If you have a turbo with an automatic waste gate, which is the case Craig was addressing, the fuel/air ratio is NOT changing as you climb.   Also typically you don't have as much cooling available in climb as in cruise so you want less heat going to the cylinder walls.  This is aggravated by thinner air as you get higher.  Rich mixture = slower burn = lower intra cylinder pressures = less heat transfer to the cylinder walls.

On Oct 18, 2013, at 7:53 AM, Keith Smith wrote:

Question about climbing "full rich".  Would it not make sense to maintain sea-level EGT's through the climb, rather than truly full rich all the way up to 17K? As you climb higher, 'full rich' is a whole lot richer than the mixture you had during takeoff. This is something I learned through John Deakin's Pelican Perch articles a few years back when I first got the Lancair. I usually 're-lean' every 1000ft or so during my climbs to maintain around 1320 EGT.

Keith
LNC2 N360JH