If you fly 250 kts (fms shows 250kts in turn)and use lnav during the turn,you may turn too early therefore your track will be offset and you may get noise busted!
So i suggest you make sure ur speed is appropriate for the turn,Normally for a 90 degree turn clean speed 210/220 is ok..thinking about also vertical noise restriction,and once your on the radial in the proper direction ,,ie flying level wings,,,accelerate...
Trickiest ive had was london stansted, tight turns when time to accelerate to meet with vertical noise abatement ,all this added with step climbs...