Split Lobe Separation Angles?

Here is another example. Yellow Rose, I included the valve events here just for you.

Smooth Idle (1200-5000 rpm range)

Intake Exhaust
Valve Lash .008 .012
Valve Lift . 440
Duration @ .050" 230
Lobe Center 102 / 118


Intake Opens 13BTDC
Intake Closes 37 ABDC
Exhaust Opens 45BBDC
Exhaust Closes 5 ATDC


It seems like they're using Lobe Centers, not LSA. IT also seems like this cam has advance cut into it.

On this cam for example.

The Exhaust lifter reaches the centerline of the exhaust lobe 118 crank degrees before TDC.
The Intake lifter reaches the centerline of the intake lobe 102 crank degrees after TDC.

Using Yellow Roses math, you can add them together to figure out that the distance from Exhaust centerline to Intake centerline is 220 crank degrees. The cam spins half the speed of the crank, 220 crank degrees is 110 cam degrees.

That makes the cam's LSA 110 cam degrees.



Damn good math in this post. And it's correct. Now, for giggles, move either the intake or exhaust CL and see what it does. So start the intake sooner (wider LSA) or open the exhaust later (wider LSA) even though the duration stays the same.


You can play with that for a while and you can learn a lot. Every move changes the overlap triangle and that's what you want to watch when it comes to LSA, while considering low lift port flow characteristics.