Poor gas mileage in 100F weather

[jackalopetx]

For what it is worth... solar car fan

 

Or this dual fan model! 

 

Solar powered fans are too weak to do anything. I've used a 10x2" solar panel to power a 40mm fan and it created about as much airflow as a turtle's breath.

 

To help with cooling when parked I'm going to try mounting two 80mm fans to the battery vents and powering them from the rear cigarette lighter port. I'm hoping they'll be able to create through-flow from the cracked windows, exhausting through the battery enclosure. Not sure if that will work because low amperage fans don't generate much pressure. 

 

I may also try mounting them close to the right rear window so that with the window cracked they pull in outside air

Edited July 27, 2017 by jackalopetx

[raadsel]

Consumer Reports did a video on how to cool your car quicker:

 

Of course, the part about the car's engine turning off doesn't apply to our hybrids, with their electronic A/C.

[joshg678]

I would say turning off EV+ may help with your MPG in the afternoon but lower it in the morning.

 

Also an Energi would have been the better choice for your commute but I'm sure someone said that already

Edited July 27, 2017 by joshg678

[SnowStorm]

This morning I turned the AC fan down to 2 notches, and it was 78F so only 1 degree higher than my AC setting-- Got 42mpg. I was running the AC fan at max or a couple notches below max, and I think the blower draws a lot of power

Here's a topic where I measured a bunch of stuff including the fan.  220 watts at full speed - not insignificant.

[plus 3 golfer]

This morning I turned the AC fan down to 2 notches, and it was 78F so only 1 degree higher than my AC setting-- Got 42mpg. I was running the AC fan at max or a couple notches below max, and I think the blower draws a lot of power

But your compressor is hardly working with the ambient at 78F.  About the only thing the compressor is doing is likely reducing the humidity of the air since the set point is only 1F lower than ambient.

 

I hate to beat a dead horse but the energy content of air is significantly higher at 100F than 78F.  Second, you do not have to remove very much energy content of the 78F ambient incoming air and the likely higher temperature of the cabin air and cabin surfaces to a comfortable level (say a drop to 72F).  But there is a significant amount of work that has to be done to get 100F ambient air and the likely higher cabin temp. (which if out in the sun could be 120F)  down to 72F cabin temperature.  IMO, your 4 mile trip is the issue not your fan setting which is just a small part of the equation. 

 

You need to understand the energy content in air (enthalpy) to understand how much work is really required to reduce the cabin temperature to a comfortable level.  It's a lot more than most think it is.  Excluding humidity of the air, about 5 times as much energy must be removed from 100F dry air than 78F dry air to get to 72F. To get to only 77F instead of 72F, it's a very high number.  You also need to cool the cabin air and surface areas of the cabin which are likely higher than the ambient temperature and factor in humidity.  This is why AC is such a big hit on short trips. It takes a lot of energy to get the cabin down to a comfortable level initially.

 

Using the tips in the video that raadsel posted will help to initially cool the cabin.

Edited July 28, 2017 by Plus 3 Golfer

[jestevens]

100F is rare for my area of the country, but when it did happen for a few days in a row I started looking for shade or parking garages.. Let the building soak up the heat instead of your car?

[obob]

But your compressor is hardly working with the ambient at 78F.  About the only thing the compressor is doing is likely reducing the humidity of the air since the set point is only 1F lower than ambient.

 

I hate to beat a dead horse but the energy content of air is significantly higher at 100F than 78F.  Second, you do not have to remove very much energy content of the 78F ambient incoming air and the likely higher temperature of the cabin air and cabin surfaces to a comfortable level (say a drop to 72F).  But there is a significant amount of work that has to be done to get 100F ambient air and the likely higher cabin temp. (which if out in the sun could be 120F)  down to 72F cabin temperature.  IMO, your 4 mile trip is the issue not your fan setting which is just a small part of the equation. 

 

You need to understand the energy content in air (enthalpy) to understand how much work is really required to reduce the cabin temperature to a comfortable level.  It's a lot more than most think it is.  Excluding humidity of the air, about 5 times as much energy must be removed from 100F dry air than 78F dry air to get to 72F. To get to only 77F instead of 72F, it's a very high number.  You also need to cool the cabin air and surface areas of the cabin which are likely higher than the ambient temperature and factor in humidity.  This is why AC is such a big hit on short trips. It takes a lot of energy to get the cabin down to a comfortable level initially.

 

Using the tips in the video that raadsel posted will help to initially cool the cabin.

 

This helps me understand the value of driving with the windows open at first when the cabin is very hot.  A huge volume of air relative to what the air conditioner puts out that is lower in temp than the cabin air and the cabin surfaces for the initial cool down.

 

I remember in the older cars using the vents windows (in older cars) so that they divert air directly into the car to really get the air moving, ( often used to compensate for not having air conditioning.)

Edited July 29, 2017 by obob

[jackalopetx]

But your compressor is hardly working with the ambient at 78F.  About the only thing the compressor is doing is likely reducing the humidity of the air since the set point is only 1F lower than ambient.

 

I hate to beat a dead horse but the energy content of air is significantly higher at 100F than 78F.  Second, you do not have to remove very much energy content of the 78F ambient incoming air and the likely higher temperature of the cabin air and cabin surfaces to a comfortable level (say a drop to 72F).  But there is a significant amount of work that has to be done to get 100F ambient air and the likely higher cabin temp. (which if out in the sun could be 120F)  down to 72F cabin temperature.  IMO, your 4 mile trip is the issue not your fan setting which is just a small part of the equation. 

 

You need to understand the energy content in air (enthalpy) to understand how much work is really required to reduce the cabin temperature to a comfortable level.  It's a lot more than most think it is.  Excluding humidity of the air, about 5 times as much energy must be removed from 100F dry air than 78F dry air to get to 72F. To get to only 77F instead of 72F, it's a very high number.  You also need to cool the cabin air and surface areas of the cabin which are likely higher than the ambient temperature and factor in humidity.  This is why AC is such a big hit on short trips. It takes a lot of energy to get the cabin down to a comfortable level initially.

 

Using the tips in the video that raadsel posted will help to initially cool the cabin.

 

Yep I guess it makes sense. If I drive around for a few hours I get in the high 30s, because after the first few miles the car is already cooled down. But if the fan is on max, that drops down to the mid 20s. It seems like the high fan speed causes the AC to work harder, and possibly keeps the engine fan running 

[jackalopetx]

Here's a topic where I measured a bunch of stuff including the fan.  220 watts at full speed - not insignificant.

 

I have a ScanGuage II, can I program it to show that data? I can't find any DC power listed here https://www.scangauge.com/x-gauge-commands/ford-lincoln-mercury/

Edited July 30, 2017 by jackalopetx

[plus 3 golfer]

I have a ScanGuage II, can I program it to show that data? I can't find any DC power listed here https://www.scangauge.com/x-gauge-commands/ford-lincoln-mercury/

Get yourself the ForScan App and an ELM327.  

 

BTW, I just measured the DC/DC LV amps and agree with SnowStorm on the Watts at high blower speed (around 220 W).  

 

Second, the coolant fan runs at variable speeds.  "The PCM monitors certain parameters (such as engine coolant temperature, vehicle speed, A/C on/off status, A/C pressure) to determine engine cooling fan needs."   Slow speed driving and AC on is likely a fairly bad condition relative to required airflow through the condenser resulting in the coolant fan on at a higher draw (higher speed).

 

If you set the HVAC to auto, the algorithms will likely efficiently cut compresser, blower, and coolant fan demand as the AC requirements diminish.  Appropirate AC pressure of the refrigerant circuit is easier to maintain as the cabin cools.  Bottom line again is that running the AC on short trips kills FE.  

 

One last point: for likely less than 15 cents a day in additional gas on your two 4 mile commutes each day you run your AC, you can stay "cool".   Staying "cool" for me is worth it. ;)  :)

[jestevens]

Yes, I think the variable speed electric compressor on C-MAX (and Prius) is awesome, I have a friend who paid a lot more for a Mercedes with a stop/start engine but of course when the engine is "off" the AC compressor isn't powered..

Edited July 31, 2017 by jestevens

[ptjones]

I have a ScanGuage II, can I program it to show that data? I can't find any DC power listed here https://www.scangauge.com/x-gauge-commands/ford-lincoln-mercury/

ScanGuange can be programmed to show any value that the ECM/OBDII puts out and their is a thread on this forum for inputting the values. :) I would recommend you look at my 3 YouTube videos How to drive a CMAX Hybrid to get Great Gas Mileage on this Forum. :)

 

Paul

[BIG ROCCO]

It's been a really hot Summer in Phoenix..especially June and early July.  While our '15 does not have a lifetime MPG like our '13 did, we have never reset the MPG, so maybe that means it is a lifetime average (not sure if the earliest data drops off at some point);  it was at 45MPG before the Summer, we are now at 44.7MPG at about 15K miles total.  I think the AC use is the culprit, but the important thing is it works very, very well, even when it's 115 or 120 degrees out.