There is no basis to believe that the emissions are increased.
Restricting the cold air flow across the radiator/engine does nothing
different than what a hot day with no restriction does.
What really changes is the average air temperature under the hood,
and possibly a miniscule air pressure change. The Prius is designed to operate properly on a 110 degree day with no flow restriction which will have even higher average engine compartment temperatures than a 45 degree day with the restriction of the tape.
The THS design is capable of handling very large variabilities in the ambient environment - hot air, cold air, moist air, dry air, high altitude,
low altitude, variations in gasoline, air-condition on, air-condition off, cold engine, warm engine, etc. Throughout these variations it maintains low emissions. I am doing nothing that will fool any sensors - the heat transfer due to air flow is a very strong function of velocity (think wind), humidity and air density. If the heat transfer is critical (it isn't, component temperature is) then the prius needs to measure each of these components. I have created an effect which is extremely similar to having a very specific wind speed and direction.
Further the tape should only be present over a restricted set of environmental possibilities: NO air conditioning use, No high ambient temperatures.
There is no downer here.
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