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Styling Aircon light

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Styling Aircon light

AndyRKett said:
However what we are talking about In relation to the above article is a early 2000s car, more specifically an 8.1 litre SUV which looks something like this

View attachment 182395


It's probably worth noting that the design of these cars also relates back to the 80s and even 70s without any major update to the shape and aerodynamics. Just for comparison here is a 70s version

View attachment 182396
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There's a thing aerodynamicists talk about called detail optimization. Those two look little alike aerodynamically. Somewhat ironically I could say exactly the same thing about the 60's 500 vs today's.

Fact remains the tech on a suburban released in 2000 is about the same as that on a Panda in 2003, hardly 'much newer'.

AndyRKett said:
Finally if you put any car in any gear and floor it with the aircon off, and with the air con on, there should be no noticeable difference between the two as cars are designed to kill the AC at wide open throttle to give maximum power to the engine, as long as your foot is buried in the carpet, you won't have aircon.
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I don't think you've ever driven a car, or at least not a 4 cyl. The vast majority of cars I've driven don't do this. My TA does, my Trafic does, but the Suzuki, Proton, Nissan, Mercedes, VW, Jeep & Renault don't/ didn't.

I don't know where your figures are from, but wikipedia lists the 2006 Tahoe Hybrid at .038, a Tahoe is a short Suburban. All else being equal, the better fineness ratio of a Suburban should help it over a Tahoe. Nothing short of a Jeep Wrangler (completely flat windscreen, massive flat grill, massive tyre flares) has a Cd of 0.45. You have to go well back into the 70's to find anything like that.

I already addressed CdA. The CdA of a Suburban is about double of a 500, but it's engine nearly 7 times larger, no wonder the A/C barely made a difference to it's economy, a bit of load just means it's operating in at a higher BMEP.

Fact remains, there's not a single paper any where that claims A/C usage is too small a factor to consider or measure. Fact remains the sedans tested showed similar results.

My previous Renault was rated 9.7 city, it returned 6.7 over the 20K that I had it, and that includes trailer towing. My lifetime average speed as recorded by my GPS was 26km/h- dead on for the NEDC city number. How far over NEDC are you averaging with your A/C always on?

The only possible point of debate is what speed is the cross speed in A/C on vs windows down. Only a few internet experts claim otherwise.

And I'd argue that the 500, basically a 2003 car (and it takes about three years to go into production), isn't really as modern as you'd have me believe. Most of your arguments might have some weight on a diesel S Class or something, but they almost have no relation to a 500.

You know, sedans showed similar results, so why bang on about the SUV???
 
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Mick F said:
I said up thread, that we rarely ever have the AirCon set at the extreme ends. Generally, it's set in the 500TA at 20degC ................. so it's hardly going to affect the fuel consumption at all.
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20 is pretty low. The lowest my Renault goes is 18 for comparison.

There's certainly logic to this, but away goes the idea that it keeps the system 'healthy'. The A/C is going to spend a lot of it's time off.
 
TrevC said:
. By coincidence Mick I ran a 2003 Clio for 9 years (with my daughter) and when she sold it the aircon was still blowing cold and was never re-gassed.
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My Jeep is 12 years old, only gets used every six months and still on it's original charge. And I can tell you a matte black roof (with no head liner) on a black Jeep on a 44*C day in the middle of no where, I'd know if the A/C wasn't still close to 100%.

I suspect the argument of seals drying out might have applied to cars so fitted in the 60's. It doesn't seem like you'll come out ahead running the A/C to save the seals in a modern car.
 
Mick F said:
The experiment linked up thread, had the ambient temp at 24degC .......... a rather warm and rare summer's day here in Cornwall.
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On a sunny day when the ambient temperature is 24C, the temperature inside the car will be about 45C.

That's why there are so many warnings about leaving dogs and children in cars in summer.
 
jrkitching said:
On a sunny day when the ambient temperature is 24C, the temperature inside the car will be about 45C.

That's why there are so many warnings about leaving dogs and children in cars in summer.
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It's static sunshine that makes the difference. Radiation vs conduction.

When the car has no windchill when stationary, you could well be correct in 24degC sunshine having 45degC inside - not tested this fact yet - but as soon as the car is whizzing along, the temp would decrease to ambient or thereabouts.

Biggest load on AirCon is in slow moving traffic or when stationary combined with direct hot sunshine. Small loads are normal because we rarely have direct hot sunshine here.

Someone correct me if I'm wrong here please.
AirCon works by chilling the air to remove the moisture. The car's ventilation system then mixes it with warm air to a greater or lesser degree from the heater matrix to get the desired temperature. You would then suppose that the chiller is constantly running and fixed, but it's not. The more the demand, the more air needs to be chilled, but it's on a thermostat so when not in high demand, it cycles.
As I say, correct me if I'm wrong.

Regards,
Mick.
 
Just talking about the study here and ignoring everyone antidotal stories of their own cars.. if you take something with a huge engine that is as big as, and shaped like a barn and you propel that forward at speed, the opening or closing of the windows is not going to adversely affect the overall aerodynamic properties of that vehicle. Essentially if you drill a hole through a brick then it's still a brick and will still cut through the air like a brick.

Now you take a smaller, newer and more aerodynamic car with a small engine, an engine that has been tuned to be as economical as possible and has relatively low power, and you open the windows, the windows on a fiat 500 make up a large portion of the lateral cross section, the car is small and so opening the windows will have a big impact on its aerodynamics. The little engine which is already low on power will have to work a lot harder to overcome the extra drag and so the economy will drop as a result.

A much bigger engined car that is huge and has little windows by comparison to the cars overall size, is already burning a gallon of fuel ever 15 miles a little extra drag is not going to make a great deal of difference.

However stick a mechanical load on an engine like an old big American car which harks back to the 70s or 80s with no particular attention to getting good economy then yes this will make a difference to the fuel consumption aircon is a big load and in an inefficient old car it's going to make an even bigger difference.

You may also find the old fans in these old cars are also particularly power hungry and so draw extra power from the alternator. The condenser could adversely affect the radiator efficiency. So putting the aircon on makes a big difference.

On a little fiat with a little compressor, a better balanced expansion valve and more efficient engine cooling and therefore condenser cooling, a little fan or a PWM driven fan will use less power and overall the effect on the engine'd economy is not so big.

The point here is not that aircon makes no difference whatsoever to engine economy because that is clearly impossible.

It is that newer smaller more efficient cars don't see a great deal of difference from having the aircon on or off and on a hot day a little car like a 500 will get more from having the aircon on, than having the windows open specifically at higher speeds.

The old study that keeps getting posted is in no way comparable to small little efficient cars like the 500, and to keep saying that this old study proves a rule is incredibly short sited.
 
Mick F said:
<SNIP>

Someone correct me if I'm wrong here please.
AirCon works by chilling the air to remove the moisture.
No, moisture removal is a byproduct of the cooling, not the reason for it.
The car's ventilation system then mixes it with warm air to a greater or lesser degree from the heater matrix to get the desired temperature.
No, it mixes with outside air, not heated air (except for demist on some climate control systems)
You would then suppose that the chiller is constantly running and fixed, but it's not. The more the demand, the more air needs to be chilled, but it's on a thermostat so when not in high demand, it cycles.
Correct for air conditioning and a engine driven pump. For climate control the system would tend to leave the compressor on longer and control the ratio of external to chilled air. The load on the compressor (and thus energy consumption) varies with the internal pressure differental of gas in the system between hot and cold sides. Climate control has a little more control over this than AC.

 As I say, correct me if I'm wrong.

Regards,
Mick.
Click to expand...

Robert G8RPI.
 
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Mick F said:
Someone correct me if I'm wrong here please.

AirCon works by chilling the air to remove the moisture. The car's ventilation system then mixes it with warm air to a greater or lesser degree from the heater matrix to get the desired temperature.
Click to expand...


Actually your 100% correct on this. All the air that comes into the car will pass through the air conditioning evaporator, this is what makes it air conditioning and not just air cooling.

After the evaporator there is a blend door which will pass some of that air through the heater matrix and some around it, if your want all heat then all the air will be directed through the heater matrix, if you want full cooling it will bypass the matrix. In climate control this blend door is controlled automatically, in non climate control cars it will be controlled by the knob that has a scale from blue for cold to red for hot, usually by a cable and lever system.

IMG_1152.JPG
This basic picture sums it up succinctly.

There is no difference in the workings of the mechanical side of the air conditioning between manual systems and climate control systems. With climate control the brains of the system measures the temperature of the engine coolant, the temperature in the cabin and in the air box as well as the sun load, and through some predetermined parameters, will move the blend door about to get the desired temperature.

The climate control system still has an AC button to turn the air con on and off and when turned on both work in the same way, the aircon compressor clutch engages and the system cycles on and off depending on the pressures inside the pipes and is not decided by the climate control system.
 
g8rpi said:
No, it mixes with outside air, not heated air
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I will quote/paraphrase ..........

The cooling system works in the same way as a domestic refrigerator.
.............. the gas loses heat and becomes a liquid. The liquid passes through and expansion valve to an evaporator, where it changes from liquid under high pressure to a gas under low pressure. This change is accompanied by a drop in temperature, which cools the evaporator. The cycle repeats ............

Air blown through the evaporator passes to the air distribution unit, where it is mixed with hot air blown through the heater radiator to achieve the desired temperature.

The heating side of the system works in the same way as models without air conditioning.

Hope this helps.
Mick.
 
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I beg to differ, this may be correct for older systems with manual flaps but not for a modern climate control system with servo controlled flaps. Air might pass throug the heater matrix for simplicty but the water flow through the matrix would be shut off. This is one of the reasons why modern systems are more efficent. Basic heater / aircon systems do not have any temperature sensing other than the "human in the loop"

Robert G8RPI.
 
<SNIP> The climate control system still has an AC button to turn the air con on and off and when turned on both work in the same way said:
This is not correct. The internal system pressures will only turn the compressor off when the system is overloaded, iced up or low on gas. The whole point of climate control is that it has temperature sensors and thus controls the temperature accurately. They normally have outside air temperature, internal air temperature ( usually with a small fan to suck air over the sensor) and a infrared radiation sensor (small hemisphere on top of dash) to compensate for solar irradiation. Ther system then controls the compressor, mixing flaps and hot water valve to maintain the selected temperature regardless of outside conditions.

Robert G8RPI.
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Sounds to me that you've said the same thing or thereabouts.

The air is cooled - and dehumidified - and then heated to achieve the desired temperature.

Ther system then controls the compressor, mixing flaps and hot water valve to maintain the selected temperature regardless of outside conditions.
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Further, the "outside conditions" are very much part of this. They must be.
If they aren't extreme, the system is lightly loaded and fuel consumption isn't much affected.

Thanks,
Mick.
 
g8rpi said:
This is not correct. The internal system pressures will only turn the compressor off when the system is overloaded, iced up or low on gas. The whole point of climate control is that it has temperature sensors and thus controls the temperature accurately. They normally have outside air temperature, internal air temperature ( usually with a small fan to suck air over the sensor) and a infrared radiation sensor (small hemisphere on top of dash) to compensate for solar irradiation. Ther system then controls the compressor, mixing flaps and hot water valve to maintain the selected temperature regardless of outside conditions.

Robert G8RPI.
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Nope you're wrong on this and making assumptions about how these things work and here is a simple reason why.

When the compressor switches off there is still a head of compressed gas south of the expansion valve, this can take quite a while to pass through the valve and while it's doing so the system continues to cool and the gas moves out of the evaporator to the receiver, to equalise the pressure around the system.

If you turned off the air conditioning compressor completely, every time you wanted to warm the air up, the moisture collected on the evaporator gets taken back up into the air and you would feel warm damp air being blown into the cabin.

Therefore the air conditioning compressor works continuously until the pressures inside the system need to equalise, then it will turn off the clutch till they have equalised, and turn back on again, with the occupants of the car never experiencing unconditioned air inside the car.

The reason the compressor clutch needs the space to turn on and off as in very hot weather or cold weather, the dynamics of the system are such that in very hot or very cold weather the compressor might run for very short periods or for much longer periods, to get the same level of air conditioning, depending on the outside and inside temperatures.

The inside and outside temperatures alter the way the gas expands and in the valve or the amount of heat it gathers when compressed and then loses again as it passes through the condenser and this alters the necessary duration that the compressor needs to operate for.

Once the interior of the car has cooled down the system will work much more efficiently and not require as much energy to cool the interior down as it would when the interior of the car has been warmed up in the sun for several hour.
 
Markybear999 said:
Was wondering if anyone could advise on how to make the air on switch on the fiat 500 dash any brighter?
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My all the guy wanted to know was how to get a brighter Aircon light and its produced an "encyclopaedia" but still no answer !!!!
banghead.gif
 
coolbumble said:
My all the guy wanted to know was how to get a brighter Aircon light and its produced an "encyclopaedia" but still no answer !!!!
banghead.gif
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I believe the gist was don't, otherwise you will be blinded when the sun goes down and you have a ridiculously bright light in the middle of the controls, it's all there if you go back.
 
Concerning the original post, I agree it's not a very clear indication to see at a glance. In daylight, the snowflake symbol shows in higher contrast if the a/c is off, when on the indicator lamp seems to blend in more with the knob (if it is ivory, mine was). I would imagine it would show up better with black controls, but could be wrong. It might be worth trying a black control knob if that is possible.
 
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