i-VTEC regulates the opening of air-fuel intake valves and exhaust valves in accordance with engine speeds. By regulating valve opening to match engine speed, the agile i-VTEC engine adjusts its characteristics to realize both superior power and low fuel consumption. read more
When you increase the rpm, however, this configuration for the camshaft does not work well. If the engine is running at 4,000 rpm, the valves are opening and closing 2,000 times every minute, or thirty to fourty times every second. read more
The economy i-VTEC used in K20A3/K24A4 engines is more like the SOHC VTEC-E in that the intake cam has only two lobes, one very small and one larger, as well as no VTEC on the exhaust cam. At low RPM only one valve on the intake opens fully, promoting combustion chamber swirl and improved fuel atomization. read more