VVT-i stands for Variable Valve Timing-Intelligence, which is Toyota’s name for the variable valve technology it uses in most of its vehicles.
Most manufacturers use variable valve-timing technology, and though the details differ, the systems all make small adjustments to when the engine’s intake valves open and close to feed an air-fuel mixture into the engine based on how the vehicle is being driven. This is done to maximize performance and reduce emissions. Some variable valve systems also work on the exhaust valves, which open to let the air-fuel mixture out of the engine.
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With variable valve timing, the valves are open for shorter periods during light acceleration or idling, so less air-fuel mixture goes into the engine and helps reduce emissions. Under hard acceleration, the valves are open longer, so more air-fuel mixture feeds into the engine and increases power.
With Toyota’s VVT-i, the electronic control unit — the “brain” that manages engine operations — continuously calculates the best time to open and close the valves and activates an oil pressure valve to change the timing by altering camshaft speed.
Some Toyota engines, such as the Highlander SUV’s 3.5-liter V-6, use electric motors to change the intake valve timing, and Toyota labels those as VVT-iE (for Electric). On engines such as the 3.5-liter and 2.5-liter used in the Camry sedan, the exhaust valves also have variable timing, and those are called Dual VVT-i. Toyota says that by optimizing valve timing based on driving conditions, VVT-i increases power, improves fuel economy and reduces emissions.
Alfa Romeo was the first manufacturer to offer variable timing in 1980, and others followed, including Honda in 1989 with its VTEC system. Toyota announced VVT-i in 1995, and it was introduced in the U.S. on the redesigned 1998 Lexus LS 400. The model-year 2000 Celica was the first Toyota model in the U.S. with it.
All current Toyota models in the U.S. use VVT-i engines except the Mirai fuel-cell vehicle, the 86 coupe and Supra sports car. The 86 uses a Subaru engine and the Supra a BMW engine, and both have variable valve timing.
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