>>11372790
Probably several minutes. You can survive being completely cut in half for quite some time.
watchpeopledie.tv/h/gore/post/52011/guy-cut-in-two-by-train
A huge hole through the gut would result in the same types of fatal injuries that would kill you as in bisection (namely destroying abdominal aorta, inferior vena cava, and lower spinal segment) but at a slightly slower rate. Death would be from blood loss since damaging the organs in that region wouldn’t cause instant death.