The Dirac R-matrix theory is used to calculate the collision strengths for electron impact excitation of He-like ions (S¹⁴⁺, Ca¹⁸⁺ and Fe²⁴⁺) using the Dirac atomic R-matrix code, which has been developed mainly by Norrington and Grant (Norrington P H and Grant I P 1987 J. Phys. B: At. Mol. Phys. 20 4869). The lowest 31 target levels are included in the calculation. Rate coefficients are obtained for transitions from the ground 1s² ¹S₀ state to the fine-structure levels of all excited states of 1s2ℓ (ℓ = 0,1) and 1s3ℓ (ℓ = 0,1,2) configurations. We compare our results for rate coefficients with the results of previous calculations, and indicate where significant differences arise because of our more accurate representation of resonance and relativistic effects.