[Prowler]

Originally Posted by thoma

I was thinking it only controlled the mixing of hot and cold air still. Maybe not thinking, IIRC, I've tested it on one of my previous car with climate control, to keep the AC at a higher temp and still finding that the compressor runs intermittently all the time.

Yet, I'm not too sure, but will appreciate more information on this; AC vs FE.

Originally Posted by Jeroen

Yes, it does. In practice some of the modern AC system are a bit more sophisticated, but still at some point in time at the right temperature the compressor will cut off. You can usually hear it as the engine load is less. The ECU will keep the RPMs more or less stable, but you might see a little higher RPM when the compressors cut off and then it settles back again.

Depends a bit of course but on an average family saloon running the AC could take 3-4 HP

Jeroen

Yes. As Jeroen says, even in a non-climate controlled cars, the compressor cuts off after it reaches a set temperature and you can hear the engine rpm coming down when it cuts off. I usually keep the thermostat knob at the coldest setting until the car cools down. You can hear the compressor turning on and off every few minutes in the evening.

[thoma]

Originally Posted by Prowler

even in a non-climate controlled cars, the compressor cuts off after it reaches a set temperature and you can hear the engine rpm coming down when it cuts off

Originally Posted by Jeroen

Yes, it does. In practice some of the modern AC system are a bit more sophisticated, but still at some point in time at the right temperature the compressor will cut off.

I think the compressor cuts off depending on the pressure in the line and not based on the temperature inside the cabin; and thus the compressor clutch gets engaged and disengaged several times. What I've tested is, even at higher temperature settings, the compressor is not fully off for a long time (in fact it never went off in 5 minutes when I checked at both the extreme temperature settings).

But what I do not know is whether the auto climate control is all about mixing hot and cold air alone.

Maybe we are going off topic, but what I want to know in specific is whether the compressor stays off longer in an automatic climate controlled car when the set temperature is reached, thus gaining any FE.

[ksameer1234]

Originally Posted by thoma

But what I do not know is whether the auto climate control is all about mixing hot and cold air alone.

Maybe we are going off topic, but what I want to know in specific is whether the compressor stays off longer in an automatic climate controlled car when the set temperature is reached, thus gaining any FE.

I found the answer to mixing air vs cutting off compressor in Tata Zest Manual and wrote about it here. I don't think cars in India, except for luxury brands, would opt for mixing air since it will definitely have negative impact on fuel efficiency compared to switching the compressor off.

[Prowler]

Originally Posted by thoma

I think the compressor cuts off depending on the pressure in the line and not based on the temperature inside the cabin; and thus the compressor clutch gets engaged and disengaged several times.

No. The compressor cuts off only because the thermostat sensed that the internal temperature has reached the set temperature - at least in Tata cars. I tested this in my Safari and Tiago some time back. I even waited till it turned on. In one setting it turns on at 29 degree C/85 degree F as I checked (image attached). It behaves like a domestic AC.

[kifilshah]

Originally Posted by Aroy

I have yet to see a modern car with a thermostat for AC (had one in my old M800 which would cut off just like room AC).

On a non climate control AC rotating the thermostat knob just mixes hot air (from heater) with cold AC air. In effect you are consuming more power. Keep the AC knob at its coldest, and manually switch it off when it gets too cold. That will help increase FE a bit.

Seriously? are you sure about this? :o This seems like the least efficient way to regulate the temperature inside the car.
And if this is true, adjusting the thermostat was a very very stupid thing to do

[kifilshah]

Originally Posted by Aroy

The theory behind Italian Tuneup, is to run the engine hot for at least an hour at high speed. That burns up most of the deposits, get rid of water and waste that have accumulated in the engine oil. Short drives of less than 50km in moderate traffic will not do.

Hi! As you had suggested, I took my car on nice road and drove for about 35-40 kms (I know you had suggested more atleast an hour but this is all could do then). For about three days after that, I could feel a lot of difference in the way the car responded to throttle and it was much smoother to drive. But when I turned her on this morning, it feels as if it went back to how it used to be.
Is this possible? and could this be because I drove only for 40 kms? would driving longer help in anyway now?

[Aroy]

Originally Posted by kifilshah

Hi! As you had suggested, I took my car on nice road and drove for about 35-40 kms (I know you had suggested more atleast an hour but this is all could do then). For about three days after that, I could feel a lot of difference in the way the car responded to throttle and it was much smoother to drive. But when I turned her on this morning, it feels as if it went back to how it used to be.
Is this possible? and could this be because I drove only for 40 kms? would driving longer help in anyway now?

Yes. That is why a drive of at least a 100km is recommended. In that one to one and a half hour drive, the engine is heated fully and has time to burn off all the fuel and other residues (carbon) which have built up over time. Every time after a 500km drive (to Ambala and Back) my M800 engine had a new engine feel - crisp acceleration and excellent FE.

So next day off take off and drive for two hours on open highway. That will clean up the engine for at least a few months.

[kifilshah]

Originally Posted by Aroy

So next day off take off and drive for two hours on open highway. That will clean up the engine for at least a few months.

Hmm! that makes sense. I am driving down to Kerala this weekend so should be clocking a good 350-400 KMs one way. I guess that should do the trick! I'll update you anyways! and again, thanks for the inputs!

[dailydriver]

For the first time in eight years of owning my Zen Estilo Lxi, I saw a sub 15kmpl mileage today . I drove 218km since the previous refill and the car took in 15.7ltr of petrol at auto cut off. The useage pattern has remained the same as ever. Some variations that I could think of in the 25 days are:

• The car was parked in the open for almost ten days.
• The tyre pressure was kept at 32 instead of the usual 33.
• While filling up, the car was parked leaning to it's right whereas the last time, it was parked leaning to its left - the side where the filler is located.

The low fuel efficiency is hard to come to terms with because the car was run with almost no AC. Will wait till the next refill before taking any corrective measures.

[bharatbits]

Linea Classic Plus 1.3 Multijet
City 14.x kmpl. The average speed hovers around 17kmph in Mumbai traffic.
Highways 22 to 24 kmpl. Have even achieved 27kmpl with a light foot cruising at 80kmph in 5th gear.
AC on 99% of the time.

[aniyo]

Can any Brio owners confirm their latest FE post the road digging festival in Bangalore.
I am getting a pathetic 11-11.5 with continuous ac. I drive 13-14 km one way to office and this usually takes me about 1:20 hrs to 1:45 depending on the traffic..
I use 185/65 tyres

[discoverwild]

Hadn't checked mileage on the Vista for ages, till the last fill.

City driving with AC on all the time.
Tankful to tankful method, 15 kmpl (14.97 to be exact).
Odometer: 1,33,000
Tyres are 22,000 kms old.
Model: Dec 2011

[bhpfaninblr]

Hyundai Verna CRDI SX(O) diesel mileage figures:

Bangalore city bumper to bumper: 13 km/liter
Highway runs minus the ghats: 21 km/liter
Highway runs including ghats: 18 km/liter

[self_driven]

Hello members,

Our 2014 Swift petrol delivers really poor fuel economy. I have tried changing fuel bunks, tyre pressure and driving style as well but the FE doesn't seem to get better. The car is nearing 24k kms mark. What pinches us further is that our other car, Hyundai Eon, delivers 19-20 km/l in city traffic any which way one drives it.

However, Swift has generally returned 10-11 km/l in moving traffic (30-60 km/hr speed) and 13-14 km/l only on highways even after driving with a light foot. People at Maruti service didn't find anything wrong with the car. My neighbour's Dzire petrol (same year as mine) gives 14-15 km/l in city and 18-19 km/l on open roads. A friend's Baleno petrol gives 16-17 km/l in city. In fact, I have seen many members comment about K12 motor's good fuel efficiency.

Our car was driven from factory to dealership by road which was around 70 kms. Then for the initial 2000 kms, different drivers were hired for inter state trips as none of us were well-versed with driving at that time. I think this is what has led to the poor fuel economy figures. I would like to know if at this point something can be done to improve fuel efficiency or not?

Ps. All FE figures are with 80% AC usage and calculated using tankful method.

[--gKrish--]

Sedate driving with well planned overtaking and downshifting to stops at signals. My route is through Sreekaryam Jn - Medical College which has moderate traffic even at 8pm.

PS : ACC always on and at 23 mostly.