In addition to controlling lift and duration, like other VTEC systems, the "intelligent" i-VTEC™system uses Variable Timing Control (VTC) to adjust "camshaft phasing." By varying oil pressure, VTC can continuously vary intake timing relative to the engine's exhaust timing. The result of i-VTEC is improved response and enhanced performance at low engine speeds and efficiency across a broad power band.

That is Acuras explaination from there website, i know you have been to that site many at time, lol. jk