A/C On then Off

[bfg9000d]

On my car I have the ability to turn the compressor off so that it no longer compresses and blows cold air. The air stays cool for about a few more minutes due things being residually cooled down. Of course the minute I turn the compressor off I feel a slight power boost. So my main question is. How much FE would you gain if you kept cycling your A/C Compressor on and off when needed. Of course the best thing is not to run A/C at all but when it gets up to 103 to 113 thats just not and option.

[varg]

Well, if the compressor decreases your FE by 10% (which is the usual estimate) and you run it for 50% of your drive, then you'd gain 5% over running it the whole time. Just tweak the numbers for how often you run it.

[1993CivicVX]

what's the "d" for BFG9000d? I always preferred the SSG or RL. (actually might play some Doom tonight) Anyway, I had the same question. Like anything when you turn it on, does it use extra energy to turn it on? So would it not be more efficient to leave it on rather than turning it on and then off and then on and off etc? I do this sometimes: I'll put the A/C on low, but as cold as possible--then I'll turn it off and put the blower on high. When it becomes too warm again, I put the A/C on low again on frigid and then after about 5 minutes turn it off and put the blower on high again. The idea is that I'm using the residual coolness and cycling it through a lot of air, but it doesn't last that long; only a minute or two. Is that more efficient than leaving it on low? I only have the blower on for about a minute or two before I put it back to low and turn the A/C on (for about 5 minutes). Maybe we could dub it the compress and blow method... then again, maybe not. I don't always do this, but I wonder if it actually saves any gas or maybe uses more?

[badgett]

Be careful not to ruin the clutch in the ac compressor. Those compressors are expensive. I just bought one a couple of weeks ago.

[sandalscout]

My old Mitsubishi Mirage had the coolest thing that I think I've ever seen that was A/C related, and I've wanted it on every car since. It actually had 2 levels of A/C, there was a push button. First click it went 1/2 way in, and a yellow LED lit up. In this mode it would actually cycle the A/C automatically, and I almost always used this mode. One more push to get a green LED and it was full tilt, and then one more push to turn A/C off.

[bfg9000d]

anybody with a scanguage figure this out.

I know I always get better gas mileage with it turn off. But I cant tolerate being in a car windows rolled up in 105 degree weather. I either run the A/C all the time or cycle it. The question being does it help to cycle it. As far as the clutch goes if anything you are saving the clutch more. Because normally the a/c compressor clutch turns on and off during system operation. By leaving it off for a minute or two and then turning compressor back on for a short time. You are reducing the amount of time the clutch turns on and off.

[DRW]

Originally Posted by sandalscout

My old Mitsubishi Mirage had the coolest thing that I think I've ever seen that was A/C related, and I've wanted it on every car since. It actually had 2 levels of A/C, there was a push button. First click it went 1/2 way in, and a yellow LED lit up. In this mode it would actually cycle the A/C automatically, and I almost always used this mode. One more push to get a green LED and it was full tilt, and then one more push to turn A/C off.

Hey my car has the same thing! My car is a Plymouth Laser, which is the same as a Mitsu Eclipse. My other car also has the same two step A/C. It's an Eagle Talon, which is the same as a Mitsu Eclipse. I can feel the AC cycle on and off when I'm holding steady throttle. I got in the habit of turning the AC on full blast when I was coasting to a stop. That way the energy from coasting in gear would drive the AC, not engine power.

[Bill in Houston]

Originally Posted by badgett

Be careful not to ruin the clutch in the ac compressor.

The compressor probably cycles on and off using that clutch already, so doing it manually would probably result in fewer cycles...

[bfg9000d]

Well my best guess is that you are saving more gas. The compressor cycles on and off anyways so start energy for it to turn on is minimal or not enough to effect FE. Plus keeping the compressor off for a short period of time and then cycle the compressor back on. That alone should save a fair amount of gas. Atleast some part of your trip you where riding with the compressor off. Which would result in a slight FE increase. I guess unless you got some really exotic compressor. Its the only way I see cooling the car down via the A/C as far as getting the most out of FE. The only other way would be to take a ice cooler fill it with water chill it so its one big block of ice. And plug a little fan in your car and have it blow on you. The big ice block should last a while. Although you would have to account for the extra wait in the car from the block of ice. So I dont know.

[sandalscout]

Originally Posted by DRW

Hey my car has the same thing! My car is a Plymouth Laser, which is the same as a Mitsu Eclipse. My other car also has the same two step A/C. It's an Eagle Talon, which is the same as a Mitsu Eclipse. I can feel the AC cycle on and off when I'm holding steady throttle. I got in the habit of turning the AC on full blast when I was coasting to a stop. That way the energy from coasting in gear would drive the AC, not engine power.

You know, I hadn't really thought about it, but my Galant VR-4 also had 2 stage A/C, as did the Laser parts car I owned. and of course, both of my Mirages did too. I'm just dissappointed that Hyundai didn't carry that over to their own cars after building off of Mitsus for so long.