Finally understand that variable valve tech your car's maker brags about
Cooley On Cars
If you're in the market for a new car that isn't electric, at some point you're going to encounter a bunch of manufacturer mumbo jumbo about their valves, their valve technology.
And you're going to read about it and say, okay, I get it, kind of, but not really.
And you're going to think you're missing something, because they spent a lot of time talking about it.
Let's make it clear what valves do what Advanced valve technology does to make that better and why it matters.
The valves control what goes in and out of your cylinder?.
Your cylinder is where the piston moves, and that's where all the work gets done for an engine making power.
You've got a valve or valves that let air and/or fuel in, that's your intake valve or valves.
And you've got a valve or valves that let the exhaust out, that's the burned air and fuel.
That's it, input, output.
But it's critical.
They are as essential to the engine as any other system in it.
Now what moves those valves open and close to let all that stuff happen, are the cam shafts.
Here they are right here.
Each one has cans on them, that's these lobe or egg shaped pieces of metal are mounted rigidly on the shaft.
They have a low part and a high part where it sticks up like that.
As that thing goes around, it'll press down on the valve and open it.
What closes in the spring that is mounted around the valve right here.
Now in this car you have a rocker that is transferring that energy to the valve don't get confused by that bottom line is as that cam goes around high, low, high, low, high low.
It's moving the valve up and down, up and down, up and down and the spring does the other half.
But that's actually where things start to get complicated and that's what I'm gonna make simple now.
Now to make this clear, I have pulled a camshaft out of an engine.
And here you can see are the cams.
Here is the high part of the low where it's tall and here is the short part, the low part where it's Almost flat rounded with the shaft.
As this thing rotates around, that high part hits this valve and causes it to move, got it?
The timing is the first thing you think about where on the clock of this shaft, if you look at it this way is the high point Isn't it noon two, six o'clock kind of thinking that way because you can put that high point anywhere you want when you grind this thing into its shape.
That's how you set the timing of when that valve is gonna be open.
Opened by that [UNKNOWN], and when I say timing, I mean timing in relation to other events in the engine, not time of day or minutes or seconds.
It's really about relationship to when other valves are opening and closing and this is of course geared to the operation of the entire engine.
That kind of timing.
The next factor in valve and cam design is your lift.
That's how tall this tall part of the lobe is.
Because the taller that is, the more it's going to push this valve open as it swings around.
This tells you how wide do you open the door if you will to let air and fuel in or exhaust out.
The last factor in cam design and therefore valve operations.
Is called duration.
Think of it as being how fat or narrow this lobe profile is.
Now, if it's real picky it acts on this valve very briefly as it goes around.
If it's fatter and wider with big shoulders on it, it acts on the valve longer as it opens it.
So that is your time of opening.
And we just show your degree of opening and the first thing we talked about timing is your timing of opening and those are the main three factors.
Sound pretty complex, right?
This is nothing, now car makers go and make every one these
Let's go back to timing.
How do you vary timing I mean, this high low on the cam shaft is fixed here.
It's all part of a solid piece of metal.
Well, Porsche was one of the first to figure out variable cam timing in a really sophisticated way with something called VarioCam.
And what they did was say we're going to adjust the relationship of this cam shaft.
To the gear that is driving it, you can kind of slip this thing against its driving gear so you change the shaft's clock position that allows you to vary the timing in real time not dramatically but a little bit this way or that which gives the car optimum fuel economy and power and it's all driven by a computer and sensors, of course, because cars need different valve timing.
Depending on how you're driving them in the moment.
Okay, now how do you vary valve lift again that's based on the height of this peak of the valve load.
The way you do that has to figure it out sometime ago with the legendary V tech technology and what they do is they have more than one lobe available for the bounce.
At certain RPM you use, let's say the low load, which is gonna give you a minimal amount of opening or lift.
At higher RPM, you kick it over to a higher load that is right next to it, and they do this with the mechanical linkage.
Now the valves opening more and then when the engine revs back down again, it switches back to the other load.
This allows you to have again like with the variable timing, the optimal opening at the given rpm and engine load.
Okay, finally, how do you vary duration of opening?
It would seem really complicated given the fact that this is also rigid.
Well, Hyundai recently cracked the code on that with their new CVVD technology.
Just coming out in 2020 and some of their first cars in the Korean market.
And the idea here is they're going to move the cam shaft back and forth a little bit side to side in the engine as it's turning.
By doing so you're exposing the valve to a little less or a little more of time against that slope.
Leads up to the peak of below.
It's unbearably complicated to be frank.
I stared at it for half a day and I think I finally figured it out.
But all you have to know is all three parameters of how valves or operators are now variable.
Now all this sounds like pretty impressive tech, right?
But frankly, it's a bunch of pretty impressive band aids for this technology.
Cams and lobes and valves.
This goes back a century or more, in automotive use.
The future will be much cleaner, perhaps.
Development ongoing in direct actuated valves.
These are valves that are operated by a solenoid or an electric motor, upon command by a computer.
None of this curvature timing duration and grinding of shapes nonsense that makes a cam shaft work Or you'll just be driving an electric car which has no valves at all.
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