a/c driving techniques

First off don't set it at 73 I run mine at 82, makes a huge difference. The big thing is to do everything you can to minimize how long the AC is blowing on high. Park in the shade whenever possible, crack the windows if safe, and as soon as you get in the car drop the windows and switch to non-recirculating air until its at least as cool inside the car as outside. Once the AC has throttled back into the low region, you should be able to drive the car much as before. While the AC is blowing hard I make extra effort to avoid hard acceleration (the extra load on the system makes it want to jump to less efficient higher rpms sooner), and avoid situations where the ICE may shutoff. The AC will run the battery down pretty quick, and then the ICE will have to charge it back up. If I have to do any gliding, coasting, or stopping while in the initial cool down period I often temporarily raise the auto temp or just shut the AC compressor off. Doing these things, I've been able to get back into the low 50s in the summer in Phoenix (~110F) although invariably the family ends up sitting in the car with AC on and takes it back down to mid 40s

Rob

 

Here is the best technique. Put the setting on the first or second fan speed setting with A/C off for the first 5 minute segment on your MFD and open all 4 windows. I have learned that the car warms up the engine at narrow RPM speed when warming up therefore during the first 5 minutes even though the engine may be running the car is favoring getting its propulsion from the battery when you turn on the A/C it runs the battery down further pushing the engine to immediately charge. After the first 5 minutes roll up the windows and set to Auto I like 75 myself.

By the way in the winter this method works well for the heater as well but with windows closed and entire climate control OFF for the first 5 minutes.

 

+1 on what miscrms said. If high MPGs matter, you have to minimize
use of the A/C for cooling.

I have been out side on some late spring/autumn nights and the air temp so
exactly matches my body temp, or at least my perception of feeling neither
hot nor cold, that the air itself seems to disappear. For me when I am at
rest, this occurs at ~78 degrees. So, my default A/C setting in the summer
is 78 deg, non-auto, fan on the 2nd or 3rd lowest setting, or the outside
temp if it is lower. After that, its using all the minimizing tricks posted
earlier.

But if temps go way up, say the mid/upper 90s -- as is forecast for Ballamer
later this week -- the car may be absorbing/admitting heat so fast that
inside temps go above 78 since I'm not using Auto.

What to do? You gotta make a choice, more A/C and less MPGs, or less
comfort. If I'm driving solo, I opt for less comfort. When driving with my
partner, I bite the low-MPG bullet, and turn up the fan a notch or two. If I'm
still hearing low growls from the pax seat, l relent and go to auto. Kiss the
MPGs goodbye!

As a friend of mine said yesterday, "In physics, [In our case it would be the
subdiscipline of thermodynamics.] there is no such thing as a free lunch."

 

My comfortable temp is 78 deg F. I let the interior cool down a bit and then close both of the passenger side vents. I point only the two driver's side vent on me. Recirculating also increases the air flow.

 

I drive a big L on my commutes, drop my wife off and pick her up about halfway to my work. In the afternoon on the way home a technique I've started using is to have the car cool when I pick her up, or else she gets in and cranks it down to 70 and then my mpg sucks. I leave work with windows open for first 7 minutes, then close up and put AC on 80 or 82 depending on how hot it is outside. When I pick her up 8 minutes later, the car is comfortable and she doesn't start punching buttons on the AC. At 80 or 82, your mpg is not affected nearly as much too, especially if you don't p&g as much, 42 mph with ice running at high mpg is good because you're still getting juice into the battery to replenish what the compressor is using. With the AC set that high you need to be mindful of clouds though... if you get in a shadow, due to the solar sensor your AC will cut out or maybe even blow a little heat

 

When coasting downhill, I crank up the fan speed and lower the temperature to take advantage of the 'free' energy.

 

I am going through my first summer with my Prius and here in Tel Aviv that means at means 92F (34C) most days . And my mileage suffered.

The A/C and driving with lights on during the day caused this. I had been setting my AC to between 68-72 (20-22) and sometimes suffering in the cold. By changing the setting to 77 (25), and giving the inside of the car a chance to cool off with the fan only I have seen a dramatic improvement.

I save my lights for nighttime driving when it is cooler.

The screen shows the battery usually staying at about 70-80% charge instead of 30-40%. This approach allows for more battery not gas driving and faster recharges when the battery level dips.

And I am trying far harder to monitor distances very carefully during highway driving to minimize rapid deceleration and acceleration.

 

I initially run my AC set at 75 with recirculating air. Once the system has the chance to stabilize after a few minutes, I turn it to Auto AC with the blower at a medium setting. I learned in this forum that by increasing the setpoint temp. with the AC on Auto, I can control the blower instead of it blowing on Max. I drive my Prius just as I would normally drive it without AC on.

So far, I still get 53 to 55 mpg travelling to and from work and doing errands. As long as I schedule my stops with the AC on, it does not seem to affect my mpg as much.

 

When you are in your auto alone, this has worked well for me.

Point the dash vents on your body. It will allow you to run a much higher temp on a/c than you normally would need to keep the entire cabin at said temp.

... Brad

 

When it gets into the 90's and beyond, not only are YOU more uncomfortable, battery temp management becomes more & more of an issue. DON't think your MPG's will stay high, if you run no AC at 100 degrees, because your battery efficiency goes down if you let 'em run that hot. And if it's 90 outside, your car will be maybe 10 degrees hotter with the windows up ... even if you're running the fan full blast ... because our black dash soaks up heat like a microwave. That means you're simply pumping hot air back through the battery cooling system.
So it's a trade off. You need cool, for battery management on hot days, but AC WILL drop your MPG's. To split the baby, what I like to do is cycle the AC manually ... maybe let the compressor run for 30 seconds, then switch back to vent only, for a minute or so. That way, the batteries are obtaining their dose of 'cool' (me too), but you save a bit on the MPG's. One last observation, our Prius MPG's seem to be the least affected by AC if we're driving a nice constant speed (whether 50 or 60 or whatever) fwiw.

 

And turn off the AC compressor a few minutes before you arrive.