Narrowed it down.
It appears that no matter what effect, it lasts only 2 seconds max for the wreck, then every emitter (probably the bundle itself) is killed. But I have absolutely no idea why.
Some guesses:
1) It's because the actual vehicle gets replaced by the "wreck" object then (though the LodSelector states it's still the same PCO, just switched to display a simple Wreck)
2) Perhaps because the effect actually is a simple armoreffect and perhaps this gets deactivated somehow? Armoreffects appear to be attached to their parent PCO, so this might be a possible problem. But why 2 seconds later? Because the hitpoint value of the vehicle then is changed from 0 to whatever or deactivated, leading to the death of all armoreffects?
Really at aloss there
EDIT: Oh yeah, any suggestion for a workaround is very welcome too. Already had some thoughts about perhaps spawning an invisible object when the vehicle dies and attaching the emitter to the invisible one. Disadvantage: If the vehicle dies "in movement" (e.g. plane shot down), the emitter wouldn't follow the crashing wreck, but just remain stationary...
