What is Lobe Separation Angle (LSA) and how is it used in camshaft design?
How is it measured?
What difference does a long or short LSA make?
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1 Answer
Lobe separation angle is affects overlap between the intake and exhaust valves which can effect emissions, performance and efficiency.
Example of Lobe Separation Angle
Measurement of Lobe Separation Angle Measurement would be done with a degree wheel on the crank and dial indicator on the cam.
The measurement occurs between the MAXIMUM lift of the intake and exhaust valves.
Thoughts
Lobe separation angles effects valve overlap is an essential attribute of cams being used for various applications.
For instance, you may have very little valve overlap or an increased lobe separation angle for a reduced emissions vehicle whereas a decreased lobe separation angle may be used for a higher performance, higher RPM engine in racing where emissions from too much valve overlap are not a consideration.
Increased lobe separation angles will leave the intake valve hanging open a bit as the exhaust valve opens creating a situation where the intake charge flushes out the combustion chamber of spent exhaust gasses for a better intake charge free of CO and CO2. This will increase hydrocarbon releases as some of the intake charge will escape into the exhaust.
Additional Images
Degree Wheel
Dial Indicator
answered Jan 4, 2016 at 22:30
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@paulster2 I edited the question and geared it more toward the LSA than VO. Have a look and let me know if this works. Jan 6, 2016 at 17:50