Idle Tuning (spark igntion timing )

[Gelf VXR]

I started a new thread although I have posted in another as this is not really related to EGT&CHT tuning.

https://forum.efilive.com/showthread...nd-EGT-and-CHT


So I had set about seeing the effects on EGT by advancing idle spark, however I became more interested in how far I was able to advance timing, conventional wisdom on forums say advance timing until to lowest MAP is observed, retard back a few degrees to allow for idle spark corrections.


I was able to advance timing from 10* to 50* and observe MAP decreasing from average 50kPa to 41kPa, plotting a trend line suggested MAP would level out at 55*.

Fuel consumption at stock 13* is calculated at around 3 litres per hour, reducing to around 2.1 litres at 50*. Air flow reduced proportionally from around 9g/sec to 6g/sec.


I've never seen anyone suggest such high idle timing, in another article which kind of prompted me to do this analysis http://www.carprogrammer.com/Z28/PCM...k%20tuning.htm MAP was observed to drop to 45kPa and rise again at around 34* timing, I have a similar cam 216/229 with .610" lift in an LS2 with LS3 heads.

Has anyone else increased and logged their idle timing, what were the results?