JJ, as per Phils excellent suggestion of giving you URL's rather than me having to type things out again, here is a link to a brief introduction I wrote about compressor maps, read it, get a genuine understanding of the basics, and then come back and read again what I wrote about surge and you can tell me WHY inlet cam timing effects surge so much in terms of wether the mixture blows out the exhaust or reverses and comes back out the inlet on a big duration cam
http://www.vauxhallsportforum.com/ph...urbos-t92.html
Utterly no chance of you ever understanding surge properly without fully understanding where it sits on a compressor map.