Air Condition vs Windows Down

[cfg83]

jamesqf -

Originally Posted by jamesqf

I agree, but have you asked the passenger what they prefer? Maybe they're thinking "Gee, I wish he'd just roll down the window instead of running the A/C..."

And another good point about freeway air, since I seldom drive on freeways. I get pine-scented mountain air instead - or the sagebrush-scented desert variety.

Abso-moose-ly! I observed his behavior when he drove, and I copied his A/C use. We only use A/C on the freeway and only on the drive-home leg because it's not hot at daybreak. I suspect that in July/August I may keep the A/C on longer after we get off the freeway. We start at the beach (don't need A/C) but end up inland where it gets pretty hot.

CarloSW2

[superchow]

Our previous car, a 2002 Nissan Sentra XE (base model) did have A/C, but the insulation in the roof was so poor that on it felt like your hands and feet were freezing and your head was being broiled in hot weather.

Which makes me wonder - anybody ever tried to make their roof reflective or add insulation to increase insulation? Seems like a cheap and common sense ecomod. There may however be a problem from the police for adding a reflective surface that large to your car...

[brucey]

I've heard of people paint their roof with white reflective coating, (think buses) it cooled it by about 20 degrees on a hot summer day. IIRC Seemed worthwhile to me.

[KamperBob]

Huh! I can't seem to find any controls for windows or A/C on my motorcycle. LOL

Seriously, just returned from another 2,200-mile road trip. Had to use A/C both for safety as well as comfort, but not all the time. In a 4.7L Tundra towing a trailer at 55 mph I found the A/C cost was negligible.

I missed seeing "solar effect" mentioned earlier but that puts a big bias on the ambient temp even when the sky is not completely clear. For my 1.8L Spectra hatchback I made a solar shade from foil laminated foam insulation. It only had to cover the top 1/3-rd of the rear glass to shade the seat. Previously our boxer panted even with A/C on high. Afterward we found the A/C required less often. (Errata: descending Mt. Washington (NH) in 1st gear (manual) I found the A/C button an effective compliment to engine braking.

Any recommendations for an aftermarket kit to cycle the A/C compressor? Either t-stat or duty-cycle based types would interest me. Personal experience would be particularly appreciated. If not, I can make my own but a quality kit might look nicer.

Cheers
KB

[jamesqf]

Originally Posted by Daox

Haha, I'm just the opposite. I really don't like having the windows down. You can't hear anything and certainly can't hold a conversation with your passenger(s).

I don't have much problem hearing things. I'll admit I wouldn't try playing say a Beethoven sonata, but ordinary stuff is fine. And my usual passenger is perfectly happy with an occasional ear-scratching :-)

[mcrews]

I can speak to ABA testing on a:
1999 Jaguar Vaden Plas (4.0 liter 4dr stretch sedan)
and
2002 Infiniti Q45 (4.5 liter 4 dr sedan)
At 65 over a 7 mile flat stretchof highway in texas, I suffered a 4 mpg LOSS with windows down and A/c off in the jag
and a 3 mpg loss in the infiniti
I leave the a/c on all the time in the infiniti. My best mpg ever (32mpg at 55) over 7 mile testing up and back was w/ a/c on.

I agree that the smaller engines might suffer.

[Arragonis]

Originally Posted by superchow

Which makes me wonder - anybody ever tried to make their roof reflective or add insulation to increase insulation? Seems like a cheap and common sense ecomod. There may however be a problem from the police for adding a reflective surface that large to your car...

I used reflective insulation, the kind designed to go under wooden floor kits like those from Ikea, in the roof of my old Maestro



It had no A/C and got very hot in summer - it was black. In winter the ventilation was wonderful as you could have warm toes and cold face at the same time - something few modern cars can manage.

[ShadeTreeMech]

Originally Posted by superchow

Which makes me wonder - anybody ever tried to make their roof reflective or add insulation to increase insulation? Seems like a cheap and common sense ecomod. There may however be a problem from the police for adding a reflective surface that large to your car...

As arrogonis hinted at, the placement of the reflective insulation need not be on the exterior of the vehicle to do the job. Remove your headliner, install the reflective insulation, reinstall the headliner and enjoy a cooler head.

There are 3 types of heat; conduction, convection, and radiation.

Conduction is the transfer of heat through matter by communication of kinetic energy from particle to particle with no net displacement of the particles. A frying pan cooking an egg would be a good example.

Convection is the transfer of heat by displacing particles containing the heat. Using the blower to move air past the heater coil in a car is an example.

Radiation is the process of emitting radiant energy in the form of waves or particles. An example of this would be a microwave oven or a heat lamp.

Radiation is the more interesting one. Radiant heat from the sun would come in the form of different wavelengths (such as microwave) and some of these can penetrate the steel in the roof of the car, but can be reflected by a reflective material. Don't understand all the whys to it, but that is how I best understand it. So having a reflective insulation in the headliner, such as the type that looks like bubble wrap with aluminum foil in it, would protect from all 3 types of heat.

[Weeks]

I vote for B, but it's mighty hot! You could say I've been testing the theory by default. My Jeeps AC is out plus it's been raining - try that one in Texas in July!