• Login is located in the upper right corner of all pages.

Announcement

Collapse
No announcement yet.

1966 Olds Toronado A/C

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Mikel
    replied
    Thank you. Very interesting.

    Leave a comment:


  • Cornbinder89
    replied
    Tx valves sometimes can be adjusted to set the "superheat" which is how much above the temp at the inlet of the evaporator, the outlet is.
    All that trash about "molecule size" is just that , trash!
    The Tx's job is to look at the inlet temp/pressure and compare to the outlet. If the bulb and or the equalizing line is connected some distance from the end of the finned evaporator, some superheat is called for to be sure all refrigerant leaving the evaporator is in gas form.
    The Tx valve doesn't do this by molecule size but by pressure and temp. It doesn't care how warm or cold the evaporator is, only that the inlet (just after the Tx) and the outlet are close to the same temp, Be that 70 deg or -20 deg. Size of molecule and operating pressure don't matter. Pressure will be much higher at 70 than at -20 but the Tx will meter such that the outlet and inlet are about the same.
    The same Tx is used for R 12 and R134a, and the same superheat should also be used, in otherwards, no adjustment required.
    Sure, if you lower the superheat, you can lower the suction pressure, but that does nothing to increase the capacity of the system and runs a very real risk of "slugging" the compressor with liquid refrigerant.
    That post is by someone who doesn't understand what a Tx valve does.

    Leave a comment:


  • Mikel
    replied

    Hello,
    Sorry, I just saw the latest posts.

    This was posted on another board during a discussion on POA systems. I didn't realize the expansion valve in these systems was adjustable.

    Why is no one mentioning adjusting the expansion valve? There's a brass nut in the valve (looking from underneath) that has a hex hole for an Allen wrench. Turn that in while counting the turns, take that number and divide it in half and turn it out that amount. From the factory, they are usually 7 to 10 turns, so, it will end up 3.5 to 5 turns. I ran my 72 C-10 like this for 7 years without a problem with stock evaporator and condenser.


    Since a molecule of R134 is smaller then a molecule of R12 the restriction at the expansion valve must be increased to get the correct pressure differential across the expansion valve. This also helps to bring the low side pressure down. On systems without POA valves, only the expansion valve gets adjusted or replaced. On fixed orifice systems (78 and up), the orifice tube gets replaced by a variable orifice tube which is an expansion valve. R134 needs to be squeezed more.
    Which leads me to another question. When I overhauled the A/C system in this car, I replaced the expansion valve, I believe with the AC Delco recommended below by Rockauto (I can't find the order paperwork). Any chance this valve could not be set properly for my application?



    Thanks.

    Leave a comment:


  • Cornbinder89
    replied
    Originally posted by muscle spasm View Post

    The metering device be it a POA or TXV, sets the low side pressure. That pressure equates to how cold the system will get.
    The Tx valve and the POA do different things. A POA valve system also has a Tx valve. The Tx valve meters refrigerant so it all boils by the exit of the evaporator It regulates the amount or volume of refrigerant in the evaporator, the POA regulates the minimum pressure in the evaporator.
    The Tx valve doesn't care (within a range) how cold or how low the evaporator pressure gets, only that the inlet of the evaporator and the outlet are the same temp/pressure. If you try and use it too far out of its design range, it can't control the refrigerant in the evaporator to make the best use of the surface area.
    Conversely, the POA doesn't care how much refrigerant is in the evaporator as long as the pressure never falls below its set point. It keeps the evaporator temp from going below freezing. It is more like a frost switch then a metering device. You need both a Tx and a POA in a POA system

    Leave a comment:


  • muscle spasm
    replied
    Originally posted by Mikel View Post
    Thank you both.

    A/C is working well enough, but when the car is moving at a high speed it is noticeably cooler, so I hope increasing condenser capacity will make that cooling performance independent of vehicle speed. Unfortunately the core support blocks the mounting of pusher fans in front of the condenser and I don't want to start cutting the car.

    Maybe a project for this winter.
    Get some coil cleaner for HVAC work. That car has decades of road grime on it. Also remove the evaporator. Clean it or replace both to be sure. Auto AC Kits had what I needed. Fast shipping and good pricing.

    Leave a comment:


  • muscle spasm
    replied
    Originally posted by Mikel View Post
    I don't understand is why the POA set point with compressed air matters. I was under the impression that it was a way to approximate what the low end pressure was going to be
    The metering device be it a POA or TXV, sets the low side pressure. That pressure equates to how cold the system will get.

    Leave a comment:


  • muscle spasm
    commented on 's reply
    That 65F deal was for auto climate control.

  • muscle spasm
    commented on 's reply
    Agree. The condenser is highly over looked. I just replaced mine. NO blockage or air restriction. Total free flow. New one helped my system from 46 to 29F. All I could deduct from the condenser swap was it was clean basically. Old one had 20+ years of road grime. Good HVAC coil cleaning would help a bunch of these under performing systems. Well another important one that lead to the actual replacement. Measured inlet temp was the same as the outlet. Just wasn't pulling any heat away.

  • muscle spasm
    commented on 's reply
    Recommended to charge at 1800 rpm. Just as you are driving around. You spend more time rolling than sitting at lights.

  • muscle spasm
    commented on 's reply
    Great point but most of these old monsters had huge engines. Meaning not like a 4 cyl Corolla or Sentra. Wouldn't even know the compressor kicked on in a 455 Olds or 460 Ford LOL.

  • muscle spasm
    commented on 's reply
    Open ALL the doors on the vehicle. Set for fresh air draw. Use fan speed 2 or 3. Higher the fan speed the more thermal energy extracted from the evaporator. These tips will help during cooler weather charges.

    Get out there and charge it up.

  • muscle spasm
    commented on 's reply
    Other factors that sum up to cause poor cooling. Don't just set a POA or TXV and expect ice cubes. Just saying.....

  • muscle spasm
    replied
    Originally posted by Cornbinder89 View Post
    It is more that you can't fill 100% to the top. Like a propane tank, you can only fill 80% or less to allow for expansion/vapor pressure. I just don't know how Dust-off cans are mfg and packaged. they may be made how refrigerant cans are, or they may be packaged with air in the remaining space.
    I just don't know how the packaging is done.
    Valid point. Just weigh it out of the can or into the system.

    Leave a comment:


  • Mikel
    replied
    I did. In these cars the condenser sits about 1" ahead of the radiator (which has the mechanical fan and shroud behind it), with open sides and top, so that the air sucked by the mechanical fan bypasses the condenser. I got some high temperature foam strips and sealed those gaps, which made for a significant improvement when the vehicle is at a stop. I will keep fiddling with it.

    I do have a heavy duty fan clutch. Radiator is a recored 3-core. Interestingly, I think the foam I added is helping with cooling. With the open sides and top, ram air would flow through the gaps between the condenser and radiator, whereas when those gaps are closed, the air forced through the condenser has only one path to follow now, the radiator.

    The main problem at this point is not in raw cooling power but in the dash vents. There is a large central vent that cannot be adjusted side to side, and two smaller ones, one on either extreme of the dashboard. The one on the driver's side is blocked by the steering wheel, so getting air to one's face is very problematic, which plays a big role in being comfortable in a hot car.



    In 1970 Oldsmobile put a second vent where the clock is, which would give an unobstructed shot to the driver's face/chest. Next year I might do some surgery and retrofit such a vent to mine.
    Last edited by Mikel; 07-08-2022, 08:33 PM.

    Leave a comment:


  • Tom Greenleaf
    replied
    Long thread - all fine it's what we're about. Seal it as close to air MUST go thru I doubt you need to add pusher fans? Do think that the same air has to exit generally down and out is also for the engine's heat.

    Shouldn't be a need to alter anything or mess up a total antique car in fact don't IMO. Stronger existing fan via clutch - right? Ha - once used to be able to get more with those by brand or just check out there what would just bolt up like for a truck or van but wouldn't be and Olds for trucks/vans of that time no harm in looking.

    What you get for parts must match IDK for sure nor what's available once an option called "Dessert Cooling" was a thing no chance to know that for this car??

    4 row radiators and some things noticed ONCE saw that a 60's Mustang I think ages ago now doesn't mean many others didn't offer that.

    IDK a van I had to drive plain Chevy had such a strong fan clutch took power away from engine was OE for the thing.

    Just Google around see if there is such a thing beware I don't always believe it by ads out there.

    If you don't have a 5 bladed fan I'm pretty sure you can fit one lots newer are for fan clutch vehicles (GM) was 4 if you didn't buy A/C for this when new no slippage was direct drive to belt speed whether needed or not, cold out or not special request for no A/C at all knew a few of those cars,

    Leave a comment:


  • Cornbinder89
    replied
    Look into what can be done to seal the condenser to the radiator so the engine fan has to pull air through the condenser not around it. Cooler with ram air indicates an airflow problem.
    A larger condenser can help also. excess capacity that is not needed will just store liquid refrigerant and not cause any problem. Anything to get the liquid as close to ambient as possible, wil not be a wasted effort.

    Leave a comment:


  • Mikel
    replied
    Thank you both.

    A/C is working well enough, but when the car is moving at a high speed it is noticeably cooler, so I hope increasing condenser capacity will make that cooling performance independent of vehicle speed. Unfortunately the core support blocks the mounting of pusher fans in front of the condenser and I don't want to start cutting the car.

    Maybe a project for this winter.
    Last edited by Mikel; 07-08-2022, 05:28 PM.

    Leave a comment:


  • Cornbinder89
    replied
    That is something that is almost imposable to answer. In order to compare like to like you need to know many things, fin area and total volume of tube as well as surface area exposed to refrigerant. A comparison of mere physical outside dimensions doesn't come close to comparing the other things I mentioned.
    In the 80's you could have two tube and fin units with the same outside dimensions and still have two differing capacities. Large trucks had large radiator area that could fit large condensers, but because they didn't want to impede the air flow to the radiator, they used units with a low fin count per inch. A similar sized unit with a high fin count would remove more heat from the refrigerant.
    Tube and fin have a low surface area to volume ratio, meaning the amount of refrigerant in direct contact to the tube wall is small compared to the total volume of refrigerant in the tube.
    Small thin oval or rectangular tubes have a high surface area to volume ratio. They also have a higher restriction because of this. To overcome the restriction many tubes are used in parallel. They are still a multi pass condenser.
    In between these two types is the serpentine tube type, which also used a flattened tube with multiple passages.
    The modern multi pass parallel flow has the most surface area to volume of any design and when combined with a high fin count per inch can provide more heat removal per unit volume of a similar condenser size of different construction and fin count. There are just too many variables to go on outside dimensions alone.
    Another advantage the parallel flow has, is: Heat is remove fastest when the temp difference between the cooled and cooling medium are the greatest. So the vast majority of heat is removed near the inlet of the condenser and diminishing amounts toward the outlet. By have multiple paths near the inlet, it allows for more heat to be removed early, over a single tube design. This allows the rest of the condenser to have more area to remove the rest of the heat in the refrigerant, so by the outlet the temp is reduced more than with other designs.
    It is almost impossible to compare apples to apples in this case.

    Leave a comment:


  • Tom Greenleaf
    replied
    Good question? IDK is the answer but a guess is 25% but also can be lighter by about that. TMK 134a is about 80% the possible value of R-12 so increasing efficiency by that makes sense. The down side is they are not fixable, flushable yet ones swapped over worked fine in fact at the time had no choice it came with a note to reduce system capacity by 10 oz was about 25% of what that vehicle held in total,

    Leave a comment:


  • Mikel
    replied
    Good afternoon,
    Out of curiosity, typically how much more efficiency does a modern parallel condenser offer over a similarly sized fin and tube?
    Thanks.

    Leave a comment:

Working...
X