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发帖数: 174 | 1 variable valve timing.
in a normal engine (dohc or sohc), there is a cam (with lobes)
that life the (intake / exhaust) valves in a specific manner (timing,
duration, and lift height). since a valve will be lifted by the
same cam/lobes (collective "cam profile") at all rpm, the engineers
have to make a compromise and engine performance suffer at certain rpm
ranges.
In a VVT engine, there can be multiple (usually two) cam profiles and
the computer can switch among the profiles (either discretely
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