Turbo coding (TC) has been adopted as a channel coding scheme for several 3G mobile systems, in particular 3GPP (Third Generation Partnership Project) and in upcoming 4G standards for high data rates. Turbo decoder uses Maximum A posteriori Probability (MAP), or Soft Output Viterbi Algorithm (SOVA) because it produces error correction near to Shannon's limit. A simple but effective technique to improve the performance of the decoding algorithms is to scale the extrinsic information exchanged between two decoders. Modified Log MAP (MMAP) and Modified SOVA (MSOVA) algorithms are achieved by fixing an arbitrary value of scaling factor for inner decoder (S₂) and an optimized value for the outer decoder (S₁). We proposed to enhance the performance of MMAP and MSOVA by optimizing both the scaling factors S₁ and S₂, thus achieving low bit error rate (BER). This paper investigates the effects of constraint length and code rate on the performance of the enhanced Turbo codes. A comprehensive analysis of the algorithms considering different channel conditions and iterations are also presented.