I believe it is you that does not understand. If you were to plot a theorized parcel of air passing multiple times through a evaporator, you'd end up with a chart that looks anything but linear. Now, if you integrated that chart and calculated the work done on the system, *that* would tell you just how strong the AC system is. Measuring Delta T in itself doesn't actually tell you anything, because it's not a linear relationship. C'mon, man! This is thermodynamics 101. If you're going to try and school us on AC systems, then at least get your theories right.

I'll split his hairs. My thermodynamics book is within arms reach, and his theories don't seem to be based on any kind of modern science.

No comment

....

I would love to see someone do the "wwest" mods in a 911 in south Texas and post back results.

If it works as "wwest" describes, that would be awesome for such little money to make an older 911 have cold vent temps as a modern 911 A/C.

Thank you

Mike, just be aware of the high side PSI break point

You're going to hear nothing but crickets. In fact, I haven't really seen anyone in these AC threads post the setup that wwest has that sees comfortable temps at idle in reasonably hot weather. So, that alone should tell you something.

In the 911's evolution over the years, I don't see a whole lot of expensive mods that aren't worth their weight. Drivers of these cars aren't the type to waste money on things that don't provide tangible results. The fact that these AC upgrades have been successful for a lot of people - despite the fact that there have been plenty of opportunities for people to add fans, get data, and report back, should also tell you something. If you could sit, at idle, in 95 degree weather with the AC on and it keeps you cool, all for the price of barrier hoses, 134 upgrade, and a couple fans - we would not be having this discussion because there would be a simple DIY thread, a list of parts, and we'd all be doing it. But - you don't see that. Why is that? Why is it that one man claims $500 will do the track rather than $2,000 - and yet we have seen ZERO data from ANYONE to back that up.

Now let's take your same test but make it a bit more like everyday use.

But since the Targa with the 62F delta is totally unrealistic lets just drop it.

Close the windows, start the test, MAX cooling, MAX blower. Most of us, I suspect would be perfectly pleased with that initial 56F air, with the full expectation that it will continue to decline as the system inlet airflow becomes cooler and cooler. At sone point we will realize that the system has done its "INITIAL" job and thus we will begin to moderate the system performance in order to not be discomforted.

That's the basis of the firmware control design for most modern automatic climate control systems, simply a computer replication of human thought process and resulting actions.

Anyone see this differently..?

That's an almost perfect description of the operation, manual intervention inclusive, of my '88 Carrera system(***). Wish I'd said that. The only point of disagreement is that the wife and I would not long be comfortable with that 35(F) degree system outflow, ~55F, maybe.

Which is very close to what one might get with "the AC is set at the speed next to "off"", NOT 35F.

***Assuming decent road speed, no need for the fans. High desert, stop and go, slow moving traffic, the condensor cooling fans will definitely be required.

Why is the 62F delta Targa unrealistic? I posted test results and photo of the guage above. If that is unrealistic to you...no wonder you think adding a fan to the condenser makes the AC wonderous. Your standards are just much lower than those of the rest of us. I guess that us why you don't provide test results to back your claims.

I also tested the Targa with 56F vent temps under approx the same conditions and after 8 hours of driving, the vent temps did not come down as you indicate the would and neither did the interior temps.

Obviously you close the windows after IAT drops to OAT. I did not expect that I would have to explain that to you.

Obviously once the 33F vent temps directed towards your skin make you uncomfortable, you redirect the vents...unless you are an idiot.

Okay, I can attest, gladly and truthfully of my '88 Carrera A/C system being fully capable of THAT. Not that I would ever be comfortable running the passenger cabin temperature down that low, nor even the airflow volume. I might hedge on the 32F bit though since my thermostatic control switch is very carefully set/calibrated to avoid evaporator freeze up. Probably ~35F easily.

It still freezes up in occasion but I suspect that is due to high elevation low atmospheric pressure interaction with the capillary system spring/bellows internal pressures.

Explain..?

Redirect the vents, no I find it much more comfortable if I simply turn down the cooling. That's what that control is for, right? If I needed ~35F system airflow in order to keep the cabin at/near my 72F comfort level, then yes, I would be an idiot not to simply redirect the airflow direction.

But to my knowledge and memory that circumstance has never arisen, not even in my '78 Targa, even in Memphis.

Prove it.

Wow! 35F vent temps at 95F ambient is impressive for a stock system. These cars would not even do that when new. So I should assume that adding a fan will do the same for my '89 Carrera? That is an improvement of over 20 degrees. Where do I get this fan? You should sell them for at least $2K each.

wwest has a theory that heat soak, after use, from a hot engine will create an over pressure, which I recall griffith as saying would be north of 300? ( Then there would be bleed off from the overpressure valve)

Shouldn't wwest (Or anyone) with a set of gauges be able to hook them up on a hot engine and watch the pressure? Does he have any data to show his fans prevent the dreaded pressure?

It is my belief that Porsche created a AC system, which, in perfect working order, could keep you cool..In germany or some situations. Maybe on the Autobahn at 120.

It does not cut it during summer in Orlando. BTDT. Additional flow and capacity is needed. Fact.

A/C Upgrade 1989 Porsche 911
 

I just completed upgrade using Retro Air parts for $1,320. Used my stock compressor and stock front condenser. New barrier hoses , rear condenser, evaporator/expansion valve and drier. Took about 13 hours to complete. Drier has a low and high pressure switch so when you first start charging system compressor will not start until pressure is above 20%. The great thing about this system it looks original and not a silly condenser behind the rear wheel. They also included a center vent and hose for the
Floorboard vent. This is a quality system and all hoses and parts fit perfect. I cannot believe when system was fully charged I was getting 33 degree air coming out of center vent setting in my driveway and believe it or not I had water dripping under my car.http://forums.pelicanparts.com/uploa...1366741599.jpghttp://forums.pelicanparts.com/uploa...1366741727.jpg

LOL. That's about right.

wwdoofus claims north of 500psi. Which I *do not believe*.

300+/-psi I might accept as a very outside condition.

Getting ready to replace the old York compressor and was debating changing the old hoses out for barrier hoses but then read this on an EPA webpage.

Quote from the section on Hoses and O-rings.

"More recent testing, however, has shown that oil used in automotive a/c systems is absorbed into the hose to create a natural barrier to R-134a permeation. In most cases, the R-12 system hoses will perform well, provided they are in good condition."


Here is the link to the EPA's site on Retrofitting to R-134.
Guidance on Retrofitting to HFC-134a | Ozone Layer Protection - Regulatory Programs | US EPA

Guess I'll test it out and see how long the R-134 lasts before I rip out the old ones.

Scott
_____________
78 SC Targa

LOL, don't pin me down on the old drier blow off valves,
it could (could means not conclusive) have been 450 psi, who knows.

Believe me it won't last not long. We have had many customers (DIY and shops) over the years switch to R134a with stock hoses and only to come back the next year and replace them with barrier.

The original tests on hoses came about with the concern of freon escaping.
So they tested the original non barrier hoses and determined that the hoses leak so many parts per million over a given length at a given temperature and pressure.
The hose mfg's were given the task to reduce the permeation rate and barrier hose was developed.

Logically 'oil' might reduce the permeation rate, the question is by how much.
And understand whom ever reported those results to the EPA in most likely hood
did not test cars with 40 linear feet of barrier hoses. Most of those cars tested were front engine cars which typically had less than 10 feet.

You will also find conflicting information as to whether you can mix PAG with R12 mineral oil. MAC (mobile air conditioning society) ran reports years ago produced by the compressor mfg's on the effect of using mineral oil with R134a, and or mixing PAG with mineral oil. The results were not good; the compressor bores got wiped out and the copper plating on bearings went all over the place. Not a pretty site nor an inexpensive one to fix.
And, our facility has witnessed many not good cases where clients mixed PAG with mineral oil; it produced a sludge in the system =expensive repair.
And on the topic of 'sealants', avoid them. I have seen more cases of sealants crapping up a system and damaging switches... its simply not worth the... if I may SNAKE OIL (thank you Wwest) fix.

Why Wwest. ?

I'm done here gang.

Ditto.

Me too.

The EPA is right. Leakage is negligible for the typical foot or two of hose in most cars. If you have 43-47 feet of hose like (43 in my 911)...then multiply by 43.

The last study I saw cited the non barrier hose leaks about 7 times as much R134 as the barrier...so multiply the 43-47 feet of hose by 7. Perhaps that is still small compared to the cost of hoses if you DIY. If you are paying labor for servicing, along with the time wasted and the R134 itself, it might add up.

Thanks for the entertaining thread! I think I learned something...seriously.

lines
 

I am interested in doing a custom AC application using non factory installed parts / lines on my wide body 74 911s. I have a large factory 930 turbo tail. and am considering hard lines through the passengers floor against the tunnel. Have been breaking quite a few 944 cars lately and have a bunch of parts there. In all my mess I don't see factory running long soft lines in this day and age. Also have a thread on the 997 forum where a guy snapped a image of 99 C4 pan as a guide to current technology.
http://forums.pelicanparts.com/uploa...1365909786.jpg


Since I am not running a tubo have some room for a large condenser in rear and have a few 944 BMW Behr compressors hose ends etc. I really only care if it works for me. This discussion of my vent will be so much cooler than yours is a bit silly so based on that,

I expect 32 deg and I will deliver lots of frozen Ice cream to hot chicks. You guys need to lighten up a bit !
http://pcars.us/albums/6601_porsche_cars.jpg

They are still available and the BO pressure, for the few that I found, varied from 350 to 450 PSI.

YOU would know, if you ever bothered to take the time to provide more exacting information...

Just trolling for comments? You waited 2 days before posting again in this thread? and you were the last one that posted?
Just stop - go play in the sand box and leave us alone!

Trolling, no. Kuehl was so kind as to provide a list of our various posts and I just went through them to see if an update was needed.

So by your standards, since Kuehl provided the list, wouldn'y he be the TROLL?

Question re A/C recharge for 87 3.2
 

Please excuse a new member and older purchaser of the Bird, but this looks to be the best thread to post relative questions. I have the occasional use (I do not complain) of a 1987 GUARDS RED CABRIOLET with a bit over 40K original miles. Perfect car on a second set of tires in practically new shape. Always garaged/locked except when I wax it (Autoglym of England), drive it and hear it SING. I plan to take over ownership of this car one day....Until then, planning a major mileage tuneup. A/C has worked and been recharged several years ago but has dried up since. Is it alright to ignore the A/C, not recharge or check related hoses? Any other major items to watch? The oil return tubes drip a little oil at times and it blows about a quart in a thousand miles which I understand is normal (I've checked and see oil loss is listed on the orig. sticker :) ). Your suggestions below are appreciated - except those stating the bleeding obvious: that I need to drive it a bit more. Thanks!

Disconnect the compressor clutch wire until you can have the system refilled/checked. If you operate the "raw" factory system with low refrirerant charge the compressor might soon be TOAST.

I sense in you are saying in your climate area AC is not needed often?. But, if you want to use it, as it comes in handy for those damp muggy days, I'd suggest as the minimum, replacing all the hoses with barrier hoses, replace all o-rings, add low-high pressure switch, new drier, convert to R134a with ester oil.

If you have a 'black' oil line above the compressor pulley on underside of the engine deck lid consider replacing the nose seal and case o-rings on the compressor; when the compressor case halves are separated you can inspect the wobble plate, pistons and bores for wear.

After the system is properly charged have then sniff the AC vents and condensation drain tube under the tub with an electronic leak detector; the evaporators for that year leak soon or later.

Do all of that and the AC system integrity will be good for many more years to come.

However, if you are aware that the stock system you have won't provide you with enough cold air, then you will want to consider some upgrades such as more condensers, better evaporator, maybe an additional vent. The upgrades should be done while replacing the hoses ....do it once, do it right.

Signed,
THE TROLL

The Mr. Ice Project

*** Or even less expensively, ~$200.00 range, convert to R-134a and use a trinary pressure switch with the extra element controlling 2 additional cooling fans for the rear lid condensor. Most modern day automotive A/C systems use a trinary pressure switch in very much this same manner.

Search: radiator cooling fans

LOL, nice.

Lol