Hi,
Mines takes under 10 mins to get from 0 to 90C with sub 40mph start-stop.
Ive looked at the cooling system diagram in the training manuals and the heater matrix gets its hot flow which comes from the engine block then passes through to EGR heat exchanger.
From what i can tell, higher engine RPM and high exhaust temperature will cause more exhaust gasses will be recirculated and hence more gasses will need cooled so give more heat to the heater matrix.
This flow is not controlled by the main radiator thermostat and is present when ever the engine is running.
If you put the heat to "hi" and the blower full, you will be acting to cool the engine and slow down the warming up of the car.
If you have it on climate control Auto at a set temperature (22C for me) then the fan will slowly ramp up as heat is avaliable. This way it speeds up the engine warming up and doesnt blow cold air into the car.
The heater matrix can gobble up a fair ammount of heat. Similary sized heat exchangers used in heating and ventilation systems could easilly dump 4-5kW (2 fan heaters at full power) into the air stream.
Given that at idle the car is probably producing about 10kW of heat, around 75% of this goes out the exhaust, its easy to see how at idle having the fan on full may take out more heat than the engine produces.
However, i do put the blower on full initiallu if i need to clear the windscreen, i then return to auto untill the screen mists up again.
Stuart.
ps. sorry for the long lecture, im in a hotell room on a work trip and im bored...