What does vvt i stand for

Note: Only the intake is involved. Adjustments in the overlap time, between the exhaust valve closing and intake valve opening; results in improved engine efficiency.

VVT Variable Valve Timing technology, controls three key characteristics; of the intake and exhaust valves:. Finally, using various mechanisms, to control the aforementioned valve characteristics. Visualize this as a hollow, enclosed gear inside; which two star-shaped gears are placed, one inside the other.

The inner gear, connects to the camshaft itself. Normally, the two are meshed together, cog against cog, and turn at the same rate. So, when oil pressure is introduced, the gears can be separated. Consequently, changing their speeds, relative to one another momentarily. Also, that, in turn, changes the duration of the valve lifting, to control intake and exhaust. Therefore, by continuously adjusting the timing of the intake and exhaust valves; to help improve power, fuel efficiency and exhaust emissions.

Also, dual VVT helps the engine give you the power and the fuel efficiency that you want; while maintaining optimum emissions quality. So, with dual VVT — Variable Valve Timing , the same thing happens; the difference this time is the exhaust valves are activated. Now, the camshaft has two profiles each, for both intake and exhaust. Intake and Exhaust. Some design, such as BMW's Double Vanos system, has cam-phasing VVT at both intake and exhaust camshafts, this enable more overlapping, hence higher efficiency.

This explain why BMW M3 3. Cheap and simple, continuous VVT improves torque delivery across the whole rev range. Lack of variable lift and variable valve opening duration, thus less top end power than cam-changing VVT. Most car makers, such as:. F rom the picture, it is easy to understand its operation. The end of camshaft incorporates a gear thread. The thread is coupled by a cap which can move towards and away from the camshaft. Because the gear thread is not in parallel to the axis of camshaft, phase angle will shift forward if the cap is pushed towards the camshaft.

Similarly, pulling the cap away from the camshaft results in shifting the phase angle backward. Whether push or pull is determined by the hydraulic pressure. There are 2 chambers right beside the cap and they are filled with liquid these chambers are colored green and yellow respectively in the picture A thin piston separates these 2 chambers, the former attaches rigidly to the cap.

Liquid enter the chambers via electromagnetic valves which controls the hydraulic pressure acting on which chambers. For instance, if the engine management system signals the valve at the green chamber open, then hydraulic pressure acts on the thin piston and push the latter, accompany with the cap, towards the camshaft, thus shift the phase angle forward.

Continuous variation in timing is easily implemented by positioning the cap at a suitable distance according to engine speed. Macro illustration of the phasing actuator. However, the word " Integillent " emphasis the clever control program. Not only varies timing according to engine speed, it also consider other conditions such as acceleration, going up hill or down hill. C ombining cam-changing VVT and cam-phasing VVT could satisfy the requirement of both top-end power and flexibility throughout the whole rev range, but it is inevitably more complex.

At the time of writing, only Toyota and Porsche have such designs. However, I believe in the future more and more sports cars will adopt this kind of VVT. Its powerful functions include:. Like VVT- i , the variable valve timing is implemented by shifting the phase angle of the whole camshaft forward or reverse by means of a hydraulic actuator attached to the end of the camshaft.

The timing is calculated by the engine management system with engine speed, acceleration, going up hill or down hill etc. It also has 2 cam lobes acting on that rocker arm follower, the lobes have different profile - one with longer valve-opening duration profile for high speed , another with shorter valve-opening duration profile for low speed.

At low speed, the slow cam actuates the rocker arm follower via a roller bearing to reduce friction. The high speed cam does not have any effect to the rocker follower because there is sufficient spacing underneath its hydraulic tappet.

When speed has increased to the threshold point, the sliding pin is pushed by hydraulic pressure to fill the spacing. The high speed cam becomes effective. Note that the fast cam provides a longer valve-opening duration while the sliding pin adds valve lift. However, VVTL- i offers variable lift, which lifts its high speed power output a lot.

Therefore it is undoubtedly the best VVT today. However, it is also more complex and probably more expensive to build.

Continuous VVT improves torque delivery across the whole rev range; Variable lift and duration lift high rev power. More complex and expensive. Toyota Celica GT-S. Variocam Plus uses hydraulic phasing actuator and variable tappets. Variocam of the Carrera. However, I found their mechanisms virtually share nothing. The Variocam was first introduced to the in It used timing chain to vary the phase angle of camshaft, thus provided 3-stage variable valve timing.

Therefore, the Variocam Plus used in the new Turbo finally follow uses the popular hydraulic actuator instead of chain. One well-known Porsche expert described the variable valve timing as continuous, but it seems conflicting with the official statement made earlier, which revealed the system has 2-stage valve timing.

However, the most influential changes of the "Plus" is the addition of variable valve lift. It is implemented by using variable hydraulic tappets. As shown in the picture, each valve is served by 3 cam lobes - the center one has obviously less lift 3 mm only and shorter duration for valve opening.

VTEC Variable Valve Timing and Lift Electronic Control is a valvetrain system developed by Honda that allows engines to achieve turbo level specific output without the bad fuel efficiency that turbocharging normally introduces. In an automobile engine the intake and exhaust valves move on a camshaft. The timing, lift and duration of the valve are determined by the shape of the lobes that make the shaft move.

Timing refers to an angle measurement of when a valve is opened or closed with respect to the piston position and lift refers to how much the valve is opened. With this technology. Share this comparison:. If you read this far, you should follow us:. Diffen LLC, n. More TQ TQ engines are better than high rev engines. A 1zzfe can beat a b18c1, with those same hp ratio numbers and still leave a 1 car length away thatb18c1.