you have got it right.
the reason behind this is:-
there is almost no vacuum before the throttle body (unless you have a very restrictive intake system) - answer for 2nd question.
there's no almost no above-atmosphere pressure inside the cabin, nor the aircond under normal circumstances (unless you close all the vents, at full blast) - answer for 3rd question.
So there's no pressure difference between the 2 ends of the small hose. No flow.
If there is a pressure difference (in the case if you close all the vents at full fan speed, and the small hose is connected to the aircond hose), then the air inside the aircond hoses will be forced into the engine intake hose.
But the amount?
At 3000 rpm (100kph in 5th gear), the engine is taking in about 68 cubic feet of air per minute. How much cold air is being supplied by the small hose from the aircond?
Would the amount be sufficient, even to drop the intake charge temperature by 5 deg C?
In addition, to take A % of the power (to run the aircond compressor) from the engine to generate B % of power (from the colder intake charge temp.), where A > B, at the same time sacrifying (wasting) the purpose of using the A % of power in the first place.... reasonable?
Back to the "suffocation" issue, the cabin is not air tight. Otherwise you won't feel the highland effect when you go up to genting, for example.
At the end, no one suffocate, maybe just sweat like a cow in the cabin. No net power gain.
Might as well just turn it off?
the reason behind this is:-
there is almost no vacuum before the throttle body (unless you have a very restrictive intake system) - answer for 2nd question.
there's no almost no above-atmosphere pressure inside the cabin, nor the aircond under normal circumstances (unless you close all the vents, at full blast) - answer for 3rd question.
So there's no pressure difference between the 2 ends of the small hose. No flow.
If there is a pressure difference (in the case if you close all the vents at full fan speed, and the small hose is connected to the aircond hose), then the air inside the aircond hoses will be forced into the engine intake hose.
But the amount?
At 3000 rpm (100kph in 5th gear), the engine is taking in about 68 cubic feet of air per minute. How much cold air is being supplied by the small hose from the aircond?
Would the amount be sufficient, even to drop the intake charge temperature by 5 deg C?
In addition, to take A % of the power (to run the aircond compressor) from the engine to generate B % of power (from the colder intake charge temp.), where A > B, at the same time sacrifying (wasting) the purpose of using the A % of power in the first place.... reasonable?
Back to the "suffocation" issue, the cabin is not air tight. Otherwise you won't feel the highland effect when you go up to genting, for example.
At the end, no one suffocate, maybe just sweat like a cow in the cabin. No net power gain.
Might as well just turn it off?
