What's more fuel efficient & enviromental friendly? Auto climate control? Manual AC?

[lumlum1013]

this is the first car that i have that has auto climate control....

anywayz, so wat's more fuel effiecent? turnin' on Auto climate?
or AC + fan speed manually...
say if i set it @ 20°C (68°F) and ambient temp is 32°C (90°F)

also, if it's possible, can someone give me a brief lecture on the Auto Climate Control system.

[VivienM]

Auto climate control, I would guess. The electronics can adjust things a lot better than you.

I'm not sure what lecture you want. Just set the temperature to about 24-26 unless you really like crazy cold, press the auto button, and don't touch your climate control unit until the winter. (Oh, and laugh at all your sucker friends who have manual climate controls...)

[ES_Revenge]

Fan speed has little to do with fuel economy really. The blower motor requires voltage which is produced by the alternator, more electrical demand at idle may cause the idle speed to increase but that's about it. With most cars with good alternators (over 100A cold rated) the alt will usually unregulate if high blower is selected or there is high electrical demand at idle.

A/C on/off on the other hand is a different matter. In traffic A/C systems will definitely consume more fuel. A/C compressors run by placing load on the engine (as would a traditional hydraulic power steering pump, for example). So when the compressor clutch engages it's more physical load on the engine's accessory system and that will cause more fuel to be used.

Modern day compressors are usually variable stroke meaning the compressor can vary its stroke to cool the evap core to as low a temperature as possible without freezing it. More cooling demand (e.g. when you first turn on the A/C and most of the time on particularly hot days) will have the compressor operating at near full stroke, while less cooling demand can allow the compressor stroke to shorten which consumes less fuel and of course prevents the evap core from freezing up.

Auto/electronic climate control doesn't change anything much other than varying the fan speed and temp door(s) to achieve a desired temperature in the cabin. Takes the guess work out of it, and stops you from having to fiddle with things a lot. That's really all it does for you. It probably takes up more fuel because pretty much all climate control systems are very aggressive in nature. To cool more than a couple degrees, most will set everything to maximum. However this is not unlike what many people would do with manual controls anyway.

What most auto systems also do though is always engage the compressor by default, provided the lower temp limit (usually around 5C) is not reached. That's why usually there's a way to turn off the compressor (by pressing either an "A/C" button or an "ECON" button, both of which do the same). So if you just went with the default settings on the climate control you would consume more fuel because the car will always want the compressor on (even in heating situations where the OAT is over 5C), simply to dehumidify the air. Dehumidifying the air makes it less likely to have fog up and is more comfortable in general. However it does waste more fuel.

So if you're strictly talking about cooling though (where you'd have the A/C on yourself if it was a manual system), there won't be much difference in fuel consumption because the auto system will just be changing the temp doors and the fan speed, neither of which have much bearing on fuel consumption. Fuel consumption is affected by compressor stroke and the compressor being on at all in the first place.

So really you need a third option--"It doesn't make much difference" ;)

Edit: Oh one other thing I forgot to mention is that when the compressor engages and the high-side pressure is at a certain threshold the engine cooling fan (ECF) will also come on, which takes a good deal of current from the alterntor as well. Some cars will engage the ECF whenever the A/C compressor is commanded on at all, regardless of high-side pressure; also some cars have more than one fan, some of which can be dedicated to the condenser core as opposed to cooling the engine/rad. This again will cause more electrical load, which may increase idle speed in some cars which would cause slightly more fuel consumption; however as above the slight change in idle from electrical load is nothing compared to the additional fuel consumption caused by the compressor being engaged.

[lumlum1013]

so the compressor is alwayz ON even if it's at Auto Climate Control?
i thougth it will turn it off if it reaches it's requested temperature....
and ON automatically when temperature raises...
hmph, i guess i was wrong~
Thx for the details...

Fan speed has little to do with fuel economy really. The blower motor requires voltage which is produced by the alternator, more electrical demand at idle may cause the idle speed to increase but that's about it. With most cars with good alternators (over 100A cold rated) the alt will usually unregulate if high blower is selected or there is high electrical demand at idle.

A/C on/off on the other hand is a different matter. In traffic A/C systems will definitely consume more fuel. A/C compressors run by placing load on the engine (as would a traditional hydraulic power steering pump, for example). So when the compressor clutch engages it's more physical load on the engine's accessory system and that will cause more fuel to be used.

Modern day compressors are usually variable stroke meaning the compressor can vary its stroke to cool the evap core to as low a temperature as possible without freezing it. More cooling demand (e.g. when you first turn on the A/C and most of the time on particularly hot days) will have the compressor operating at near full stroke, while less cooling demand can allow the compressor stroke to shorten which consumes less fuel and of course prevents the evap core from freezing up.

Auto/electronic climate control doesn't change anything much other than varying the fan speed and temp door(s) to achieve a desired temperature in the cabin. Takes the guess work out of it, and stops you from having to fiddle with things a lot. That's really all it does for you. It probably takes up more fuel because pretty much all climate control systems are very aggressive in nature. To cool more than a couple degrees, most will set everything to maximum. However this is not unlike what many people would do with manual controls anyway.

What most auto systems also do though is always engage the compressor by default, provided the lower temp limit (usually around 5C) is not reached. That's why usually there's a way to turn off the compressor (by pressing either an "A/C" button or an "ECON" button, both of which do the same). So if you just went with the default settings on the climate control you would consume more fuel because the car will always want the compressor on (even in heating situations where the OAT is over 5C), simply to dehumidify the air. Dehumidifying the air makes it less likely to have fog up and is more comfortable in general. However it does waste more fuel.

So if you're strictly talking about cooling though (where you'd have the A/C on yourself if it was a manual system), there won't be much difference in fuel consumption because the auto system will just be changing the temp doors and the fan speed, neither of which have much bearing on fuel consumption. Fuel consumption is affected by compressor stroke and the compressor being on at all in the first place.

So really you need a third option--"It doesn't make much difference" ;)

Edit: Oh one other thing I forgot to mention is that when the compressor engages and the high-side pressure is at a certain threshold the engine cooling fan (ECF) will also come on, which takes a good deal of current from the alterntor as well. Some cars will engage the ECF whenever the A/C compressor is commanded on at all, regardless of high-side pressure; also some cars have more than one fan, some of which can be dedicated to the condenser core as opposed to cooling the engine/rad. This again will cause more electrical load, which may increase idle speed in some cars which would cause slightly more fuel consumption; however as above the slight change in idle from electrical load is nothing compared to the additional fuel consumption caused by the compressor being engaged.

[boyoflondon]

This 'environmentally friendly' buzz is getting out of control it seems.


If you really want to know what is really environmentally friend ... its when I drive with my windows down and sunroof open! Beats any AC and does no harm to mother nature ;) :D

[masterballer]

This 'environmentally friendly' buzz is getting out of control it seems.


If you really want to know what is really environmentally friend ... its when I drive with my windows down and sunroof open! Beats any AC and does no harm to mother nature ;) :D

not at highway speeds ;) + ur still driving a gas burning car lol ... now if you took ur bike THEN u could brag about saving mother nature

[Anessa]

not at highway speeds ;) + ur still driving a gas burning car lol ... now if you took ur bike THEN u could brag about saving mother nature

Walking FTW :D

[lumlum1013]

Walking FTW :D


lol!

if you choose walkin', this "motor Vehicles & accessories" section will probably be unfriendly to you~

:cheesygri

[ES_Revenge]

so the compressor is alwayz ON even if it's at Auto Climate Control?
i thougth it will turn it off if it reaches it's requested temperature....
and ON automatically when temperature raises...

When heating (when the OAT is above 5C and the compressor can operate) this may occur, yeah; however when cooling the car, this will probably never happen.

The reason is, say it's a really hot/humid day outiside... If the compressor is on for the A/C, when the desired temp is reached the climate control is going to simply slow down the fan and/or move the temp doors to hold the temperature steady. If the compressor were to shut off, then the humid air would instantly enter the car heating it up and making it uncomfortable from the humidity. So that's typically not allowed by the system unless you manually turn the compressor off. Some systems may do this if the OAT is not that hot, but mostly with auto climate control systems the compressor is usually kept on unless the temp drops enough that the compressor is no longer effective (usually 5C and below as mentioned).

But everything depends on the programming of the particular system in your car. It does vary from manufacturer to manufacturer. Almost all cars I've seen with auto climate have a clearly visible indication as to whether the compressor is on or off. If the system does turn off the compressor you'll see the A/C light go off or the A/C indication on the LCD go away or change to "A/C OFF". However usually this does not occur unless you command the A/C OFF manually. Otherwise, as mentioned, in absence of that, it will have an ECON button which is essentially the same. (ECON ON = A/C OFF; ECON OFF = A/C ON)

Out of curiousity, what car do you have?

[ichpen]

this is the first car that i have that has auto climate control....

anywayz, so wat's more fuel effiecent? turnin' on Auto climate?
or AC + fan speed manually...
say if i set it @ 20°C (68°F) and ambient temp is 32°C (90°F)

also, if it's possible, can someone give me a brief lecture on the Auto Climate Control system.

The 'auto' part simply regulates the fan/blowers to maintain the desired temperature. With Auto the AC compressor is always on. Most newer climate controls will have an Economy mode whereby the fan speed will continue to be regulated but this time without the aid of AC. This is ok for regular not hot or humid days but it does not work when it's 35C outside as it will blow hot air on you.

[lumlum1013]

unfortunately, i don't have a "ECON" button.....
i guess my car was not built for fuel efficiency since the beginnin'...
maybe that is why the japaneses feel there is no point
of addin' the "ECON" button into my car.....

thx newayz....