Partial transmit sequence (PTS) is a distortionless technique used to reduce the peak-to-average power ratio (PAPR) of an orthogonal frequency division multiplexing (OFDM) signal. However, PTS has a relatively high computational complexity due to the computation of multiple inverse fast Fourier transforms (IFFTs). To reduce this complexity, fractional subblocking was introduced where a subset of inputs to identical inverse discrete Fourier transforms (IDFTs) (within an N-point IFFT) were used for subblocking. Unfortunately, the PAPR performance is degraded as the number of identical DFTs is increased. In this paper, we exploit the periodic autocorrelation function (ACF) of the PTS sequences to improve the PAPR performance with fractional subblocks. We show that a PAPR reduction is achieved which is better than with pseudo-random subblocking.