Fg Air Con Performance

[Pete A]

Hi all,

I've now set up thermocouples in the 6T to test the A/C performance usder as many conditions as I can. While it's still bloody hot in Sydney it should give me some real data. BTW I think my AC works well but this should give some useful data.

I am going by reference of the outside temp measurement which I have confirmed is within 2 Degrees of accruate on aveerage.

I have a thermocouple in the cabin just about in the middle behind the centre console (I don't expect this to be of great significanceactually. I'll move it round till it does)

I have a thermocouple mounted in the centre vent of the air outlet. This is the important one.

What I want to confirm is how the temperature out of the vent variies and under what conditions. I'll post my findings over about a week. Hope the data means something.

I used it this morning while the temperature was modest and already have found some interesting data.

With the OS temp at 25 Deg the vent temperature was constantly at 16 Deg (the internal temp setting foir the system was 22Deg) this meant that the internal temp had been reached and the vent temp needed to be 16 Deg to maintain it. Also noticed that when idling (standing still) the temp in the vent definately goes up! More important data later when it's really hot. Cheers

[tab]

Will be good to see.

I mentioned it in the other thread about the very low idle speed affecting a/c performance and a few ignorant people ridiculed me. But it's definitely what lets it down, sitting in traffic on a hot day it struggles if the cabin isn't already cool.

[dre]

I'll be watching this with some interest! Keep up the good work.

I hate the climate control and want to know where the problems are so I can replace the dodgy parts.

[Pete A]

Hey Guys,

OK, here’s the results. Instead of posting a whole raft of numbers I’ve made a number of judgments on the AC performance based upon a number of operational tests. As I mentioned earlier, these are real measurements.

HOT DAY

Ambient Temp = 40 Deg

Internal Temp = 58 Deg

Vent temp = 54 Deg

AC set to AUTO and 22 Deg

On switch on the AC vents went straight to RECIRC (which I would expect) It seems like it switches to recirc automatically when the outside temp hits about 37 deg irrespective of what the internal temp is. Not yet totally confirmed.

After 20 minutes driving (no idle) the vent temperature has reached 13 Deg and the car was already quite comfortable to drive. The internal temperature was in the high 20”s and is very difficult to accurately measure because of sunlight and hot surfaces etc. But it was comfortable.

At the end of the trip (45 mins) the vent temperature was at 11 Deg fairly constantly. The internal temperature was measuring 25 Deg but as I said that can be misleading. Ambient temp was 36Deg.

Important to note that the minimum vent temperature reached during the trip was at about 30 mins. That was 7.8 Deg at the vent. Soon after the vent changed to fresh and the temperature increased to about 11 Deg and the fan speed reduced. Not a lot but you could hear it.

Also note that the vents changed from fresh to recirc and back a couple of times as the ambient temp changed from about 42 Deg to 36Deg during the trip.

Now the interesting bits.

Recirc allows the car to cool probably about 30% quicker than Fresh. This is a bit of a guess as the real data doesn’t reflect fan speed to vent temp. But it is noticeable.

When the car starts on the hot day, the speed of the decrease in temperature of the AC vent is logarithmic. It takes some time to cool the AC components and build up pressure in the compressor. So it seems to take a while to cool but in actual fact the temperature measurements show a steady increase in the cooling performance as time goes on. The longer it’s on the better it works.

When on AUTO the vent temperature is controlled by the sensors and computer and varies quite a bit during driving. However when you get to idle it all changes. Over about a 3 minute idle the vent temp went from 11 Deg – 15Deg. Moving on it then took about 2 minutes driving to get back into the 11 Deg temperature range. This phenomenon was identical of FRESH or RECIR vent operation.

When manually selecting the lowest temperature LOW. While driving the temp vent went pretty much straight to its lowest temperature 7.8 Deg and stayed there. EXCEPT when idle! When at idle the same problem happens, the temperature slowly increases by about 4-5 Deg.

Summary and Comments

At 7.8 Deg min temp, the car AC unit is cooling properly.

RECIRC definitely cools the car faster.

The efficiency of the AC is reduced when the car idles for extended periods. Therefore.

Stop/start driving is significantly less efficient for the AC.

Adjusting the temp to LOW turns on the AC flat out all the time except at idle. If you are stop/start driving a lot I would recommend this setting!

On a very hot day acceptable driving comfort should be reached in about 20 mins.

It was noticed that the AC works much harder when direct sunlight is coming through the front screen of the car. This also gives a perception that the AC is not working well even though it probably is.

What does all this mean?

Well, I think the FG AC is working fine. Particularly now that I know how it works.

I think that it is reasonable to expect the AC efficincy to decrease when idling for extended periods, but testing other cars will verify that.

The missus has a Pug with climate control. Wouldn’t mind doing a few of the AC functionality tests on that as a comparo. If I do, I’ll post the findings.

Hope this helps. Cheers

Edited 09/02/11 02:43 AM by Pete A

[dule]

For all of you complaining about the AC performance. Would it be too much of a hustle to get a slightly smaller compressor pulley?

This should make the compressor spin faster and in theory perform better.

Unless the problem with idle performance is the lack of airflow through the AC radiator (whatever the actual name is)

[arm79]

Would be interesting if anyone can get hold of the AC system performance charts from an FG workshop manual.

I have the EF/EL ones and B-series charts here and its an interesting comparison.

The charts are basically an acceptable centre vent tempterature level based on the ambient temp.

And going by these charts, an acceptable B-series temperature is anywhere from 15% to 25% warmer than an EF/EL. Would be interesting to see an FG chart to see how it compares to these 2. I suppose we are only talking a matter of 2 to 4 degrees in some cases, but in our weather, every little bit helps.

For instance, the minimum temp range for an EF/EL is 1 to 5 deg. For a B-series, its 2 to 9 deg. So the minimum temp the OP recorded is unacceptable in an EL, but at the high side of acceptable in a BF.

I've always felt my old EL had better cooling than my BF, which isn't all that bad. But I have been in many FG rentals and taxi's that the aircon can be called lacklustre at best.

Just a thought to see what Ford consider is acceptable nowadays.

It's probably more that Ford are more concerned with engine performance and fuel economy over a cool interior at the moment. My XF Ghia would freeze my nads off in about 20 sec of turning the aircon on, but at the expense of 30kw and 3l/100km.

[dre]

If anyone knows what parts to change and where to get them changed I'd be willing to spend my $$ to experiment a little and inform everyone of the results

[tab]

You'd just have to be careful that it won't fck your compressor by running too fast at higher throttle positions. The clutch on it does cut out at WOT to protect it as it is in stock form, so by decreasing the pulley size this automatic cut-out may no longer come in soon enough thus potentially stuffing your compressor.

It's probably more that Ford are more concerned with engine performance and fuel economy over a cool interior at the moment.

That's certainly my theory, it's all about the fuel economy sticker on the windscreen.

I think there's a few fridgies kicking around on here that would confirm/deny, but I believe the key test on any refrigerant/air-through-the-evaporator based A/C is a temperature drop of at least 10 degrees after the coil. So that's probably all Ford are worried about, even the idle speed temperature drop is acceptable by this standard.

Good work on the stats there Pete

[glensim]

Interesting results

[FAST-XR]

if you want to squeeze some more performance out of your air con, you will have to insulate all of the piping from the Evap and condensor.

The alloy suction line from the evap is absorbing engine bay heat and reducing efficiency. Same as the accumulator, youll notice they are always covered in condensation.

Insulate these with the black/grey air con foam insulation, the ones they use on copper pipes in refrigeration and air con systems...

the less heat that is absorbed after the evap the better. This makes the condensor more efficient as the discharge temp from the compressor will be slightly cooler.

This now means that the condensor has to deal with lower heat loads and can get the refrigerent down to a lower temp.... its a flow on effect