Thanks for clarifying with the links. I'm guessing Peugeot went into the joint-venture for financial reasons - quite surprised that they'd need anyone's technical help developing a diesel engine after their older DT engines
Sorry that I misinterpreted - the curse of text, you have to be so careful not to offend
Allows faster warm up. BMW have been using them for years (since the M52TU) - the wax bulb won't fully open until around 105 degrees, but there's a small heater that's ECU controlled to allow it to open the 'stat at a more 'normal' temperature. This means the warm up part of the process happens very quickly, as the 'stat isn't opening by a gradual amount, bleeding hot water into the radiator. Instead it 'cracks' it open, more quickly.