How do overhead camshafts work

A camshaft is a relatively basic component — a simple length of rod, or shaft, with shaped lobes positioned along it, these have been christened ' cam lobes '. When the shaft is rotated, the shape of the cam allows it to act upon a valve or switch to a degree matching the severity of its shape - with the speed of rotation controlling the rate of action. In a modern internal combustion engine they are typically, but not necessarily, positioned directly above the cylinder banks where they act to control the valves.

Their calibration precisely controls the amount of air-fuel mixture that enters the chamber, and how efficiently the spent exhaust gases from the previous ignition can exit the chamber making way for the next charge. This makes them not only critical to the operation of an engine, but because the opening and closing of the valves must be carefully and perfectly synchronised with the movements of pistons, they also have a drastic effect on performance.

To ensure this timing, the camshafts are connected via a timing belt or chain to the turning of the crankshaft - which is directly moving the pistons inside the cylinder. Moreover, the shape of the cams themselves is also carefully crafted to control the speed at which the valves open and close.

This is better known as variable valve timing. The basic action of a cam. There can be a varying number of camshafts in an engine, depending on its cylinder arrangement and valve operation. Because you need at least one camshaft per cylinder bank, inline engines need as few as a single camshaft, whereas a V arrangement would require at least two. Some engines use double overhead camshafts DOHC , so would have as many as four across two banks of cylinders.

The use of an additional shaft per bank provides numerous advantages over a single overhead camshaft design SOHC despite the additional weight and cost. With a W16 to keep in shape, the Veyron employs a quad-cam setup with a total of 64 lobes. Crankshafts are generally made from steel and sit below the cylinders and pistons in the engine block.

Their job is to convert the vertical movement of the pistons into a rotation to be transferred through to the flywheel and then the transmission. The rotation of the crankshaft is then transferred through to the flywheel which sits at the end of the shaft to balance it in case of irregular engine pulses and to complete the torque conversion from the internal combustion occurring in the cylinders.

This is the big reason why the V8 engine took over from an engine configuration like an in-line eight, due to its relatively small and controllable crankshaft setup that stops any unwanted flexing occurring. They essentially start and end the engine cycle - from inlet stroke to exhaust stroke - keeping the different mechanical processes of each cycle in perfect harmony through their belted connection.

Please confirm you agree to the use of tracking cookies as outlined in the Cookies Policy. Sign in or register. Michael Fernie 5 years ago. This type of engine can particularly increase your vehicle's engine power at high speeds. What are dual overhead camshafts? A dual overhead camshaft is an engine that features two camshafts per bank of the cylinder head.

One camshaft is for the intake valves and the other is for the exhaust valves. How does a camshaft work? Camshafts push against valves, which opens the valves. The camshafts rotate while this happens, and this in turn affects engine performance and speed. Why is dual overhead cam better? Dual overhead cams can be better if you're looking for increased performance and high speeds. The unique designed of a DOHC engine can result in both of these benefits.

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