Griffith's AC upgrade for '84 911 install thread

[kuehl]

Eric,

What Willy can't "absorb" is that he thinks a deck lid condenser is going to absorb AND transfer into the refrigerant enough heat to push the pressure in a static system above 450 psi or whatever. In order to reach 450 psi with R134a you'd have to raise the entire high side near 195F ..... complete absorption! It ain't gonna happen. You can cover the deck lid with 10 feet of insulation foam, it ain't gonna happen.

Regardless as to how much heat, radiant, convected or conducted, or a combination of the 3, the engine compartments residual heat loss when turned off simply can't raise that much total value of heat (btu's if you wish) to push the high side up to 450 psi or higher.

Now, the other hand, if we want to use some old school heat transfer with our refrigerant we can wrap the headers with metal tubing and let them 'pump' up the juice and toss away our compressors.

[SilberUrS6]

Originally Posted by kuehl

Eric,

What Willy can't "absorb" is that he thinks a deck lid condenser is going to absorb AND transfer into the refrigerant enough heat to push the pressure in a static system above 450 psi or whatever. In order to reach 450 psi with R134a you'd have to raise the entire high side near 195F ..... complete absorption! It ain't gonna happen. You can cover the deck lid with 10 feet of insulation foam, it ain't gonna happen.

Regardless as to how much heat, radiant, convected or conducted, or a combination of the 3, the engine compartments residual heat loss when turned off simply can't raise that much total value of heat to push the high side up to 450 psi or higher.

Now, the other hand, if we want to use some old school heat transfer with our refrigerant we can wrap the headers with metal tubing and let them 'pump' up the juice and toss away our compressors.

I already did the calculation here. Ronnie remembers, I'm sure. In order to get to 450 PSI with an ideal gas in a perfect, closed system, the rear condenser would need to be over 400 degrees Fahrenheit. It's not an ideal gas, and the system is not perfect, AND the system has a built in leak to the cold side! To get the whole system to 450 PSI, the condenser would have to be heated to over 600 degrees F, IIRC.

And maintained there, for a significant time. wwest is just plain WRONG. Not mistaken, but stupidly, idiotically, and painfully WRONG.

[Bob Kontak]

Originally Posted by SilberUrS6

I fully encourage all of you, who want these threads free of this off-topic and tangential (and mostly imaginary) bullschitt.

This is the sixth summer.

It's filibustering simply to disrupt continuity for spiting Griffith.

[Tippy]

How can someone bash another, but then follow up with a question back at the person they bashed for a better understanding of the argument they started?! WTF?!

Borderline psycho.....

[SilberUrS6]

Originally Posted by Bob Kontak

This is the sixth summer.

It's filibustering simply to disrupt continuity for spiting Griffith.

Of course it is. And to chase folks with real concerns off. To Wayne Dempsey: Are you seriously so laissez-faire that you'll allow this sort of crappola in the tech forum? I understand this kind of schitt in the FS forums, but this ain't a FS forum.

[SilberUrS6]

Originally Posted by Tippy

How can someone bash another, but then follow up with a question back at the person they bashed for a better understanding of the argument they started?! WTF?!

Borderline psycho.....

Psychotics do not think they are psychotic.

[Ronnie's.930]

Originally Posted by SilberUrS6

I already did the calculation here. Ronnie remembers, I'm sure.

Yep, and the funny thing about all this is that people with a/c setups that place condensers near heat sources, and in the deck lid without a supplemental fan of any sort (Turbos do not have the cabin heater fan that other 911s do), do NOT report problems with shutdown over-pressurization, or that their systems are incabable of delivering ball freezing temps in very hot climates. Very, very strange behavior from the wild one.

[SilberUrS6]

Originally Posted by Ronnie's.930

Yep, and the funny thing about all this is that people with a/c setups that place condensers near heat sources, and in the deck lid without a supplemental fan of any sort (Turbos do not have the cabin heater fan that other 911s do), do NOT report problems with shutdown over-pressurization, or that their systems are incabable of delivering ball freezing temps in very hot climates. Very, very strange behavior from the wild one.

The reason is very simple. Radiative heating is very low efficiency. In addition, convection heating of the AC parts is a very small component of the whole system. That's the upside to having 40ft of hose (insert childish sexual innuendo here). The problem is that wwest isn't approaching this from a standpoint of science or tech, but of emotion. His irrational hatred of Griff. This makes him post things that are stupid and contrary to any kind of science or rational thought.

[Tippy]

Originally Posted by SilberUrS6

Psychotics do not think they are psychotic.

eek.....eek......eek.....eek. LOL

[SilberUrS6]

Originally Posted by tippy

eek.....eek......eek.....eek. Lol

lol

[wwest]

Originally Posted by kuehl

Eric,

What Willy can't "absorb" is that he thinks a deck lid condenser is going to absorb AND transfer into the refrigerant enough heat to push the

pressure in a static system

No one has proposed that this might happen with a static system. Start at 325 PSI (166dF) the Red Dot compressor clutch binary pressure switch high side limit.

above 450 psi or whatever. In order to reach 450 psi with R134a you'd have to raise the entire high side near 195F ..... complete absorption! It ain't gonna happen. You can cover the deck lid with 10 feet of insulation foam, it ain't gonna happen.

Regardless as to how much heat, radiant, convected or conducted, or a combination of the 3, the engine compartments residual heat loss when turned off simply can't raise that much total value of heat (btu's if you wish) to push the high side up to 450 psi or higher.

Now, the other hand, if we want to use some old school heat transfer with our refrigerant we can wrap the headers with metal tubing and let them 'pump' up the juice and toss away our compressors.

Back when R-12 was used available binary pressure switch high side limit was 380 to 450 PSI.

So 450 PSI was not unheard of for an R-12 system, possibly quite common.

Our systems do not come with a pressure switch, our compressors will run until the thermostatic switch setting is satisfied, max setting, 30dF, or according to Griffiths, 27dF.

How tightly closed will the TXV be as the evaporator temperature declines to that level?

My Porsche owners manual indicates that at idle with the A/C loaded, widows open, the R/D sight class should indicate a level of liquid. Oh, and it does exactly that.

How high might the pressure go at 2300 RPM and the cabin Rockwall comfortable..?

Any guesses..??

No wonder the EPA requires that R-134a conversions include a pressure switch upgrade. Otherwise tripping those ~500 PSI HPRVs would be a regular event.

[Bob Kontak]

Originally Posted by wwest

Back when R-12 was used available binary pressure switch high side limit was 380 to 450 PSI.

So 450 PSI was not unheard of for an R-12 system, possibly quite common.

Our systems do not come with a pressure switch, our compressors will run until the thermostatic switch setting is satisfied, max setting, 30dF, or according to Griffiths, 27dF.

How tightly closed will the TXV be as the evaporator temperature declines to that level?

My Porsche owners manual indicates that at idle with the A/C loaded, widows open, the R/D sight class should indicate a level of liquid. Oh, and it does exactly that.

How high might the pressure go at 2300 RPM and the cabin Rockwall comfortable..?

Any guesses..??

No wonder the EPA requires that R-134a conversions include a pressure switch upgrade. Otherwise tripping those ~500 PSI HPRVs would be a regular event.

You are an inconsiderate, sick SOB.

[dentist90]

Originally Posted by wwest

Back when R-12 was used available binary pressure switch high side limit was 380 to 450 PSI...

The high side in our systems is normally 200-250psi when working hard. The low side will probably be about 35-40psi at the same time. These two sides are connected by a small orifice called the TXV that does not normally close 100%, as far as I know. Refrigerant from the high side will continue to leak from the high side to the low side at shut down, thus equalizing the pressures at roughly 80psi. Simply put, you could probably put a propane torch to the rear deck condenser at shutdown and not be able to maintain 250psi on the high side. Have you felt how hot the rear condenser is to begin with? Heat rising from the engine isn't much hotter.
A low pressure cutoff is there to protect the compressor in the event that refrigerant is lost... not a normal event. Likewise, reaching pressures of 400 psi is not normal. A high side cutoff is there for protection, not normal function. HPRV is for a blockage in the TXV that could result in catastrophic bursting of the system. How many threads have we seen that started with "My AC system just burst and spewed out hot oil all over my engine bay"? None. So why do you persist in answering the questions not asked?

[SilberUrS6]

Originally Posted by dentist90

So why do you persist in answering the questions not asked?

Because of his monomania. He hates Griff, so he'll say anything, anything at all, to cast doubt.

Report his posts as spam and trolling. Every time, all of them. I am removing him from my ignore list to do just that.

[Bob Kontak]

Originally Posted by SilberUrS6

Because of his monomania. He hates Griff, so he'll say anything, anything at all, to cast doubt.

Report his posts as spam and trolling. Every time, all of them. I am removing him from my ignore list to do just that.

Pieholio says "Game on".

Let's kill this snake.

[Ronnie's.930]

Originally Posted by Bob Kontak

Pieholio says "Game on".

\

[SilberUrS6]

[Bob Kontak]

LOL.

Is that Squidward?

[SilberUrS6]

No, it's Moses.

[Bob Kontak]

Originally Posted by SilberUrS6

No, it's Moses.

That's gonna be expensive.

Although it's Patrick.