|
Among all the components that make up an engine, the camshaft plays the most significant role in determining the behavior and character of the engine. As for the engine's behavior, most OEM camshafts offer idles that are smooth and polished. A radical aftermarket full-race camshaft may produce an idle that is rough and raw. As for character, one camshaft may regulate an engine to produce massive low-end torque, while a different camshaft in that same engine may soften up the power production at the low end while allowing the engine to pull strong up to redline. Understanding the function, design, and limitations of the camshaft will allow you to maximize your performance experience.
Function of the Camshaft
The four-stroke process that occurs in your car's engine is as follows: intake, compression, power, exhaust. While the crankshaft's position, crankshaft's stroke and rod length ultimately determine where the piston will be in the cylinder at any given degree of rotation, it's the camshaft that determines the position of the intake and exhaust valve during all four strokes.
An engine's camshaft(s) is/are responsible for the valve timing in the engine. Proper valve timing is critical for any four-stroke automotive engine to operate at maximum efficiency. When the valves open, how high the valves open (lift), and for how long they stay open (duration) all determine the performance characteristics of the engine.
In the performance symphony, the camshaft is the conductor of valve events. It orchestrates which instruments play (intake or exhaust valves), when they play (opening and closing events) and how loud they play (valve lift). Whereas OEM conductors (cams) offer a classical sound, aftermarket cams can really make your engine rock.
The Band of Power
As mentioned earlier, the camshaft will determine an engine's character. The engine's character in terms of power |
production is often termed the "powerband." Where does the engine begin to make power? Where does the engine begin to fall off in power production? Is the power delivery flat and consistent or aggressive and peaky? These questions are answered in the description and understanding of the engine's powerband. Some powerbands are narrow, while other are deemed broad. Some are peaky, some are flat. An engine that makes appreciable power from only 6000 to 8000 rpm (a range of 2000 rpm) would be considered to have a narrow powerband. A comparable-sized engine that makes power from 3000 to 7000rpm (a range of 4000 rpm) might be considered to have a broad powerband. More so than any other internal components of the engine, the camshaft and its complimentary valvetrain components will establish the powerband of the engine.
The Ideal Cam
So how do you get the perfect cam? The cam that has tremendous low-end torque, a 10,000 rpm redline, an idle like mom's car and a powerband from idle to redline doesn't exist.
Fortunately, an aftermarket performance camshaft that optimizes the rest of your performance combination to provide the performance that you desire probably does exist. Dollar for dollar there is a good chance that aftermarket cam(s) may be the best performance investment that you make.
Lift, Lobes and Symmetry
For every action, there is always a reaction. From a performance standpoint, the faster a valve opens and reaches full-lift, the better. Why? Horsepower is directly related to how much air and fuel can be stuffed into the cylinder. Air and fuel can't get into the cylinder unless the valves are open. Camshafts that quickly open the valves are said to have an aggressive lobe profile. Unfortunately, the laws of physics govern the maximum amount of possible valve acceleration or "aggressiveness." If the camshaft profile tries to accelerate the valve too fast, excessive wear or valvetrain problems can occur. When returning a valve to |
