The World's First CVVD Engine - Genius!

Hello everyone and welcome. In this video, we are learning about the

world

's

first

CVVD

engine

, which stands for continuously variable valve duration. This technology is currently used in the 2020 Hyundai Sonata's 1.6-liter turbo

engine

. This is a cool technology, but to understand how it works, we need to understand how the valves work, so here we have a simple single-cylinder engine and, of course you have the intake compression power and the four stroke exhaust, so during the intake stroke you open the intake valve to allow air in. the cylinder the same for the exhaust to allow the air to escape you open the exhaust valve so the air can get out now in the most basic engines everything about how that valve opens and closes is fixed because the valve opens and it closes based on the cam profile path doesn't change, but in modern engines there are actually three valve related variables that we can change, so we are changing the valve timing, when do we actually open this valve before or after? changing how much we actually open the valve a little bit or a lot and then finally what Hyundai is adding to the mix here is the duration of the valve, so do we open it for a very short period of time or do we open it for a long time ? amount of time, so graphically this is what it looks like, we're looking at time versus valve lift and with variable valve timing, as you can see, you can change where that profile occurs, that cam profile that makes the valve stand up and therefore you can change that. counterclockwise or you can change it clockwise with variable valve lift, you can actually change how high the valve actually opens or how low the valve actually opens and often this will also change the duration but not of independently, so you can independently change the variable valve duration.

We're changing how wide that cam profile is or how narrow that cam profile is and that reduces or increases the time that the valve stays open. Now I have a video that goes into great detail how variable valve timing and variable valve lift work. We're interested, so in this video we're going to focus solely on variable valve duration. Up to this point, no mass-produced engine has been able to continuously vary the time a valve stays open in relation to engine speed, and you may be wondering about Koenigsegg's free feature. valve, we'll talk about that later in the video, so how does Hyundai do it right?

Let's start with the valve and then move back so here you can see the two valves for a single cylinder, both are intake valves and on top of that intake. valve, we have our camshaft and as you can see, that camshaft and the cam rotate, they force this rocker arm to rotate and as this rocker arm rotates, it forces the intake valve to open and then when the profile of the cam goes over that rocker arm, a spring forces the intake valve back up, so if we had a four-stroke engine running, the cycle would look like this:

first

we would have our intake stroke, then we would have our compression stroke, then we would have our power stroke and then we would have our exhaust stroke and then the cycle would repeat now.

What's very special about this setup is that the camshaft and the cam lobe are not connected directly, so you can see this little line here on the camshaft and then you can see that black. point on the cam lobe and as it rotates you can see that its position always stays the same. They both always point in the same direction, however, I can change their relative position by turning this knob and as you can see now, when it turns. their relative velocities are actually different at any given time, so what I can do by turning this knob is change the position of this wheel and by changing that wheel position you can see that I changed the duration of the valve, so here in the bottom you can see those three little dots and that's to help visualize how this wheel moves left or right and see what happens with the cam lobe versus the cam shaft and so on with the position all the way to the left here We can see that the camshaft actually goes past that point, the line goes past the point, which means that at the top the camshaft rotates faster than the cam lobe , but then once we get to our intake valve, you'll see that the dot goes through the line, so the cam lobe actually moves faster than the camshaft, which means the duration of our valve is actually shorter now.

If I move this to the other end, you'll notice the opposite happens, so our camshaft now goes through the cam lobe, meaning up. the cam lobe moves quickly but once we get to our intake valves the cam lobe slows down and as you can see the camshaft speed remains the same but the cam lobe has slowed down, so the valve duration actually increases now if we take our positioner and return to center, then again, they both rotate together all the time and remember that both the camshaft and the cam profile cam always have the same rpm.

What is changing is that through that revolution your relative speeds will change, so on course. of one minute they will rotate exactly the same number of times, however, when changing this positioner, the relative speed through that revolution is what is really changing, so I will do my best to show them side by side and you will be able to see . that on the left the amount of time the valves stay open is significantly less than the amount of time the valves stay open on the right and this is all done by simply changing the position, okay?

So, mechanically, how do you change the relative speed of the cam? lobe versus camshaft so let's start with the big picture and then move down to the details so first we have an actuator and this will be electronic; however, in this case we have a small crank to show how it works. This actuator rotates this shaft right here. You can see that there is a helical gear that makes the positioner rotate, so it essentially does the same thing as this positioner here, so when I turn it, it positions the cam wheel to the left or to the right as I turn it. positions the cam wheel to the left or to the right, so now we need to figure out how positioning this wheel to the left or to the right causes the cam lobe to have a different speed than the camshaft, e.g.

So the key to understanding this will require an animation that Hyundai has sent out. what we are looking at is a simplified version of the linkage between the camshaft in purple and the cam lobe that rotates with the blue cylinder, the speed of the camshaft will always be the same, so as we rotate the set every 90 degrees, you will notice that In all scenarios, the purple axis always points in the same direction, which means it always rotates at the same speed. This is our camshaft. The cam lobe is attached to the blue shaft. So let's first look at the simplest configuration in the middle.

Here you will notice the The blue and purple shafts always rotate at the same speed and that is because the center point of the orange linkage is also the center point of the camshaft, but what happens if you move that orange center point to the left? That gives us our leftmost example. Notice that this causes the blue axis to move very slowly when it is on the left side and very quickly when it is on the right side. If you look at the rightmost example, where the center point of the orange linkage is to the right of the center point of the camshaft, you will notice that the camshaft moves very quickly on the left side and very slowly on the right side, so, for example, if you placed an intake valve to the left of the leftmost camshaft, it would have a very long life if you placed it. an intake valve to the left of the rightmost camshaft would have a very short life, so that's exactly what this mechanism does: it uses a linkage that alters its center of rotation as you position it from left to right, which which causes the cam to have a relative speed difference versus the camshaft, so what does this mechanism actually look like?

Here you can see it on the model as I turn the knob from left to right, you can see the position change, but it's easier to see if you take apart the actual shaft. camshaft, so here we have our camshaft and as you can see, the cams on three of the cylinders are perfectly intact and then one of the cams on one of the cylinders has been removed from this camshaft, so now let's see how the forces pass through this so finally a timing chain is what's going to make this whole camshaft turn and then you can see we have a hole here and this slider goes into that slot so now the camshaft forces this slider to rotate now that the slider is connected to a wheel and so the wheel is now forced to rotate from the slider which rotates from the camshaft and then another control is placed slider on this side of the wheel and now once again the power comes from the camshaft to this final slider here and finally we put our cam in and this slides and goes into that slot there, so now everything the system is driven by the camshaft however the rotation speed is off so I can see I can turn the cam without turning the camshaft so once again if I remove that cam and the wheel you can see the link inside that allows that relative speed differential so the camshaft stays exactly in place and you can put the wheel left or right.

Now you can overlay the actual parts on the simplified animation to see how this all ends up working, slide the wheel left or right and the center point of the link changes altering the duration of the valve. Now this is where the lovely YouTube commenters come in and let me know that this system is too complicated and there is no way for it to work. It could be reliable because after watching a quick video on the Internet, you certainly know more about this technology compared to the engineers who spent nine years developing it. Yes, nine years to develop this technology.

Nine years that went into creating it, testing it and making sure it was. Reliable by the way, it comes with a 10-year, 100,000-mile warranty. You may have also noticed the holes and slots in the mechanism while taking it apart, as there are oil lubrication ports throughout the camshaft to keep everything running smoothly. Hyundai also has a system in place to ensure that when these parts are manufactured, all of their tolerances are matched for final assembly. What's also nice is that this is a purely mechanical system for something to fail, something has to fail mechanically, meaning a part has to break for things to go wrong.

With design material selection, part sizing, and lubrication, you can minimize the chances of failure. My bottom line here is you and I can't tell just by looking at this how reliable the system will be. I don't have the data to prove it one way or another. the other one, so there's no reason for me to just say it's not going to be reliable and I'm going to assume that Hyundai did its homework and ultimately time will tell us if these things actually turn out to be reliable or not, okay? The real benefit of this system, well, Hyundai says it enables up to five percent better fuel economy, up to four percent better performance, and up to 12 reduced emissions.

So how does this system actually increase horsepower? Think about your two different extremes here, so if your intake valve is only open for a very short period, it doesn't allow much air into the cylinder, so it can't make as much power, but by the same token, if Leave it open for too long, the piston will pop. coming back up pushing the air out of the cylinder and therefore it won't have as much air and therefore it won't be able to make as much power, so somewhere in the middle will be the ideal duration for the valve. to stay open and that duration changes depending on what rpm you're at, so at any given load at any given rpm, there's an ideal, there's a peak in the amount of power you can make for that given rpm, depending What I want to do with that duration is optimize it for each rpm, not just one or two, which is what most engines will do if they have variable valve lift, so you know they have two different lengths that they can choose from so the beautyof this system is its flexibility by allowing you to optimize at any rpm and thus improve horsepower over a wide range from an efficiency standpoint, by allowing really long valve durations, it means you can run the Atkinson cycle so that the piston recoils during the compression stroke. it leaves the intake valve open expelling some of the air and fuel and therefore its compression ratio is less than its expansion ratio and this is a more efficient way to operate the engine and again that timing will depend on the rpm, so a specific valve duration will be optimal to achieve maximum efficiency at any given rpm and any given load.

Emissions are now improved by altering valve timing and duration to ensure that when the engine is started cold, the catalytic converter warms up as quickly as possible now from the Since the beginning of this video, you may have been asking, wait a minute, what about the Koenigsegg free valve? This system can completely vary the duration of the valve and is a cool technology, although we haven't seen it used in a mass produced vehicle yet, but yes. It has its advantages, so I asked this question, hyundai, do you know why not use a system like free valve?

And they gave me three reasons, firstly, cost, which will always be a reason not to adopt certain technologies if it is ultimately too expensive in the long run. It's not going to end up happening second, second, efficiency, so they were concerned about how much energy it takes to actually run the valve system versus how much energy benefit you get from that valve system and whether that tradeoff doesn't work. Maybe it wasn't worth doing and then the ultimate concern was reliability, so Hyundai wanted to have a purely mechanical system so that the failure event would be caused purely by a mechanical failure, something that is quite easy to predict. through testing, you know, through design, through testing, and those are the three reasons they gave me why they didn't choose to use a system like the free valve.

Now, this doesn't necessarily mean that this is a better or worse system overall. We're just looking at the logic of why Hyundai went the route it did and it's great to see this technology actually end up in a production engine, so if you want to learn more about variable valve timing, variable valve lift or Koenigsegg . free valve I have additional videos on those topics. Thank you all so much for watching and if you have any questions or comments, of course, feel free to leave them below.