How Does it Work
1. Reading the ECU
To
tune an engine, the first step is to read the original manufacturer software in
the engine management system. This is normally done by connecting a computer to
the OBD2 port. The computer downloads the original software from the ECU and saves
it as a normal file which can then be modified. Sometimes it is not possible to
read the original software via the OBD2 port. In such cases, the ECU must be removed
from the car and the software retrieved by other means.
2. Modifying the ECU Software
This
is the difficult bit! The original software is modified by altering
lots of parameters
in various "maps" or data tables. Special software is normally used to do this in
a user friendly fashion. The trick is knowing which parameters to change and which
parameters to leave well alone. Altering the software correctly results in a highly
optimised engine tune. Only the parts of the software responsible for engine performance are changed. No diagnostics or safety systems are changed, and no MOT emissions
related parameters are changed. So your car remains fully service compliant and
the emissions will pass the MOT test. The parameters which are normally altered
include ignition timing, turbo pressure, fueling, speed limiters, rev limiters,
and many other associated data tables such as torque limiters.
3. Reprogramming the ECU
The
final step is to reprogram the ECU with the modified software. This is normally
done using exactly the same method as is used for reading the ECU, where the computer
is connected to the OBD2 port and the modified file is loaded into the ECU. This
process is often called "reflashing" because the ECU
has a "Flash" memory chip which
is being reprogrammed. The programming process is also the most critical part and
must not be interrupted, otherwise the ECU will end up only partially programmed
and the car will not start! But don't worry - there are special recovery procedures
should this happen. Once the ECU is reprogrammed with the modified software, it
is stored there permanently. You do not lose the modified software when you disconnect
the battery for example.
Did you know...
OBD stands for On Board Diagnostics. The OBD port is an industry standard interface
connection which is used to read fault codes, reset the service light, reprogram
various control modules in the car, and to data log sensor information in real time.
Suitable diagnostics hardware or computer software is required to communicate via
the OBD port.