Lobe Separation Angle or Lobe Centerline Angle (LSA/LCA)
Lobe separation angle is just a generic label used to provide a general idea of how several different cam timing events are working together. The two components these terms intend to represent are overlap and intake/exhaust centerlines, but other implications include all cam events. As a result, LSA is probably the most confusing element of camshaft timing. When someone says to “tighten up the lobe centerline angle”, they could be referring to increasing the overlap, advancing the intake lobe, retarding the exhaust lobe, or any combination. Each action carries unique characteristics and should be looked at individually, and as a whole.
Even when you have a good understanding of the basics, several things can make lobe separation angle difficult to understand. Two cams with identical LSA, durations, lift and opening/closing points can run very different because differences in ramp acceleration rates can change the area under the overlap curve. The timing points may be the same but the overlap triangle will look completely different. It’s very similar with duration. Two cams can have the same LSA but have different degrees of overlap because they differ in duration. A 240* cam will have a lot more overlap with a 112* LSA than a 200* cam on the same 112* LSA.
Lobe Separation Angle can be used to give a general comparison between similar cams in the same family but it is also important to look at all the critical timing factors to get a true picture of a camshafts capabilities.
We’ve covered each of the cam events so now it’s time to look at some practical application.