AIR CONDITIONING NOTES:
While the principles of evaporative refrigeration have been known for centuries, the fundamentals of mechanical (artificial) refrigeration were first discovered and presented by William Cullen at the university of Glasgow in England in 1748.
In simple terms, refrigerant is used to move heat from one place to another. In the case of a car, this means from the cabin to the outside environment. The diagram at right shows a Porsche's AC refrigerant system. A third condenser in the driver's side rear wheel well is added for improved heat evacuation efficiency.
HOW IT WORKS:
Starting with the compressor as a pump, refrigerant is pushed and compressed in the high pressure side of the system (red line in diagram at right) and on through the condensers. Heat captured in the gaseous refrigerant is transfered to the atmosphere via the condensers. As this occurs, the refrigerant progressively condenses into a liquid. Once in the receiver / drier, the refrigerant is fully condensed into a liquid and any moisture in the system is trapped by a drying agent contained within the receiver / drier unit. Entering the evaporator the liquid refrigerant is turned into a vapor by the thermal expansion valve. This conversion of the refrigerant from a liquid on the high pressure side to a gas on the low pressure side causes a drop in temperature throughout the evaporator. As warm cabin air is circulated through the evaporator by the AC's blower, the refrigerant gas inside the evaporator captures and stores heat from the cabin. What we feel in the cabin as a result of this activity is the cold given off by the evaporator. Heat laden refrigerant gas is sucked back to the compressor (blue line) to begin the cycle again.
The challenge with AC systems is to correctly charge a given system with just the right weight of refrigerant. Too little and the system will not cool to it's full potential. Too much refrigerant results in high internal system pressure---stressing components. Just the right amount of refrigerant and... maximum cooling is achieved with acceptable operating pressures.
Where interior refinements and/or restorations for the street are concerned, I look to you to say what you want to achieve with your Porsche's seating. For instance, when refining... quite often this involves seat reformation---going from a non or slightly bolstered seat to a highly bolstered seat similar to a 930 sport seat. You can define the look you're after by providing visual reference. Choose the material you like... and provide me samples if you can. I and my "seat team" will create your seats... just the way you want them. Or, I can install seats bought off the shelf. Before buying seats, I recommend ensuring the seats you plan on purchasing do indeed fit your Porsche without question. The seats manufacturer should be able to answer this question for you. Be cautious about taking a seat retailer's confirmation on this as they may get it wrong.
Bottom side of a severely clogged evaporator (below). Allowed to get to this condition, it renders a Porsche's AC system useless. A thorough cleaning is required to revive this AC's cooling ability.
High humidity in South Florida together with the condensation created inside the blower housing fosters the growth you see here. Metal blower will be bead blasted. Plastic housing will see all the growth on it cleaned away. The result is not only a more efficient blower housing but the elimination of the musty smell this growth creates.
Something not right with your Porsche's interior? Whether electrical, seating, headliner, dashboard, or AC, I can offer you 30+ years of Porsche specialist experience to address the issue you're facing. What my shop does not do is upholstery work. I will show you work supervised by me for my customers. The #1 Porsche interior interest in Miami is:
To get heat out and cool into your Porsche's interior, the AC system needs to have all components working correctly. One area not in proper order results in a slow or abrupt decline in your AC's cooling performance. To better understand your Porsche's AC system, here's rundown of the main parts. If AC is of no interest to you, click here to jump to the next section.
1.) Compressor - Basically a pump. There are both electrical and mechanically driven units with mechanical being most common. Compressor purpose is to circulate refrigerant while creating a low pressure on its suction side, and a high pressure on the compressing side. If these pressure differences do not happen, your Porsche's AC will not work to capacity.
2.) Oil - For a compressor to endure, it must have lubrication. This lubrication is the oil that is put into the AC system together with the refrigerant. Too much oil and the oil acts as an insulator preventing the proper thermal performance of your Porsche's AC system. Too little oil and the compressor with progressively wear out from friction. The correct amount of oil is essential. The amount of oil is based on a compressor manufacturer's specs based on an AC system's hose lengths.
3.) Hose - Transports refrigerant throughout the AC system. Old hose is typically non barrier-hose meaning it's permeable. This type of hose is prone to leak-through thereby progressively degrading the cooling capability of a Porsche's AC system. For optimal continuing performance, it's advisable to replace old hose with new barrier hose. Hose must be installed correctly in order to protect it from damage. Your Porsche itself must be handled in a manner respecting your AC hose as well as other parts of the car that may be damaged from inappropriate handling of your car. The greatest concern is when a Porsche is placed on a lift or is jacked up. Anyone doing this MUST know how your Porsche is configured in order to avoid damaging AC hoses.
4.) Condensers - Transfers cabin heat absorbed by the refrigerant to the outside environment thereby condensing gas refrigerant into a liquid. This is done on the high pressure side of AC systems. Condensers must be clean and have sufficient air flow through them to work efficiently. It is not unusual for Porsche owners to add a condenser unit to increase the thermal efficiency of their AC system's condensing process.
5.) Condenser Fans & Blowers - These serve to increase air flow through a condenser and so improve the removal of heat from your Porsche's refrigerant. Any installed condenser fans / blowers must be in working order. If not, thermal efficiency declines.
6.) Receiver / Drier (R/D) - Collection area for liquid refrigerant to be fed the expansion valve that follows. It is also where a degree of moisture within the AC system is trapped by the desiccant inside the R/D. Moisture (water) in an AC system is unwanted because it ruins the efficient performance of an AC system. It will also freeze in the thermal expansion valve rendering your Porsche's AC useless. When charging your Porsche's AC, it is important to properly vacuum the system. This process draws moisture within the AC system out of it. This vacuum is immediately followed by charging the system with refrigerant.
7.) Expansion Valve (TXV / TEV) - A valve that meters the flow of refrigerant injected into the evaporator. On one side of a Porsche's TXV / TEV there is high pressure. That is the liquid side. When a TXV / TEV injects refrigerant into the evaporator, which is the low pressure side of the AC system, the refrigerant instantly evaporates inside the evaporator.
8.) Evaporator - This unit begins the low pressure side of your Porsche's AC system. This low pressure is created by the compressor sucking on the refrigerant and the TXV / TEV limiting refrigerant flow. The high pressure liquid, when injected into the low pressure evaporator, instantly evaporates. This evaporation process is what absorbs heat or in other words, creates cold. For an evaporator to work efficiently a few things must be in order. First, the system must be charged with the correct amount of refrigerant to optimize high and low side pressures. The compressor must also be sucking to create the low pressure needed and pumping to create the high side pressures needed. Finally the evaporator must be clean in order for it to absorb heat and so cool the air passing through it. Clean also enables air to more easily pass through the evaporator. Whereas condensers rid your Porsche's AC system of heat, the evaporator does the opposite---it absorbs heat resulting in the evaporator's cold exterior surface.
9.) AC Blower - Circulates cabin air with the main function being to move cabin air through the evaporator. As cabin air passes over the evaporator's surface, the air is cooled and then blown out of the AC's vents. Of course the AC blower must work or there will be no circulation of air through the evaporator. Your Porsche's AC system can be working perfectly in all other areas without the AC blower working. A non working AC blower is the simplest AC failure to detect.
10.) Thermostat - This serves to prevent an evaporator from turning into a block of ice. It does so by sensing evaporator temperature and at a given point, switching off the compressor. With the AC blower continuing to circulate air through the evaporator, and there being no flow of refrigerant continuing to cool the evaporator due to the compressor being off, the evaporator slowly decreases it's cooling of the air passing through it and doing so, it warms. At a given point, the thermostat senses the warmed temp of the evaporator and switches the compressor on again to continue the cooling cycle. A broken thermostat will result in an evaporator freeze, a non working compressor, or if the settings are not optimized, the system running too cold or not cold enough.
10.) Refrigerant - R12 was used and still is in rare occasions. R134a is the most common refrigerant for cars and works well given a proper AC set up. The key to refrigerant installation is eliminating moisture within the AC system in advance, and introducing the optimal charge/weight of refrigerant. Too much refrigerant in your Porsche's AC and the system is basically drowning. Not enough and the opposite occurs---it's starving. With the correct charge of refrigerant, there is always an optimal supply of liquid refrigerant delivered to the TXV / TEV and pressures on the low and high side are correctly balanced.
11.) Leaking - In order for everything in your Porsche's AC system to serve its purpose, your AC system MUST be 100% sealed. This requires integrity of all components to be 100%. Generally speaking, age wears AC components out so that no AC system will cool indefinitely. Eventually something will leak. The good news is leaks can be found and resolved.
If you've read the above AC system details, you should have some appreciation for the integrity required of the whole system in order for your Porsche's AC to create a cool, comfortable environment, and do so consistently.
EXAMPLE: With a well-working compressor & thermostat, 3 condenser system, barrier hose, clean evaporator & condeners, all fans & blower working, proper evacuation, correctly weighted charge of refrigerant, no leaks in the system, an intact engine seal, and the rear condenser's perimeter sealed to the lid, a Porsche AC performs exceptionally well. Below is an example---click on photo to enlarge it.
Moments in history are inevitably frozen in time by the visual style of the era. This is true of all creations from fashion to architecture... and automobile interiors. Below, a 1954 356 interior next to a 2015 918.
Customer Sport Seats in for a comprehensive rebuild. Owner's special request: seats covered in full grain leather... not top coated leather which is commonly used. Full grain leather's surface is the genuine hide whereas top grain leather is coated. This coating is done to minimize/hide blemishes and to create a consistent appearance across batches of material---a treatment done for commercial purposes. Lost in this top coating process is leather's natural silky feel and the patina achieved over time given adequate care. For this rebuild, we've stripped these Sport Seats to the bone. Metal will be rust reformed & painted, errors in engineering corrected, mechanisms will be blasted & refinished, and new support bottom & back will be installed along with new tilt cables. Side bottom bolsters---which can be counted on to wear before anything else due to seat entry & exiting scrubbing---are made independent from center cushion. This allows them to be easily replaced in the future. Steering wheel is recovered using same leather.
Porsche "standard" 911 seat before and after.
With age, headliners naturally become brittle and will eventually break under the lightest touch. I replace headliners with quality material that will last many-many years. And in the doing, I take special care to ensure the outcome equals Porsche's factory installation. While replacing headliners, it's an efficient time to service other areas, particularly where a sunroof exists. Since the sunroof must be removed, the mechanics of the sunroof system are now accessible. So too are the roof drains. It's a smart time to inspect and lubricate sunroof mechanicals, and, clear roof drains. New sunroof seals should also be considered. This is a good example of how work in one area can translate into efficient work in other areas. We advise of such things not as an "upsell," rather as an intelligent service & repair approach for your Porsche. Bottom line, "I treat customers the way I want to be treated. If I sense someone pushing an upsell on me, I just don't like it." ---George Perdomo." I offer best-practice advice and options, and it's up to you to decide what path to go.
Sunroof's chrome trim has been restored to near-new brightness from polishing alone. Air has been reinvigorated so it now rises fully when the roof panel is retracted.
Old headliner was cracked and falling to pieces . New material is positioned to retain all systems in working order---temperature sensor and sunroof most notably. In initial discussion with Porsche's owner, I advised of other services that might be economically accomplished while doing this headliner and with approval, proceeded to lubricate the cables, inspect the motors, ream the drain channels of debris, install new plastic seats, make the air dam rise fully, install the dams missing rubber bumpers, polish the chrome trim, and place new roof seals front and back. Was all this necessary to do? No. Was it practical to do now? Yes. Was it economical to spend more money now attending these areas in one shot than dealing with them later and possibly piecemeal? Yes.
VIDEO BY: PORSCHE®
Porsche® Onboard footage -
Record Run 918 Spyder
Video presentation courtesy of Porsche N.A. Permission on file.
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GP AutoWerks is an independent Porsche service & repair shop located in Miami, Florida, U.S.A. Serving both street and race track enthusiasts, GP AutoWerks provides a full range of Porsche mechanical capabilities from simple adjustments to comprehensive engine and transmission rebuilding for both classic and contemporary Porsches. Porsche, the Porsche crest, and Porsche car model names are under licensed use by Porsche Cars North America, Inc. (PCNA) from the owner Dr. Ing. h.c. F. Porsche Aktiengesellschaft, Porsche AG ("Porsche.") No association or affiliation with Porsche, PCNA or AG is intended or implied by GP AutoWerks who happens to
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