Air system design for vintage car

[bill5900]

Hello. I hope to retrofit the Classic Retrofit AC system in a vintage Porsche. The nice thing about this is the electric compressor. The bad thing is that my car is earlier than the original CR design was for, so some of the « easy » installation cues aren’t available in my existing ventilation system. Even so, I don’t think people are installing systems effectively even in the anticipated age cars. For example, people insist there must be AC inlets into the foot wells. At the same time, they put concentric outlets around the inlets for the recirc air to be sucked out. And set the fresh air portion to be conditioned at 30%. I understand there are limitations to what can be done in these cars that are 50 years old, and are short on space. My hope is that someone here can point me in the right direction. I can find all kinds of info on how the car AC systems work, but not how the air handling is set up. Air handling in and out of the passenger cabin, and how it is controlled, is critical. I can see ways to reimagine it my existing system but I need advice. Thank you. Bill

[tbirdtbird]

For the vintage cars we setup, we have dash vents only. Nothing in the footwells. Nothing under the seat. Nothing in the back seat. No exchange with outside air. Don't wanna condition the entire state, just the inside of the car

With my experience with moderns, the recirculate setting does not fully block off outside air which I find very annoying. (It used to).
Just wait till you go by a farm with a huge manure pile .....

[bill5900]

Thanks. That seems logical to me. My car is not tight to begin with—so there will still be some fresh entering the cabin but no where near 30%! Where do you put the recirc vent for the system? Seems like the footwell is the place.

[tbirdtbird]

There is no recirc vent. Nothing in footwell.
4 cold air supply vents in or under dash. The evap has its own air intake from the cabin, so it just recirculates the cabin air.
No car is air tight to begin with. If so, they would not sink when submerged. Don't worry you won't be asphyxiated.
One of the experts here, Ice-N-tropics, worked with a well know vintage AC outfit to develop these under dash units.
Will post a pic of one later

[tbirdtbird]

Here ya go, keep it simple. Just an example of many. Too many mfg make AC too complicated when it is actually very simple.
There are many companies making similar after market evaps, at least in the USA
If you Google "Vintage AC evaporators" I am sure you will be able to come up with something from your country. Racing concerns often have them, also.
If you take a Sanden 508 comp, one of these underdash units, a TXV, and the largest condenser you can possibly fit , along with a filter/drier, you will have very good AC. We do this all the time. Lots of custom work to fit up the evap and the condenser, and then of course fabbing or sourcing the brackets for the comp.
You can also get a ducted air box if you have room under/behind the dash and bring the ducts out to holes cut in the dash, or individual vents screwed underneath the dash, depending on preference
If you have a popular USA made vehicle some of the companies actually have an entire package for you which includes all the components you need, including brackets, etc. You can get the evaps AC only or heat/AC combo. By ripping out the stock heater box that may give you the room you need under/behind the dash.

You will also have to consider if you have enough grooves on your crankshaft pulley to drive the comp. In an ideal world, the alternator and the comp should each have their own fan belt.
A year ago we added air to a 1947 Studebaker which only has a 1-groove pulley, with absolutely no way to make it a 2 groove pulley because of the way the harmonic balancer is made. And since Studebaker has been out of business for over 60 years, and because no one is making custom parts for this lesser-known vehicle. We had to make it work. We custom fabbed a mount for the Sanden, and then another custom fabbed mount for the alternator, which we put directly above the comp.
So we drive the Sanden from the one and only crank pulley groove, then since the Sanden has a 2-groove pulley, we drove the alt from the comp.
The crank pulley ended up not being large enough in diameter to make everything spin up properly, so we machined up a different, larger diameter crank pulley, using the stock pulley as our starting point. We obtained the smallest possible diameter alt pulley, and use a cogged belt because of that. A lot of work but we got it done. There is no kit for this, and we are the only ones with AC in this particular Stude truck model.

This was a heater/AC evap combo and the cooling was off quite a bit initially. We puzzled and made ourselves crazy trying to figure out what was wrong. It was JohnHere from this forum who brought up the issue of reheating and sure enough our hot water heater valve was not closing all the way. This was a first for us.

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[bohica2xo]

So the only clue about the car is "50 years old" and Porsche. 912? 911? 914?

Electric A/C compressors have limited capacity, and the 50 year old Porsche cars have a charging system borrowed from a VW Beetle.

What sort of local climate do you plan to operate the A/C in?

.

[bill5900]

Thank you again. The attraction of this kit is the electric compressor. As you can see below the evaporator and blower are packaged together. So the evaporator only intakes air from the front compartment if not plumbed to cabin. The front compartment is poorly sealed to cabin but is space I don’t want conditioned. This setup is pretty standard for older Porsches—-condensers in wheel wells, distribution crammed randomly around stuff behind dash. My car, a 1968 911, will get an upgrade to a 175 amp alternator. The concern to me, and from what I see of others just following the install instructions , is controllability and air intake/outtake for the blower. We are being told that the system is set for 30% fresh air. I asked why. Crickets. Everyone tells me you must have conditioned air in the foot wells (the blowing air makes your knees and you feel cooler). And as I’ve said, one opening with concentric hoses takes air for recirc and blows air into cabin onto knees. This whole thing is controlled by an on off button. Ok, so I want fresh access but only when I want it thru the system (aspirational). I agree with people here that you can run recirc all the time. (Engine in rear;). I can’t understand why precious conditioned air must be sent to knees. If I can modulate or turn off compressor then I can either run all fresh air or tone down the amount of conditioned air. I think this is correct as I understand modern pulley driven compressors cycle. I may be missing something here. The one thing I don’t know about is modern flap valves that may be required or how to safely cycle the compressor (system) to have more control.

[bill5900]

Oh, and I understand the system may not have capacity. But I realize I can’t jump in the car, run errands, and expect the system to keep up. Porsche’s have too much glass. But hey it is something. Bill

[bohica2xo]

Why 30% fresh air?

Well, it is an air cooled car with a heating system that includes heat exchangers on the exhaust system. I have owned a few air cooled cars, and many times if something was not right in the heating system you could smell the engine compartment. In the worst case you get pumped in Carbon Monoxide.

VW and Porsche cars of that vintage leak air / take in fresh air in the front of the cabin. It was the manufacturer's way of covering their butt.

I can't tell you why they are so worried about the footwell air. Turn it off if you wish. Picking up the cabin return air from the footwell should cause enough flow in that direction to cool your lower extremities anyway.

Make sure the heater valves shut off all the way regardless of anything else you do. If you elect to make it 100% recirculating please open a window a bit in the winter months.

[tbirdtbird]

It is fallacy and myth that cold air to your knees will cool you off. Have you ever sweated from your knees? Of course not.
On the other hand cold air to the head and chest will do just that.
We haven't had cold air to anywhere on the body except face and chest on any of the many vintage cars we have fitted with AC. And this is Texas, and it is 100°F right now. Come to think of it, I cannot think of one modern car I have owned or rode in that had air to anything below the waist