Using this charging method we found that 26 ounces worked perfectly with this Mr. Ice Project (depending upon how many condensers you have the final quantity of refrigerant will vary). With an outside temperature of 85 F and 26 ounces of R134a we achieved a vent temperature of 33 degrees F. During this situation our low side gauge pressures were 30 to 32 psi. More important our high side pressures were only 200 to 210 psi.., perfectly acceptable. Below 33 degrees we noticed the compressor shut off because at this point the thermostatic tube, in the evaporator from the a/c temperature control, shuts off the compressor to prevent the evaporator from icing up.
You can’t get any better than this? Well maybe we can: (i) as we said we were using only 1.5 cfm. vacuum pump. I know if we had something with a little more muscle we could achieve a better evacuation. In later projects we found that by replacing our vacuum pump oil more often we could achieve lower levels of vacuum. Our vacuum gauge with this first project was a typical analog unit. After as string of “gauge” problems, such as needles falling off, we finally spent some money wisely and purchased a digital “micron” gauge that is more accurate. Our high side pressure was conservatively low. We could probably put in some more R134a and safely raise the high side a little bit. I believe that if we used more accurate equipment and spent some more time to tweak the system we could do much better. But, at some point there is a cost benefit analysis you must consider, after all 33 degrees F does feel colder than 50 or 45 F!
Here are the documented readings we achieved in the testing situation mentioned
* with engine’s deck lid down
As you will note in the column headings the tests we performed are the standard 2000 rpm test with the deck lid down, and a median driving condition test at 40 mph. During these tests the outside air temperature was 85 F, the humidity level was 45% (humidity does effect vent temperatures and the period required to reduce cockpit temperatures). Naturally the fan speed effects vent temperature as the the slower the fan speed the greater the period of time the air contacts the evaporator, as well as the volume of air.
After this initial Mr. Ice Project we continued to improve our procedures and began marketing the Kuehl system products. Customer results either equal or surpass our first scores. And we continued exploring air conditioning components which we felt needed further improvement for the 911 and 930’s with factory air.
Based on those studies we have developed the following new items:
- The “new” high performance rearward Kuehl Condenser using serpentine tubing.
- The serpentine Duehl Kuehl Condenser (mounted in front of the rear tire) which runs in series with the rearward Kuehl unit.
- The serpentine Kuehl 930 turbo deck lid condenser.
- The serpentine Kuehl Evaporators for 911, 964 and 993 models.
- The Tri-Kuehl Vent system for 1978-1985 911 and 930’s.
- The Kuehl Variable Speed Fan Controller to replace the the three speed unit found in all 911 and 930 models.
Most of these new items will be discussed in our 2nd Mr. Ice Project where we are running 4 condensers, the new serpentine evaporator, Kuehl vent, and variable speed fan controller in a 1987 911 Cabriolet (convertible). So far the results from this second project are spectacular! Can you imagine a cockpit temperature of 67-69F when the outside temperature is near 105F …. in a black top convertible! Can you guess the license plate number of this vehicle?