A 'Thermal Management Module' is effectively an electronically controlled thermostat that uses rotary valves to regulate the flow of coolant and other fluids.
Using a TMM grants several benefits, including the ability to restrict or completely stop the flow of coolant around the engine for an extended period - which, for example, can greatly reduce its warm-up time. This improves its emissions and fuel consumption, helping manufacturers meet ever-tightening regulations and customer demands.
These electronically actuated multi-purpose thermostats were co-developed by technology group Schaeffler and Audi, and introduced in 2012.
How do TMMs work?
A conventional thermostat features wax elements that are specified to melt when they reach a certain temperature, causing them to expand - which opens the thermostat and allowing coolant to circulate.
In a TMM, this function is instead carried out by electronically controlled rotary slide valves. Besides allowing the flow to be shut off entirely whenever desired, this method of actuation allows for precise and quick adjustments to suit the load and conditions at any moment. One valve closes off the pressurised flow of coolant from the water pump, while the other is used to distribute the coolant between the intake of the pump and the return to the radiator.
The precise control permitted means that the temperature stays more consistent while the engine is operating, further improving efficiency. Reportedly, using a TMM, the engine's temperature can be controlled as accurately as +/-2 degrees Celsius.
Crucially, the TMM can also be used to regulate the flow of coolant through ancillary systems, such as the cabin heater or a water-cooled engine oil heat exchanger - typically a compact plate-type unit.
Again, this allows for more accurate temperature regulation and quicker warm-up times; the time taken to hit the desired water temperature is reputedly cut by 30 per cent, compared to a conventional wax thermostat set-up, while the target oil temperature is achieved in half the time.
Is this degree of complexity really beneficial?
Potential emissions and efficiency benefits aside, manufacturer Schaeffler claims that the use of a TMM can reduce the time taken to warm up the car's heater core by 40 per cent. Consequently, owners don't have to endure a cold cabin for as long.
There are fail-safes in place to ensure that damage won't occur even if the TMM packs up, too. Many units use a conventional wax-based thermostat which will open if the coolant reaches a critical temperature. This will allow the driver to get the car home, or to a safe stopping point, should the worst happen. Some manufacturers, such as Magna, offer this as an optional upgrade to their TMMs.
The fact that several functions are handled by one unit further reduces development cost and complexity for manufacturers - and they can even be used in hybrid and battery cooling systems. TMMs also reduce assembly time, which again helps a manufacturer cut costs.