I know when you have the AC on it sucks power but I thought that having the vent on it wouldn't....It seems on the IROC when I have the vent on (just had windows tinted...2 more days b4 I can roll windows down) it doesn't seem to have as much pep as it does when the vent is off. Am I tripping or is this a possiblity?

 

The AC drops power because it takes a lot of energy to run the compressor. Since the compressor does not run on the heat or vent functions, there should be no noticable loss of power. Defrost causes the compressor to run, however, so there would be power loss with it.

 

The electrical load from leaving the fan on full blast has been known to cost a repeatable fraction of a mph in the 1/4.

<---used to have a car w/o electric fans, running the heat in staging is free alternative, forget and leave heat on, and where did that 0.5mph go.

edit, but no, you wouldn't really feel that power loss, just pointing out that there is no such thing as a free lunch

 

Unless your car is messed up, you are tripping. I believe the vent to pull say 80 watts(maybe more maybe less, not sure). That is .1 HP. The alternator must produce this power thus robbing it from the front of the engine. If the alt has and efficiency of 80% that means this will rob .134 HP. Doubt you feel that. Now if you decided to run your blower fan all the time and your car has .5 BSFC assuming that the average density of gasoline is .8 grams per ml then it would take .067 pounds pounds of gasoline per hour you run it. That would take 100 hours of driving to need one gallon of gas from your blower motor. Take into account I used averages but I believe my calculations to be somewhat secure. Think about that next time you buy a car with daytime running lamps (assuming similar load to the blower fan) You will have to drive aprox. 3000 miles use one gallon extra.

 

Thanks guys. I was just going to leave the blower motor out of it and go for the main thing. I shoulda known better!

 

I thought you guys would appreciate this more.