i dont get it

[Katebell1977]

ok so i have watched the myth busters on discovery channel because i love watching them blow stuff up and such.


anyway, they did a test where they had two cars both the same with the same equipment . They ran them on a track at the same time one with the ac on and one with the ac off. Both got the same gas mileage.


So why does using the ac effect the prius? i live in sunny southern california where it gets hot a lot. haha i rhymed. anyway, in my suv i have not noticed a difference with or without the ac. So is the prius special or something? just curious. my husband is a mechanic and says its a fallacy that a/c effects mpg.

So now i told him like i did when i got my bmw in03 that this car is different. ok so someone explain it please. TIA

kate

[efusco]

At highway speed with windows down the reduced aerodynamics pretty well makes things equal when using AC. The test they didn't do was a vehicle with windows UP and no A/C.

But yea, use the A/C when it's hot, just be conservative...run it at around 78F if you can for improved FE.

[rwhoyle]

<div class='quotetop'>QUOTE(KateBell1977 @ Oct 14 2007, 10:28 AM) [snapback]525432[/snapback]</div>

ok so i have watched the myth busters on discovery channel because i love watching them blow stuff up and such.
anyway, they did a test where they had two cars both the same with the same equipment . They ran them on a track at the same time one with the ac on and one with the ac off. Both got the same gas mileage.
So why does using the ac effect the prius? i live in sunny southern california where it gets hot a lot. haha i rhymed. anyway, in my suv i have not noticed a difference with or without the ac. So is the prius special or something? just curious. my husband is a mechanic and says its a fallacy that gas effects mpg.

So now i told him like i did when i got my bmw in03 that this car is different. ok so someone explain it please. TIA

kate
[/b]

Kate,

The Prius a/c is powered off of batteries and has nothing to do with the ICE. A conventional car ICE has a belt drive that powers the a/c compressor and thus, draws power from the engine with the additional a/c compressor load. The addition of the a/c load requires more fuel to be used by the ICE to power all of the load demands. By running the a/c in the Prii, you reduce the amount of electrical power stored in the batteries which requires the ICE to run more to kept the charge level at design parameters. Thus, you use more gas recharging the batteries than you would if the a/c was not running.

Now for your second question, the term "gas" covers a lot of fuels. Normally, running regular or premium gas will not effect MPG to any great extent (except for pinging, knocking, etc.) Where your husband is wrong is with ethanol containing fuels. Fuels containing 10%, 15%, etc., ethanol have less BTU contentper unit volume than straight gasoline fuels. In laymans terms, less energy per unit volume because of the ethanol addition (It is displacing 10%, 15% of the gasoline volume which has a higher BTU content). Because of the lower BTU content per unit volume of ethanol blended fuels, it takes more of the fuel to provide the same amount of energy to the ICE. With more fuel consumption because of the lower BTU content fuel, your MPG suffers. Esample, a car getting 20 MPG with regular gasoline will only get around 18 to 18.5 MPG with an ethanol blend.

Hope this short explanation helps.

[Katebell1977]

i have no clue why i typed gas affecting mpg i meant a/c


i am not awake yet

i meant he said the fallacy is a/c affecting the mpg

when i run my ac i dont have it on full blast despite the kids yelling im hot! when its not really hot. i dont let the kids roll the windows down because it makes this noise that hurts my ears its weird every car i have had does it from my honda my mom drives to the two beemers i had to the suv to my pri it makes that darn noise. But i will figure out how to do that fan thing they talk about in the gas saving tips pinned topic.

[prius2go]

I reckon the A/C knocks 3mpg off the mpg on the consumption MFD
All I needhere in the UK is the system letting in some cold air and me directing where it goes
I havent worked out how to do that with A/C on or off
The opening windows are a useful feature

[brick]

<div class='quotetop'>QUOTE(KateBell1977 @ Oct 14 2007, 12:26 PM) [snapback]525450[/snapback]</div>

i dont let the kids roll the windows down because it makes this noise that hurts my ears its weird every car i have had does it from my honda my mom drives to the two beemers i had to the suv to my pri it makes that darn noise. But i will figure out how to do that fan thing they talk about in the gas saving tips pinned topic.
[/b]

If you roll down just a rear window in a four-door car it sets up an oscillation...just like blowing over the top of a soda bottle but at a much lower frequency. Sounds kinda like a helicopter. Is that it? If so, the solution is to roll down a front window to kill it.

[IsrAmeriPrius]

As efficient as the Prius is, it is not a perpetual motion machine. The energy to run the air conditioning compressor has to come from somewhere and the somewhere is gasoline. Thus, using it impacts the car's fuel economy. According to this government website, operating the air conditioner can reduce MPG by up to 5 to 25% compared with not using it. My hunch is that the more powerful and less economical the car, the less its mileage is affected by using the air conditioning system.

[prius2go]

If I can work out where to put it , I might put a switch in the aircon pump, so that I can still use the heater system but without the load of the pump

[IsrAmeriPrius]

<div class='quotetop'>QUOTE(prius2go @ Oct 14 2007, 02:39 PM) [snapback]525529[/snapback]</div>

If I can work out where to put it , I might put a switch in the aircon pump, so that I can still use the heater system but without the load of the pump [/b]

You can turn off the air conditioning compressor by touching the A/C button on the MFD. The yellow bar will go out to signify that the compressor is off.

[prius2go]

I think I lose temperature control as well when I hit the A/C button
or am I mistaken?