Thread: Cam duration

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i just wanted to shine some light on *Lobe Separation Angle* (LSA)

You have the intake opening @ .050" and the intake close @ .050". Together these items make duration @ .050" and the intake center (IC).

You have the exhaust opening @ .050" and the exhaust close @ .050". Together these items make duration @ .050" and the exhaust center (EC).
Anyone how grinds camshafts goes about it from this avenue. They may look at different aspects of the engine in the designing phase by looking at velocity, pressures, cylinder pressure, etc, but in the simplest of terms, this is how it starts.

Basic math here.
The (IntakeCenter) + the (ExhCenter)/(2) = LSA
the average of the centers is the LSA. When you speak of camshafts in terms of LSA, When a person says LSA, what is he really saying?
Example.
I design a camshaft and I feel as though the events at .050" need to be:
IO = 15
IC = 55
EO = 66
EC = 14
Now put these together. The in @ .050" = 250* and the ex @ .050" = 260*. These events make the IC = 110 and the EC = 116. Thus.......
110 + 116 = 226.......226/2 = 113 LSA
In the above example, those EXACT opening & closing events yield the specs above. Period. Now when a guy comes along and says that a 113 LSA is a NOS cam, a motor cam should have tighter LSA (or more common going from motor to NOS) that ALL you need to do is change the LSA, you cannot just magically change the LSA. Its impossible.

Backwards. 116 + 110 = 226/2 = 113 EVERYTIME. But if I come at it and say I want a 113 LSA, how many different combinations of numbers can you have and get to 113? infinate amount... remember that all events of a cam happen in 180* cycles. with the ivo,ivc,evo,evc numbers you can tell the cam spec's other then lift. the other thing to consider is lifter acceleration rate. thats how fast the valve is opening.