Steve,

I've started doing the same thing. Turn off the A/C to accelerate and turn it back on when I reach speed. I also will turn it off when I'm trying to get a little extra out of EV mode. Of course I just leave it on when my wife's in the car. She already thinks I've gone crazy.

 

That's really the only down side to the HCH-1. When I'm running the AC, the fuel economy truely suffers. But when it's 100 degrees (thanks to global warming), I have to keep it blasting!

 

Given the TCH compressor is a 3 phase electric motor which runs off the batteries, I don't know if manual cycling is going to help. I could be wrong, but since there's no physical connection between the ICE and the compressor, the only harm that would come from hard acceleration and leaving the AC on is a more rapid depletion of battery level.

 

I understand what you're saying. I've shut off the A/C when the battery was close to fully charged while going a constant speed on the highway and the mpg went down by 3 - 5 mpg. I'm guessing that since the charge has to be replenished more power is being provided from the ICE for that reason.

 

Regarding turning the A/C off while under load, and back on while not under load, has anyone looked at whether or not this significantly increases wear and tear on the compressor, potentially shortening its lifetime? Replacing A/C compressors is very expensive...

 

They are designed to be turned on and off.

Bob Wilson

 

Touche'. But just because something different comes along does not necessarily mean it is better. It's all a matter of perspective. Washing machines are more convenient, yes. But they also use energy and pollute. And who has verified that convenience is the path to happiness, self fulfillment, or any other sought after state of mind? And btw, my wife (and I) hang out the laundry whenever we get a chance. And we do often wash things by hand if it means not having to fire up the washer. We just like to tread lightly on the earth when we can.

And there are several threads in the GH forum that discuss windows open vs. windows closed in relation to speed of the automobile. The general concensus is that windows open at highway speeds may be worse for FE than AC. But at around 45 mph and below, you're better off FE-wise with the windows open. Since I'm almost always driving in the city, I opt for open when needed. Yes, it is less comfortable than running the AC. That doesn't bother me a bit.

 

I think anything which disturbs airflow over an object traveling through the atmosphere will affect its efficiency. The PII (Prius II), just looking at its lines you know that it is designed to slip through the atmosphere with everything buttoned up (or down). For heaven's sake, the designers are even concerned about trim.

So, at speed, I'd keep the windows up. The slower you're moving, perhaps the less important (or maybe, more important) the window up/down is important.

What to do with AC (air conditioner), or on the '06, its climate control? Turn it off, turn it on, going up hill, down dale? Can you say for sure that, lets say on a drive of 1000 miles or more, that that will have a real impact on FE?

What I've noticed about hills/mountains is that no two are the same, either in the angle of their grade or their length - straight up, or switchbacks. Wind blowing down, or up, or across. At 70 years of age (my wife being somewhat younger), comfort rules the day, or the miles.

This past July we returned from Vancouver, Canada to Long Beach, Ca. via IS 5 which runs down the California Central Valley. The temp was 100+. The climate control kept us comfy, and the mpg ran somewhere around 45-47 mpg/tank.

Hypermiling is great fun - but I want to do it in comfort.

Listen, if I want the best mileage, I can ride a bike 100+ miles. Talk about the feel of the wind through ones hair. . .

centrider

 

I would tend not to roll the window down at highway speed not because of efficiency, but because it lets in a very high level of road noise. When coasting downhill however, even at 75+ mph, cracking the windows open generates FAR less resistance than running the AC compressor. Lowering the windows enough to generate circulation (a couple inches) makes no noticable difference on terminal speed (speed at which car will rolls down a grade without assistance), yet turning on the AC compressor load slows the vehicle significantly, by several MPH. This suggests that AC load far outweights a marginal increase in drag from having the windows down, even at very high speeds.

Rolling the windows down is limited though in that it can't reduce humidity, and it can't cool air below ambient temp (usually eliminating the solar heating beyond ambient temp is sufficient for me, whether I do so with AC or windows down). In terms of circulating air though it is potentially better.

There are several situations, especially at around 50mph (best speed for window-circulation I've found), where I actually prefer running the windows down to AC -- there are two methods I use: one involves cracking both the rear windows, and turning on the circulation fans. The fast-moving air will help suck the air out of the vehicle, which will be replaced by cooler incoming air. All the incoming air will pass through the air-filter this way as well. Another alternative involves both running AC directed at the feet, and having the left and right rear windows cracked to circulate the hotter air above.

The other method is to open the left-front window, and the right-rear window. This creates a strong current across the drivers' seat -- stronger than can be produced by the circulation fans. I would bet that generating the airflow this way (producing extra drag) is actually more efficient than using larger elecrtic fans to accomplish the same thing would be, anyway, as automotive electrical systems tend to be very inefficient.

 

2006 HCH not included but comparable to prius or 2005 HCH most likely.