More theoretical tech questions.
Why is a cams intake center line usually around 102 to 112?
I'm asking the theory behind this, not how to degree a cam.
From what I have noticed, this sets the maximum valve lift when the piston is about 72-73% down the cylinder bore (varies by rod ratio.)
Usually changing duration, just changes the open/close points equally on each side, but centerline remains fairly constant
Because that's the area that works the best. 112 ICL is stretching it IMO. Even comp cams recommends around 4* advanced from their normal 110 LSA cams. Meaning 106* ICL
The tech reason why, is the piston reaches max speed between 72* to 78* ATDC where peak air demand occurs, depending on rod ratio.
Be nice to have the Full lift ICL there. But cant do that, because we need duration too. Cant lift the intake valves that soon and get them up to max lift. Hence it occurs Later then the desired Max piston speed event.
We also have to deal with overlap and we also want that event occurring around TDC to take advantage of the exhaust pulse pull cycle event thats very important.
So Everythings a compromise of things tested over many years. We get to enjoy the fruits of labor and testing of times past.
IMO, some of the newer cams don't have anything to offer except slightly faster ramps. The Centerlines and LSA have been figured out long ago.
