can someone describe what vtec lower engagement unengagement and vtec upper engagement and unengagement means?
I see this option in Ktuner. i have done research but still do not understand.
lower i believe is lowest point vtec can come on but then unengagement is what gets me. same with upper? i thought vtec only comes ON at certain rpm point ie 4700 on my J37

 

VTEC switch over is a window. Light load might be 5000 and heavy load might be 4000. Would need dyno time to figure out where the crossover should be for best power at each load.

There is also a window for deactivation as well for the same reasons. Typically VTEC will stay active to a lower RPM on deceleration with the intent you will be right back in the throttle.

Look at the stock tune values to get a sense of what is happening.