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. . .The AFR is pretty irrelevant to what I meant for this discussion.
The AFR is going to stay between 12(this depends on how much power per lb your engine is allowed to output) up to 15-16(if you have lean burn its the latter, former for the rest of us).
The most fuel you can possibly burn in your cylinder is about 1 gram of fuel for 14 grams of air. If you go below 14:1 you don't get more power from the fuel(you get cylinder quenching which keeps the charge from expanding while its in the intake and compression which gives you more power).
Example that this truck is displaying. I shut the throttle valve completely no air gets in. MAP(MAF not sure off the top of my head which it uses) reads I still have 2K rpm worth of air(ish, it fluctuatues with flow patterns in the engine bay) and it dumps that much fuel. I have 0 power. Power is a function of fuel and air and its limited 14.7:1(ignoring lean burn possibilities). for example at 3K rpm I have 300 grams of air the engine wants to burn 20 grams of fuel. If I close the throttle to idle I have about 50 grams of air now, so the most fuel that I can possibly get power from is 3.4 grams of fuel. Even if the engine still tries to dump the other 16.6 grams in I get no extra power than I Would have from just 3.4 grams(realistically with cylinder and piston quenching you might get what you would from burning 5 grams of gasoline total).
If the map sensor reads that I am intaking 5000 RPM worth of air but the throttle is at idle. . .the engine rpms will be at idle.
The test as I stated earlier is just going to be shut off from 3K rpm and watch the throttle body. If it takes a while to wind down and its not due to momentum(would have to be a really heavy crank and flywheel) the throttle body will not snap to idle position. It might jerk down some but i can promise you its slowly actuating towards idle from whatever throttle position it takes to spin 3K rpm freewheel.
It probably is a method for softening shift jerk, but if its really important for your hardware to survive just teach your drivers to double clutch. Its really not that hard.
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