All About Camshafts

2 min read

Learn a little more about engine camshafts and how they affect your car’s performance.

The camshaft is an important part of your car’s engine.

As it rotates, it uses lobes or cams to actively regulate the opening and closing of the intake and exhaust valves. This motion in turn manages the amount of air/fuel mixture that powers the engine.

If you think of the engine as being your lungs, the camshaft would be the key to determining the amount and timing of air you inhale and exhale. The speed and efficiency with which this happens helps to optimise your body’s potential to run faster or swim further. So for your car, the camshafts work and function to help boost horsepower and engine performance by optimising the amount and speed of airflow.
Modern cars employ a camshaft position (CMP) sensor that monitors the camshaft positioning and performance. It uses this information to regulate the operation of the fuel injectors, which affects fuel economy, emission control, and engine efficiency. In the event that the sensors fail, the engine-warning symbol will be triggered, signalling that it’s time to take a trip to the workshop.

The difference between SOHC and DOHC
Apart from the function of the camshafts, how they are arranged also affects a car’s performance.

Car manufacturers develop various camshaft arrangements to determine the type and profile of their cars. Some of the more common valve train configurations are the single overhead cam (SOHC) and the double overhead cam (DOHC).

SOHC means the engine has one cam per head while DOHC has two. This simply means that the DOHC has double the inlet and exhaust valves of an SOHC, which makes for a cooler engine with equal distribution of operations. This in turn leads to more power and a smoother, more effective drive. An SOHC may lack the power of a DOHC, but it is more fuel-efficient and has a better low-end torque because the engine is lighter.

Depending on the market or demand, similar car models may offer DOHC and SOHC engine variations. Examples include the made in Thailand Honda Vezel versus the made in Japan Honda HRV, identical in looks but sporting an SOHC and a DOHC engine respectively.