VVT-i

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VVT-i, or Variable Valve Timing with intelligence, is an automobile variable valve timing petrol engine technology manufactured by Toyota Group and used by brands such as Groupe PSA (Peugeot and Citroen), Toyota, Lexus, Scion, Daihatsu, Subaru, Aston Martin, Pontiac and Lotus Cars. Introduced in 1995 with the 2JZ-GE engine found in the JZS155 Toyota Crown and Crown Majesta, VVT-i varies the timing of the intake valves by adjusting the relationship between the camshaft drive (belt or chain) and intake camshaft. Engine oil pressure is applied to an actuator to adjust the camshaft position. Adjustments in the overlap time between the exhaust valve closing and intake valve opening result in improved engine efficiency. VVT-i replaces the previous VVT system introduced in 1991 with the five-valve per cylinder 4A-GE "Silver Top" engine found in the AE101 Corolla Levin and Sprinter Trueno, which was a 2-stage hydraulically controlled cam phasing system. Variants of the system, including VVTL-i, Dual VVT-i, VVT-iE, VVT-iW and Valvematic have followed. Direct injection systems such as the D-4 (VVT-i D-4) and D-4S are also used in conjunction with VVT-i.