How does vvti engine works

This head, or camshaft gear, is where the timing system belt, scissor-gear, or chain give the rotational force to the camshaft itself. The gear head is a hollow structure in which oil pressure can be raised or lowered to allow a two-piece floating system to speed up or slow down the head's rotation in relation to the actuator.

Visualize this as a hollow, enclosed gear inside which two star-shaped gears are placed one inside the other. The outer gear is the camshaft gear's connection to the belt or chain that drives it. The inner gear connects to the camshaft itself. Normally, the two are meshed together, cog against cog, and turn at the same rate. When oil pressure is introduced, however, the gears can be separated, changing their speeds relative to one another momentarily.

This increases or decreases the speed of the camshaft in relation to the engine's drive timing. That, in turn, changes the duration of the valve lifting to control intake and exhaust. The system has been very well received by engineers and mechanics and has shown marked improvement in engine performance output under varied driving conditions and has improved fuel economy in many of Toyota's vehicles by double digit percentages.

Several advantages are had with this system, including faster catalytic converter heating through exhaust control, compression can be minimized to improve idle economy, and the timing allowed by the VVT-i system is improved to include more variation thanks to the added control of exhaust timing.

Variable Valve Timing and Lift with intelligence is an enhanced version of VVT-i that allows control of valve lift to go with the timing control. Matching lobes appear on the exhaust side, giving eight lobes per cylinder four valves. Unlike a conventional VVT system, however, there is only one rocker arm lifter for each lobe pair, rather than two.

He rocker arm has a slipper follower mounted with a spring, which it move up and down the high lobe without affecting the arm. Toyota's tuning usually means that the lower lobe operates the rocker arm at sub RPM and the larger lobe at RPM above that. The slipper follower is controlled by oil pressure, which engages a sliding pin to lock the follower and cause it to lift the arm on rotation.

VVTL-i is no longer being used in most markets due to its inability to meet European emissions requirements. Additionally, to conform to stricter emissions norms, manufacturers have developed many other supportive systems. These are electro-mechanical or electro-hydraulic valve-lifters and cam-less valves systems etc. Read more: What is Engine Valve Timing? CarBikeTech is a technical blog. Its members have an experience of over 20 years in the automobile field.

CarBikeTech regularly publishes specific technical articles on automotive technology. View all posts by CarBikeTech. Get Car Bike Tech directly in your inbox. You May Also Like. What is Disc Brake, what are its types And How it works? Know Here. As you possibly know already, motor vehicle engines and transmission are designed to work together so the RPM could drop to just above the lowest RPM to move the car comfortably.

Based on this, there is a popular view that one should accelerate gradually i. But there is another view; that it is better to press the throttle harder so that higher RPM is attained at a faster rate. Since the higher the RPM the more horse power the engine delivers depending on size, it is logical that the longer one stays at high RPM the more energy the engine consumes. Therefore, the quicker you press the throttle the quicker you reach desired RPM and this means you will shift into the next gear more quickly and attain low RPMs.

Since the time is reduced and the RPMs are reduced, you end up reaching the desired speed with reduced fuel consumption. Depending on your views regarding the above physics, you now need to analyse how your VVT-i engine behaves in different driving situations. That is the point at which you feel the car accelerating faster at a specific RPM.

Next, you need to check the lowest RPM that your engine can work to move your car on a straight and level road. Check it on each gear.