Terrence,
LOP starts when the mixture is LOP of course!
Sorry, for the smart ass response. There are a number of good article on engine management and LOP operation written by John Deakin on “Pelican’s Perch” on avweb.
There is also an excellent course on engine management given by the GAMI folks called “Advanced Pilot Seminars” - http://www.advancedpilot.com/ I took it and learned a lot.
The short answer to your question is that you want to be approximately 50 deg LOP in most situations and it is best if all your cylinders are LOP to the same degree.
Doug Brunner
N241DB
Jeff,
May I ask for a little more detail on when the LOP condition starts? Do all EGTs have to be LOPP, or is it when just the leanest one goes? And, how lean constitutes enough to be considered LOP?