Hotline s web cam
If increased duration is the only change, then the longer cam normally robs power from the bottom end of the rpm range and adds to the top.
In this feature we are going to deal with the gas dynamics, as precise valvetrain motion means nothing unless the valves are opened and closed at the appropriate moments.Because we repeatedly hear the same questions-and because it’s a subject many don’t really know, including amateur and professional engine builders alikewe felt a technically sound primer on one of the most often asked and least written about subjects would be a great help to many.The subject: camshaft lobe centerline angles, or LCAs.In reality a cam for maximum output for a given duration must have a good balance of opening at both ends of the induction stroke.If a valve is opened at a suitably early point, the intake port velocity tends, later in the induction stroke, to increase enough to offset any negative effects of a marginally earlier closing.Starting the valve motion sooner means more velocity and lift before the beginning of the induction stroke.
It is often argued that opening duration after BDC is more effective at producing power than opening before the induction stroke starts.
Increased valve flow area in the first half of the induction stroke has significant importance for many reasons.
The principal one is that a typical production-based 2-valve race engine inevitably lacks adequate valve area in relation to its displacement.
Generally speaking, the majority of cams fall between 98 and 120 degrees LCA.
Let’s hold cam advance in the motor constant and look what happens to valve events with LCA changes.
For the first and most important half of the induction stroke the intake valve is opened farther by a cam with a tight LCA than one with a wide LCA.