Add this to your LiveSplit layout as "Scriptable Auto Splitter" and the script will automatically split after each completed race and class-finish cutscene. First "New Game" will have incorrect timing; sit through the intro cutscenes on the first load, then start a new game from the menu again. Ending split has to be done manually.

LiveSplit Autosplitter & Load Remover Script

A split file with segments for all the races in the game, including the intro event, adjusted to fit into Subsplit formatting in LiveSplit. Split names are mostly opponent names, though some multi-stage races towards the end also include brief descriptions of what they consist of.