[DeTomaso] AC Condenser: Front Mount vs. Stock Rear Location

[JFFR]

I would tend to conclude that your 134 A/C system conversion has not 
been properly engineered or was an early conversation. If you have the 
proper evaporator valve installed the 134 pressures should be less than 
your traditional R-12 pressures. R-12 needs an 8:1 pressure reduction to 
cool optimally. IE 240 PSI (16X atmospheric pressure) High side then 30 
PSI (2 atmospheres) through the evaporator. The 134 refrigerant needs a 
12:1 pressure drop to cool optimally. We use an evaporator valve that 
drops the low side pressure into the teens, like 1 atmosphere of 
pressure 15 PSI so the high side pressure doesn¹t need to exceed 200 PSI 
(13X atmosphere) with also generates less heat to have to after cool in 
the first place. This application of physics did not happen initially 
when the 134 platform was imposed on us. We initially kept the R-12 
evaporator valve and saw 400+ PSI high pressures to get the 134 to run 
cool. Things didn¹t start out well for R-134 conversions. Pantera¹s and 
other European based vehicles use a fixed orfice evaporator valve 
system. GM used replaceable orfice tubes. People could experiment with 
different size tubes to refine the efficiency process with R-134 
refrigerant. With that we were able too then refine what fixed based 
orfice evaporator valves worked best. Conclusion was Less is best. Larry 
I actually bought the R-134 expansion valve from you Larry. Then I 
installed the larger capacity condenser and all new R-134 type hoses 
along with a higher speed condenser fan. I believe that my high pressure 
problems and lack of cooling capacity was due to the exhaust crossover, 
which was heating the air that was being circulated back through the 
condenser. It sounds like a strange conclusion, but before the 
installation of the crossover pipe, the stock system with R-12 worked 
fine. To date I have only seen two other Panteras with an exhaust 
crossover pipe. I never had a chance to speak to the owners about how 
their air conditioning systems worked or if they even did use them. The 
front mounted condenser eliminated the exhaust heat problem and works 
like a normal modern system. Living in Arizona and driving the Pantera 
in the summer time is a pretty good test of the air conditioner.
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   I would tend to conclude that your 134 A/C system conversion has not
   been properly engineered or was an early conversation. If you have the
   proper evaporator valve installed the 134 pressures should be less than
   your traditional R-12 pressures. R-12 needs an 8:1 pressure reduction
   to cool optimally. IE 240 PSI (16X atmospheric pressure) High side then
   30 PSI (2 atmospheres) through the evaporator. The 134 refrigerant
   needs a 12:1 pressure drop to cool optimally. We use an evaporator
   valve that drops the low side pressure into the teens, like 1
   atmosphere of pressure 15 PSI so the high side pressure doesn^1t need
   to exceed 200 PSI (13X atmosphere) with also generates less heat to
   have to after cool in the first place. This application of physics did
   not happen initially when the 134 platform was imposed on us. We
   initially kept the R-12 evaporator valve and saw 400+ PSI high
   pressures to get the 134 to run cool. Things didn^1t start out well for
   R-134 conversions. Pantera^1s and other European based vehicles use a
   fixed orfice evaporator valve system. GM used replaceable orfice tubes.
   People could experiment with different size tubes to refine the
   efficiency process with R-134 refrigerant. With that we were able too
   then refine what fixed based orfice evaporator valves worked best.
   Conclusion was Less is best. Larry I actually bought the R-134
   expansion valve from you Larry. Then I installed the larger capacity
   condenser and all new R-134 type hoses along with a higher speed
   condenser fan. I believe that my high pressure problems and lack of
   cooling capacity was due to the exhaust crossover, which was heating
   the air that was being circulated back through the condenser. It sounds
   like a strange conclusion, but before the installation of the crossover
   pipe, the stock system with R-12 worked fine. To date I have only seen
   two other Panteras with an exhaust crossover pipe. I never had a chance
   to speak to the owners about how their air conditioning systems worked
   or if they even did use them. The front mounted condenser eliminated
   the exhaust heat problem and works like a normal modern system. Living
   in Arizona and driving the Pantera in the summer time is a pretty good
   test of the air conditioner.