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In engineering terms, Honda doesn't do anything by half measures. Take the new 2003 Accord, for instance. Technology is a given in the luxury and sport-sedan market, but the Accord is supposed to be a high-volume plain vanilla sort of car for people who want reliable, comfortable transportation and good value. For a "family car" (excepting the Accord Coupe, which has sporting aspirations and decent technical credentials) the '03 Accord is loaded with enough tech to keep a rocket scientist happy. Available under the hood are two new engines, a 160 horsepower four cylinder displacing 2.4 litres and a 3.0 litre V-6 with 240 horses. Both power ratings are significant, and both come through a group of technologies that individually contribute little, but cumulatively sum to horsepower figures that were V-8 territory fifteen or twenty years ago. The SOHC four-valves-per-cylinder V-6, for example, has been redesigned with a new tuned intake system and manifold flowing through larger intake valves actuated by a three-rocker version of Honda's VTEC variable valve timing system.
VTEC makes it possible to vary the relative timing and lift of the intake valves to optimize overall performance, netting good low-end torque as well as improved high-end horsepower.
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Basic operation of the 3-rocker VTEC setup used on the 2003 Accord's V6 is similar to that of the 2-rocker version used on the DOHC 4-cylinder, where rocker arms fitted with low-friction roller followers actuate the intake valves.
The heart of the VTEC system is a unique camshaft and rocker arm system. For each cylinder's set of two intake valves, there are three rocker arms and three corresponding lobes on the camshaft. The two outboard lobes each have a profile maximizing cylinder swirl to suit low- to mid-rpm operation. The third or centre cam lobe has a dramatically different profile designed for longer duration and higher lift. This lobe profile...