Variable Valve Timing: What Is It? Who Needs It?
And no We Didn't Copy This From The Internet.
Toyota VVT-i
Toyota came somewhat late to this party; its Variable Valve Timing with Intelligence (VVT-i) system was introduced for the V-8, V-6, and I-6 engines in '98-model-year Lexus LS400s, SCs, and GSs. But the company is making up for lost time, as VVT-i is now on virtually every Toyota and Lexus car in the line.
VVT-i works much like Honda's VTC system. An engine control unit monitors various inputs (including engine speed, airflow, coolant temperature, and so on). Using oil pressure to actuate a camshaft timing pulley, it then advances or retards the intake camshaft to suit the engine's operating needs.
Since the introduction back in 1997, Toyota has developed a two-step, rpm-related variation of VVT-i called VVTL-i, which stands for Variable Valve Timing and Lift with Intelligence. Found aboard the 1.8L, 180hp engine in Toyota's Celica GT-S, the VVTL-i combines the continuously variable cam phasing with new, dual-lobe camshafts for both the intake and exhaust valves. At engine speeds below 6,000 rpm, a set of rocker arms follows a set of low-lift, short-duration lobes. At six grand, a pin under the rocker arms pushes them so they engage the second lobe set, which has been ground to make significantly higher lift. As with the VTEC system, the taller lift is better matched to the air-gulping needs of an engine spinning between 6,000 rpm and its 7,800-rpm redline.
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The new intake-only version of i-VTEC is also found aboard the current Civic Si, giving it
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Recently, Toyota added a variable-lift component to its VVT-i system, called it Variable V
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Toyota's Variable Valve Timing with Intelligence (VVT-i) takes the cam-phasing approach to
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