I know everyone make the pe a straight line across the board, i'm just wondering why GM does not. Been searching the net but i'm not finding much. On my ZR1 it looks like mountains until GM flat line it at 5500 and up. They obviously have a reason and was wondering if anyone knows it.
Emissions and likely for cylinder temps.
My guess is that when they create these engines and calibrations in a dyno cell they figure out what they have to do to keep emission in check, spark knock at a minimum and cylinder temps within a specific range. Figure they run 8 or more lambda sensors and EGT sensors on a engine like this to figure out what's best for them.
Of course the aftermarket will change these parameters to gain extra power while not caring so much about what an engineer has to care for.
2016 Silverado CCSB 5.3/6L80e, not as slow but still heavy.
If you don't post your tune and logs when you have questions you aren't helping yourself.
it's really before 4250, past that rpm the fuel ramps up smoothly to then flat line from 5500 and up. It leans out at 3500 to then richen up by 4000, to then lean a little right at 4250. I wonder if it has anything to do with the ecm going full MAF right around that rpm, and thus before it they are using PE to get the fuel where they need it to be, effectively raping the table... which kinda made me grin since it's considered a bad thing to do but ok for gm to do... and those engine tuning engineers are probably at a while diff level of expertease than 99% of us including "pro tuners".
I doubt it is for emissions per se: i.e., most engines will never hit PE during the standard EPA emissions test. However, the PE is probably adjusted at each RPM to maintain the catalytic converter temperature within a certain range for cat longevity. If the cat were to overheat, it might fail before the federally mandated 50K mile emissions warranty period.
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