Fuelly Forums - A/C Usage and Impact on FE

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Quote:

Originally Posted by JoeBob (Post 151331)

Well, it looks like the Geo will probably get its A/C back this year. Since my wife has decided to ride with me in the little car, and summer is coming, she is voting for fixing the A/C. (When I bought the car, the condenser was trashed, and the compressor was missing.) I voted against fixing it, so it looks like we'll have to compromise...I'll have to fix it.

If you do fix it, try a hydrocarbon refrigerant..seriously. https://www.duracool.com/

Yes, I recently went from 40 MPG on my VX combined to 34 MPG on my last 'estimated' trip. No scan gauge. This was my first use of A/C for a long period this year.

Also, my first summer with this car. It is a '92 with a small engine, and without a crazy engineering breakthrough, aka lots of money, to completely overhaul the way the blower and a/c compressor affect the power consumption in whatever way possible...its going to be a hassle during summer months.

Quote:

Originally Posted by bowtieguy (Post 151288)

i'm w/ ya fully. this is just a notation. in the summer, i generally do not run the a/c in the morning to work(still dark), but on the way home, i always run it(90*F+ often w/ heat index in the 100s).

Well, at some point your discomfort will affect your ability to implement FE driving techniques as well in a fatigued state(i.e. hot car)

Quote:

Originally Posted by add|ct (Post 152029)

Well, at some point your discomfort will affect your ability to implement FE driving techniques as well in a fatigued state(i.e. hot car)

typically it is comfortable enough to just run the fan in the am, even perhaps cracking open a window. with the heat of the afternoon, and subsequent quicker warm-up, my FE is generally very near the am run, even w/ a/c on.

Quote:

Originally Posted by bowtieguy (Post 152030)

Yes, it was quite surprising how much my last two fill ups varied based on how I used the a/c. Of course, it took me realizing the drop in FE by 5 MPG. :eek: :D

I typically have been able to get another 40 miles than where I was when I filled up again. My VX has a 10 gallon tank(?) and I've been putting in 5 gal/stop to get an accurate idea of how much gas I'm using. Typically, for every 5 gallons I could reach 200 miles solid until the A/C had to come on. After that I got barely over 160 before needing to fill up. You can't always rule out a tank of bad gas either. Now I'm at 120 with 2 1/2 gallons left.

I don't want to run the tank bone dry every time; as contaminants tend to settle to the bottom of said tanks, but since I just got the car I need to know what it can do now compared to the work being put into the car. Long overdue, but educational. Of course, with 240k ish miles, it will need SeaFoam and Lucas in the tank from time to time anyway. I'd rather burn out whats in there as far as those additives before replacing the LAF sensor that's shot...but all of that is another story.

Quote:

Originally Posted by JoeBob (Post 151331)

$150 new compressor plus shipping... ;)

Since the lines are probably open...you'll want to flush everything out really well... :D

Back in the day, when I had a car with that fancy AC thing, I had a long down hill drive. I did my best to only turn the A/C on when I was likely in DFCO mode. And on the way back up the hill, I made due with open windows. After turning it off, I would still get a good min. of cool air. I would have liked a more direct way of turning the compressor on and off. With the button on the dash, it seems like it takes a second or two to react. With a toggle switch connecting directly to the clutch pulley, one could flip it on every time you where slowing down, and off at a stop or accelerating. (just leave the fan on)

Currently my car's biggest problem is the passenger window isn't working 80% of the time. My girlfriend is not too happy about this, with the lack of AC and all. It seems like a loose wire in the switch, so that will be easy, then I should focus on those really crappy brakes, and that vibration it makes over 60mph (maybe a loose tie rod?).

don't know where you're from, but a/c is considered a necessity, not luxury, in florida. it's been near 100*F, w/ heat index WELL into the 100s lately. btw, if your brakes are really that crappy, i'd def get them fixed first!

I know my outer tie rods/boots are going to need replacing. I still need front brakes myself, though, rotors turned etc. I've got some old tires on the front from when I bought the car used, but they still have good tread and can hold up to 44 PSI. I'll grind them into the ground and save for a new set of 4 by the time I get the outer rods/boots finished. That way the alignment is done with the new tires on and all is well again.

Back to the original thread info: Last fill up with more efficient use of A/C was back over 40 MPG easily. Probably could have gone another 10 miles at least.

Lately my VW has felt really sluggish with the A/C on, more so than having 3 passengers in it. I don't recall it being like that in the previous two summers. It is over 37,000 miles and manufacturer's schedule for spark plug replacement is 40,000 miles, so maybe that's related.

Of course, with it sluggish I'm forced to shift at higher RPM and it definitely affects my FE.