Editing VTEC (section)

=== R-Series ===
{{main|Honda R engine}}

The i-VTEC system in the
R-Series engine uses a modified SOHC VTEC system consisting of one small and two large lobes. The large lobes operate the intake valves directly while the small lobe is engaged during VTEC. Unlike typical VTEC systems, the system in the R-Series engine operates in a 'reverse' fashion engaging only at low to mid RPMs. At low RPMs, the small lobe locks onto one of the larger lobes and keeps one of the intake valves partially open during the compression cycle, similar to the [[Atkinson cycle]]. The ability for Honda to switch between Atkinson cycle and normal cycle allows excellent fuel efficiency without sacrificing too much performance.