This paper deals with cyclic stress and strain responses during thermo-mechanical fatigue (TMF) on ferritic stainless steels, which is used for an exhaust manifold in automobiles. With the new developed life prediction model parameters, the plastic material response and the lifetime in TMF test can be accurately described. H<SUB>D</SUB> parameter was applied to predict the number of cycles to failure of τ-ENG exhaust manifold using finite element simulations. Good agreement between the predicted and the tested number of cycles to failure in real components is acquired. A further optimization of the design of the manifold is now possible based on computer experiments, thus saving development time & cost and leading to more reliable prototypes.