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Old 29th November 2011, 23:46   #31
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Default Re: Air condition in a diesel Car does not trip

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Originally Posted by misquitas View Post
Are you sure about the A/C cutting off in the i10? When we did the Goa-Mysore-Coorg-Goa trip in our i10 recently, I had used the AC continuously on with the fan on 1 position. After some time, the cabin would get cold and were were left with two options -- either to switch off the AC or to decrease the thermostat (turn the knob away from the maximum 'blue' position and somewhere in between the 'blue' and 'red' -- 9 o'clock position).
Since the car is new and we have used A/C in the month of november I am pretty sure its cutting off. I haven't driven the car much so can't notice the exact engine/compressor behavior. But I am cent percent sure for WagonR and Honda City. Will confirm for i10 soon.

Last edited by bluevolt : 29th November 2011 at 23:54.
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Old 29th November 2011, 23:47   #32
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Originally Posted by anilisanil View Post
I did not realize this until I drove my diesel figo continuously for 400 odd kms with a/c on. It so happened that the a/c unit started forming ice or something and clogged the blowers because of which the a/c had to be stopped, I though it was some issue and visited the service center and they dismissed it as a normal occurrence and that the a/c would be back to normal once i switch off and switch it on after say 5 minutes.

But not too sure why the a/c does not cut off!

This is an actual issue because of a faulty thermistor design. Please make sure you tell them you know about this thermistor issue and get it replaced with the new type. Apparently they are only replacing this if you report the issue three times. I got mine replaced after constant issues. I have not had an issye for the last 10k kms including a 1300km non stop drive.

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Originally Posted by Abes View Post
Is it that the min temp on the temp control is so low that when the temp knob is kept at max blue, the thermostat doesnt cut off? Has anyone tried it with the knob at minimum blue, i mean minimum cold?

Actually in non climate control cars ie: the ones with the manual knob, keeping the knob at minimum or maximum does not make the compresseor cut off. What happens is that the hot air which derives the heat from the circulating coolant (not exactly sure how the heat is transferred I think the pipes run close enough or around it) is stored in a seperate pipe. when you adjust the thermostat to medium, this hot air gets mixed in the vents.

You can find this hot air pipe for the Figo above the front passenger footwell. Keep the car running and feel around next to the glove box. you fill find this.

Last edited by Jaggu : 30th November 2011 at 00:11. Reason: Back to back posts, please use Multi Quote (Quote +) instead. Thanks
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Old 30th November 2011, 00:09   #33
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Default Re: Air condition in a diesel Car does not trip

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Originally Posted by mtnrajdeep View Post
You meant 100 rpm or 50 rpm right? I only see the rpm moving from 800 to 850/900 when the ac is switched on.
Yes absolute mistake from my side.

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Originally Posted by Aroy View Post

A thermostat has nothing to do with ACC, it is there just to maintain temperature.
Reply below by libran.

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Originally Posted by libranof1987 View Post
Not "maintain" in the true sense of the term actually. It just constantly provides temp. at the desired "cool/hot" level.

It doesn't maintain the temp. of the cabin.
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Originally Posted by drpullockaran View Post
I doubt that this technique is employed in our mileage conscious Maruti but will be news to me if it does.

Yes they do.

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Originally Posted by misquitas View Post
Are you sure about the A/C cutting off in the i10? When we did the Goa-Mysore-Coorg-Goa trip in our i10 recently, I had used the AC continuously on with the fan on 1 position. After some time, the cabin would get cold and were were left with two options -- either to switch off the AC or to decrease the thermostat (turn the knob away from the maximum 'blue' position and somewhere in between the 'blue' and 'red' -- 9 o'clock position).
This has to do with ambient temperature also, in my swift on a summer day its pleasant on long drives. But at night it can become quite irritating.

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Originally Posted by figo_mba View Post
No this is not true. I do not think all diesels are void of this compressor control.
I can vouch for Figo diesel because I have experienced the cutoff of the compressor on long drives where you experience a small shake and then after some time it comes back again. Smooth roads, zero traffic is required to notice this.
My friend who drove my figo came back asking what it was because the vibration is certainly distinctive than what happens in a petrol car that he drives.
I guess so and i never said all diesels and have asked fiat guys to clarify.

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Originally Posted by humyum View Post
In the Swift Diesel, when you jam the accelerator down the compressor cuts off. Just to see this phenomenon in action, rev the car with the AC on in neutral, when you leave the accelerator, the AC will be off, I ll go to the idle rpm (800 rpm) which is minus the AC rpm and then suddenly after a second the compressor will start again. This is to I guess provide the entire engine power for momentum when it senses the user want's absolute power.

yes otherwise in traffic situation's, i ve never seen the compressor cut off in my Swift D !
Free rev cut off never tried, i guess its the old accelerator pedal sensor doing its job like ol esteems, if thats the case. Will have to try though in driving i never felt it, maybe coz i dont floor even for hard acceleration. I gas down based on how engine responds.

Quote:
Originally Posted by Abes View Post
Is it that the min temp on the temp control is so low that when the temp knob is kept at max blue, the thermostat doesnt cut off? Has anyone tried it with the knob at minimum blue, i mean minimum cold?
Nope it just opens the hot air side and keeps the compressor running in swift and most of the other MUL cars without ACC system.
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Old 30th November 2011, 09:20   #34
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Default Re: Air condition in a diesel Car does not trip

I also felt that it was the AC compressor that switches on and off in the Figo diesel resulting in those sharp jerks. Had it not been the case, similar jerks would have been felt in winters also, but they are not there now.

Also, when it comes to the compressor switching off & then on again, I believe it has to do with the thermostat & not the power requirements of the car. For instance, when my Alto is driven with full load & AC on, then at times, it feels really sluggish & I have to manually switch off the AC. Had there been a provision wherein the ECU would automatically do this job, I wouldn't have had to do it manually on my own.
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Old 30th November 2011, 09:47   #35
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Default Re: Air condition in a diesel Car does not trip

Yes the minimum position is very cold, and the thermostat will not cut off till the inlet temperature reaches 16 degrees or less. In all my cars if the thermostat is kept at minimum it cuts off only in winter, when the car is chilled. In fact in dead winter in Delhi, when the temperature is in the region of 10-, the compressor does not switch on.

If the thermostat is kept a point or two above minimum it will cut off at a higher temperature. I have experienced this when the cleaner shifted the knob, and the AC kept switching on and off at a relatively high temperature.
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Old 30th November 2011, 10:23   #36
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Default Re: Air condition in a diesel Car does not trip

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Originally Posted by TaurusAl View Post
when i asked the same to the service guy of Maruti, he said something like 'The Pump will work less if your keep your blower low'.

I really did not understand what he said. Can anyone put a light on this ? If there is any point in keeping the blower low in a diesel car, and will it save anything at all ?

Can anyone confirm this ? That the a/c will perform same and burn same amount of fuel irrespective the blower position as DDiS engines are not equipped with the thermostat ? I assume it will but the service guy that I have quoted above has put me in 2 minds.
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Old 30th November 2011, 10:51   #37
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Default Re: Air condition in a diesel Car does not trip

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Originally Posted by TaurusAl View Post
Can anyone confirm this ? That the a/c will perform same and burn same amount of fuel irrespective the blower position as DDiS engines are not equipped with the thermostat ? I assume it will but the service guy that I have quoted above has put me in 2 minds.
Blower(which runs on battery power) has got nothing to do with fuel consumption. So irrespective of the blower position, the fuel consumption would remain same.
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Old 30th November 2011, 11:45   #38
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Default Re: Air-con compressor in a diesel car does not trip?

Though the blower has no direct relation with fuel consumption, keeping the blower on minimum speed does actuate the cutoff for the compressor earlier than it would have done on a higher position (except few Diesels where cutoff does not happen at all).

This early cutoff will definitely improve fuel efficiency.
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Old 30th November 2011, 12:23   #39
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Default Re: Air-con compressor in a diesel car does not trip?

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Originally Posted by Jaggu View Post
Yes DDiS does not have compressor cut off based on temperature. It just stays ON all the while.
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Originally Posted by Jaggu View Post

But fact is it (cut off) is not there, why? well the suzuki guys have hit some road block at design that they designed it this way.
This is strange, I was wondering how the ice formation in Evaporator (due to excessive cooling) will co-relate with the AC compressor's working. Do share once you get more concrete info on this.

The design is pretty simple to incorporate. Will need money though.

Spike

PS- Road block during design leading to this situation (that too from Japanese), is something I find difficult to comprehend.

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Old 30th November 2011, 12:39   #40
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Default Re: Air-con compressor in a diesel car does not trip?

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Originally Posted by SPIKE ARRESTOR View Post
This is strange, I was wondering how the ice formation in Evaporator (due to excessive cooling) will co-relate with the AC compressor's working. Do share once you get more concrete info on this.
===========
PS- Road block during design leading to this situation (that too from Japanese), is something I find difficult to comprehend.
The grill temperature is not that low that ice forms, maybe thats how they are avoiding the issue. Till date i never had icing up issue.
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Old 30th November 2011, 13:35   #41
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Default Re: Air-con compressor in a diesel car does not trip?

^^ How is the grille temperature monitored and fed back to the ECU? There must be some loop, that is what I am thinking on. You have not seen icing as there must be some feedback mechanism which is conveying the temperature values.

Spike
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Old 30th November 2011, 13:43   #42
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Default Re: Air-con compressor in a diesel car does not trip?

Yes i had the same doubts as your ^^ If that is the case why are they not using it to cut the compressor off?
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Old 30th November 2011, 14:52   #43
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Default Re: Air-con compressor in a diesel car does not trip?

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Originally Posted by SPIKE ARRESTOR View Post
^^ How is the grille temperature monitored and fed back to the ECU? There must be some loop, that is what I am thinking on. You have not seen icing as there must be some feedback mechanism which is conveying the temperature values.

Spike
A/C compressors need not necessarily be cut off. Even in auto A/C for a petrol car, if the thermal load is never overcome by the A/C, the compressor works on constantly to relieve the thermal load. By thermal load, I mean the temperature difference the A/C need to maintain. If the amount of refrigerant is less, or if the compressor runs at reduced capacity, or if the A/C is designed for low efficiency, the A/C may never be able to overcome its thermal load. It is not good for the compressor motor to be ever on and I am bit surprised by the findings that the diesel engine cars do not have a compressor cut-off.

In any A/C, leave alone the one in a diesel car, if the compressor is able to overcome the thermal load on the A/C at a quick rate, say running the A/C in heavy winter or a bad designed (by making it over efficient) A/C running without cutting off using a thermostat, there is a chance that the liquid refrigerant not to get enough heat to evaporate into gaseous form in the evaporator. Thus if liquid refrigerant enters into the compressor, the compressor can get damaged. This is as per theory. Might be the A/C that never cut off are designed to be never over efficient. Moreover, the person inside the cabin will automatically switch off the A/C in such a situation. I guess someone from the automobile A/C industry can comment better on the nuances.
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Old 30th November 2011, 15:00   #44
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Default Re: Air-con compressor in a diesel car does not trip?

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Originally Posted by thoma View Post
A/C compressors need not necessarily be cut off.
Why?

Quote:
If the amount of refrigerant is less, or if the compressor runs at reduced capacity, or if the A/C is designed for low efficiency, the A/C may never be able to overcome its thermal load.
AC designed for low efficiency? But why?

Spike
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Old 30th November 2011, 15:20   #45
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Default Re: Air-con compressor in a diesel car does not trip?

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Originally Posted by SPIKE ARRESTOR View Post
Why?
My very next few sentences of the post should have cleared your doubt on why.

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AC designed for low efficiency? But why?

Spike
By low efficiency, I am really not meaning poor efficiency of the A/C as such. An automobile A/C is designed keeping in mind the space it is required to cool too.

Imagine a very high capacity A/C in a small car which can freeze the cabin in a couple of minutes. Here the A/C is highly efficient. The other way round, imagine fitting a car A/C to a Volvo bus. You can term this A/C as inefficient. The speed of the compressor motor, the refrigerant used, space to be cooled all lead to making the A/C efficient or not.
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