Effectiveness of the VVTi System

Operation State

Objective

Effect

Earliest Timing Latest Timing (EX) (IN)

During Idling

Earliest Timing Latest Timing (EX) (IN)

Eliminating overlap to reduce blow back to the intake side.

• Stabilized idling rpm

• Better fuel economy

At Light Load

To Advance Side (EX)

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To Retard Side (IN)

Eliminating overlap to reduce blow back to the intake side.

Ensured engine stability

At Medium Load

To Advance Side (IN)

To Retard Side (EX)

Vvti Controller
IN

Retarding the intake IN valve close timing for volumetric efficiency To Advance improvement.

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To Retard Side (EX)

Increasing overlap increases internal EGR, reducing pumping loss.

• Better fuel economy

• Improved emission control

In Low to Medium Speed Range with Heavy Load

To Retard Side (EX)

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Advancing the intake valve close timing for volumetric efficiency improvement.

Improved torque in low to medium speed range

In High Speed Range with Heavy Load

To Retari Side (IN)

Retarding the intake IN valve close timing for volumetric efficiency To Advance improvement.

Improved output

Earliest Timing Latest Timing (EX)

At Low Temperatures

Earliest Timing Latest Timing (EX)

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Eliminating overlap to reduce blow back to the intake side leads to the lean burning condition, and stabilizes the idling speed at fast idle.

• Stabilized fast idle rpm

• Better fuel economy

Earliest Timing-Latest Timing

• Upon Starting

• Stopping the Engine

Earliest Timing-Latest Timing

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Eliminating overlap to minimize blow back to the intake side.

Improved startability

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Responses

  • Kim
    How to improve efficiency in vvti engine?
    2 years ago

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