Not So Happy MPG Talk

[acdii]

There are many components to the AC system besides the Evaporator, Condenser, and Compressor. There is an accumulator, and some valving that regulates fluid flow, since you only want to compress gas, not liquid, compressing liquid is a bad thing in AC.

 

The regulator will pass the gas but not the liquid R134a. So when demand is low, the volume of gas to compress is also low, so less draw is required on the compressor. When there is a high demand on the system the transfer of heat to the coolant turns it into gas, so the more heat it pulls out, by the fan forcing it past the coils at a high rate, the quicker it turns into gas, so the higher volume of gas the compressor has to pump, the more current is needed to pump it.

 

On a standard AC compressor bolted to an ICE, you dont notice the load as much, as the compressor will cycle on and off as the pressures rise and fall in the system. If you lisen to the AC in the FFH, the compressor is on constant, I have not heard it cycling when the cabin is at a constant temp, so it can only suggest that it varies pressures, as needed and doesn't cycle like the conventional one.

[corncobs]

Just based on the 2 kW draw for the AC between full blast and 5 min later with the first heat wave out off the car it drops down the 1kW. This tells me that the electrical AC is variable in the power consumption and only runs as hard as necessary to keep the cabin comfortable.

 

I knew acdii would have a much more technical explaination and he was faster than me.

Edited June 22, 2013 by corncobs

[milleron]

acdii and corncobs, both. Thanks for the explanation. This makes sense. I have a little reluctance to employ apparently-unusual methods until I understand enough to be pretty sure that what I'm doing is logical.

This methodology could really help, I think.

[kuzzi]

Got the car back from service and tint. Apparently the AC was set on MAX and they let it go while they worked on it. It cut off a good 50 miles from my tank, dropped my lifetime MPGs by 0.7.

 

The History screen showed 0 mpg for at least 30 minutes, with the AC on MAX. This was going to be my first tank above 40 mpg, but I'm still breaking it and myself in.

 

But it looks damn good, worth it.

[djminfll]

What I have been doing since the weather has heated up for summer is to use the "remote down" on the windows before getting in the car. Even having them open for 30-60 seconds before getting in lets a lot of heat and humidity escape from the interior. Once I start the car, I leave the windows down for just a few blocks. By the time I roll them up, the A/C is usually running on automatic at between 72 and 75 degrees. A minute or two later, I turn the fan down to Low. If the interior gets too warm, I turn the temp down a degree rather than turning the fan up. My current tankful is at just about 45mpg. I am hoping to bump it up over 45 tomorrow, as I'm taking a route that has a speed limit of 45mph and almost consistently green lights.

[lolder]

The AC compressor is a variable speed high voltage unit.

[fusionTX]

Well, the load on an AC compressor would never change would it? I don't think it requires any more or less work to recompress the evaporated refrigerant when it's trying to lower the temp from 85 to 80 than it does when working to lower it from 80 to 75. The fan may operate at different speeds in those two phases, but I'm working on the assumption that by far the biggest fraction of the electricity usage is by the compressor, not the fan. It's my belief that energy usage by the compressor is uniform as long as it's running.

HOWEVER, I'm no AC engineer, and that's why I'm asking if that belief is valid. In hot, humid midwest summers, the AC is going to be a major hindrance to fuel economy, so I'm really interested in knowing just how it works. I don't want to be committing any sins of commission or omission.

 

You should be able to monitor the A/C load by monitoring the climate in MyView. That's the surest way to tell.

[kuzzi]

Yup, tinting dropped tank to 34mpg. Oh well, car looks Sexy now.

[aaronj1159]

Yup, tinting dropped tank to 34mpg. Oh well, car looks Sexy now.

Speaking from experience with a Bordeaux and tinting... I agree. It adds a lot to the look and helps keep the heat down a little.

[neod192]

Speaking from experience with a Bordeaux and tinting... I agree. It adds a lot to the look and helps keep the heat down a little.

Tinting should help MPGs, not drop them. My guess is that Kuzzi's shop kept the engine running while they tinted the car? Why else would tinting "dropped tank to 34mpg"?

[kuzzi]

Tinting should help MPGs, not drop them. My guess is that Kuzzi's shop kept the engine running while they tinted the car? Why else would tinting "dropped tank to 34mpg"?

Yeah, sorry, I mentioned that in post 29. http://fordfusionhybridforum.com/topic/6715-not-so-happy-mpg-talk/page-2?do=findComment&comment=58891

 

aaron was just agreeing that tint on the BR makes it a Sexy McSex Machine.

[terryb]

It's a good thing my hair is 3/8" long or I'd have pulled it all out by now. 1.5 mile trip to grocery was 23mpg outbound, 124mpg return. Low humidity and temp in 70s didn't require A/C. Just mandatory HVB charge after EV+ and heat up of pollution controls. Long term is still showing 37.

[corncobs]

It's a good thing my hair is 3/8" long or I'd have pulled it all out by now. 1.5 mile trip to grocery was 23mpg outbound, 124mpg return. Low humidity and temp in 70s didn't require A/C. Just mandatory HVB charge after EV+ and heat up of pollution controls. Long term is still showing 37.

I wouldn't call this necessarily unhappy MPG I had a very similar round trip yesterday. 28.1 outbound 115 inbound @ 1.3 miles that's still an average of 45 MPG yours should in the same neiborhood.

Edited July 4, 2013 by corncobs

[HenryVIII]

Ugh I must've had some kind of aberration in my last fill up or my fill up from before. I did way more highway miles yet my fill up was at 24.7 mpg. Weird because my trip meter stated 27 mpg. It was an entire gallon off! Oh well road trip and better gas this time around. Should see more accurate results this time. Especially since I'm into the "broken in/ more accurate mileage" mileage.

[Rupert]

I wouldn't call this necessarily unhappy MPG I had a very similar round trip yesterday. 28.1 outbound 115 inbound @ 1.3 miles that's still an average of 45 MPG yours should in the same neiborhood.

This happens quite frequently with a short trip after the car has been off for a while. MPG is low on the first trip but the subsequent trips are really good. It all evens out :)