What About The AC? - Page 2 - Toyota Yaris Forums

scape · 07-21-2009, 12:46 PM

Quote:

my mileage went up 1.5 to 2 mpg in the hot weather just by buying premium

i'm not sure how that can be possible? premium is usually just for octane to reduce knocking in high compression engines.

Yaris Hilton · 07-21-2009, 02:29 PM

That could result in a mileage improvement, if the lower octane fuel was causing the engine's knock sensor to retard the ignition timing to limit the knock, making it burn the fuel less efficiently. This has been discussed endlessly in other threads.

IllusionX · 07-21-2009, 02:59 PM

The AC compressor runs regardless the fan at min or full blast. there is no advantages to not threat yourself the extra cold air.

I tend to try to turn off the AC when i'm driving in the city with lots of stop and go as the heat turns on the radiator fan on and off often.

Zaphod · 07-21-2009, 03:12 PM

And here I thought that running the fan at higher rpms increased the efficiency of the AC delivery.

What does the temperature control do, turn on/off the compressor at intervals?

Yaris Hilton · 07-21-2009, 05:23 PM

No, the compressor does not run continuously. It has an electric clutch. It cuts in and out keeping the cold air output at a constant temperature. When it's cooling less air, it runs less.

scape · 07-21-2009, 08:32 PM

Quote:

Originally Posted by Yaris Hilton

No, the compressor does not run continuously. It has an electric clutch. It cuts in and out keeping the cold air output at a constant temperature. When it's cooling less air, it runs less.

one: I run my AC at 75%, just to add a bit of senseless input to this conversation :D
b: how often does gas not contain the proper octane rating, may you please link me to this thread you spoke of-- I'm rather interested :)

R2D2 · 07-21-2009, 09:11 PM

Scape,

I don't believe Yaris is insinuating that the octane rating is improper-what he is saying is it is conceivable that using a higher octane fuel than recommended for the vehicle could result in better fuel economy.

This is potentially possible because the vehicles knock sensor prevents detonation by retarding the timing. Therefore a higher octane fuel MAY yield better fuel economy by allowing for more timing advance. It is this mechanism that would make gains possible as there is actually LESS energy in a gallon of premium gas than in a gallon of regular. I'm not a fan of running higher octane than recommended however because the octane rating actually indicates a fuels resistance to ignition and there is risk this could lead to deposit issues long term.

R2

deerebilt · 07-21-2009, 10:28 PM

your a/c system will last longer with fan at a higher speed and temp set warmer. this keeps more air moving past evaporator amd condensor cooler which in turn lowers radiator temp and a/c compressor temp thus longer life. and with a/c temp set closer to warm and fan speed higher compressor will run less and engine load reduced

Yaris Hilton · 07-21-2009, 11:24 PM

That's true, if the Yaris's AC control system is smart enough to cycle the compressor to reduce the cooling of the air to get a higher output temperature. Many systems run the compressor to chill the air coming out of the evaporator to a constant minimum temperature, and mix hot air from the heater core with the cold air to get anything warmer than the coldest temperature. In that case you don't save anything by running the temperature higher, but you do by running the fan slower as you're chilling less air.

scape · 07-22-2009, 12:58 AM

I always viewed the AC as a system of percentage, like how activated or open the coolant throttle may be for the system. I usually prefer 75% and number 2 fan, when people are in the car, I run the fan at 3 and front vents only (people seem to think cold dry air in the face means they are cooler, lol). I don't think the throttle is always fully open (can you call it a throttle?) and mixing with heater core temp (some cars do this, my bronco did!), but I don't think the yaris mixes heater air until 50% or below (then again this is all stipulation on my part!)

@r2: I agree about deposits, I gotta look up this pre-det problem with regular-- never heard of this and the knock sensor problem

Kaotic Lazagna · 07-22-2009, 02:36 AM

I use my A/C when there are others in the car at temp settings one click before max, and fan speeds of 2-3 on recirc on front/face vent. I'll notice a drop in mpg at this settings, but if I must use the A/C by myself, I'll have it to the same settings except for a fan speed of 1 and in between front/face and the front/feet setting (the dot). I haven't noticed a drop in mpg, and at times have actually gained mpg (probably due to me staying at a constant speed oppose to dosing off without the A/C and fluctuating my speed).

gammaray · 07-27-2009, 08:34 PM

Use the Recirculate setting to cool the interior quicker, with higher outside temps. Usually when your car has been sitting a long period and very hot inside. Then cut it off. Back to the fan speed...... It does not affect mileage.

Yaris Hilton · 07-28-2009, 11:17 PM

Quote:

Originally Posted by gammaray

Back to the fan speed...... It does not affect mileage.

The fan itself doesn't, but it does because you're cooling less air with the compressor when the fan's turned down.

CtrlAltDefeat · 07-28-2009, 02:46 AM

Actually the interior of the car, on a hot day, can get well above the ambient temp outside. From what I figure, it's best to turn the ac on lowest fan/coldest temp/outside air and roll the windows down until the interior temp reaches the same as the outside. Then you switch to recirculate. When the air con is outputting cold air, change the temp to the middle/cool setting, and turn up the fan. When the AC is first turned on, a high fan speed will wick all of the cool out of the coolant, and the AC will run longer before getting cool. This is all just imho, but I think my logic is correct...

07-21-2009, 09:11 PM	#7
R2D2 Crazy Oil Sniffer Drives: MM 09 Yaris 5 Dr LB "Click" Join Date: May 2009 Location: ME Posts: 498	Scape, I don't believe Yaris is insinuating that the octane rating is improper-what he is saying is it is conceivable that using a higher octane fuel than recommended for the vehicle could result in better fuel economy. This is potentially possible because the vehicles knock sensor prevents detonation by retarding the timing. Therefore a higher octane fuel MAY yield better fuel economy by allowing for more timing advance. It is this mechanism that would make gains possible as there is actually LESS energy in a gallon of premium gas than in a gallon of regular. I'm not a fan of running higher octane than recommended however because the octane rating actually indicates a fuels resistance to ignition and there is risk this could lead to deposit issues long term. R2 __________________ "The howl was the sound of God’s casting pot, the morphing of my cells into shape, the forming of oceans out of molten premordial plasma. And I could feel it. I could cry for it. I could cry with it." -The Fitful One

07-28-2009, 02:46 AM	#14
CtrlAltDefeat I ♥ Yaris View User's Garage Drives: Black 08 LB MT & red 97 Miata Join Date: Oct 2008 Location: Indianapolis IN Posts: 1,313	Actually the interior of the car, on a hot day, can get well above the ambient temp outside. From what I figure, it's best to turn the ac on lowest fan/coldest temp/outside air and roll the windows down until the interior temp reaches the same as the outside. Then you switch to recirculate. When the air con is outputting cold air, change the temp to the middle/cool setting, and turn up the fan. When the AC is first turned on, a high fan speed will wick all of the cool out of the coolant, and the AC will run longer before getting cool. This is all just imho, but I think my logic is correct... __________________ The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt. - Bertrand Russell

07-21-2009, 02:29 PM	#2
Yaris Hilton Half a Bubble Off Plumb Drives: 2009 Yaris Sedan Join Date: Mar 2009 Location: Bristol, Tennessee, USA Posts: 1,593	That could result in a mileage improvement, if the lower octane fuel was causing the engine's knock sensor to retard the ignition timing to limit the knock, making it burn the fuel less efficiently. This has been discussed endlessly in other threads.

07-21-2009, 02:59 PM	#3
IllusionX It's the illusion you see View User's Garage Drives: 07 Yaris Sedan Aero Join Date: Oct 2006 Location: Brossard, QC Posts: 3,888	The AC compressor runs regardless the fan at min or full blast. there is no advantages to not threat yourself the extra cold air. I tend to try to turn off the AC when i'm driving in the city with lots of stop and go as the heat turns on the radiator fan on and off often.

07-21-2009, 03:12 PM	#4
Zaphod Drives: Big Yellow Join Date: May 2009 Location: Somewhere in the vacinity of Betelgeuse Posts: 179	And here I thought that running the fan at higher rpms increased the efficiency of the AC delivery. What does the temperature control do, turn on/off the compressor at intervals?

07-21-2009, 05:23 PM	#5
Yaris Hilton Half a Bubble Off Plumb Drives: 2009 Yaris Sedan Join Date: Mar 2009 Location: Bristol, Tennessee, USA Posts: 1,593	No, the compressor does not run continuously. It has an electric clutch. It cuts in and out keeping the cold air output at a constant temperature. When it's cooling less air, it runs less.

07-21-2009, 10:28 PM	#8
deerebilt View User's Garage Drives: 2008 Yaris sedan S Join Date: Mar 2009 Location: cheney,ks Posts: 46	your a/c system will last longer with fan at a higher speed and temp set warmer. this keeps more air moving past evaporator amd condensor cooler which in turn lowers radiator temp and a/c compressor temp thus longer life. and with a/c temp set closer to warm and fan speed higher compressor will run less and engine load reduced

07-21-2009, 11:24 PM	#9
Yaris Hilton Half a Bubble Off Plumb Drives: 2009 Yaris Sedan Join Date: Mar 2009 Location: Bristol, Tennessee, USA Posts: 1,593	That's true, if the Yaris's AC control system is smart enough to cycle the compressor to reduce the cooling of the air to get a higher output temperature. Many systems run the compressor to chill the air coming out of the evaporator to a constant minimum temperature, and mix hot air from the heater core with the cold air to get anything warmer than the coldest temperature. In that case you don't save anything by running the temperature higher, but you do by running the fan slower as you're chilling less air.

07-22-2009, 12:58 AM	#10
scape View User's Garage Drives: 2007 Yaris Hatchback Join Date: Jul 2007 Location: Beaufort, South Carolina Posts: 388	I always viewed the AC as a system of percentage, like how activated or open the coolant throttle may be for the system. I usually prefer 75% and number 2 fan, when people are in the car, I run the fan at 3 and front vents only (people seem to think cold dry air in the face means they are cooler, lol). I don't think the throttle is always fully open (can you call it a throttle?) and mixing with heater core temp (some cars do this, my bronco did!), but I don't think the yaris mixes heater air until 50% or below (then again this is all stipulation on my part!) @r2: I agree about deposits, I gotta look up this pre-det problem with regular-- never heard of this and the knock sensor problem

07-22-2009, 02:36 AM	#11
Kaotic Lazagna View User's Garage Drives: '14 GT86, '08 Vitz Join Date: Dec 2006 Location: Central Valley, CA Posts: 9,873	I use my A/C when there are others in the car at temp settings one click before max, and fan speeds of 2-3 on recirc on front/face vent. I'll notice a drop in mpg at this settings, but if I must use the A/C by myself, I'll have it to the same settings except for a fan speed of 1 and in between front/face and the front/feet setting (the dot). I haven't noticed a drop in mpg, and at times have actually gained mpg (probably due to me staying at a constant speed oppose to dosing off without the A/C and fluctuating my speed).

07-27-2009, 08:34 PM	#12
gammaray Drives: 09 3D Liftback Join Date: Jun 2009 Location: Tn Posts: 37	Use the Recirculate setting to cool the interior quicker, with higher outside temps. Usually when your car has been sitting a long period and very hot inside. Then cut it off. Back to the fan speed...... It does not affect mileage.