the reason there's such a variance is because each engine combustion characteristics is different, no two are exactly alike, but also far more to the point the EGT gauge is akin to building a new house with a 3 foot piece of conduit as your only measuring device.
the egt probe only tells you a small amount of data, the temp of the exhaust. primarily this data, accumulated OVER TIME, tells you when your going to hurt exhaust valves or turbines/manifolds, preventative maint schedule (replace valves after 6 runs, etc), etc....
your using it as a diagnostic tool to prevent failure. since a 1/2mile run at 1300* can be just as harmfull to the engine components as 9 seconds at 1600+.
far more important is onygen content, aka wideband. this provides relevant, true data concerning how well the engine is burning the fuel injected. lean is mean and all but without you seeing the engine at 13to1 afr under boost for a few seconds, and take note what the EGT gauge next to it does....your not gonna find out much, and even then youll find variables.
idealy youd have a wb and egt on each primary or baring that using a single WB/egt gauge and just use and switch through 6 egt probes in the primary's under 12-24 identical dyno pulls and use that to skew the injectors for the leaner cylinders...since with that large of a data grouping youd have good data to at least marginally fix the variance in cyl to cyl fueling/airflow.
where the hell did you read about 4 being lean? 4 is almost never lean, it is however always loaded with oil due to poor oil windage control which promotes detonation, so yeah its more detonation prone on the high acceleration cars.
lean cylinders dep on the build, SC cars without IC tend to run leanest on 1&2 as the blower discharge angle is 30* and directly at em. with an IC this is spread out but even then the majority of the airflow through the core is through the area directly below the outlet, dep on which side of the dual pass core is the inlet one bank will always receive more of the warmer air and tend to be a bit richer than the cooler air. the restriction of the core at least dows help in uniformly distributing the air to the plenum, its just unevenly cooled.
then you get the turbo uppers for l67 lowers these always run leaner opposite the TB, as does the L36's with the runners removed. even the F body that our TR uses. our cyl 5&6 are way leaner than 1&2 and marginally so than 3&4. wanna know how i tune for it without an egt probe and a single wideband?
i read the plugs, thats it, one high load run, shutoff, pull plugs, adjust skew, note wb changes, rerun.
the reality is its not the gauges, its noting and documenting a long period of data that get your tune perfect....how do you know whats abnormal without seeing whats normal.
besides its why im making a custom mailbox for the top of our F body, fix the airflow disparity and the cylinders fire at even power which means the engine parts last longer....yay fer science
