Ok,
the riddle is solved.
The S4 8D0907551C and 8D0907551D ECU has both only a 8bit value for KRKTE.
The factor of this 8bit value is 0.001776 for both ECU`s.
It`s at address hex 18D61 for the 8D0907551C ECU,
and at hex 18DA8 for the 8D0907551D ECU.
I`ve tested it today by a friends S4 551D.
Good luck...