In Two Temperature Model calculations of the inelastic thermal spike produced by swift ions, the electron–phonon coupling factor is often treated as a constant. However, recent first principles calculations in 3C-SiC have shown that this factor is strongly dependent on the electron temperature. The evolution of the electron and phonon temperatures were calculated using both an electron-temperature-variable electron–phonon coupling as well as constant couplings. Temperatures were compared for different stopping powers and at different radii from the ion path. While the use of constant couplings appears to be justified for certain combinations of radius and stopping power, the high energy densities at the center of ion paths formed by swift heavy ions are capable of greatly enhancing the coupling, sometimes by several orders of magnitude. This work emphasizes the importance of the temperature parameterization of the electron–phonon coupling in Two Temperature Model calculations.