A high-expansion cycle (Atkinson cycle) is used to improve heat efficiency.
On the intake side, Variable Valve Timing-intelligent Wide (VVT-iW), which is provided with an intermediate lock mechanism that optimally controls the intake camshaft (camshaft) to the valve timings according to driving conditions, is used.
On the exhaust side, Variable Valve Timing-intelligent (VVT-i), which optimally controls the exhaust camshaft (No. 2 camshaft) to the valve timings according to driving conditions, is used.
Figure 1. Valve Timing Variable Range
A timing rotor for the camshaft position sensor is provided on the back of the intake and exhaust camshafts.
The No. 1 valve rocker arm sub-assembly is used as a valve mechanism and by achieving size reduction while drastically reducing the amount of friction that occurs between the sliding parts and cams, low fuel consumption is achieved. Also, an oil pressure type valve lash adjuster assembly is used to make valve clearance adjustment unnecessary in consideration of serviceability.
Together with the use of the No. 1 valve rocker arm sub-assembly, the cam profile has been designed with an indented R (radius). This results in increased valve lift when the valve begins to open and finishes closing, helping to achieve enhanced output performance.
The cam that drives the fuel pump assembly (for high pressure) is positioned directly above the No. 4 cylinder of the exhaust camshaft (No. 2 camshaft) to achieve size reduction. Also, a pump cam with 4 peaks is used in the cam that drives the fuel pump assembly (for high pressure) and by synchronizing fuel pressure-feeding and fuel injection, the difference in fuel pressure between cylinders is reduced.
The vacuum pump assembly is driven by the end of the exhaust camshaft (No. 2 camshaft).
A valve spring (inner compression spring), whose upper portion is shaped like a beehive, is used to reduce inertial mass. As a result, the load on the valve spring (inner compression spring) and friction are reduced.
The diameter of the valve spring retainer has been decreased to reduce inertial mass and friction.
The exhaust valves improve valve cooling performance and reliability by using sodium as a refrigerant. Holes are provided in the valve stems and sodium with high heat conductance and a low melting point is inserted to support high exhaust temperatures. Also, the valve stems are made hollow to achieve weight reduction and reduce friction.
|*1||Camshaft Timing Gear Assembly||*2||Cam Timing Exhaust Gear Assembly|
|*3||Camshaft Timing Exhaust Gear Assembly (for VVT-i)||*4||Cam Timing Oil Control Solenoid (for VVT-iW)|
|*5||Exhaust Camshaft (No. 2 Camshaft)||*6||Vacuum Pump Assembly|
|*7||Intake Camshaft (Camshaft)||*8||Fuel Pump Assembly (for High Pressure) Driving Cam|
|*9||Fuel Pump Assembly (for High Pressure)||*10||No. 1 Valve Rocker Arm Sub-assembly|
|*11||Valve Stem Cap||*12||Valve Spring Retainer Lock|
|*13||Valve Spring Retainer||*14||Valve Spring|
|*15||Valve Spring Seat||*16||Valve|
|*17||Valve Lash Adjuster Assembly||-||-|
|*a||Lift Amount Increase||*b||Indented R Portion of Cam (Profile)|
|*c||Cam with Indented R||-||-|
Figure 2. Valve Timing