B aby ▁D elt ic ". ▁ ▁History ▁and ▁design ▁The ▁D elt ic ▁story ▁began ▁in ▁ 1 9 4 3 ▁when ▁the ▁British ▁Admir alty ▁set ▁up ▁a ▁committee ▁to ▁develop ▁a ▁high - power , ▁light weight ▁Dies el ▁engine ▁for ▁Motor ▁Tor ped o ▁Bo ats . ▁H ither to ▁in ▁the ▁Royal ▁Navy , ▁such ▁boats ▁had ▁been ▁driven ▁by ▁pet rol ▁engines , ▁but ▁their ▁highly ▁fl amm able ▁fuel ▁made ▁them ▁vulner able ▁to ▁fire , ▁unlike ▁the ▁oppos ing ▁dies el - power ed ▁E - bo ats . ▁ ▁Until ▁this ▁time , ▁Dies el ▁engines ▁had ▁poor ▁power - to - weight ▁ratio ▁and ▁low ▁speed . ▁Before ▁the ▁war , ▁Nap ier ▁had ▁been ▁working ▁on ▁an ▁av iation ▁Dies el ▁design ▁known ▁as ▁the ▁C ul ver in ▁after ▁lic ens ing ▁versions ▁of ▁the ▁J unk ers ▁J um o ▁ 2 0 4 . ▁The ▁C ul ver in ▁was ▁an ▁opposed - p ist on ▁two - stroke ▁design . ▁Instead ▁of ▁each ▁cyl inder ▁having ▁a ▁single ▁p ist on ▁and ▁being ▁closed ▁at ▁one ▁end ▁with ▁a ▁cyl inder ▁head , ▁the ▁J um o - based ▁design ▁used ▁an ▁el ong ated ▁cyl inder ▁containing ▁two ▁p ist ons ▁moving ▁in ▁opposite ▁directions ▁towards ▁the ▁centre . ▁This ▁ob vi ates ▁the ▁need ▁for ▁a ▁heavy ▁cyl inder ▁head , ▁as ▁the ▁oppos ing ▁p ist on ▁filled ▁this ▁role . ▁On ▁the ▁down side