A/C "upgrade" questions

[e p slick]

I scrounged up an old full width under belly A/C condensor and installed same with all new hoses. Eliminated engine lid condensed because of new/repositioned intercooler. New condensor measures 45" x 14" (630 square inches) old eliminated condensor measures 15" x 8" (120 square inches). I did retain front of car condenser. QUESTION 1: Is the size difference proportional to amount of refrigerant used? I achieved 52 degrees at cockpit vent with 30 lbs on low side and 200 lbs on high side. After 10 minutes of driving the temp rose to 64 degrees almost immediately. QUESTION 2: Why? Ambient temp 105 (Tucson)

QUESTION 3: Compressor (Seiko SS 170PSV ) occasionally screeches. I believe it is the electric clutch engagement face. Make any sense? Took compressor off and can manually turn freely and hear pump working. No shrapnel or silver millions in the oil.

Any guidance appreciated since this is my first foray into the world of A/C.

EP Slick

[86 911 Targa]

There are may reasons for your A/C performance.

What were the numbers (center duct temp, H/L pressures ect.)
prior to your modifications?

Was the system well purged?

Are you using 12 or 134?

Your high side v/s low side pressure(s) should be about 10:1

kuehl posted an excellent and highly informative tutorial on A/C.

Check his post.

Also, check a few of my A/C posts.

Good luck,

Gerry

[e p slick]

Originally Posted by 86 911 Targa

There are may reasons for your A/C performance.

What were the numbers (center duct temp, H/L pressures ect.)
prior to your modifications? Car came with A/C in a cardboard box - No numbers

Was the system well purged? YES - Vacuum pump

Are you using 12 or 134? 134
Your high side v/s low side pressure(s) should be about 10:1

kuehl posted an excellent and highly informative tutorial on A/C.

Check his post. Will Do
Also, check a few of my A/C posts. Will Do

Good luck,

Gerry

Thanks

EPS

[Barrpete]

#1. Probably not 1:1. I would think it would be proportional to the volume, not square footage.
#2. Possibly because the underbelly condensor is passive i.e. no fan. The decklid condensor uses the engine fan to move air across it to facilitate heat exchange. The underbelly would rely on the car being in motion to move air, so when you stop there's no air flow. The pressures you posted are consistent with an ambient temperature of 80 F. See here: http://www.ackits.com/aacf/ptchart.cfm. Did you take your measurements with the car inside? That could explain some of the difference as well.
#3. The 3 possibilities I can think of - but now I'm just guessing - are either the clutch as you mentioned, the belt slipping or the compressor shaft itself. It's possible that the shaft could spin freely with no load on it but screech with the belt tightened up.

[86 911 Targa]

EPS,

No front condenser fan in the trunk?
If not, install one.

Gerry