i dont get it

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

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.

 

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

 

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

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.

 

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.

 

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

 

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

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.

 

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

 

<div class='quotetop'>QUOTE(prius2go @ Oct 15 2007, 01:01 AM) [snapback]525558[/snapback]</div>

if you hit ac on the wheel yes you loose temperature control, that's why you have to hit ac on the mfd to simply shut down the cooling function but not the others...

 

<div class='quotetop'>QUOTE(prius2go @ Oct 14 2007, 04:01 PM) [snapback]525558[/snapback]</div>

You will only lose the ability to chill incoming air. You will still be able to set the temperature and the climate control system will continue to heat cold outside air, as needed.

 

<div class='quotetop'>QUOTE(Sliderule @ Oct 15 2007, 01:38 AM) [snapback]525444[/snapback]</div>

I think the increased consumption using E10 fuel (that is petrol with 10% ethanol in it) is over stated.
If petrol has 100% of the energy of petrol (kinda obvious)
and ethanol has 70% of the energy of petrol roughly
then petrol with 10% ethanol will have a 30% x 10% less energy or 3% less energy per gallon not 20% less.
The higher octane will mean the vehicle wont ping as easily therefore the knock sensor is less likely to retard the timing optomising the engine for the fuel so it may be better than 97% to the wheels.

My personal experience with my Camry was no loss at all. I run my Prius on E10 only.

AC with windows up is cheaper than hearing aids and easier to live with. Ask my dad, an ex truck driver if you don't believe me. I turn the fan up to half without AC but if it's still to hot I hit the auto AC button and set temp at 25C. Windows only get wound down at very low speeds.
My 2c

 

<div class='quotetop'>QUOTE(patsparks @ Oct 14 2007, 07:43 PM) [snapback]525609[/snapback]</div>

I have the same response here, Pat. In order for a 20 MPG car to have a drop to 18 to 18.5 MPG due to ethanol blending (based only on the drop in BTUs), it seems to me the ethanol BTU factor would have to be 30% that of the straight gasoline. In that case, E10 would bring 18.6 MPG and E15 would drop to 17.9 MPG.

Of course, there could be other factors, but that seems to be the straight math. Use of E10 (assuming a 70% BTU equivalency) should result in a very small drop from 20.0 MPG to 19.4 MPG.

 

My guess on the MB tests where the A/C car lasted longer was experiment variability. I don't think they did multiple rounds to get a good average and low standard deviation. They probably just did it once.

In a case like that, there could have been variables they didn't account for - humidity, external temperature (both will change the aerodynamic drag on a car). I didn't see the episode, so I odn't know if someone was driving it - they could have driven it differently each time. Was it a car witha big engine? If so, the a/c effect would have been negligible compared to a car with a small engine (like a 1.5 L Prius or equivalent).

 

<div class='quotetop'>QUOTE(KateBell1977 @ Oct 14 2007, 09:28 AM) [snapback]525432[/snapback]</div>

Comparing AC on a Prius and a different car is like comparing apples and oranges.

AC in a Prius and a different car get their power from different places (OK.... ultimately from the ICE).

A Prius has a display showing mpg. Most people go driving around happily ignorant of their mpg.

A Prius is such an efficient vehicle the slightest change can produce a visible mpg effect, and you can be aware of it. Even having your kid in the back seat might produce a visible effect.

Spend 15 minutes with the AC on in a Wendy's drivethrough when it's 100 degrees... You will see the impact on your traction battery and on your mpg when you leave on 100% ice.

 

The Mythbusters revisited that item in a later episode, where they clarified that there's a crossover speed where A/C becomes more efficient than windows down. At the test track, due to the curves they had to keep the speed to 45mph, where the windows down was more efficient. Above that speed, however, the drag makes the A/C more efficient.