A visual from
www.japanesecarfans.com /
www.worldcarfans.com showing when iVTEC in the 1.8L engine kicks in is
HERE.
Update: VTEC as implimented in the R18 is actually sorta "backwards" from that of the K20Z. That is, the R18 is in VTEC at low loads, and kicks out of it under higher loads.
Don't take my word for it though, see:
Asian 8G Civic R18A Engine Tech Overview
Regards,
Glenn in CT