The camshaft lobes uses (called cam) that act on the doors open and the rotation of the camshaft, valve springs to return to its closed position. This is critical work, and can have a major impact on engine performance at different speeds. On the next page of this article, you can see the animation we built to really show the difference between a camshaft and a level of performance.
Cam Basics
The most important parts of any camshaft overlap. As the camshaft rotates, the flaps open and close intake and exhaust in the process of moving the piston. It turns out that there is a direct correlation between the shape of the cam overlap and how the engine produces in the range of different speeds.
To understand why this happens, we imagine that the engine is running very slowly - only 10 or 20 revolutions per minute (RPM) - while making the second piston to complete one cycle. It would be impossible to effectively run a normal engine this slowly, but could imagine. At this slow speed, as we cam lobes so that:
* As the piston starts moving downward in the intake stroke (called top dead center or TDC), the intake valve is open. The closing of the intake valve at the bottom of the piston.
* The drain valve opens right into the lower piston out (called bottom dead center or BDC) at the end of the combustion stroke and would close as the piston meets the exhaust stroke.
This configuration should work very well with the engine running until this very low speed. But what happens if you add the RPM? Let's find out.
By increasing the rotational speed, setting 10 to 20 rpm for the camshaft does not work properly. If the engine is running at 4000 rpm, the valves open and close 2000 times per minute, or 33 times per second. At these speeds, the piston moves very quickly so that the air / fuel on the ground in the cylinder is moving very fast as well.
When the intake valve opens and the piston starts its intake stroke, air / fuel mixture in the inlet channel begins to accelerate into the cylinder. When the piston reaches the bottom of its intake stroke, air / fuel is moving at a fairly high speed. If we had to close the inlet valve closed, all air / fuel stop and not enter the cylinder. By leaving the intake valve open a little longer, the dynamics of fast moving air / fuel continues to force the air / fuel into the cylinder when the piston begins its compression stroke. So the more the engine goes, the more air / fuel mixture is moving, and we want the intake valve remains open. We also want the valve to open wider at higher speeds - this parameter, called valve lift, covered by the cam profile.
Each cam is perfect with a single speed. A second engine, the engine to its full potential. camshaft drive is always a compromise. Therefore, manufacturers have developed systems to vary the cam profile of changes in engine speed.
There are several different systems for engine camshaft. We are talking about some of the most common. You've probably heard the words:
- Single overhead cam (SOHC)
- Double overhead cam (DOHC)
- Pushrod
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