I created a custom engine in Blender and I tried to export it into KSP, everything seems to work except for the flames and smoke particles. It seems like the problem has something to do with the export and also my part seems to be missing something. I imported a stock engine with the .mu plugin and exported it again from within Blender, this did give me the missing particles but the nozzle was rotated by 90 degrees. This is the reason I use the Unity exporter because Blender always destroys my geometrie. Then I tried to export my custom model from within Blender this gave me an invisible mesh ( only nodes visible ) and the particles still didn't show up. Maybe someone can point me in the right direction.