The only way I can think of is to create an animation (motion study) that uses your explode steps. If you start the animation wizard it allows you to select explode, which creates an animation from your explode steps. Then if you change the duration of the animation, it should time the explode steps accordingly, would take some expirementation or multiple tries to get the speed where you want probably.
Could some of the other settings have an impact? Perhaps Tools/Options/System Options/Performance/Assemblies Mate animation speed or Tools/Options/System Options/View/Transitions?