Automotive Air Conditioning Information Forum

tbirdtbird wrote: ↑Sat Dec 16, 2023 11:50 am I should have specified getting into first gear (non-synchro) can be the challenge. Glad you are gonna try it first

Gotcha. I have an old school habit of always go into 3rd then to 1st or reverse to stop the input shaft as 1st and reverse usually weren't synchronized in those days. A clutch brake would of been nice those days.


Earl

I have been busy with other things, but I did not forget this thread.

That is a mighty evaporator you have there. Looks to have been built for a significant mass flow.

The TXV is of course the big question mark. If it does not work, replacements will be a little complicated. It appears to have an equalization line and a feed line in that picture, I am assuming a line or two on the other end to the tubes in the evaporator?

There is nothing "modern" about cycling a clutch. It is more like a board track motorcycle, running wide open and controlling power with the kill switch.

The only way to make more flow from a 9.5 CID pump is to turn it faster. Sanden marketing claims a 15% increase in cooling. Yet they don't provide a dyno sheet for the "enhanced" SD7.

You can buy a bigger compressor. A TM21 will get you to 12kw of cooling without issue. It really is a 13 CID unit.

http://www.valeocompressors.com/en/tm21

Personally I would put a V5 compressor on it. The V5 can go toe to toe with the TM21, in fact it maxes out around 13kw capacity. 4.9 inch pulley is better choice than the TM21 as well.

The V5 is a variable displacement compressor. It has a clutch so it can be turned off, but during operation it de-strokes to maintain evaporator pressure rather than the bang-bang control of cycling the clutch.

If your TXV is failed, the V5 offers a way to keep it in the system. By using it as a fixed orifice to meter liquid refrigerant in to the evaporator. V5 compressors were installed on many cars with fixed orifice tubes.

bohica2xo wrote: ↑Wed Dec 27, 2023 7:50 pm I have been busy with other things, but I did not forget this thread.

That is a mighty evaporator you have there. Looks to have been built for a significant mass flow.

The TXV is of course the big question mark. If it does not work, replacements will be a little complicated. It appears to have an equalization line and a feed line in that picture, I am assuming a line or two on the other end to the tubes in the evaporator?

There is nothing "modern" about cycling a clutch. It is more like a board track motorcycle, running wide open and controlling power with the kill switch.

The only way to make more flow from a 9.5 CID pump is to turn it faster. Sanden marketing claims a 15% increase in cooling. Yet they don't provide a dyno sheet for the "enhanced" SD7.

You can buy a bigger compressor. A TM21 will get you to 12kw of cooling without issue. It really is a 13 CID unit.

http://www.valeocompressors.com/en/tm21

Personally I would put a V5 compressor on it. The V5 can go toe to toe with the TM21, in fact it maxes out around 13kw capacity. 4.9 inch pulley is better choice than the TM21 as well.

The V5 is a variable displacement compressor. It has a clutch so it can be turned off, but during operation it de-strokes to maintain evaporator pressure rather than the bang-bang control of cycling the clutch.

If your TXV is failed, the V5 offers a way to keep it in the system. By using it as a fixed orifice to meter liquid refrigerant in to the evaporator. V5 compressors were installed on many cars with fixed orifice tubes.

Excellent! Thanks for the help, I appreciate it! Sorry for the delay, I didn't get an email alert that there was a reply.

I say modern pressure switch cycling as back in the day they didn't use that. Such as my Packard. It uses a bypass loop control by a solenoid valve. Compressor doesn't have a clutch. Winter you took the belts off.

The V5 is intriguing. I assume it controls it's variable displacement internally mechanically? Variable compressors are something I don't know anything about. So there wouldn't be any pressure switches used? Maybe system protection? The Packard has a mercury thermostat that originally control the bypass loop solenoid valve to maintain cabin temperature. I was planning to use this control circuit to control the clutch. Could I still do that with a v5 or would I need another way to control the temperature? There is no blend doors or such in the EVAP housing. There is left and right 3 speed fans. The main switch turns the system on and is also a rheostat to work with the mercury thermostat. When turned on the blowers run all the time on user selectable low med or hi speeds. The left and right blower speeds are controlled individually. Not sure a variable compressor would work well with this system? I guess it would vary itself until the cabin temperature was met then open the clutch. I'm sure they grossly oversized the EVAP, so maybe the variable compressor wouldn't short cycle as much as a fixed displacement? Note, the bypass loop will be removed. It's part of the original condenser that's coming out for a much larger parallel condenser.

The txv has 3 connections with one being an equalizer line. There is a tube that runs along the bottom from the right side of EVAP core to the valve. That one and the equalizer line you can see in the pics. The 3rd connection isn't showing in the pic. This txv is adjustable. Finding an NOS replacement would be impossible and no guarantee it would function after 70 years laying around.


Thanks,
Earl

The TXV regulates flow in to the evaporator coil to attempt to keep it from freezing. If you reduce airflow over the coil, the TXV reduces refrigerant flow based on temperature feedback.

The GM A6 type system had two controls on the evaporator. A TXV at the inlet, and a POA valve on the suction side. The POA controlled flow out of the evaporator to maintain the evaporator temperature. A POA system could hold the evaporator very close to freezing through a wide range of airflow

The V5 & V7 compressors moved that evaporator pressure control from a complicated inline POA valve - to the valve inside the compressor that controls piston stroke. Since the P/T relationship of the refrigerant is well known, you can set the evaporator temperature by controlling suction pressure.

Because the variable compressors can control mass flow, a simple orifice can be used to meter refrigerant in to the evaporator inlet.

In your case this means you could modify an impossible to repair or replace TXV to a fixed orifice by moving the pintle to the max flow position in the valve and locking it there. The equalization port in the valve can be plugged. It would look 100% original from the outside.

You can achieve the cabin temp control by changing the blower speed. Since your Packard lacks blend doors the fan speed is your tool.

As far as electrical goes, there are ports in the head on the V5 /V7 for standard GM switches. High pressure, fan control etc. A high pressure cutout switch should be used in the clutch circuit on any A/C system.

I did research variable compressors and the v5/v7. I'd like to use a v7 due to the large evaporator, but couldn't find one with v-belt pulley. Car uses double v-belts so would prefer double but would settle with a single. I did find the v5 with single and and double v-belts. Ideally a v7 with ear mount with double belts, if you happen to know a source? Any particular brand(s) of the v5/v7 I should look for? Here is a v5 with double v-belts and a small pulley. Appears to be a no brand compressor though. https://www.apairinc.com/shopping/produ ... x?i=134310
I thought about using a v5 v-belt pulley on a v7 but couldn't find a source for the pulley.

How would I charge the system since the capacity is unknown due to component removal and upgrades? Especially if I used a variable compressor as it would effect gauge pressure? Originally I planned to charge using superheat/subcooling method. Also oil capacity? Sanden has a method for determining oil capacity by running the system to their directions and then measuring the oil from the compressor. Pretty involved.


Thanks,
Earl

You only need a single V belt. Many A6 compressors were single groove on some very large cars.

There are ear mount V7 compressors, but to get one with a V belt you need to swap the clutch from a V5.

The site sponsor can probably help you with the hybrid V7 compressor.
https://www.ackits.com/

The V7 is an impressive performer. Yet it can de-stroke to accommodate mild conditions.

The V5 /V7 units use a replaceable control valve to set pressure, and because of the long run you have on the suction line you may need to change to a different control valve pressure based on evaporator temperature.

Initial charge is a guess, based on system size estimations. We recently went through this in detail with a custom system in a Vanagon, and an H1 Hummer. The variable compressor will attempt to control suction line pressure. If badly undercharged it will act odd.

You can make a V5 change stroke with a heat gun on the suction line in low ambient temps.

OCR is always a question in a custom system. So the first guess should err on the side of too rich. The V5/ V7 does hold some oil in the case. There are a few people here that can help you with the system startup once all of the components are known.

Thanks! I contacted the sponsor you mentioned asking if they could help me with a V7 4 ear mount with a v-belt pulley.

I assume a V5/V7 4 ear mount would be the same as Sanden? That's why I'm looking for that mount. There are universal mounts that fit the Sanden 4 ear mount.

Your thoughts on using the V7 over the V5? I assume the V7 would be more desirable for that large EVAP. I want the AC to perform including at idle. But I don't want to have to turn they system on and off if it over cools. The only control will be the main on and off and two individual blower speeds. I won't be able to turn one blower off and leave the other on, they both run all the time the system is on.

From what I can find, the displacement of the V5 and V7 are 150cc and 179cc. How does one figure out what for displacement compressor is needed?


Thanks,
Earl

Nothing specific popped up. I'll contact the compressor division on Tuesday to see if they can make one.

Tim wrote: ↑Mon Jan 01, 2024 2:43 pm Nothing specific popped up. I'll contact the compressor division on Tuesday to see if they can make one.

Thanks. I appreciate that! I be willing to buy the v7 and a v-belt pulley/clutch kit to make a V7 v-belt.

Just need to be sure a v7 will handle the large evaporator and not under perform before I throw out some money. I'm not an engineer, so I have no idea how to spec a compressor. I assume you spec the compressor to the EVAP and the EVAP to the load. But this EVAP is massive, so I would say it's grossly oversized. So I don't know if you'd still size the compressor to the EVAP or to the load. While it's a large sedan, it's not a limo it's 127" wheel base. It's painted black without tinted windows. I'd say the interior is not much larger than a modern full size sedan. It is likely less insulated and less air tight though. Everything is steel, unlike plastics in a modern car. Like the whole dash is bare steel. The air discharge and return are all located in the rear window package shelf. Two discharge vents on the outer sides and two return in the center.

Thanks,
Earl

Compressor refrigeration capacity is the best way to size one. Most manufacturers provide a dyno sheet that indicates the cooling capacity in kilowatts.

Converting Kw to btu/H may give you an idea of the scale. 12 kilowatts = 40,945 Bth/h or 3.4 tons of refrigeration.

The important part of the curve is where you will be driving it. And how soon it gets to say, 6kW The variable displacement helps with that.

The V5 / V7 compressor ears are nothing like the Sanden. A direct mount style case might actually be easier to adapt to that flathead.

If you can get your compressor removed from that beautiful cast iron bracket on the engine and get us a picture of the passenger side of that bracket it would help.

https://www.ackits.com/1999/chevrolet-7 ... 7-pv6-3273