How does vvti work

So, most VVT systems and its components, depend on the constant circulation of engine oil. But, can also be confused with the same symptoms; caused by issues with your ignition or fuel injection systems.

But, when the crankshaft position sensor CKP fails; it stops transmitting the signal. Also, the crankshaft position sensors CKP signal […]. The most important sensors, in any engine, are the crankshaft and camshaft position sensors. Modern computer-controlled vehicles; must have the air and fuel ignited, at the proper time, in order to operate efficiently. Most of the images displayed are of unknown origin.

We do not intend to infringe any legitimate intellectual right, artistic rights or copyright. So, as engine technologies improve and become less expensive; VVT variable valve timing, continues to improve performance and economy.

Manufacturers have now adopted, various VVT variable valve timing, design approaches and technologies. Most importantly, to control the valve timing and how long; the intake and exhaust valves remain open. Engine Testing. September 11, Engine Testing , Ignition System. September 22, Engine Testing , Ignition System. Therefore, fast timing and high lift are obtained in both valves. Very similar to Honda's system, but the right and left cams are with the same profile.

At low speed, both rocker arms are driven independently by those slow-timing, low-lift right and left cams. At high speed, 3 rocker arms are connected together such that they are driven by the fast-timing, high-lift middle cam. You might think it must be a 2-stage system. No, it is not. Since Nissan Neo VVL duplicates the same mechanism in the exhaust camshaft, 3 stages could be obtained in the following way:. Stage 1 low speed : both intake and exhaust valves are in slow configuration.

Stage 3 high speed : both intake and exhaust valves are in fast configuration. C am-phasing VVT is the simplest, cheapest and most commonly used mechanism at this moment. However, its performance gain is also the least, very fair indeed. Basically, it varies the valve timing by shifting the phase angle of camshafts. This movement is controlled by engine management system according to need, and actuated by hydraulic valve gears.

Note that cam-phasing VVT cannot vary the duration of valve opening. It just allows earlier or later valve opening. Earlier open results in earlier close, of course. It also cannot vary the valve lift, unlike cam-changing VVT. However, cam-phasing VVT is the simplest and cheapest form of VVT because each camshaft needs only one hydraulic phasing actuator, unlike other systems that employ individual mechanism for every cylinder. Continuous or Discrete.

Obviously this provide the most suitable valve timing at any speed, thus greatly enhance engine flexiblility. Moreover, the transition is so smooth that hardly noticeable. 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.

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A typical engine's intake and exhaust valves are opened via the lobes on a camshaft. With dual overhead cam engines, there are separate camshafts for exhaust valves and intake valves. These camshafts are made of hardened iron or steel and are connected to the crankshaft via timing belts, chains, or gears.

Since modern gasoline engines incorporate the four-stroke cycle, this means that the camshafts rotate once for every two crankshaft rotations. To reinforce this point, consider the intake stroke of an engine.

The intake valve is open, meaning the camshaft lobe is pushing against the cam follower and opening the valve. Lets trace the motion of this cam lobe and compare it to the motion of the crankshaft. While the intake valve is open, the piston moves down toward bottom dead center. Once the engine has reached bottom dead center, the crankshaft has rotated degrees. Then the piston moves up to compress the fuel mixture. Once the piston has reached top dead center, the crankshaft has made a full rotation.

Next, the spark plug ignites the fuel mixture, sending the piston back down to bottom dead center. At this point, the crankshaft has turned one and a half full rotations. Now the exhaust valve opens, and the piston moves back up to top dead center.

The crankshaft has rotated two full revolutions. Now that the piston is at approximately top dead center, the camshaft lobe that we are monitoring comes back around and opens the intake valve and the piston moves back down. Thus, after two revolutions of the crankshaft, the camshaft has rotated once. Check out this gif to see it all in motion.