Have I complained about this already? I have a strong feeling I did, but don't see it listed here.
Anyway, long of the short of it is, it doesn't appear that impulsefactor has any bearing on a units explosion or self-destruct. For instance, I can set a crawling bomb's explosion to have 0.000000001 impulsefactor, but it will still create a big crater and throw things across the map when it explodes.
Would be great if that could be fixed with the next release.