Window "tint" saves fuel through reduced AC load (duh, but nice to see quantified)

[Super22LL]

It's funny that I should see this two days after I tinted the windows in my S10. I did it because of the heat here on the Mississippi coast. Using the AC on my truck drags my FE down about 2 MPG. Since I have tinted the windows I am able to turn the AC off at times and still have the truck cabin cool enough to be comfortable. I "pulse and glide" it as mentioned by one of the previous posters. My next mod will be to identify which wire supplies power to the AC compressor and install a toggle switch on it. S10's do not have an on/off switch for the AC and I would like to be able to run the AC on "max cool" recirc mode with the compressor off recircing the cool air .

[Seek]

To get the most from this WOULD require setting up an a/c switch to turn on/off as necessary and it is true that most cars just adjust the hvac doors inside the dash. Even with it on 100% of the time though, there is some misinformation in this thread. The a/c compressors cycle on and off based on refrigerant pressure. Heat exchange is what causes refrigerant to switch between gas and liquid states, low and high pressure. When less heat is transferring into the evaporator in the vehicle cabin (due to less cabin heat), the pressures do not change/rise as much on the low pressure line as in a warmer cabin. This in turn requires the compressor clutch to cycle on less to retain the proper high and low pressure in the a/c system. Because it is a closed system that uses an orifice for phase change, pressures do even out between the low and low side with time so there are other variables involved but basically, you will save energy from the a/c compressor being engaged on less.

Noticeable at the pump, likely not at all.

[dremd]

cooling Load does affect A/C horsepower use; my dad had an 84 dodge 3500 van when I was a kid; when we painted the roof white not only did FE improve, but hill climbs were posable with cruise on (with A/C) that were not posable (without downshifts) on similar days before. I know poor data.

More data; my new central A/C draws ~2000 watts with the inside blower on low and ~4100 watts blower on 3 ton. (borrowed TED installed on exterior unit only).

In the TDI I can see a 3 hp difference (on sgII) when changing blower speeds from low to high (more pronounced with variable displacement compressor).

[Piwoslaw]

Last week I saw an old car (20 yo Citroën AX) which had an interesting alternative to window tinting. Its rear and side-rear windows were covered with perforated vinyl film.



It's the stuff used to wrap busses, trains and cars in advertisements, but the AX's film was the same plain white color as its paintjob. This would be a nice alternative to tinting since it reflects sunlight before it gets to the window, reducing the amount of light that gets through by 50%-90%, depending on the size and spacing of the perforations. It can blend in with the paintjob, or double as an (EcoModder.com) ad I can see this covering the huge glass of a boattail, reducing heat gain. No idea about cost.

[Laurentiu]

I was curious so I looked around, have a look LINK

LINK 2

Seems to be quite expensive, probably better to head off to a local advertising/printing business that buys bulk and see if it's possible to get a deal. I did ride in a small vehicle (VW Golf) and I must say, although I wasn't driving , it seemed a bit obtrusive and kind of affecting the driving but I guess it takes time getting used to...Also, I'm not sure on this, but I think you need to have a bit of a distance to focus through these things, what I'm trying to say is that maybe having this stuff on your side windows might not be such a good idea...

[Piwoslaw]

Originally Posted by Laurentiu

I did ride in a small vehicle (VW Golf) and I must say, although I wasn't driving , it seemed a bit obtrusive and kind of affecting the driving but I guess it takes time getting used to...Also, I'm not sure on this, but I think you need to have a bit of a distance to focus through these things, what I'm trying to say is that maybe having this stuff on your side windows might not be such a good idea...

Yeah, I get to look out of busses and trams covered with ads and you're right that distance seems to help. Also, it's better if what you're looking at is moving (relative to you), so this may hinder searching for cars in your blind spot. Maybe there are versions with larger holes? The window underneath could still be slightly tinted.
Or maybe it does take getting used to?

[dremd]

there are at least 2 hole sizes, probably more.

[zhillz]

Almost 10mpg from just tint? I thought you only gained a few mpg with ac vs no ac...

[mcrews]

Most mid to upper end cars actually have a thermostat for the a/c. I can digitally set a number and the fan will reduce and the a/c get 'warmer' if I go from 65 to 74 degrees.
when I first get in everything is going full blast but after a few minutes the a/c reduces and just keeps it at the temp I set.
actually as i think back, most cars have some type of temp control. Some just a silde others are digital. But the a/c isnt just blowing the coldest air it can make all the time.

[shovel]

I'm only speculating here, but it seems that if the temperature in the cab is lower, and the a/c is recirculating (vs. cooling air from outside) then there would be less of a temperature difference between the cabin air and the cold R134 as it enters the evaporator, it would pick up less heat, build up less pressure, and be easier for the compressor to pump around the circuit.