Involved in defensive oleoresin formation in conifers in response to insect attack or other injury. Involved in diterpene (C20) olefins biosynthesis. Monofunctional enzyme lacking the DXDD motif in the class II active site relevant for the cyclization of geranylgeranyl diphosphate (GGPP). Requires (+)-copalyl diphosphate ((+)-CPP) as substrate, but no activity with GGPP or ent-CPP. Pimaradiene is the major products of the enzyme. (+)-copalyl diphosphate = diphosphate + pimara-8(14),15-diene Binds 3 Mg(2+) ions per subunit. Terpene metabolism; oleoresin biosynthesis. The Asp-Asp-Xaa-Xaa-Asp/Glu (DDXXD/E) motif important for the catalytic activity in the class I active site is degenetated, but the Mg(2+) binding sites are conserved. Belongs to the terpene synthase family. Tpsd subfamily.