This is for those: without the vacuum secondary throttle or with it in full open position (disabled), and who have their cruise AFRs leaned out for best smooth runing engine mileage.

(1) Using the Commander, measure VTA1 for when the mechanical secondary throttle just starts to open.
(2) While cruising around 55mph and viewing the same screen, slowly increase your speed until VTA1 equals the value from step1.
(3) remember this speed
(4) if you ever noticed that once in a while driving near this speed and at some undetermined throttle position, your engine leaned bucked a little; now you know why. The slight leaning out of AFRs is due to the sudden change in air flow through the ports at light throttle.

The secondary ports will start to flow air long before fuel is directly injected into their air flows.
This is another good reason to reduce the Pri/Sen Inj transistion % down from the fake 40% (about 47% logged) to
at lease a fake 30% (about 37% logged).

 

as always, you impress me with some great info.