The specifications on an engine camshaft provide detailed information about its design, dimensions, and performance characteristics. Engine Camshaft specifications are crucial for engine builders and tuners to select the right camshaft for their specific application.
What is an engine camshaft?
For a car engine to operate, all its components must perform their functions at very precise intervals in relation to the motion of the piston. To accomplish this, a component called a camshaft is used. A camshaft is a long bar with egg-shaped eccentric cm lobes, one lobe for each valve and fuel injector (if engine does not have a common rail fuel injection system). Each lobe has a follower. As the camshaft is rotated, the follower is forced up and down as it follows the profile of the cam lobe. The followers are connected to the engine’s valves and fuel injectors through various types of linkages called pushrods and rocker arms. The pushrods and rocker arms transfer the reciprocating motion generated by the camshaft lobes to the valves and injectors, opening and closing them as needed. After the valves have been forced open by the rocker arms, the valves are again closed by springs.
Here are the key specifications found on a camshaft:
Duration
Duration refers to the amount of time, measured in degrees of crankshaft rotation, that the camshaft keeps the intake or exhaust valve open during each cycle. It is typically specified as both the intake duration and the exhaust duration. Longer duration cams keep the valves open for a greater portion of the engine cycle, allowing more air and fuel mixture to enter the combustion chamber or exhaust gases to exit. This can increase power output but may affect idle quality and low-end torque.
Lift
Lift refers to how much the camshaft raises the valve off its seat during operation. It’s usually measured in inches or millimeters. Higher lift camshafts open the valves further, allowing more air and fuel mixture to enter the combustion chamber or exhaust gases to exit. This can increase power output but may require modifications to the engine’s valvetrain components to accommodate the increased lift.
Lobe Separation Angle (LSA)
The lobe separation angle is the angle in camshaft degrees between the maximum lift points of the intake and exhaust lobes. A wider LSA generally results in a smoother idle and broader powerband, while a narrower LSA can improve high-RPM performance at the expense of low-end torque and idle quality.
Overlap
Overlap is the number of degrees of crankshaft rotation during which both the intake and exhaust valves are open at the same time. This occurs at the end of the exhaust stroke and the beginning of the intake stroke. Overlap helps scavenge exhaust gases from the combustion chamber and can improve engine efficiency and performance. However, too much overlap can lead to poor idle quality and decreased low-end torque.
Ramp Rate
Ramp rates refer to how quickly the camshaft lobes lift and lower the valves. Faster ramp rates allow for more aggressive camshaft profiles and can increase valve lift and duration without sacrificing reliability. However, they may also increase wear and stress on valvetrain components.
Valve Timing
Valve timing refers to the precise relationship between the position of the camshaft and the position of the crankshaft. It determines when the intake and exhaust valves open and close relative to the piston’s position in the cylinder. Optimal valve timing is essential for maximizing engine performance, efficiency, and drivability.
Finally
Understanding these specifications allows engine builders and tuners to select the right car engine camshaft profile for their specific application, whether it is optimized for street performance, drag racing, or other motorsport disciplines. It is important to carefully consider factors such as engine displacement, compression ratio, cylinder head flow characteristics, and intended usage when selecting a camshaft for an engine build.
