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.