Classic Retrofit: Lightweight Electric Air Conditioning

[Mr. Merk]

I'm pretty excited for the upcoming revised CR electric HVAC with heat and dash controls!

The last roadtrip to Luft through 113* temps was brutal. I was actually worried about my four legged co pilot. We munched on ice from Flagstaff to LA and literally resorted to pouring ice water in my lap as I drove down the highway. My wife joined us on the road home which and swore off any further road trips until my Carrera has AC again.

[Industrialando]

Originally Posted by Joesmallwood

My 2 cents:

I have a CR first gen compressor and upgraded to the 2nd gen blower box last year. The air has always been cold, mostly, but as noted above, a second condenser really helps when in traffic and/or moving slow. It just provides more capacity for extreme conditions.

The problem that I have noted many times is simply the volume of air that is turned over by the overall system. The CR blower is capable of moving a generous amount of air, but I have always been convinced that the stock blend valves and the stock 60mm plumbing were the restrictions. Turns out, at least in my case, that this is true. I went on a mission to change the plumbing from 60 mm to 75 mm both for the INPUT side of the CR unit (which I believe is the overall bottleneck of the system) and the output side of the CR blower and blend valves.

Results shown below and it has been well worth the effort. The volume of cold air that is now moved through the system is dramatically improved over the stock setup. Please keep in mind that I don't have heat exchangers or heat from anywhere, but I do have some small PTC heaters hidden inside the, still factory, plumbing just before the defrost/windshield inlet port. This works really well, but it is only useable for defrost and is not nearly enough to "heat" the cabin.

The blend valves are controlled by some switches in the stock location (sliders and bowden tubes are history) and by a really simple Arduino program/setup (credit to Julian for the idea/inspiration). Their function is 1) Fan 0~3 speeds), 2) A/C on/off, 3) Footwell/dash OR Defrost, and 4) Defrost (PTCs) on/off.

I still plan to coat the windows with a film, but it's lower down the list of priorities at the moment. I still want to do some faceplate updates and I am working on a valve to include fresh air ahead of the CR Blower (currently 10% blocked). I know this will move even more air when complete and also add a fresh air only option.

Good idea to increase diameter, I'm currently installing a Gen 1 blower and this would be a great modification. Did you 3D print this and if so could you share the STL file? I'm running a Bambu P1S so I should have the clearance to print this design.

[hbrand]

How about using a Renogy 200AH LiFePO with the stock SC alternator to run the electric AC ??
Greetings, Harold

[Jonny H]

Originally Posted by alasorte1

My CR system install was completed three weeks ago by Weissach Motors in Miami (a CR authorized installer). We went with the upgraded alternator and two condensers. (Car has a 3.6 liter 993 Varioram motor).

Having lived with the system for a few weeks now in sweltering, humid South Florida weather, I'm impressed with the quality and performance. I highly recommend you invest in the alternator and second condenser.

The car is a '75 Carrera. No prior A/C system. Hernan at Weissach did a masterful job. We went with the clock-replacement vent and three vents under the dash. (The tiny in-dash side vents are hooked up as well, although their airflow is minimal.) The compressor is forward in the frunk, not in the smuggler's box, as we will be installing a power steering kit in there.

Even in 90 degree-plus heat, the system produces plenty of cold air. Sometimes, at extended traffic light stops the temp of the airflow rises somewhat, but not enough to be a problem. And once you get moving and the condensers have some air flow to work with, the temp drops quickly to where it belongs.

Another thing that has helped is we installed clear UV and infrared-blocking tint on all windows first (including windshield). This noticeably reduced interior temps even before the A/C install.

Overall, the project (so far!) is a complete success. True, it does not blow as cold or as hard as a new 911, but it really does work well. The best thing about it is the clock vent. Blows nice cold air at the driver. Nice!

Thanks for posting this. Hernan is a great guy and - we met him at Goodwood! I think this demonstrates that the system, when installed 'by the book' is capable and efficient. Sometimes folks get a bit carried away with over analysis perhaps?

I had another bit of feedback recently. The Tuthill's guys were over at Car Week with the 911K. Originally the gold car did not have AC but the customer wanted it retrofitted so they took the parts out to do it. The car did 2 days full on driving in the mountains with a hire car following. Temps were hitting 113F and they pulled over for a break. The cabin was ok but not 'cold' so the driver went to sit in the hire car thinking it would be icy cold. It was not - in fact it was worse than the 911 and the crew were complaining about it!

Proper update on heat pump soon - lots of loose ends but getting there. Targetting start of next year.

[usera]

Johnny, I love seeing the innovation. I had Gordon at Autometrics install my single compressor system with the upgraded alternator. I simply cannot get cold air out of the right side of the unit. It has been bled and refilled by two different shops who all know your system, but for whatever reason, the air out of the left outlet is 50 degrees and the air out of the right (passenger side) is 74 degrees.

Any guidance?

[mike sampsel]

Very clean install, nice work! Those hoses attached to the blend valves look great, are they Porsche hoses?

[mike sampsel]

Originally Posted by Joesmallwood

I tried this at one point and it DOES make a difference, for sure, but still - the factory 60mm limitations...

This setup was pulling air from the footwell and pushing it through one of the 6mm intake ports on the side of the CR unit.

Different approach than mine (actually Targa80's), which runs the stock blower in series to the top dash vent.

Thanks for the inspiration, sorry about the late reply.

[mike sampsel]

Originally Posted by jrwilson

So, got the car back from the installer. Took a bit longer because they had to remove the existing tint on all the windows except the windshield. Previously the car would be an oven after sitting in the sun for about 10 minutes.

I went with XPEL Tint: PRIME XR BLUE VLT 80 on the windshield and PRIME XR BLACK VLT 55 on the rest.

The result is night and day. Even without A/C it's much more comfortable in the cabin, and with the A/C it's even better. 27C yesterday and I was driving with the windows up no problem.

Good to know the result was what you wanted.

Originally Posted by alasorte1

I had ceramic tint installed. Virtually clear, no darkening of the windows whatsoever. But it is said to effectively block UV and infrared rays.


https://www.caranddriver.com/car-accessories/a37068466/top-car-window-tint-for-heat-reduction/

Thanks for this info, very nice looking "cool" car too.

[Jonny H]

Originally Posted by usera

Johnny, I love seeing the innovation. I had Gordon at Autometrics install my single compressor system with the upgraded alternator. I simply cannot get cold air out of the right side of the unit. It has been bled and refilled by two different shops who all know your system, but for whatever reason, the air out of the left outlet is 50 degrees and the air out of the right (passenger side) is 74 degrees.

Any guidance?

Undergassed most likely. Although this is a Honda, this guy explains well:

https://www.youtube.com/watch?v=w-NX26knA88

[Wildthings]

Any update on the heat/AC version that would work in a 72 911?

[Jonny H]

Originally Posted by Wildthings

Any update on the heat/AC version that would work in a 72 911?

We are aiming for end of Q1 next year. If that changes will report on our SM.