NOx and timing question (1 Viewer)

[Bruce Minney]

My 1994 FZJ80 failed CO emissions test on High NOx. My question: What is is the best timing setting for reduced NOx? If retarded - how much? I reset it to 3 degrees BTD center according to the manual and the NOx level increased a bit on my second test.

Part two of my question: My rig has no heat shields on the cat's could this result in lower cat temperatures causing higher NOx levels?

Part three of my question: What is the optimal ambient (outdoor) temperature for the Emissions test?

Any and all help would be appreciated as I am far from being an expert.