BA,
You asked if the change is a constant across aircraft types: given that Vmca is a function of the resultant between thrust couple and rudder couple, the temperature effect on engine thrust will be one issue and the offset of the thrust line will be another. As Vmca is measured in IAS, which is (all things being equal) self-compensating for altitude and temperature, there will be no apparent change if the thrust couple remains constant. Thus, for flat rated engines, the Vmca should remain unchanged until reaching the flat rating temperature and then decrease as thrust falls off.
The apparent change will vary between aircraft as a function of their engine/airframe configuration.
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