The Hindu Business Line : VTEC at work

THE latest version of the original Honda Variable Valve Timing and Lift Electronic Control (VTEC) engine technology employs compact combustion chambers and a new-design intake port with narrow valve angles for rapid fuel combustion and reduced friction.

This leads to its unique and unusual advantage of fuel economy and a powerful, dynamic engine performance.

For maximising performance at low engine speeds, the valves need to open and close differently than they do at higher engine speeds. Honda's VTEC system incorporates features to change valve timing and lift parameters in response to the engine's speed characteristics.

Its action allows combustion properties to match the demands of engine operating conditions to the best possible extent, hence delivering both higher performance and efficiency.

Each valve in the VTEC engine has a number of individually-shaped cam lobes. These are all formed on the same camshaft and, through electronic control, are switched in response to engine conditions using hydraulic pressure, thus enabling the above-mentioned features to be realised.

The 16-valve, Single Overhead Camshaft VTEC engine powering the CITY ZX has high- and low-speed cams with different profiles on the intake camshaft.

Like its DOHC counterpart, the low-speed cam operates valves in the low- and mid-speed range and the high-speed cam operates in the high-speed range (only for the intake valves in this case).

This technology allows the engine to offer the best possible combination of ease-of-driving in normal speeds and driving conditions, high power at high speeds and continued optimisation of fuel efficiency.

At low rpm levels, only one intake valve opens in the VTEC, to let the air swirl in, resulting in clean and complete combustion and good fuel economy at low engine speeds.

At high rpm levels, both the intake valves open at full lift to let the fuel-air mixture at intake flow in totally, giving high power at high engine speeds. Honda's VTEC technology was developed from technology initially seen in the world of Formula One racing.

The technology not only ensures better fuel economy, but also lowers emissions, even while retaining the performance characteristics of the engine. Honda uses an even more advanced version of this technology — the i-VTEC — in the Accord and the CR-V compact sports utility vehicle.