E38-resurrection 88 degree thermostat question

[johndownunder]

Hi all, could someone give a brief summary of the idea of the 88 degree thermostat ? I understand that it lets the car run cooler but I've been reading and now understand that the M62 is a map controlled thermostat that is supposed to open/close the thermostat depending on load to improve efficiency and emissions?? Does this then mean that if you use an 88 degree thermostat you don't connect the plug? There was also mention of a heating element that is affected in some way.

thanks
john

[DrCharles]

The heating element you mention is inside the stock thermostat and is how the ECU controls it. By sending current to the heater, the thermostat opens at a lower engine temp than the super-hot 108C cruise temps.

I bought the lower temp stat (for a diesel IIRC) from Schmiedmann.com but haven't installed it yet. This one does not have the heater, therefore no plug. There will be an error code stored (Thermostat Final Stage) with it disconnected, although it doesn't light the Check Engine light. Some people hook up a hefty power resistor to the harness to eliminate this code, but I don't think anything else is affected except the hidden code.

[oldroller]

The DME control of the stock thermostat heating element occurs at full or WOT power to allow greater flow to offset the increased heat during those conditions.
Installing an 88c thermostat promotes cooler running all through the power range, hence no need for DMW controlled heater-assisted opening. The reduced temperatures
via the 88c unit produces less pressure in the cooling system overall, reducing stress on radiator, hoses, heater core, trans, engine components, etc etc while causing no detrimental effects
on power or fuel economy.
Less heat under the hood, better for all the stuff under there. Leave the heater plug disconnected and taped up, good to go.