Chery A21 2005 Service Manual page 41

2.VVT PROFILE
VVT Principle
VVTi is the abbreviation of variable valve timing with intelligent. During the operation of
engine, the valve opening time is called as valve timing. When the engine operates at
different rotation speeds, we need different valve timings to provide the optimal valve closing
control, so that the power and combustion efficiency can achieve the best effect. For this
purpose, we shall install VVTi mechanism onto the camshaft controlling the air intake valve
to regulate valve timing. The VVTi system installed on the air intake camshaft of engine is
equipped with oil- pressure clutch device between the camshaft and drive sprocket, which can
alter the rotation phase difference between the air intake camshaft and drive sprocket. The
controlled oil pressure mechanism connects with the engine oil system, and can be regulated
by solenoid valve and control loop. When the engine operates at different rotation speeds,
there are different angles between the camshaft and sprocket, which facilitates the air intake
valve to open and close at different times in an effort to achieve variable valve timing. On the
other hand, when the engine operates at different rotation speeds, abundant and appropriate
oil gas can be supplied to generate mighty power.
When the car engine equipped with VVT-I system fails abnormally, ECUs controlled by the
engine shall automatically lock the preset parameter value (come-home function), ensuring
the driver to drive the car to the maintenance station. This kind of engine lodges a strictly
demand for the quality of petroleum and lubricant; therefore, you must adopt the standard
materials in compliance with the stipulations of original car manufacturer in order to avoid
unnecessary damages.
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