Chip tuning

Chip tuning refers to changing or modifying an erasable programmable read only memory chip in an automobile's or other vehicle's electronic control unit (ECU) to achieve superior performance, whether it be more power, cleaner emissions, or better Fuel efficiency. Engine manufacturers generally use a conservative electronic control unit map to allow for individual engine variations as well as infrequent servicing and poor-quality fuel. Vehicles with a remapped electronic control unit may be more sensitive to fuel quality and service schedules.

This was done with early engine computers in the 1980s and 1990s. Today, the term chip tuning can be misleading, as people will often use it to describe ECU tuning that does not involve swapping the chip. Modern electronic control units can be tuned by simply updating their software through a standard interface, such as On Board Diagnostics. This procedure is commonly referred to as engine or electronic control unit tuning. Electronic control units are a relatively recent addition to the automobile, having first appeared in the late 1970s.

As technology advanced, so did the electronics that go into cars. The electronic control unit in a modern automobile, together with advanced engine technology, makes it possible to control many aspects of the engine's operation, such as spark timing and fuel injection. The electronic control unit may also control electronic throttle control (drive-by-wire), poppet valve timing, boost control (in turbocharged engines), Anti-lock braking system, the automatic transmission, speed governor (if equipped), and the Electronic Stability Control system.

...
Wikipedia