It's been awhile, so I stand to be corrected.
Ram Rise - will raise the static air temperature by about 10C when over 250kias. Since most icing happens between 0C to -20C this will raise the temp out of the icing range for a SAT down to -10.
Here's an old thread that covered the topic of ice collection efficiency:
http://www.pprune.org/archive/index.php/t-175794.html
Cheers,
FTP