Has anyone noticed a drop in the HVAC's fan strength after they grill blocked? I noticed this recently after I had did the lower block, although I could not remember if it was just as weak before applying the block. On the one bar setting for the fan speed, the breeze was barely noticeable. In my previous cars, especially on the highway, I have always noticed an increase in the breeze from the vents as it does correlate to the car's speed, but not lately(after the block). I remember that the air source from the HVAC comes from the bottom of most cars from changing out air filters in the past. I did not do a back-to-back before and after comparison as I had already used up my last zip ties for the foam wrap for the block, but will once the weather starts getting warm again. What I did do was remove about a 2" segment on the sides of the foam just to let a little more horizontal airflow pass through the lower grill, but did not notice much of an improvement. If anyone has any foreknowledge of this beforehand that would be greatly appreciated.
No way. That could potentially introduce engine odors and emissions. I've never seen what you describe on any car and seriously doubt it was ever used on any car.
True for modern cars, but ... Heater intakes in the engine compartment were fairly common about 80 to 90 years ago. I think they were usually after market heaters and often used heat from the exhaust manifold For later examples, air cooled VW's used the exhaust manifolds for heat and the engine cooling fan to move the air into the passenger compartment. Corvairs used air that had been blown over the engine.
Then why is it that I am not noticing an increase in the air force from the vents when transitioning from local streets to the highway(i.e. when there is a significant increase in the car's speed)? In my previous car, I've always had to dial down the fan speed from two bars to one once I am on the highway, and even then, the air flow was still quite strong. On the Prius, the one bar setting provides very sluggish flow. At two bars, it is just barely adequate, even on the highway. Again, this is just something I just noticed recently, after the grill block. It could just be that the Prius HVAC fan is on the weaker side.
There is some increase but not to much. My guess is the high pressure at the base of the wind shield on the Prius may be less than in most other cars because of the aerodynamics. More of the air probably slips up the windshield and over the top without building up at the base of the windshield.
