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Originally Posted by KATSCAN
so, in your opinion, MB air is as good as it's ever going to be?
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Ones that are already built, yes. Most people complaining own older cars, so they may have already addressed this issue.
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Originally Posted by KATSCAN
Yes you can run the evaporator below your "practical limit" as it is being done today. Yes doing that brings consequences and danger if it's not engineered while the car is being designed or operating in the proper heated environment.
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The practical limit remains the temperature at which water freezes on the evaporator. The thermistor measures temperature wherever it is. If the thermistor location requires it to be below freezing for the evaporator to be at this practical limit, it does not mean that the entire evaporator is held below freezing temperature.
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Originally Posted by KATSCAN
My problem is I will have to develop a "false temperature reading" of the ets to get the performance that I want. There's the danger, but it can be made up. The hybrid system I'm talking about will get you cold fast, but it takes operator monitoring. If the evaporator "freezes" you will notice the drop in vent temp; you must manually shut off the AC. You cannot count on the TXV to control, you cannot count on the ets to control. The point is that on really hot days I know you can run a very low evap temp because of the extreme heat flow over the finns;
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No, you cannot. Any time the evaporator surface drops below the freezing point of water, it'll ice up. That the air moving through the evaporator is hotter merely means that it takes more cooling capacity to get the evaporator temperature to that point.
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Originally Posted by KATSCAN
i'm going to make an effort to do it. Perhaps put a switch in line to change ets resistance on days above 100. A complete worry free system? not at all. But I can manage it. On normal days switch off and run MB specs 2to4degreesC.
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You are still going to find that you run up against limits. Without increasing the ability of the system to move heat, you will not increase the heat it is able to move.
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Originally Posted by KATSCAN
BTW the TXV can sense a warmer temp also when it "freezes" opening up even more; adding more refridgerant flow danger. The potential for x-tra refridgerant flow is the main reason for adding an accumulator. I understand others are not even putting in that extra safety measure.
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Fixed-orifice systems typically have the receiver/dehydrator in the suction line after the evaporator so as to allow any refrigerant that is still in liquid form to boil off to vapor before reaching the compressor. Variable-orifice systems monitor the low-side pressure or temperature to control the rate of flow. I find it interesting to note that Ford and GM use fixed-orifice systems. Not that I think fixed-orifice is superior. I believe they use fixed because it is cheaper, and their systems are designed with cooling capacity that MB lacks.
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Originally Posted by KATSCAN
With today's technology in the car and temps being registered, monitored, even can be displayed thru the radio; it would be very hard to convince me that outside temp does not adjust the evap temp sensor/switch in todays car with a default setting for protection in case the outside temp sensor fails. My car is an 86. I do not believe it can do all that.
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Any 'climate control' system has to take ambient air temperature into consideration. Manual A/C does not. Cadillac has had the ability to display A/C parameters for almost 25 years now, although they used the climate control digital display and not the radio.
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Originally Posted by KATSCAN
Why is there a "dessert ets spec" on GM cars shipped to the dessert? I guess they run at 32f evaporator but feel special because their car is called dessert spec. NO! Perhaps they know the evaporator can operate below it's "practical limit" and perhaps they know it must run below its "practical limit" for effective cooling/comfort.
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You continue to confuse thermistor temperature with evaporator temperature.