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      06-12-2012, 10:21 AM   #1
blaknite7
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Question A/C Temps and Pressures – Can Arizona Freeze Over?!?

Can any of you guys tell me what the following are (should be) on the 335I:
1. A/C temperature (at vent) vs. ambient outside temperature?
2. A/C pressure (low side) vs. ambient temperatures?

Das-en Story:
Im trying to make my AC as cold as humanly possible, enough to wear an arctic suit while driving and rival the equipment used to climb Mount Everest. I live in Arizona and the average temperature in the afternoon is between 105-god*awful°F (now, but its expecting to get hotter). I started to recharge my AC with some R134a and I follow the directions stating if the outside temp is over 100, the low side pressure should be between 50-55psi. With a pressure of about 40-42 PSI I naturally thought I was low and added cold goodness “magic gas”. As soon as I did that the pressure started to spike randomly (sounded like compressor stall) and was hitting 75-80 psi and virtually no cold air. I then proceeded to bleed out some of the gas from the low pressure port back down to 40PSI and everything started to work fine again. (This is really messy with the oil so heads up if you ever do this…) So I am curious to know what the actual pressures should be for this particular car. Also how cold does the air come out of the vents on a normal 335I?

My stats:
Stationary: All vents ~52°F
Moving: All vents ~41° except for the center (left side) vent which is about 47°F.

I just recharged my girlfriends car which blows about 37 while moving… there’s no way im going to let a buick take me so help me out guys and let me know what you think…. I want hell (Arizona) to freeze over!
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      06-12-2012, 02:16 PM   #2
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It depends on the humidity and the fan speed. Granted AZ should be pretty dry - it's a lot less challenging for an AC system to cool dry air than humid, sticky air.
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      06-12-2012, 02:38 PM   #3
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Quote:
Originally Posted by Surly73
It depends on the humidity and the fan speed. Granted AZ should be pretty dry - it's a lot less challenging for an AC system to cool dry air than humid, sticky air.
That is true. I have "max cool" on thr jb4 active so the fan speed is pretty high. Still it would be nice to compare it to something...
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      06-13-2012, 08:03 AM   #4
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That is true. I have "max cool" on thr jb4 active so the fan speed is pretty high. Still it would be nice to compare it to something...
JB4? You mean engine fan speed or interior fan speed?

At lower interior fan speeds your vent temperature should be about 37F. As you increase the fan speed, and the wet bulb temperature of the intake air (i.e. humidity is a factor on the evaporator side of the system) increases then it won't be able to maintain this.

As the AC system load increases, eventually you'll need more condenser coil cooling (airflow over the rad) and compressor revolutions (engine speed) to maintain required cooling.

I've only had one really hot day since getting my E90 and I wasn't terribly impressed compared to my E39. In 14 years, my E39 only needed a slight top up with R134a.

Note: If you got oily stuff all over when purging your overcharged system, that oil is no longer in your compressor so you're now low on oil which could lead to expensive repairs.
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      06-13-2012, 08:34 AM   #5
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Quote:
Originally Posted by Surly73
Quote:
Originally Posted by blaknite7 View Post
That is true. I have "max cool" on thr jb4 active so the fan speed is pretty high. Still it would be nice to compare it to something...
JB4? You mean engine fan speed or interior fan speed?

At lower interior fan speeds your vent temperature should be about 37F. As you increase the fan speed, and the wet bulb temperature of the intake air (i.e. humidity is a factor on the evaporator side of the system) increases then it won't be able to maintain this.

As the AC system load increases, eventually you'll need more condenser coil cooling (airflow over the rad) and compressor revolutions (engine speed) to maintain required cooling.

I've only had one really hot day since getting my E90 and I wasn't terribly impressed compared to my E39. In 14 years, my E39 only needed a slight top up with R134a.

Note: If you got oily stuff all over when purging your overcharged system, that oil is no longer in your compressor so you're now low on oil which could lead to expensive repairs.
Thanks for responding, to answer your questions:

I was talking about the electric fans for the rad and condenser. The jb4 modifies when they kick on and what speed to provide extra airflow over the stock algorithm. The climate airflow fan was set to max for all my testing. But If most people only see 37 than I'm in the ball park. So I, understand you hit 37 with the lowest fan (internal) setting while not moving correct?

Regarding the compressor oil, it gets injected with the r134a boost. So bleeding some of it out isn't so bad, but you are right, without it not good news. I would really like to drain and vacuum the system but I'm not in the mood to spend 200 bucks to do it...
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      06-13-2012, 09:48 AM   #6
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Add ICE 32 to your system. I did it to mine towards the end of last summer, and it's definitely made it colder. It also helped a Mazda3 which have a notoriously weak A/C system. It's already in some of the cans of R134a, and rebuilt compressors. I have the injector for the oil, if you're close by.

http://www.ice32.com/

http://www.midwayautosupply.com/p-17...e-32-ec-2.aspx

http://www.brakeandfrontend.com/issu...ontentid=44055

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      06-13-2012, 12:05 PM   #7
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Quote:
Originally Posted by blaknite7 View Post
Thanks for responding, to answer your questions:

I was talking about the electric fans for the rad and condenser. The jb4 modifies when they kick on and what speed to provide extra airflow over the stock algorithm. The climate airflow fan was set to max for all my testing. But If most people only see 37 than I'm in the ball park. So I, understand you hit 37 with the lowest fan (internal) setting while not moving correct?

Regarding the compressor oil, it gets injected with the r134a boost. So bleeding some of it out isn't so bad, but you are right, without it not good news. I would really like to drain and vacuum the system but I'm not in the mood to spend 200 bucks to do it...
There are control systems which limit the minimum temperature so that the evaporator coils don't freeze up. The coldest you're going to see is 2C or about 37F. You're extremely unlikely to see temps like that on high interior fan speed unless you're on recirc and the car is already cold inside.
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      06-13-2012, 01:26 PM   #8
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Quote:
Originally Posted by Surly73
Quote:
Originally Posted by blaknite7 View Post
Thanks for responding, to answer your questions:

I was talking about the electric fans for the rad and condenser. The jb4 modifies when they kick on and what speed to provide extra airflow over the stock algorithm. The climate airflow fan was set to max for all my testing. But If most people only see 37 than I'm in the ball park. So I, understand you hit 37 with the lowest fan (internal) setting while not moving correct?

Regarding the compressor oil, it gets injected with the r134a boost. So bleeding some of it out isn't so bad, but you are right, without it not good news. I would really like to drain and vacuum the system but I'm not in the mood to spend 200 bucks to do it...
There are control systems which limit the minimum temperature so that the evaporator coils don't freeze up. The coldest you're going to see is 2C or about 37F. You're extremely unlikely to see temps like that on high interior fan speed unless you're on recirc and the car is already cold inside.
I figured there was some limit switch to prevent the could from turning into a sheet of ice, but I haven't been able to confirm what that number was. Sounds like 37 is it. I'm actually impressed it gets that close now I such hot weather here. Thanks for the input.
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      06-14-2012, 09:20 AM   #9
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Quote:
Originally Posted by blaknite7 View Post
I figured there was some limit switch to prevent the could from turning into a sheet of ice, but I haven't been able to confirm what that number was. Sounds like 37 is it. I'm actually impressed it gets that close now I such hot weather here. Thanks for the input.
When there is a large difference between set point and interior temp, or set point and exterior temp, the IHKA will force recirc mode even though the indicator lamp on the button does not illuminate to indicate this. Just because it's 100F out doesn't mean that you're cooling 100F air all the time.

As a related note - if it's really hot, humid and sticky (not referring to AZ) I recommend manually setting recirc mode. Humidity extraction is a greater load on the AC system than temperature reduction and setting recirc means that once the humidity is reduced in the cabin the only additional humidity to be removed is from the occupants sweating and breathing. Trying to dehumidify 100F+humidity outdoor air in one pass will not be nearly as effective or comfortable.

When low(er) humidity air is drawn into the system, it is more easily able to handle temperature rise due to outdoor temp and solar load.
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      06-14-2012, 11:25 AM   #10
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So I'm looking at systems to drain, vacuum and recharge the ac. When you release the r134a how much oil comes with it? Prior to recharging the system how much oil should I put in? I was told the system capacity was 5 oz and you shouldn't need to add more than an 1 oz of PAG if you just evacuate the 134a.

Also this ice32 stuff... Is that an oil or an additive that shouldn't be counted as oil towards the total capacity?
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      06-14-2012, 03:12 PM   #11
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Quote:
Also this ice32 stuff... Is that an oil or an additive that shouldn't be counted as oil towards the total capacity?
It's an additive, and doesn't count towards the amount of PAG that's put in.
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      06-15-2012, 09:57 AM   #12
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Sweet. I decided to drain, vacuum and recharge the system. I'm going to try that ice 32 stuff too so hopefully it will blow snowballs! Just waiting for the gauges to get here butt I'll let you guys know why the final temps are!
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