fuel fuel injection cut off when engine brakes the car

[THE NEW GUY]

Originally Posted by oab_au

I am sure it does the fuel cut off all the time, even in N.
It is to prevent the fuel on the walls of the manifold from vaporising under the vacuum conditions, and causing it to go rich as soon as the throttle is opened.

Harvey.

yes, ecu does FI cutoff when in Neutral, when you press the gas untill certain rpm and release it suddenly. you can see how revs goes down fast until 1250rpm.
about the rich mix as soon as you pres the throttle, the ecu fuel mapping consider enriching the mix only when necesary by controlling the injector on time.
I believe that by pass valve is not completely closed when engine brake except when in cruise control... that would explain why engine brake power is greater under cruise control... this would means that, actually, our ecu does FI cutoff but bypass valve controls the amount of air getting into combustion chambers. Maybe that is why car industry does not use this kind of bypass valves anymore, they replaced it by stepper motors (syncronized cero magnetic slip, fast, precise and huge torque)