r134a numbers with stock Condenser & replacement POA - Page 4 - Chevelle Tech
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post #46 of 78 (permalink) Old Sep 6th, 19, 11:52 AM
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Re: r134a numbers with stock Condenser & replacement POA

Glad all is well....... I shot mine with around 52/54??? Way to much. Had to suck it out. I have 48 Oz. of 134 in mine and its FRICKEN KOLD, The wife said turn it down or let me out.
REMEMBER: When you make the lady happy with a KOOL KAR in the daytime. You may need the A/C at night IF things get WARM !.............
Bob
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post #47 of 78 (permalink) Old Sep 6th, 19, 1:12 PM Thread Starter
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Re: r134a numbers with stock Condenser & replacement POA

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Originally Posted by Robinls5 View Post
Glad all is well....... I shot mine with around 52/54??? Way to much. Had to suck it out. I have 48 Oz. of 134 in mine and its FRICKEN KOLD, The wife said turn it down or let me out.
REMEMBER: When you make the lady happy with a KOOL KAR in the daytime. You may need the A/C at night IF things get WARM !.............
Bob
yes, thanks for your help. My little Sanden SD7 compressor has less displacement than the original GM, so, I calculated that out to be 2.1 oz less freon required. So, I think mine should be between 45-46 oz of R134a. I think I am close to that now, maybe still a little over. Here is a pic of my old parts pile --- all going to the dust bin. lol.


Harry
1970 Chevelle SS396 (408), Fathom Blue,
Original Block & Forged Crank, KB Pistons, Edelbrock 6045 Heads,Comp Cam 292H, March Serpentine, RPM AirGap,750HP,100hp Nitrous
A/F Wideband,Tremec TKO 600, 12 bolt,
30 spline Moser Axles, Richmond 3:73's, Hotchkis control arms, swaybars, springs, Wilwood 12" rotors D/S, 4 piston calipers
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post #48 of 78 (permalink) Old Sep 6th, 19, 4:01 PM
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Re: r134a numbers with stock Condenser & replacement POA

Make sure that heater control valve is shuting correctly. I had couple different valves in mine, I swear, the aftermarket valves are nothing like the original factory stuff. Both feed and return hoses were always hot, so the AC was fighting the heater core. Eventually, I put manual valve in there that I just closed during the summer.
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post #49 of 78 (permalink) Old Sep 6th, 19, 4:11 PM Thread Starter
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Re: r134a numbers with stock Condenser & replacement POA

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Originally Posted by GRN69CHV View Post
Make sure that heater control valve is shuting correctly. I had couple different valves in mine, I swear, the aftermarket valves are nothing like the original factory stuff. Both feed and return hoses were always hot, so the AC was fighting the heater core. Eventually, I put manual valve in there that I just closed during the summer.
Thanks ! I am on my third or fourth one. Two of the other ones started leaking. Both sides of my hoses have always been hot no matter what aftermarket valve I put in there. My test for the heater shutoff has been to run the "vent" on "cold" and make sure the air is outside temperature and not any hotter. The vacuum line going to the valve is good, but, with my big cam I idle around 9 or 10 in. hg.. I wonder if that lower vacuum makes a difference on the heater valve. The manual valve is a good idea...

Harry
1970 Chevelle SS396 (408), Fathom Blue,
Original Block & Forged Crank, KB Pistons, Edelbrock 6045 Heads,Comp Cam 292H, March Serpentine, RPM AirGap,750HP,100hp Nitrous
A/F Wideband,Tremec TKO 600, 12 bolt,
30 spline Moser Axles, Richmond 3:73's, Hotchkis control arms, swaybars, springs, Wilwood 12" rotors D/S, 4 piston calipers
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post #50 of 78 (permalink) Old Sep 6th, 19, 5:53 PM
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Re: r134a numbers with stock Condenser & replacement POA

Harry, I applaud all the hard work (and documentation) you've put into this and especially the results. I may copy/paste all the dialog and photos into a word document and save it for reference.
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post #51 of 78 (permalink) Old Sep 6th, 19, 6:06 PM
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Re: r134a numbers with stock Condenser & replacement POA

I put a manual valve in mine too and the hoses still get hot on both sides. Makes sense since even though the water doesn't move the heat will still travel through the water via conduction. Maybe not quite as hot at the heater core but still hot.
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post #52 of 78 (permalink) Old Sep 7th, 19, 12:14 AM
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Re: r134a numbers with stock Condenser & replacement POA

Great job Harry. I'm glad all your hard work finally paid off.

Pressures look good after you removed some freon. What's most telling is your vent temps. Lookin good. Try running on a cool morning with the fan on low speed and watch your vent temps.
If they drop below 35* you'll want to hook up an ambient temp switch to avoid ice ups of the evaporator. If you see cool vapor coming out of the vents, you're getting into ice up territory.

Your pictures made this thread a keeper.
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post #53 of 78 (permalink) Old Sep 7th, 19, 2:35 AM Thread Starter
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Re: r134a numbers with stock Condenser & replacement POA

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Originally Posted by DUTCH MAX HEADWORK View Post
Great job Harry. I'm glad all your hard work finally paid off.

Pressures look good after you removed some freon. What's most telling is your vent temps. Lookin good. Try running on a cool morning with the fan on low speed and watch your vent temps.
If they drop below 35* you'll want to hook up an ambient temp switch to avoid ice ups of the evaporator. If you see cool vapor coming out of the vents, you're getting into ice up territory.

Your pictures made this thread a keeper.
Thanks Al, I am very happy. My girlfriend and I took a 66 mile (33 miles each way) drive to Bob's big Boy Car show. It was over 100 deg. out when I left and I was getting 49, 48 degrees out of the center vent on max. high. We were very cool in the Chevelle, even in traffic. On the way home, at night, I got 37 deg. out of the center vent on max. high. My girlfriend complained a few times that she was freezing. I am also getting a lot more air volume on high which cools you off a much faster. Honestly, this work completely changed my car. I moved my high idle ( with air cond. on) to 950 rpm, and my normal idle stays at 850 rpm. This seems the sweat spot. Thanks again for all your help !

PS. Plenty of water coming out of the bottom of the suitcase and condensation on the cold lines and POA.

Harry
1970 Chevelle SS396 (408), Fathom Blue,
Original Block & Forged Crank, KB Pistons, Edelbrock 6045 Heads,Comp Cam 292H, March Serpentine, RPM AirGap,750HP,100hp Nitrous
A/F Wideband,Tremec TKO 600, 12 bolt,
30 spline Moser Axles, Richmond 3:73's, Hotchkis control arms, swaybars, springs, Wilwood 12" rotors D/S, 4 piston calipers
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post #54 of 78 (permalink) Old Sep 7th, 19, 7:35 AM
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Re: r134a numbers with stock Condenser & replacement POA

i would be pretty happy with those vent temps. I have peeked in my suitcase through one of the switches mounted on top. it looks pretty clean, but i know deep down inside theres many many years of crud in there, which im sure is why air flow through my vents is weak.
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post #55 of 78 (permalink) Old Sep 7th, 19, 11:21 AM Thread Starter
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Re: r134a numbers with stock Condenser & replacement POA

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i would be pretty happy with those vent temps. I have peeked in my suitcase through one of the switches mounted on top. it looks pretty clean, but i know deep down inside theres many many years of crud in there, which im sure is why air flow through my vents is weak.
Yes, probably... I was one of those guys that went through all my vents, loosened the other side of the suit case, and replaced my blower motor, then fished my air compressor line in there and blew some stuff around. Afterwards, I went from "high" blowing on "low" to "high" blowing on "3/4". I felt pretty good and called it done. My suitcase is "clean". Note: the stock air cond. blower motor has a different part number than the stock non-air cond. blower motor. The former is more powerful, so, you want to make sure you get the right one for Air cond...

But, now that I actually took the system apart and was able to get the Evaporator out, replace it, and clean out the suit case, I can say, that this seems to be the most important part of the process. The new air flow amount on "high" blows on "super high". There is a big volume difference between 3/4 and "high" now, and that makes a big difference in cooling off the back seats and how fast the passengers cool off when the car has been in the sun. I have to say I am pretty surprised. I did not expect it.
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Harry
1970 Chevelle SS396 (408), Fathom Blue,
Original Block & Forged Crank, KB Pistons, Edelbrock 6045 Heads,Comp Cam 292H, March Serpentine, RPM AirGap,750HP,100hp Nitrous
A/F Wideband,Tremec TKO 600, 12 bolt,
30 spline Moser Axles, Richmond 3:73's, Hotchkis control arms, swaybars, springs, Wilwood 12" rotors D/S, 4 piston calipers
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post #56 of 78 (permalink) Old Sep 7th, 19, 11:43 AM
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Re: r134a numbers with stock Condenser & replacement POA

On my 70 Sta. Wgn. I have a water shut off valve. ( LOWES ,& painted black). I have it close to the firewall. Now no worries about heater doors or some flappers not sealing well or radiant heat that may impact the evaporator.
Another item, 70 owners & others.........." LOOK " at the---- SPACE---- between the Rad. tanks & the core support. I bought some Black foam tape with the sticky back side. 1" X 1" or 3/4" X 3/4".... Slide the foam tape in place then with needle nose, Pull the tape covering.
WHY?........ When you are going slow or near a static position, With "" NO "" outside air pressure pushing air into the engine bay, The engine powered fan blade will pull this super heated air ( from the engine bay) through this large gap, AND... Right back into the ALREADY HOT, AKA " Heat Exchanger " or Rad.
Blocking this airflow passage will drop your Temp,,by 3 to 6 degrees.
Be KOOL and have fun!
Bob
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post #57 of 78 (permalink) Old Sep 7th, 19, 1:43 PM Thread Starter
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Re: r134a numbers with stock Condenser & replacement POA

Quote:
Originally Posted by Robinls5 View Post
On my 70 Sta. Wgn. I have a water shut off valve. ( LOWES ,& painted black). I have it close to the firewall. Now no worries about heater doors or some flappers not sealing well or radiant heat that may impact the evaporator.
Another item, 70 owners & others.........." LOOK " at the---- SPACE---- between the Rad. tanks & the core support. I bought some Black foam tape with the sticky back side. 1" X 1" or 3/4" X 3/4".... Slide the foam tape in place then with needle nose, Pull the tape covering.
WHY?........ When you are going slow or near a static position, With "" NO "" outside air pressure pushing air into the engine bay, The engine powered fan blade will pull this super heated air ( from the engine bay) through this large gap, AND... Right back into the ALREADY HOT, AKA " Heat Exchanger " or Rad.
Blocking this airflow passage will drop your Temp,,by 3 to 6 degrees.
Be KOOL and have fun!
Bob

Ok Bob, you managed to get me motivated again. You guys have not steered me wrong yet. I have a bunch of high and low density foam strip in that size. Here is a pic, is this the area you are talking about ? The space between the Aluminum radiator and core support - yes, roughly 3/4".
I should have done it from the front when I had the condenser out, it would have been easier to position perfectly on the passenger side where the battery tray is in the way -- new tip for everyone, lol ---. Well, I have the foam, so, I will try it. I think I will try the high density first. Thanks again.

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Harry
1970 Chevelle SS396 (408), Fathom Blue,
Original Block & Forged Crank, KB Pistons, Edelbrock 6045 Heads,Comp Cam 292H, March Serpentine, RPM AirGap,750HP,100hp Nitrous
A/F Wideband,Tremec TKO 600, 12 bolt,
30 spline Moser Axles, Richmond 3:73's, Hotchkis control arms, swaybars, springs, Wilwood 12" rotors D/S, 4 piston calipers
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post #58 of 78 (permalink) Old Sep 7th, 19, 2:21 PM
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Re: r134a numbers with stock Condenser & replacement POA

If you decide to adjust your pressures, make sure you bleed your gauge lines every time you hook up or you risk introducing air into the system.

Bob's recommendations of sealing the evap to the radiator are spot on and I think will help even more if you are using electric fans because it forces the fans to pull through the condenser which would help at idle. Removing the rad top plate will allow you more room and a way to seal the top. On the bottom just push in some sort of insulation.

The positive heater shut off valve is also a good recommendation because the stock heater valves always seem to leak some hot coolant through the system.

I wish I would have been here before you got to the point of charging, I would have given some more advice on charging the POA system. My real job got in the way.

Your pressures may still be a bit high, but hard to determine when you are running the car in a garage. I figure the garage temp is much higher than the ambient temp due to the heat generated by the running engine. So that's possibly throwing off your pressures and causing them to read a bit higher. You can tell if your cooling airflow is affecting the vent temps and pressures by running water over the condenser, but that can make a mess of your clean engine. I run 2 big fans into the condenser while charging to help cool the condenser. Even with this, I'll see a drop in head pressure when I run water over the condenser, so at some point, you call good enough.

Your temp increase at idle is likely due to lack of airflow and your pressures are going up. If your pressures go down at idle, it may be due to the smaller displacement of the a/c compressor.

When charging the POA SYSTEM I watch the recommended charge quantity and the vent temps carefully. When I get close I take the time to add refrigerant slowly and watch the pressures and vent temps. You'll notice a point where both gauges will start to climb and vent temps go up. Charging slowly at this point is key because the system needs time to stabilize after adding refrigerant.

Your vent temps may benefit in a reduction of pressures, The POA system dumps excessive pressure to the low side to keep the TXV pressure constant. The increase in lowside pressure negatively affects cooling performance. So like an engine, tuning a Frankenstein A/c system is a tool for best performance. With the factory system, the factory already did this for us and we charge by weight.
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post #59 of 78 (permalink) Old Sep 7th, 19, 4:31 PM Thread Starter
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Re: r134a numbers with stock Condenser & replacement POA

Ok, I put 3/4 inch high density foam in, but, I recommend 1 inch instead. I think I will switch mine to 1". I used my cheap grab tool to set the line. Here are some pics:






I put the two big house fans in front of the Chevelle and ran some tests from cold start. My gauges are still charged with freon, so, no worries about air in the system. Here are my results.

Engine off - low side, high side - 92 psi, garage temp 93 deg. ambient.

engine started:

low side, high side, vent temp, approx. time
34 psi, 148 psi, 49 deg. - 1 min.
32.5 psi, 152 psi, 47 deg - 3 min.
31.5 psi, 155 psi, 46 deg. - 5 min.
33 psi, 173 psi, 46 deg. - 8 min.
33.5, 188 psi, 48 deg. - 10 min.
36.5, 200 psi, 50 deg. - 12 min.

What do you think about the freon quantity ? The system tried to stay at 46 for a while, but, then, the pressure started going up and it could not maintain 46 deg... The times are approx... I noted down the numbers when I saw things start to change. It looks like the best numbers were 31.5, 155 with 46 deg. vent temp...

Harry
1970 Chevelle SS396 (408), Fathom Blue,
Original Block & Forged Crank, KB Pistons, Edelbrock 6045 Heads,Comp Cam 292H, March Serpentine, RPM AirGap,750HP,100hp Nitrous
A/F Wideband,Tremec TKO 600, 12 bolt,
30 spline Moser Axles, Richmond 3:73's, Hotchkis control arms, swaybars, springs, Wilwood 12" rotors D/S, 4 piston calipers
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post #60 of 78 (permalink) Old Sep 7th, 19, 4:55 PM
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Re: r134a numbers with stock Condenser & replacement POA

At the current ambient temps it looks like these numbers are your target.33 psi, 173 psi, 46 deg. - 8 min. to 33.5, 188 psi, 48 deg. - 10 min. Set here between these 2 and take a test drive to verify your work.

Vent outlet temps will prove you're on the right track when running down the road and getting good airflow through the condenser and steady output from the compressor. If your vent temps rise on the road, it puts you back to not having sufficient charge and your stationary issues are condenser temps/lack of airflow. It appears your compressor has plenty of output to supply the needs of the system. I actually expect to see temps in the lower 40's going down the road. Maybe that heater control valve is not doing its job. This will affect temps at cruise and at idle as your coolant heats.

Your static pressure is right on. It shows about 1 psi for each degree in temp. All that really shows is that the system is does not have air contamination or refrigerant cross contamination and you have enough to trigger the low pressure switch. The state of charge must be read with the engine running.

The pressure building is a result of heat in the system and lack of airflow through the condenser. Might even be related to heat building in the garage. There's only so much you can do here and you've done or are doing all you can short of higher flow cooling fans. At some point, you can continue to chase the dragon or call good is good. As this crazy humidity we've been having here diminishes to regular levels, so will your perceived cooling from the a/c unit.
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