Author Topic: AirCon compressor  (Read 2996 times)

jazzaro

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AirCon compressor
« on: August 16, 2016, 03:32:27 PM »
Good morning.
I've noticed that the GK Jazz/Fit has a fixed displacement scroll compressor for the aircon, while other same price cars use  variable displacement piston compressor. When variable displacement compressor can smoothly modify their power following the request of cold air, fixed displacement can only work in off/on mode, so drivers can usually feel this switchings while driving; and I remember that they are a little annoying (i.e. in a Rover 214si, in a Fiat Panda and other old cars) with the cabin fan at slow speeds because there are many on-off-on-off cycles.
So the question is this: how is the jazz a/c compressor, especially in the auto climate control trim? Do you perceive the cycles?
Thanks 

VicW

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Re: AirCon compressor
« Reply #1 on: August 16, 2016, 03:47:06 PM »
None of the Jazz's that I have owned, five in all manual and CVT, have showed any signs of hesitation when the aircon compressor cuts in. The idle revs speed up slightly as the compressor cuts in however.
The two previous cars I had before the first Jazz, a Peugeot 2.0 litre and a Mondeo 2.0 litre both hesitated slightly as the compressor cut in.

Vic.

jazzaro

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Re: AirCon compressor
« Reply #2 on: August 16, 2016, 03:50:12 PM »
Ok.. and what about the lack of power during a overtake or climbing an hill (with aircon ON)?

Skyrider

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Re: AirCon compressor
« Reply #3 on: August 16, 2016, 04:37:33 PM »
If you are worried about aircon compressor load while overtaking maybe you should reconsider your driving style.

jazzaro

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Re: AirCon compressor
« Reply #4 on: August 16, 2016, 04:47:37 PM »
If you are worried about aircon compressor load while overtaking maybe you should reconsider your driving style.
Now I own an old Clio1.2, 75ps.  Considering that the A/C drains 3-5hp, the difference can be easily perceived, more at low revs than at high rpms.
 
« Last Edit: June 22, 2017, 10:09:04 AM by jazzaro »

culzean

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Re: AirCon compressor
« Reply #5 on: August 16, 2016, 08:12:02 PM »
Good morning.
I've noticed that the GK Jazz/Fit has a fixed displacement scroll compressor for the aircon, while other same price cars use  variable displacement piston compressor. When variable displacement compressor can smoothly modify their power following the request of cold air, fixed displacement can only work in off/on mode, so drivers can usually feel this switchings while driving; and I remember that they are a little annoying (i.e. in a Rover 214si, in a Fiat Panda and other old cars) with the cabin fan at slow speeds because there are many on-off-on-off cycles.
So the question is this: how is the jazz a/c compressor, especially in the auto climate control trim? Do you perceive the cycles?
Thanks 

Scroll type compressors are more reliable, more efficient and wear less than piston type,  and have very few moving parts.   Many large companies have changed over from old piston type to scroll type compressors for their compressed air supplies because of this,  and saved a lot of money in repairs and maintenance.

I was under impression that the aircon clutch is automatically disengaged for engine starting and also when inlet manifold vacuum drops below a certain level (ie when engine in under load - may be down to throttle position sensor on more modern cars) to take aircon load off the engine.
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

jazzaro

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Re: AirCon compressor
« Reply #6 on: August 16, 2016, 10:29:56 PM »
Scroll type compressors are more reliable, more efficient and wear less than piston type,  and have very few moving parts.   Many large companies have changed over from old piston type to scroll type compressors for their compressed air supplies because of this,  and saved a lot of money in repairs and maintenance.
Ya, I know. On the other hand they cannot be regulated.
Quote
I was under impression that the aircon clutch is automatically disengaged for engine starting and also when inlet manifold vacuum drops below a certain level (ie when engine in under load - may be down to throttle position sensor on more modern cars) to take aircon load off the engine.
Yes, all compressors are automatically disengaged during engine start and in some other conditions: my 10 years old Renault disengages the compressor (a variable displacement 4 piston Sanden) in case of overheating, ice over the cabin evaporator, less than 2 celsius degrees,   full throttle in 1, 2 and 3 gears and rpms between 1600 and 3500, and in case of  some engine faults (throttle sensor, kat, lambda, spark plugs and others..). Modern cars have many parameters to be considered for the AC compressor engagement.
« Last Edit: August 16, 2016, 10:47:29 PM by jazzaro »

TG

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Re: AirCon compressor
« Reply #7 on: August 18, 2016, 03:47:35 PM »
I was under impression that the aircon clutch is automatically disengaged for engine starting and also when inlet manifold vacuum drops below a certain level (ie when engine in under load - may be down to throttle position sensor on more modern cars) to take aircon load off the engine.
Yes quite right. On the Jazz, a/c demand switches and sensors are fed to the ECM, it then feeds the compressor clutch and fan relays, so I guess it can prioritise engine over a/c as needed. 

On earlier models, the differences between standard a/c and climate control according to the service guides seem purely down to the controls rather than the production side of things - CC gets two extra sensors, but the production side is still only switched on or off, there's no variable output.
--
TG

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