Three-stage VTEC

Three-stage VTEC is Honda's variable valve timing arrangement that joins two earlier systems, VTEC-E and standard VTEC, in a single cylinder head. It appeared in some Honda D series engines from 1995 and is described as in use up to the present day. At low engine speed it runs in a twelve-valve economy mode, with one intake valve per cylinder held mostly shut so the engine can burn a lean mixture and save fuel; the source cites about 30 kilometres per litre at a steady 60 kilometres per hour. Around 2500 revolutions per minute it moves to ordinary sixteen-valve operation for mid-range driving, and from about 5200 revolutions per minute to the limiter a high-lift cam lobe engages for maximum airflow and power. The price of covering economy, standard and high-power modes in one engine is extra complexity and cost compared with plain VTEC or VTEC-E.