Originally Posted by BMWM.D.
Yes, it is very normal for the coolant temp to drop after making a full throttle burst. One of the great things about the N54 platform is that the DME has a lot of control over coolant temps in the cylinder head. Between the electric water pump, the MAP thermostat (controlled by a heated wax core) and electric fan.
There are several operating modes the DME will choose for cooling strategy. When you got WOT, it will open the thermostat and crank up the water pump speed. Normal coolant temp for the N54 is targeted around 104 C. It runs warmer when cruising for better fuel economy, reduced friction, etc. , but when putting a heavy load on the engine, it will try to reduce temps to 90 C (which is about 194 degrees).
This is actually how the MAP thermostats have worked for years, even on the E46. Now with the electric water pump, BMW has made it that much more effective. Hope that helps.
Good to know! Thank you. I assumed it was the thermostat opening but I wasn't sure and this car makes me too paranoid sometimes so I had to ask.