thats a pretty broad question. Yes they are but if you are putting a S14 KADE in a S13 then you want to run the S13 electronics and smog. i.e. the ecu.
S14 is OBDII which means its a lot pickier . If you put a S13 DE in the S14 than you would have to run the OBDII electronics to make it smog legal.
does that clear up your question ? <img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/smile.gif" border="0" valign="absmiddle" alt=':)'>