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FJR Motorcycle Forums
Technical & Mechanical Problems
Valve Theory 101
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<blockquote data-quote="bem136" data-source="post: 1329103" data-attributes="member: 4383"><p>Just a comment on the higher lift, it is my understanding that on modern bikes that a higher valve lift by itself will not really improve performance with the exception that you are changing the valve open and close times. Any higher lift of the valve does not guarantee more flow through the valve port as the flow is not a linear function and increases very little at or near full lift. Rather a quicker rise of a valve would have a much more significant effect on performance as it opens the area for initial airflow sooner within the cycle. I understand that is the advantage in having two smaller valves rather than one valve with the same total flow capacity, the rate at which flow area opens on initial lift, in addition to weight and spring size advantages of course. I would guess there may also be some advantages to the smaller valves in reducing free radicals in the combustion chambers and intake mixture distribution.</p></blockquote><p></p>
[QUOTE="bem136, post: 1329103, member: 4383"] Just a comment on the higher lift, it is my understanding that on modern bikes that a higher valve lift by itself will not really improve performance with the exception that you are changing the valve open and close times. Any higher lift of the valve does not guarantee more flow through the valve port as the flow is not a linear function and increases very little at or near full lift. Rather a quicker rise of a valve would have a much more significant effect on performance as it opens the area for initial airflow sooner within the cycle. I understand that is the advantage in having two smaller valves rather than one valve with the same total flow capacity, the rate at which flow area opens on initial lift, in addition to weight and spring size advantages of course. I would guess there may also be some advantages to the smaller valves in reducing free radicals in the combustion chambers and intake mixture distribution. [/QUOTE]
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FJR Motorcycle Forums
Technical & Mechanical Problems
Valve Theory 101
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