when starting in cold conditions

[poisas]

Hello, i would like to ask about engine idle rpm, when starting cold, does it has to be the same ? 650rpm ? nothing to richen a mixture to rise up rpm?
my fathers audi tdi is starting about 1200rpm idle, then drops down .

 

[Dieselman]

On a diesel car with electronic idle speed control there is no need for the revs to be higher on cold start.
The Audi is advancing the timing to overcome poor fuel ignition but the mercedes doesn't have electronic timing control so can't. In addition the Audi may be elderly so employing a mechanical cold start device and no idle speed control.