Double-Overhead
Cam (DOHC)
A
double-overhead cam (DOHC) engine is an engine which features
two camshafts located above the combustion chambers in the cylinder heads. Compared to pushrod systems with the same number of valves the reciprocating components of the OHC system are
fewer and have a lower total mass. Though the system that
drives the overhead cams may be more complex, most engine
designers accept the added complexity in trade for better
engine performance and greater design flexibility. Another
performance advantage of an overhead cam engine is the superior
port configurations made possible with overhead camshaft designs.
Compared to push-rod overhead valve (OHV) engines, which use
an arrangement by which the camshaft is located in the engine
block and opens the valves via long push rods and rocker arms,
it eliminates the need for both of these components. With
fewer moving parts, there is less inertia. So, an overhead
cam engine can run at a higher speed and produce more power
than a comparably sized pushrod engine.
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