▁providing ▁increased ▁" boost " ▁as ▁engine ▁speed ▁decre ases ▁under ▁load ▁have ▁made ▁" absolute ▁pressure " ▁a ▁useful ▁and ▁important ▁manifold ▁pressure ▁measurement . ▁Out side ▁of ▁M AP ▁sensor ▁data ▁" g au ge ▁pressure " ▁is ▁typically ▁used ▁for ▁engine ▁system ▁vac u um ▁and ▁pressure ▁measurement . ▁Which ▁is ▁why ▁" boost ▁gau ges " ▁almost ▁univers ally ▁indicate ▁ 0 ▁p si ▁at ▁idle ▁speed ▁and ▁load . ▁ ▁Ram ▁jet ▁assistance ▁In ▁an ▁attempt ▁to ▁boost ▁the ▁performance ▁of ▁the ▁Sp it fire ▁M k 1 ▁in ▁May ▁ 1 9 4 0 , ▁RA e ▁scient ists ▁( including ▁Hay ne ▁Constant ) ▁developed ▁a ▁' prop uls ive ▁du ct '. ▁This ▁was ▁in ▁ess ence ▁a ▁simple ▁ram ▁jet , ▁fed ▁by ▁pet rol , ▁util ising ▁the ▁Mer ed ith ▁effect . ▁It ▁was ▁hous ed ▁in ▁a ▁ ▁deep ▁du ct ▁mounted ▁on ▁the ▁fus el age ▁centre ▁line ▁and ▁res emble d ▁a ▁third ▁radi ator . ▁ ▁Ben ch ▁tests ▁showed ▁that ▁the ▁increase ▁in ▁speed ▁was ▁not ▁significant ▁and ▁the ▁device ▁was ▁not ▁flight ▁tested . ▁In ▁ 1 9 4 3 ▁the ▁idea ▁was ▁re cons ider ed ▁as ▁a ▁counter ▁to ▁the ▁threat ▁of ▁the ▁V 1 . ▁A ircraft ▁such ▁as ▁the ▁Haw ker ▁Temp est ▁and ▁G loster ▁Meteor ▁were ▁not ▁widely ▁available ▁and ▁the ▁Sp it fire ▁would ▁only ▁be ▁able ▁to ▁intercept ▁in ▁a ▁div ing ▁attack . ▁A . ▁D .