Last Updated on September 10, 2022 by John K. Clifford
VVT-i stands for variable valve timing with intelligence; Toyota’s variable valve timing technology is designed to improve engine efficiency. The main difference between VVT-i and dual VVT-i is that the VVT-I adjusts timing only on the intake camshaft while the dual VVT-I adjusts valve timing on both intake and exhaust camshafts.
The VVT-I system was first introduced in 1995 on the 2JZ-GE engine used in the crown Majesta and JZS155 Toyota. This technology works by varying the timing of the intake valve by adjusting the relationship between the camshaft drive and intake camshaft. Engine oil pressure is applied to an actuator to adjust the camshaft position. The overlapping adjustments between the intake valve opening and the exhaust valve closing result in better engine efficiency.
The VVT-i system is widely used in most Toyota and Lexus models to ensure they have excellent engine efficiency. The system has different variations: dual VVT-I, VVTL-I, VVT-Ie, VVT-iW, and valve Matic.
This article looks at the technology and its variations in detail to help you understand how it works. In the end, you will be able to differentiate each variation and also answer any questions or dilemmas you might have had. Let’s get into it.
What Is Variable Valve Timing? VVT
The internal combustion engine is designed with inlet and exhaust valves that control the flow of intake and exhaust gases into and out of the combustion chamber. The lift, timing, and duration of these valves greatly impact how the engine performs. The variable valve timing is the process of altering the timing of a valve lift event to improve fuel economy, performance, and emissions.
Without variable valve lift or variable valve timing, the valve timing is the same for all engine conditions and speeds, so compromises are necessary. When the engine is equipped with a variable valve timing actuation system, it is freed from this constraint and improves performance over the engine’s operating range.
Piston engines use valves driven by camshafts; these camshafts open for a specific duration during each intake and exhaust cycle. The timing of the valve opening and closing in relation to the crankshaft position is essential to ensure the required amount of air gets in for the better functioning of the engine.
What Is Variable Valve Timing With Intelligence? VVT-i
The VVT-i system replaces the variable valve timing technology; it varies the intake valves timing by adjusting the relationship between the camshaft belt or chain and the intake camshaft. For Toyota’s VVT-i, the engine operation’s electronic control unit calculates the best time to open and close the valves. It also activates an oil pressure valve to change the timing by altering the camshaft’s speed. VVT-I improves fuel economy, increases power, and reduces emissions by optimizing valve timing based on driving conditions.
This system has several variants that we shall look at; they include dual VVT-I, VVT-iE, VVTL-I, VVT-iW, and Valve Matic.
1. Dual VVT-i
The dual VVT-I system adjusts timing on the intake and exhaust camshafts. This technology was first introduced in 1998 on the RS200 Altezza’s 3S-GE engine. It is also found on Toyota’s new generation V6 engine, the 3.5L 2GR-FE that debuted on the 2005 Toyota Avalon. The engine is also used in various Lexus and Toyota models such as the 1LR-GUE(V10) used in Lexus LFA, UR engines (V8), GR engines (V6), AR engines (large I4), ZR and NR engines. The technology adjusts the valve timing allowing the engine to start and stop unnoticeably at minimum compression. It reduces hydrocarbon emissions by allowing fast-heating of the catalytic converter to its lights-off temperature.
VVT-iE stands for variable valve timing- intelligent by the electric motor. It is a version of dual VVT-I that uses an electrically controlled actuator to maintain and adjust the intake camshaft timing. For this variation, a hydraulic actuator still operates the exhaust camshaft timing. This type of variable valve timing technology was developed for Lexus vehicles and first introduced in 2007 Lexus LS 460 as the 1UR-FSE engine.
As the engine is running, the electric motor in the actuator spins together with the intake camshaft. The actuator motor operates at the same speed as the camshaft to maintain camshaft timing. To increase the camshaft timing, the motor rotates slightly faster than the camshaft speed, while to reduce camshaft timing, the motor spins slightly slower than the camshaft speed.
The difference in speed between the camshaft timing and actuator motor operates a mechanism used to vary the camshaft timing.
Electric actuation benefits-improved response and accuracy at lower engine speeds and temperatures and a greater adjustment range. All these factors work together to allow more precise control, resulting in better fuel economy, emissions performance, and engine output.
VVTL-i also denoted as VVT-IL, stands for Variable valve timing and lift intelligent system. It is an enhanced version of VVT-I that can change valve lift and duration and valve timing. This system was first used in 1999 Toyota Celica with 2ZZ-GE; it was also used in corolla XRS and Toyota Matrix XRS. Toyota ceased production of this engine for most markets because it didn’t meet euro IV specifications for emissions.
VVT-iW stands for variable valve timing intelligent wide. It was first introduced with the 2.0L turbocharged direct-injected 8AR-TS fitted to the Lexus NX200t. this technology uses VVT-iW on the intake valve and VVT-i on the exhaust valve. The intake camshaft has a lock mechanism at the mid position to retard the continuously variable timing. This technology offers wider valve opening angles to enable the engine to operate in a modified cycle. The engine operates in the Atkinson cycle at low rpm with this technology for improved economy and lower emissions. The Otto cycle at high rpm for better performance and high torque.
5. Valve Matic
The valve Matic system gives continuous variation to valve lift and timing to improve fuel efficiency by controlling fuel and air intake using valve control instead of the conventional throttle plate control. This technology debuted in 2007 in the Toyota Noah and 2009 in the ZR engine family used on the Avensis.
Frequently Asked Questions
Q. At What RPM Does VVT-i Kick In?
The variable valve timing is always on, and in use, so it never kicks in; it has to work all the time for the engine to function most efficiently.
Q. Are Toyota VVTi Engines Good?
Yes, engines with the VVTi technology have better fuel efficiency and power; they also have reduced emissions making the more environmentally friendly
Q. What Happens When VVT Fails?
When the VVT is malfunctioning, the entire system is compromised, and the intake and exhaust valves will open and close at the wrong intervals. This reverses all the benefits of the VVT, thus causing reduced fuel economy and power output.
The Variable valve timing technology in Toyota cars plays a huge role in improving the engine’s performance, maintaining impressive fuel economy, and controlling emissions. The technology keeps getting better, and every invention makes the performance even better. If you wondered how the different variations work, we hope you are now well informed.