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Who needs google for this, dick? Maybe U, so use it first and be so generous to public to post answers instead of questions.
Unlike VTEC, which controls both lift and duration (not fluently, has 2 modes, short for low rpm and long for higher rpm above 5300), DVan controls only timing (and Valvetronic lift and timing, if combined with vanos). Let's focus on VTEC VS DV. VTEC (and ValveTronic) were intended for use with N/A engines primarily, where adjusting lift and duration are important and effective. But In high reving FI engines if U need to put more air in the cylinder, increase pressure + after certain point change cams, but to sharp ones (with much stronger strings certainly, forged valves), so lift it more to let the air in, then close it asap and press it. This usually goes hand2hand with some decent head porting to open and optimise air flow, but some ppl say it's not THAT important in FI setups. But everything relates...
Allowing the valves be opened longer would maybe bring benefits on higher rpms, but would definitely cause loss of low end performance, what is unacceptable.
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