A/C Usage and Impact on FE

[theholycow]

Originally Posted by Jay2TheRescue

I keep my vehicles for a very long time, and I get my money's worth out of them.

That strategy is the best for people who buy new vehicles. It's fine for used buyers, but used buyers also have the option of selling sooner.

[Dr. Jerryrigger]

I really like that you can get a car for $1000 and it's value doesn't change, as long as it keeps running. Your never going to beat that with a new car (with the exception of a few collectible cars that you can't drive). Even if you junk a $1000 car every 6 months, you'll still spend less than payments and insurance on a new car.

wait... what was this thread about anyway?

[theholycow]

Originally Posted by theholycow

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.

Ok, I figured it out. When the A/C is on, it's really hot out. I generally don't use A/C until it's very hot. I really enjoy open windows.

So today it was really hot, I had the A/C on, and I was in city stop & go traffic. Come to think of it, I was in quite a bit of traffic the last time I used A/C and noticed it being really sluggish. Today it was awful, there was no power at all under 2000rpm. Usually I don't get above 2000rpm (until I run out of gears). I was driving around at 3000-4000rpm trying to avoid holding up traffic. Launching was tough!

IAT was 182 and coolant temperature was up to 243. I think the grille blocking combined with traffic, hot weather, and A/C are to blame. I think:
- high IAT reduced my power
- A/C leeched plenty of power
- A/C further heated the intake air and the air around the radiator
- overheating caused the computer to pull timing and reduce power

It wasn't just A/C, but rather a bunch of things that were severely exacerbated by A/C, almost in a feedback loop.

I think it's worse this year because I don't think I ran 100% grille blocking in previous summers.

[Dr. Jerryrigger]

Originally Posted by theholycow

Ok, I figured it out. When the A/C is on, it's really hot out. I generally don't use A/C until it's very hot. I really enjoy open windows.

So today it was really hot, I had the A/C on, and I was in city stop & go traffic. Come to think of it, I was in quite a bit of traffic the last time I used A/C and noticed it being really sluggish. Today it was awful, there was no power at all under 2000rpm. Usually I don't get above 2000rpm (until I run out of gears). I was driving around at 3000-4000rpm trying to avoid holding up traffic. Launching was tough!

IAT was 182 and coolant temperature was up to 243. I think the grille blocking combined with traffic, hot weather, and A/C are to blame. I think:
- high IAT reduced my power
- A/C leeched plenty of power
- A/C further heated the intake air and the air around the radiator
- overheating caused the computer to pull timing and reduce power

It wasn't just A/C, but rather a bunch of things that were severely exacerbated by A/C, almost in a feedback loop.

I think it's worse this year because I don't think I ran 100% grille blocking in previous summers.

Have you tried flipping the A/C on and off, off when accelerating, on when cursing or slowing. It would give you back the power the compressor is robbing, but wouldn't help with the other thing going on.

Careful you don't burn out your cooling fan with that grill block. I would guess it's running non stop, unless you disconnected it.
I use a 85% radiator block, but only in months I'm using heat. It makes me nervous to see that needle clime above where it normally sits, and listening to that fan blast away doing almost nothing.
Also that fan is using electricity it's getting from the alternator, which is getting it's power from my gas tank. I'd like to try and tweak my thermostat so that it runs a little hotter, without the ICU trying to cool things down.

[theholycow]

Originally Posted by Dr. Jerryrigger

Have you tried flipping the A/C on and off, off when accelerating, on when cursing or slowing.

LOL!

Anyway, the car automatically disables A/C at WOT, so now that you mention it the power loss was actually not including A/C.

Careful you don't burn out your cooling fan with that grill block. I would guess it's running non stop, unless you disconnected it.

It was still running when I parked the car and shut it off.

Also that fan is using electricity it's getting from the alternator, which is getting it's power from my gas tank.

It was definitely NOT efficient.

[Dr. Jerryrigger]

Originally Posted by theholycow

It was still running when I parked the car and shut it off.

Ha ha ha, only in a German car.

[Jay2TheRescue]

I don't know about current models, but small 80's model Fords did that as well.

[i-DSi]

Originally Posted by Dr. Jerryrigger

Ha ha ha, only in a German car.

Watch out what your laughing with. Japanese cars start the cooling fan up even under these circumstances:
- automatic AC on
- Ignition switch on, engine off (!!)
- Engine + radiators stone cold

About AC: I definitely feel it when my AC switches on and off when driving at steady speed. I can't tell the exact difference but it influences my consumption as my fuel consumption doesn't seem to change between summer and winter. So I guess that the better FE I should get in summer is lost by my AC. What contributes to this: my engine is small and its power is low. What makes that AC is responsible for a big percentage of fuel consumption in summer.
You can see this in my gasslog: very steady, from September last year till now.

[theholycow]

Most modern cars come with a warning sticker under the hood saying that the electric fan can start and run when the car is off. I don't think it's limited to German cars.

[add|ct]

I'm hoping my AC won't be as much of a 'drag'; no pun intended, now that my new drive belts are on. No more squealing pulley! Though, it may have been belt slippage all along. Still, the car feels much smoother now w/ AC on, especially when under engine load.