When you check out the Engine Valves features of a new car, you’ll probably be bombard with glowing words about its engine’s “advanced valvetrain technology.” How did this happen? They don’t shower us with details of how viruses work when they sell us cold medicine. Here’s a quick explainer of what car engine valves do and why carmakers spend so much time telling you how great theirs are.
What Are The Functions Of Valves?
The valves present in the engine’s head and are responsible for allowing air and/or fuel into the cylinders to be combusted (intake valves) and allowing the exhaust from that combustion to exit the cylinders (exhaust valves).
Although valves may sound like a couple of horns in an orchestra, they are crucial to an engine’s power, economy, and emissions.
How Do Valves Function?
The rotation of a camshaft with eccentric, egg-shaped lobes controls the engine valves. The upper section of the cam lobes’ egg shape presses on the valve as they rotate, causing it to open.
The high section of the cam lobe slides away from the valve as it rotates, and a spring returns the valve to its closed position.
Timing, lift, and duration are the three key criteria that govern the nature of that open-and-close dance. (This is where the video near the top of the page comes in handy!)
Timing
A camshaft, like anything else that rotates, rotates 360 degrees while it works. The valve timing, or when the cam lobe presses on the valve during the shaft’s rotation, is determine by where the apex of the egg-shape lobe is point in that 360-degree circle.
Because everything in an engine is mechanically bound together, timing defines when the valve opens in relation to what’s going on in the rest of the engine at any one time.
Lift
Lift is determine by the height of the cam lobe, or how tall its egg-shaped point is. The valve will move or “lift” further if that end is taller. The size of the aperture generate in the cylinder to allow air or fuel in or exhaust out is mostly determined by the amount of lift.
Duration
The duration, or how long the cam lobe lifts the valve, is determine by its width or breadth. The amount of time a cylinder has to breathe in or out is determine by this.
As the camshaft spins, a narrow, peaky cam lobe opens a valve briefly, whereas a wider, broader cam lobe spends more time keeping the valve open.
Adding All Of Those Variables
As you can see, the egg-shaped cam lobes are deceptively intricate, and their organic structure contains a plethora of “commands.” Even so, for modern engines, such complex characteristics aren’t adequate; in recent decades, carmakers have made timing, lift, and duration flexible while the engine runs.
Timing is flexible
Cam lobes should push on valves at different periods depending on engine speed and load, which is difficult to conceive with a set, machined camshaft form. However, Porsche’s VarioCam technology was one of the first to accomplish so by altering the camshaft’s interaction with the gear that turns it.
Porsche was able to change the timing of the intake valves in relation to the position of the pistons in the cylinder, as well as the timing of the exhaust valves, as a result of this. The manufacturer picture of how VarioCam affects intake valve timing is a little unclear, but it’s there. Most modern gas-powered cars now employ some form of valve timing variation.
Variable Time Frame
The duration of a cam lobe’s action on a valve was likely the most difficult variable to achieve, but Hyundai’s new CVVD technology did it lately. The camshaft rotate laterally off its rotational midline, which changes the duration. It’s an excruciatingly classy process, which is one of the reasons it took decades longer than the previous two variable technologies to emerge. In late 2020, it should be available in select new Hyundai vehicles.
The Near Future
All of this is fantastic technology, but it’s really just a bunch of Band-Aids for a century-old automobile technology: camshaft-actuated valves. We may be able to do away with the entire Rube Goldberg system in the future and drive automobiles with direct, camless valve actuation. Each valve is control by a simple solenoid or electric motor in this new technology.
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