A/C and fuel economy & How to use aircon optimally.

toiingg · 26th March 2008, 23:21

Reduce the blower speed to 1 or 2 (once its cool inside) and let the ac run continuously. Let the temperature knob be at max cooling.

esteem_lover · 26th March 2008, 23:22

Plenty of threads on this praveen. Honestly, can you drive with anything less than max in chennai summer (which is always) ? Even if it is cold, the atmosphere inside the car when only the blower is working is intolerable. Moreover i do not think you save anything worthwhile. Maybe you can sweat it out & get yourself a cone ice cream from the wayside with the money that you saved.

praveen_v · 26th March 2008, 23:29

Quote:

Originally Posted by esteem_lover

Honestly, can you drive with anything less than max in chennai summer (which is always) ? Even if it is cold, the atmosphere inside the car when only the blower is working is intolerable. Moreover i do not think you save anything worthwhile. Maybe you can sweat it out & get yourself a cone ice cream from the wayside with the money that you saved.

Hehe.. I agree chennai summer needs full aircon. BUt even in winters, i have never seen the compressor cutoff with the temp set at max cool. It gets really cold inside the cabin well before the max cool temperature. The thing is, if I can find my comfortable temperature and reduce the temperature accordingly, will it do any harm since the compressor will turn off and on frequently??

Quote:

Originally Posted by toiingg

Reduce the blower speed to 1 or 2 (once its cool inside) and let the ac run continuously. Let the temperature knob be at max cooling.

I was looking for some way to minimize the compressor usage (without turning off the ac ofcourse

) and still maintain a comfortable temperature

alto99 · 26th March 2008, 23:30

Quote:

Originally Posted by praveen_v

What's causing the confusion to me is, some people say that frequent cutting off and switching on of compressor will kill it. is that true??

I don't think that it will kill the compressor. I have been switching off ac while overtaking and switch on immediately later on highway 100s of times (on non-4 lane NH4 few years before) and by now I am sure I would have killed it. Add to that automatic cut-off that happens even if the temperature hadn't dropped significantly in spite of knob position at the coolest level.

esteem_lover · 26th March 2008, 23:35

Actually toiingg has a point. when you set the blower speed to 1 or 2, then the air closer to the blower gets recirculated, which means that only the coldest air gets back into your blower, this would make the compressor to switch off earlier than otherwise.

here's another thread that discusses a similar issue http://www.team-bhp.com/forum/techni...old-start.html

a.ashokdurai · 26th March 2008, 23:42

praveen, i follow this but i dont know wether it truely saves the fuel or not.. when ever i feel the load on engine(while i am overtaking an vehicle/shifting down to lower gears/slwoing down for some reason) i usually switch off the AC compeltely but with the blowers ON.

hrishig · 27th March 2008, 08:32

You can use ~80 - 90 % heat rejection films on every glass including the front glass.

This will definitely reduce the A/C usage and will improve mileage.

esteem_lover · 27th March 2008, 08:39

Quote:

Originally Posted by hrishig

You can use ~80 - 90 % heat rejection films on every glass including the front glass.

This will definitely reduce the A/C usage and will improve mileage.

Like 2 drops per litre ? I am yet to hear of increased FE due to sun films. You want FE, turn the AC off & do not over rev.

sukiwa · 27th March 2008, 09:04

Quote:

Like 2 drops per litre ? I am yet to hear of increased FE due to sun films. You want FE, turn the AC off & do not over rev.

Well, yes it does help. Having a front windscreen film along with sun control films on all glass panels does help in getting better fuel efficiency.

try these two things.

1. Front windscreen film (Vkool/Llumar)
2. Use blower at speed of 1 or 2

lambuhere1 · 27th March 2008, 10:46

Quote:

Originally Posted by sukiwa

Well, yes it does help. Having a front windscreen film along with sun control films on all glass panels does help in getting better fuel efficiency.

try these two things.

1. Front windscreen film (Vkool/Llumar)
2. Use blower at speed of 1 or 2

I used both options, but my FE droped by 2km/l by full usage of AC before the current full tank. Previously it was 11.5 kmpl, now its 9.5 kmpl. Wonder why, Probably, my run in is not yet over. Currently at only 1200 km in 6 month

harsha.cs1 · 27th March 2008, 12:37

My minus 2 cents to this. How does turning the AC in heating mode (turning the knob to red) affect the FE? would it still load the compressor and affect pick up etc? i understand this heater is often used for windscreen defogging, right?

trrk · 27th March 2008, 14:59

Hi,

> temperature. The thing is, if I can find my comfortable temperature and
> reduce the temperature accordingly, will it do any harm since the compressor > will turn off and on frequently??

You can do this withou problems. Even in cars which I have used for long periods never had problems with the compressor as I have been using the AC the way you describe.

Though I don't remember the source now, I read long back about this. If your car is hot, you start off with the temperature knob in the maximum and the blower also in the maximum position (recirculation mode). Lower the front windows an inch or so for a couple of minutes and then put them up. When you feel it is cold enough, turn the temperature knob away from the maximum position in gradual intervals until you find the position you feel is comfortable for you. Beyond this it won't be comfortable anymore. If after a couple of minutes, you can try and reduce the blower speed again in steps. If only the front seats are occupied, a blower speed of 2 or max 3 (in a 4 speed unit) with the temperature knob at around 10 o'clock postion (when the max is at the left end as you look at the temp knob for most of the day.

When there are rear passengers the situation is different.

In my CVT, the temperature knob is usually around the 10 o' clock position with the blower at 2 when I am alone or only the front seats are occupied. If it is hot maybe a notch to the left is sufficient here.

The methodolgy is same for my Marina too!

> I was looking for some way to minimize the compressor usage (without
> turning off the ac ofcourse

) and still maintain a comfortable temperature

You can try this. You can also check if there is mileage improvement. Temperature knob at maximum always makes the compressor work longer.

abhik · 27th March 2008, 23:54

Guys i appologise for my ignorance but why does everybody keep saying that the blower speed regulates the power of the air-con?
My understanding is the the tempature guage(marked my blue for cool going to red for hot)regulates the cooling and the power of the a/c. the blower(marked by 1.2.3.4 for speed) just regulates the fan speed. The cooling effect differs due to the speed of the cool air being thrown at you but the cooling power by the compressor remains the same if temperature regulator is constant in one position. So the blower at 2nd level(speed 2) or 4th level should not make a difference to FE. If the temperature regulator is adjusted then it should affect FE.

alto99 · 28th March 2008, 11:17

Quote:

Originally Posted by abhik

Guys i appologise for my ignorance but why does everybody keep saying that the blower speed regulates the power of the air-con?

The amount of air flown over the evaporator coils will be less, hence the heat transfer would also be less resulting into less rise in temperature of AC gas. Less rise in temperature of AC gas means cut-off of ac compressor and less usage of AC.

harsha.cs1 · 31st March 2008, 15:56

Quote:

Originally Posted by harsha.cs1

My minus 2 cents to this. How does turning the AC in heating mode (turning the knob to red) affect the FE? would it still load the compressor and affect pick up etc? i understand this heater is often used for windscreen defogging, right?

folks, still looking forward to hearing on the effects of turning the AC on heating mode? Thanks...

26th March 2008, 23:21	#46
toiingg BHPian Join Date: Oct 2006 Location: Calcutta Posts: 639 Thanked: 266 Times	Reduce the blower speed to 1 or 2 (once its cool inside) and let the ac run continuously. Let the temperature knob be at max cooling.
	() Thanks

26th March 2008, 23:22	#47
esteem_lover Senior - BHPian Join Date: Jul 2006 Location: Madras/Py Posts: 7,556 Thanked: 502 Times View My Garage	Plenty of threads on this praveen. Honestly, can you drive with anything less than max in chennai summer (which is always) ? Even if it is cold, the atmosphere inside the car when only the blower is working is intolerable. Moreover i do not think you save anything worthwhile. Maybe you can sweat it out & get yourself a cone ice cream from the wayside with the money that you saved.
	() Thanks

26th March 2008, 23:35	#50
esteem_lover Senior - BHPian Join Date: Jul 2006 Location: Madras/Py Posts: 7,556 Thanked: 502 Times View My Garage	Actually toiingg has a point. when you set the blower speed to 1 or 2, then the air closer to the blower gets recirculated, which means that only the coldest air gets back into your blower, this would make the compressor to switch off earlier than otherwise. here's another thread that discusses a similar issue http://www.team-bhp.com/forum/techni...old-start.html Last edited by esteem_lover : 26th March 2008 at 23:36.
	() Thanks

26th March 2008, 23:42	#51
a.ashokdurai BHPian Join Date: Nov 2005 Location: Chennai Posts: 36 Thanked: Once	praveen, i follow this but i dont know wether it truely saves the fuel or not.. when ever i feel the load on engine(while i am overtaking an vehicle/shifting down to lower gears/slwoing down for some reason) i usually switch off the AC compeltely but with the blowers ON.
	() Thanks

27th March 2008, 08:32	#52
hrishig BHPian Join Date: Apr 2007 Location: Pune Posts: 466 Thanked: 180 Times	You can use ~80 - 90 % heat rejection films on every glass including the front glass. This will definitely reduce the A/C usage and will improve mileage.
	() Thanks

27th March 2008, 12:37	#56
harsha.cs1 BHPian Join Date: Feb 2008 Location: Bangalore Posts: 224 Thanked: 2 Times	My minus 2 cents to this. How does turning the AC in heating mode (turning the knob to red) affect the FE? would it still load the compressor and affect pick up etc? i understand this heater is often used for windscreen defogging, right?
	() Thanks

27th March 2008, 14:59	#57
trrk Senior - BHPian Join Date: Feb 2004 Location: Alleppey, Kerala Posts: 2,114 Thanked: 34 Times View My Garage	Hi, > temperature. The thing is, if I can find my comfortable temperature and > reduce the temperature accordingly, will it do any harm since the compressor > will turn off and on frequently?? You can do this withou problems. Even in cars which I have used for long periods never had problems with the compressor as I have been using the AC the way you describe. Though I don't remember the source now, I read long back about this. If your car is hot, you start off with the temperature knob in the maximum and the blower also in the maximum position (recirculation mode). Lower the front windows an inch or so for a couple of minutes and then put them up. When you feel it is cold enough, turn the temperature knob away from the maximum position in gradual intervals until you find the position you feel is comfortable for you. Beyond this it won't be comfortable anymore. If after a couple of minutes, you can try and reduce the blower speed again in steps. If only the front seats are occupied, a blower speed of 2 or max 3 (in a 4 speed unit) with the temperature knob at around 10 o'clock postion (when the max is at the left end as you look at the temp knob for most of the day. When there are rear passengers the situation is different. In my CVT, the temperature knob is usually around the 10 o' clock position with the blower at 2 when I am alone or only the front seats are occupied. If it is hot maybe a notch to the left is sufficient here. The methodolgy is same for my Marina too! > I was looking for some way to minimize the compressor usage (without > turning off the ac ofcourse ) and still maintain a comfortable temperature You can try this. You can also check if there is mileage improvement. Temperature knob at maximum always makes the compressor work longer.
	() Thanks

27th March 2008, 23:54	#58
abhik BHPian Join Date: Aug 2007 Location: New Delhi Posts: 848 Thanked: 12 Times View My Garage	Guys i appologise for my ignorance but why does everybody keep saying that the blower speed regulates the power of the air-con? My understanding is the the tempature guage(marked my blue for cool going to red for hot)regulates the cooling and the power of the a/c. the blower(marked by 1.2.3.4 for speed) just regulates the fan speed. The cooling effect differs due to the speed of the cool air being thrown at you but the cooling power by the compressor remains the same if temperature regulator is constant in one position. So the blower at 2nd level(speed 2) or 4th level should not make a difference to FE. If the temperature regulator is adjusted then it should affect FE.
	() Thanks