Compressor Upgrade

We removed the original Porsche spec’d York crankshaft compressor from this Porsche 911 SC. Though the York compressor did the job in the past, technology changes and there were better options available. In simple terms the air conditioning compressor is a pump that compresses the refrigerant gas. The York design is a crankshaft type pump which is of the oldest designs and least efficient of compressor choices. There are more efficient compressor designs available today: wobble plate, swash plate, true rotary vane and scroll type pumps. To replace the old York compressor we selected a 507 compressor which is akin to our Kuehl and the Sanden brand. The 507 compressor family has maintained a reputation for reliability and performance. The 507 compressor is a “wobble” plate compressor having five pistons that reciprocate back and forth as they are pushed by a plate mounted to the compressor shaft. The original York compressor had a capacity of 169 cc as compared to our 507 compressor which has only 115 cc, a 32% reduction in capacity. At first you might wonder “Why use a smaller compressor. Bigger is better. Right?” Not in all cases is bigger better. What is more critical is matching the size of the compressor to the needs of the entire refrigerant system. The 507 wobble plate design runs smoother, consumes less engine horsepower, and takes up less space; it is lighter too. If you are wondering whether you need a “more efficient” pump other than a wobble plate or swash plate, the answer (based on our observations and market experience) is no. You will not see any noticeable improvement in cooling by attempting to adapt a true “rotary vane” or scroll type. The wobble and swash plate designs do the job perfectly and are still used in new car designs today.

If you are considering doing a Mr. Ice Project on your Porsche 911 or 930, and your old York compressor is leaking, has clutch or service valve problems, or it has high mileage or is simply old, you’ll want to consider replacing the compressor with our Kuehl 507. Note: for the Porsche 911, from 1984 and later years, and the Porsche 930, 1983 and later, Porsche switched over to a Nippondenso brand swash plate compressor. We prefer to use the Nippondenso to replace a Nippondenso. There is no advantage in using 507 to replace it (exception is the 1978-79 930 which used the radial Nippondenso, here we do suggest the 507 because remanufactured units of that odd radial are not easily found).

911-930 Porsche Air Conditioning Compressor Upgrade

The new 507 compressor was initially attached using an aluminum adapter plate. This assembly is then attached to the old York’s “slider” plate and bolted down on the engine’s main a/c plate. In a later Porsche ac upgrade project we developed a better adapter plate, made of light weight steel, to replace the aluminum version, what we call our Kuehl Kwick mounting plate. The Kwick plate is much more easier to bolt on and align, saves you lots of time. Pulley clearance is not a problem and belt alignment and adjustment is quick with the Kuehl Kwick plate design. And you can use your stock ac belt. Our 507 has charge ports on it’s main body and they are positioned so you can easily access them for connecting the a/c service gauge hoses. Our 507 model comes with R134a charge port adapters as well.

What we found missing in the Porsche 911 and 930 air conditioning systems were pressure switches, a low and a high. The low side pressure switch prevents the compressor from operating in the event of a refrigerant leak or insufficient refrigerant. Compressors need a constant stream of refrigerant oil to keep them lubricated otherwise they will seize or lock up; lock-up damages compressors. The compressor gets its lubrication via the stream of refrigerant constantly circulating through the system. If you don’t have enough refrigerant you don’t have enough lubrication. A low side pressure switch provides this safety feature of preventing the compressor from operating if the system pressures are too low. A high side pressure switch works at the opposite end of the pressure range. Excessive or too high pressures create excess heat and can blow seals. Excess heat can damage a compressor quickly, and excess pressures can blow out the shaft seal. So we designed into the system a “high-low” or if you prefer “low-high” all-in-one pressure switch; instead to two switches we installed a “binary” or single switch that has two functions built in, to protect the system. This is a very simple “plug in and forget” device that is placed between the compressor power supply and the compressor; simply sliced into the circuit in series; actually you don’t have to splice anything as we use quick disconnect terminals that mate up with the existing electrical system terminals. Our high-low pressure switch option protects the compressor in two ways:

  1. Since compressors rely on the refrigerant to carry the oil through the compressor, compressor life is dependent upon oil flow. Should refrigerant level (pressures) be too low the switch prevents the clutch from engaging; a very simple yet effective way to prevent compressor lock up.
  2. Compressor life is also affected by temperatures. When high side pressures rise the temperature increases correspondingly. Should the high side pressures get too high the switch will cut off the power to the clutch as well. In addition to protecting your compressor investment there is another side to the “high” side pressure issue. AC systems can release (leak) refrigerant when pressures get too high (such as found with pressure release ports) so the EPA requires that when you convert to R134a with systems that have high pressure release ports you will need to install a cut out switch. In either case the switch is a very smart idea if you want to extend compressor life and these switches are typically found on most modern a/c systems.

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