'89 Carrera AC conversion?

[pfhump]

What steps/changes are needed to convert my AC charged with R12 to a system with R134A? The car has a 'PerformanceAir' compressor, ball gauge shows full, but systems is not producing 'cold' air...It gets to 100* here in Central WA, and 'PA' tech says that is just too hot for the current AC to cool! Some ideas/help would be appreciated...

[billybek]

Ball gauge? In the receiver drier in the fender well?
Can be an indicator of charge but will not tell you if the rest of the components are functioning correctly.
See these guys website Griffiths Technical Inc,Porsche Air Conditioning,Posche a/c upgrades,Porsche ac upadates,Porsche air conditioning upgrades,Porsche air conditioning updates,Porsche barrier hoses,Porsche compressors,Porsche condensers,Porsche condensors,Porsche receiv for some good information or these guys RennAire Porsche 911 Air Conditioning Products.
To get some real performance you will be spending a bit of cash to make it all work.
Search air conditioning on this forum and you will find a whole bunch of information, not all of it good!
Good luck!

[AlfonsoR]

For the best performance, I'd replace the whole thing including compressor & hoses. Griffin and Rennaire are good websites.

[wrinkledpants]

Looking back through my records I have, the owner spent 12 years and 2 grand trying to make the original AC system functional (car was a texas car). He finally converted to R132, barrier hoses, better compressor, added a condenser with a fan in the rear wheel well, and the system now performs as good as any modern car. Total cost of the conversion (paid an indy shop to do it) was 2300 bucks for parts and labor. Seriously, every other receipt was related to the AC system.

[JQ911]

+1 if you want the A/C to be at par with newer cars blows really cold specially during summer months above 100F, the above a/c system is recommended.

When I had an AC shop convert mine to R134A, I spent roughly $250 (parts and labor) for the retrofit kit, valves, ester oil, drier, o-ring, dye and vacuum/evac the old R12 and R134 freon recharge. Being an old ac system, it cannot be compared with the new ones. Mine blows cold in spring and fall but mildly cold only in the summer. I read the Griffins and Rennaire upgrades have good end results.

[kuehl]

Read The Mr. Ice Project

[wwest]

Ther factory A/C system is perfectly adequate for highway cruising, relatively consistant engine RPM above ~2000. The questionable area becomes operation in city stop and go traffic or the desire for QUICK(er) cooldown of the cabin on a HOT sunny day, especially after sitting out in the sun for a period of time all closed up.

In this latter case some folks would even complain of the lack of adequate cooling in an LS400.

Even in an LS400 it can take more time that some folks are comfortable with to cool down the cabin after an afternoon spend sitting out in a hot TX sun.

The secret(s).

Don't, NEVER, buy a car with a dark interior wherein the surfaces will soak up the sun's radient heat rather than reflect a goodly portion away.

And remember, the human body comfort level is as much a function of radient heating effects from the "surround" (cabin interior, etc.) as it is to atmospheric temperature.

So, have the windows tinted to the legal limit.

On a hot day if the interior is already "hot" roll the windows down slightly during the initial part of the drive, not just until the hot cabin atmosphere is purged but a bit longer to allow a bit of cooldown period of the interior surfaces.

You OEM A/C system operates strictly in "recirculate" mode so there will be no "active" purging of the cabin atmosphere unless you activate the outside air intake blower.

OUTSIDE AIR..??!! Wouldn't that be counter-productive..??

No, if the interior atmosphere is above OAT, as it often is, forcing that HOT atmosphere out of the cabin is better than requiring the A/C to cool it down to OAT.

What I discovered here in WA, Seattle area, was that the factory air, even converted to R134a, was adequate as stated above. Simply put, the system lacks sufficient refrigerant cooling capacity except with the engine RPM being sustained above 2000 RPM. With respect to cooling capability sustained higher engine RPM results in TWO position effects. More compressor pumping "capacity", higher level of cooling airflow through the rear lid condensor. The increase in pumping capacity with engine RPM might well also result in higher condensor pressure/HEAT thereby also increasing the condensor to air heat transfer efficiency.

In my case I found that providing "make-up" cooling airflow through/for the rear engine lid condensor when the engine RPM alone cannot sufficed to increase the A/C capability to a satisfactory level.

And a point of caution...Some of the compressor "upgrades" out there in the aftermarket, one that is highly recommended even, have a lower pumping capacity vs the OEM compressor. Swap in one of those and expect to need additional upgrades, for certain sure.

What I found was that by adding two 12 inch radiatior cooling fans to force/suck more airflow downward through the rear lid condensor provided a near perfect solution. When I converted to R134a a pressure control switch was added and I used that to control the fans. If the compressor is engaged the fans run a full speed, otherwise, assuming the A/C is in operation, they are connected in series.

I was even able to disable the mostly ineffective front condensor cooling fan and still have more than adequate cooling in August, Yakima (Gleed), Tri-cities, Id, MT, etc.

I've actually had more problems with evaporator freeze up in this new configuration rather than cooling inadequacy. Traveling over mountain passes results in low atmospheric pressure changing the thermostatic switch calibration is the best guess for this effect.

[wwest]

Oh, the best, most, dehumidification efficiency will be obtained at the lowest possible blower speed setting and MAX cooling. The SLOWER the system airflow moves through the evaporator the COLDER it will become thereby increasing the system capability of bringing that airflow mass down to the current dewpoint.

A note of CAUTION: Since the system is ALWAYS in recirculate mode it should NEVER be used for dehumidification, defogging/demisting alone, when cooling is not a requirement.

[wwest]

Originally Posted by kuehl

Read The Mr. Ice Project

And then toss the entire, OUT-DATED, subject matter into your mental WASTEBASKET.

When it is so well know that the OEM system is already lacking in cooling capacity why would anyone recommend an "upgrade" to a lower displacement compressor..

Except maybe for the purpose of selling you more "bits" now that the system is even less adequate.

[SilberUrS6]

Originally Posted by wwest

And then toss the entire, OUT-DATED, subject matter into your mental WASTEBASKET.

When it is so well know that the OEM system is already lacking in cooling capacity why would anyone recommend an "upgrade" to a lower displacement compressor..

Except maybe for the purpose of selling you more "bits" now that the system is even less adequate.

And yet, folks in the most hot and humid portions of the country report that cars equipped with this system are every bit as good at conditioning the air as the most modern vehicles.

Many reports over many years.

I wonder - are they all lying to make you look bad?

Or maybe by exploring and examining the system and removing the bottlenecks to efficient operation, a talented air conditioning expert could indeed find out which modifications to implement to get the most refrigeration out of the least amount of heat exchangers and working fluid?

Which scenario seems most likely, if one were to use Occam's Razor?

[SilberUrS6]

Originally Posted by wwest

Ther factory A/C system is perfectly adequate for highway cruising, [...]

Well, when you start like this, none of the rest of what you write can be worth much.

The factory system, as implemented for the 1985 911 model year, is not in any way "adequate" for cooling the interior volume of the car in hot weather at highway speeds - even with a recent, correct charge of R12 and the system functioning properly according to the Bentley manual. In fact, it can't keep up with the radiant IR gain through the greenhouse when OATs are above 100 F. This is when the engine fan is spinning at ~2500rpm.

The vent temperature will eventually stabilize, and the cabin *will* be cooler than the OAT, but not by a lot.

And this is when the relative humidity is in the low teens. I shudder to think what it must be like for those folks on the Gulf Coast or in the Southeast in the summertime, with heat index readings over 150 degrees.

And I suppose those folks with dark interiors will now run right out and sell their Porsches because you think getting them cool in the summer just can't be done?

Brad will be along soon with a nice word or three. I will just leave this one right here.

[wrinkledpants]

You basically have two choices - do it right, or do it half assed. To me, the hottest points of my drive are during slow driving in the city, stop and go traffic, sitting at lights, or basically - just moving slowly. Many cars are going to have issues keeping the inside of a car cool while sitting on a black road in traffic - and a quasi-AC system in a 911 is going to struggle at best. This is especially true if you're car is still warm on the inside. My definition of struggle is anything less than what a modern car could do. AC should make the car cool inside. If it can't, it's struggling.

I don't know about wwest, but I'm not going to skip on a dark interior just to save a few bucks from doing a proper AC upgrade, or do all these other things with the evacuation of hot ambient air - etc. My AC blows cold - not matter what. Stopped on the interstate, the devil himself sitting next to me, or after the car sat in the sun all day. It's damn cold. I'd say it's more effective than my previous Audi S4. I don't need to bother with opening windows, keeping the RPMs up, or any of that ****. I turn it on, it gets cold, I turn it down to the first fan setting, and I stay comfortable without the loud sound of a fan blowing at mach 5. You're going to spend money on the conversion, so just do it right from the start and enjoy years of comfortable driving in any kind of heat.

So, you should ask yourself if it's worth having all the weight in the back end for an AC setup that only works during specific conditions, or do you want an AC setup that works like a modern car? I got lucky in that my car came with it, but it would have been the first sizable investment I made into the car if it didn't.

I love driving the 911, but there is nothing fun about being stuck in traffic and having swamp ass.

[brads911sc]

here we go again. the stock system is good in the pacific northwest and only marginal there. anywhere where it hits 90+ all summer it will be inadequate. Do a search. WWEST is a resident expert with an extensive collection of crack pipes. Most of what he says has been proven to be crap. forget spal fans theory. forget switches theory. forget his computer swamp cooler, forget his compressor theory. forget his high pressure theory. Its all bunk. The only think that works is taking the system from the 993 and retrofitting it to the 911. which, in short, is the griffith system. period. and the Porsche engineers and griffiths took that to the bank and were successful.. pay now or pay later. just depends on how miserable you want to be in the meantime. lets see.. WWEST or 100's of Porsche Engineers. Who are you going to believe?

Originally Posted by wwest

And then toss the entire, OUT-DATED, subject matter into your mental WASTEBASKET.

When it is so well know that the OEM system is already lacking in cooling capacity why would anyone recommend an "upgrade" to a lower displacement compressor..

Except maybe for the purpose of selling you more "bits" now that the system is even less adequate.

[wwest]

Originally Posted by SilberUrS6

And yet, folks in the most hot and humid portions of the country report that cars equipped with this system are every bit as good at conditioning the air as the most modern vehicles.

I agree, absolutely. If you follow the "Ice Project" upgrade(s) in totality you will more likely than otherwise find yourself fully satisfied with the result, a little lighter in the wallet, but hell, what the hey...

But that was YESTERDAY, a new day, with NEW technology, has DAWNED!

Many reports over many years.

I wonder - are they all lying to make you look bad?

No one has supposed that those that have used the Ice Project as guidance have any need for lying..! Old, out-dated, obsolete methods often still work.

Or maybe by exploring and examining the system and removing the bottlenecks to efficient operation, a talented air conditioning expert could indeed find out which modifications to implement to get the most refrigeration out of the least amount of heat exchangers and working fluid?

Which scenario seems most likely, if one were to use Occam's Razor?

Occam's Razor: States that among competing hypotheses the one that requires the fewest assumptions should be selected, or is most often the correct one.

MY singular assumption is/was that the factory A/C lacks sufficient refrigerant condensing capacity.

And..at the very BASE isn't the ICE PROJECT carried through on that very same singular assumption??

[wrinkledpants]

Do you have a car that can keep the inside cold at 100 degrees, sunny, and stationary in traffic without being at max capacity? Yes or no? Because it seems that's what the OP is asking.

[wwest]

Speaking "modern" car and A/C...

Just a few years ago I spent a week in Tucson driving a friend's 2004 LS400, black exterior but ivory interior. The side and rear/back windows were tinted much darker than would be legal in my home state of WA. My friend explained that in Tucson the summer IR gain to the interior was so great that he had to live with CHILLING system airflow or else add the extreme tint so the airflow rate and chill factor could be moderated moreso to human comfort level.

As good as the LS400 climate control is, it remains with a rather strange anomally, design flaw. When you start up the car after a hot day in the sun with the interior super-heated the system will automatically initially switch to recirculate. Most Lexus driver's are confounded by this since the owner's manual states that one should initially run with the windows lowered (***) slightly to combat this interior heated condition.

So the best thing to do is the inverse, over-ride the system to FRESH initially, and then back into recirculate once HOT/Stale cabin airflow above OAT has been purged.

*** So, say what you will, object to the need for lowering the windows slightly to more quickly purge the HOT interior atmosphere, but Lexus and logic both indicate otherwise regarding the need to most quicker cool the interior in this situation.

[SilberUrS6]

Originally Posted by wwest

MY singular assumption is/was that the factory A/C lacks sufficient refrigerant condensing capacity.

Wrong.

It has sufficienty capacity for most climate situations in the CONUS. Not all.

It has insuffient heat transfer capability to make use of the condensing capacity it does have.

The Mr. Ice project does several things to address multiple problems. And by addressing all of those issues at once, it minimizes the installation costs and the on-going costs of maintaining the system. Part of the expense is to modernize the system such that modern (non-banned) refrigerants can be used. Another improvement is to use a more-efficient compressor so that there is less parasitic loss to keep the car cool. Another improvement is to get the system to be somewhat over-built so that heat-soaked interiors can be cooled rapidly without the need for reupholstering in white.

With barrier hose, a more modern evaporator (more surface area) and a more powerful evaporator fan, my car's original condensers and compressor can keep the interior of the car reasonably cool in the same kind of weather the OP is talking about. Since he and I both live in E.WA, I would say that the modifications I made will suit his car just fine.

[wwest]

Originally Posted by wrinkledpants

Do you have a car that can keep the inside cold at 100 degrees, sunny, and stationary in traffic without being at max capacity? Yes or no? Because it seems that's what the OP is asking.

"..Keep the inside COLD..."

Mine, and my wife's comfort level, for cooling, seems to be about 75F. The 88 Carrera is diamond blue with matching blue/grey interior. Side and rear/back windows are tinted 30%

Our hot climate experience with the 88 is confined to visits to the central WA area, Yakima, Tri-cities, and central MT. Not much encountering of slow moving or stop and go traffic involved other than a few construction zones here and there. So it's hard to really answer your question objectively other than to say that if the system had not perfromed to our satisfaction at those few times we would have taken note of same.

But.. Other than providing for a quick cabin cooldown I have NEVER had the need to operate the system at MAX cool or max blower. It seems both of us are more comfortable with only "coolish" and low volume system airflow, just enough overall cooling to keep the cabin at our ~75F comfort level but not so much as to be discomforted.

[wrinkledpants]

Interior thermodynamics is pretty straight forward. You have incoming solar radiation and a method to cool the system. At some point, the car will reach a dynamic equilibrium that is independent of wether you roll the windows down or not. The only difference is time to get there. I can think of a lot of reasons to not want to roll the windows down. Have you been in a sandstorm when it's 130 degrees? How about where there are ***** loads of bugs out side? Or when it's windy as hell and dust/dirt is getting blown around everywhere? Rain? I've slept in dark green tents in Iraq when the ambient temp was 132. The AC outside kept us cool for one simple reason - it was correctly designed.

I don't care about a lexus. I've driven plenty of vehicles through the worst summer temps you could imagine, and we never had to roll windows down to get the car to cool down. Might it help to alleviate the initial uncomfortableness of being in a really hot car? Sure - but it's most certainly not a requirement to get the car to cool down.

This is a Porsche. Why would anyone half-ass a design for half-assed results? The only difference between any of our opinions is value. For me - given that we see 300+ days of clear blue skies here in Denver, the incoming solar radiation is more potent due to a thiner atmosphere, and the fact that our summer temps are often in the 90s - the 2500 investment in an AC system that is reliable, and is not constantly at max capacity, given how much time I spend in the car - it's money well spent. For others - that's a huge waste, and they either do things like what you're talking about, or they remove it.

But, when someone drops a tripple digit temperature, and asks about AC - it's my assumption they're not look for all these band-aid solutions to get marginal AC.

[wwest]

Originally Posted by SilberUrS6

Wrong.

It has sufficienty capacity for most climate situations in the CONUS. Not all.

Direct knowledge..or hearsay..??

It has insuffient heat transfer capability to make use of the condensing capacity it does have.

Your basis for this statement is..??

The Mr. Ice project does several things to address multiple problems. And by addressing all of those issues at once, it minimizes the installation costs and the on-going costs of maintaining the system. Part of the expense is to modernize the system such that modern (non-banned) refrigerants can be used.

I have had more than 3 vehicles converted, inclusive of the 88 Carrera, for less than $200 each.

Another improvement is to use a more-efficient compressor so that there is less parasitic loss to keep the car cool.

"..more efficient compressor..." By what measure..?? 5HP of engine workload vs 7HP, 2HP gain (even if that) for/with a 180HP engine? And how much of that efficiency is lost due to the recommended compressor having a lower pumping displacement?

Another improvement is to get the system to be somewhat over-built so that heat-soaked interiors can be cooled rapidly without the need for reupholstering in white.

On the subject of over-building...My wife would tell you that NONE of our vehicles have a satisfactory initial cabin cooldown rate, not even our LS400, not even using the window lowering method.

With barrier hose, a more modern evaporator (more surface area) and a more powerful evaporator fan, my car's original condensers and compressor can keep the interior of the car reasonably cool in the same kind of weather the OP is talking about. Since he and I both live in E.WA, I would say that the modifications I made will suit his car just fine.

And MY belief is that the op would just as satisfied with the solution I suggest.