that could not be re-written. The only option available to have the fuel and ignition maps modified was to purchase a memory chip (or an ECU with a new memory chip) that had the revised map data pre-loaded by expensive industrial memory writing software and hardware. This is what was commonly known as having a “chipped” ECU. There are still manufacturers that provide the chip or the replacement service for older platforms still on the market.
ROM tuning provides a similar function; it allows a tuner to alter the maps in the ECU to optimize spark and fuel delivery for maximum power. When these maps are optimized, a ROM tune can deliver just as much of a power increase as a full stand- alone tuning computer. However, because the maps in a ROM tune are unchangeable and inaccessible after they are programmed, they do not allow optimization for future changes or additions to your setup.