An experimental investigation was carried out on a multi-cycle pulsed detonation engine, running on a propane-oxygen mixture using a rotary-valve injection system and a low energy ignition source, to study the effectiveness of Shchelkin spiral parameters on the deflagration-to-detonation transition (DDT) phenomenon. Various configurations were tested using spirals with blockage-ratios ranging from 34.7 to 55.6 % and spiral length to diameter ratio of 12.5 and 24.4. The results showed that only spirals with the highest blockage-ratio were able to achieve successful and sustained DDT in the shorter length configuration. However, further studies revealed that lower blockage-ratio spirals were able to achieve successful DDT when their lengths were 24.4 times that of the detonation tube diameter. Higher levels of peak thrust production were observed in these cases. Hence, applications which do not place any operating constraints on the PDE tube length may benefit from using lower blockage-ratios but longer Shchelkin spirals. Lastly, practical operating issues regarding the use of Shchelkin spirals are discussed in this paper.