To GTB or not to
AO Silver Member
Join Date: Nov 2007
I don't have exact specifications how things work, but what nutron said is close to reality.
There are 9 alphanumeric characters in the code.
When injector is tested they test different operating modes. Like, pilot injection (low and high pressure), idle operation (low pressure, short injection), slow speed cruise (medium pressure, medium injection), and full throttle acceleration (max pressure, max injection). Also injector reaction time is measured.
Measured values are then compared to factory specifications, and the deviation between measured and specified values defines the code (to simplify we can say that positive deviation is represented by numbers and negative deviation by letters), if deviation is too high, you cant generate a new code, as there is a limit how much can the algorithm compensate. Each of fist 6 characters represents different parameter, and last 3 characters are used for "checksum".
The most noticeable thing that you notice if injectors are not calibrated properly is very rough idle. Sometimes it sounds like engine is knocking.