Major AC upgrade

[mppickett]

Keywords: removing rear AC condenser; 993 condenser; underdash ventilation; more airflow; drilling bulkhead; modifying evaporator plenum; ES-12a

I thought I'd share my AC upgrade to help those who might be considering their options or trying to track down some info. My car is an '83 SC that has been converted into a 993 turbo cabriolet clone (actually I'm not sure clone is the right term since Porsche never officially produced 993 turbo cabs, just a few one-offs for company friends). The previous owner removed the compressor and rear condenser and when I rebuilt/hot rodded the 930 engine, I added a full bay intercooler so there wasn't much room for restoring the original SC condenser. The PO had also upgraded the dash vents to the 962 style so they had pretty good airflow. This is not a track/race car nor a pristine, original specimen, just a fun GT style touring beast and a source of interesting projects.

My top goal was effective cooling. My wife's biggest complaint about the car is that there are times when the black leather interior and black cab top make it uncomfortably hot - really hot (not as much in New England as when we lived in NC, but still something that begged to be fixed). OK, here's where I'll lose a few of you, I liked the idea of being able to beat the heat and still keep the top down. That meant good cooling and great airflow.

Here's what I did and why. I can't claim these are the best approaches, but I like the outcome. I can especially say that today because it is 29*F outside, we've got 8" of snow (thunder snow to be precise) and with the top down, I am not very hot while sitting in the garage. To be fair though, I'm kind of doubtful that my car's upgraded AC lowered the ambient temperature in Rhode Island by any significant amount :-)

1) Eliminate the rear condenser to lower engine heat load and to gain more condenser efficiency.

The old rear condensers aren't very efficient. The later 993 condenser is much more efficient and has a fan to help. On the 993, it is located in the driver's side (left) front wheel well. I fabricated a couple of brackets (top and bottom). The top bracket is short, connects to the headlight bracket and bears most of the weight. The bottom bracket is very long (runs from the sway bar bolt, under the condenser, and up to the fender). It doesn't bear much weight but keeps the condenser in position. If I were going to do it again, I'd see if I could find a used 993 condenser, fan and bracket to save some of the fabrication time. I had to convert to a window washer tank inside the trunk to make this work. I also bought a used Spal fan and made a fan shroud out of a baking pan. Get the whole 993 condenser package if you can. It will save you some headaches. Here's a link to a guy's story of putting one into an '86 http://www.pcaucr.org/site/page.jsp?pageid=221

Looking into the wheel well towards the front of the car, the condenser's open side is towards the trunk and the fan side is towards the left fender (air is pulled thru the fan). Here are a few pics.

Side view:


Top view:


Bottom view:


2) Upgraded compressor. I used the Sanden 507. Seems like a reasonable size that has worked for many of us.

3) Upgraded the evaporator. Our host carries the Rennaire Serpentine Evaporator. Nicely done.

4) Upgraded the evaporator fan (blows air into the cabin). I went with the RetroAir/Mrjaguar kit. Rock was very helpful. A high output motor can be found many places. Rock put together a nice mounting plate and motor mount that saves a lot of time. Part of this upgrade removes the obstructing fan speed resistors in the air return path. Documentation is spotty, but there's a great thread describing the process: RetroAir Evaporator Fan Install

5) Opened up the airflow from the evaporator into the underdash area (important for the cabriolet part). Performance Aire worked out a bulkhead vent that involves removing the bowtie under dash vent and drilling a second hole into the output area of the evaporator. Not for the faint of heart, but it works well. I made my own instead of buying the PA kit. I used a 1 1/2 inch hole drill bit (heavy duty) and with patience, it cut right through the bulkhead. To get it started, I drilled into the right hand screw hole that was originally used to secure the bowtie. Once you're through the bulkhead, you carefully drill into the plastic plenum where the air exits the evaporator right beside the other feed to the bowtie. For that step, I used a hole drill that was the same size as the pipe I used to carry the air into the cabin. After drilling, I inserted and sealed a short length of pipe into the plenum/bulkhead. With the higher speed fan, this more than doubles the output of cold air into the lower part of the cabin. You can attach a fixed or directional vents to the two tubes. I've got the parts but haven't decided if it is needed yet. Some pics:

Drilling the bulkhead where the bowtie was using right hand bowtie screwhole


View of pilot hole inside plastic evaporator plenum (see drill bit)


Plenum drilled


Pipe for plenum to cabin


Tube inserted into plenum


6) Bought/built barrier hoses. The PO had replaced most of the OEM (leaky) hoses with newer hoses. I bought a drier to evaporator hose from our host and built a couple more with bulk barrier hose and beadlock fittings. I bought one of the "cheap" AC hose crimping kits (around $200) and it worked very well. It was light and small enough to use inside the wheel well when I was altering one of the OEM hoses. This would be a reasonable club buy to share.

7) Flushed lines. I bought a small pressure flusher and used mineral spirits until they ran clear.

8) Added oil to compressor and charged with Eviro-Safe ES-12a.

Very cold air and lots of it. Hope this is helpful to those of you considering one of these steps.

[DRACO A5OG]

Nice Job!

I also converted to the ES-12a Industrial. No issues what so ever. I was thinking of adding the additional hole but after removing the bowtie, it was enough.

Again Congrats!

[mppickett]

Originally Posted by DRACO A5OG

Nice Job!

I also converted to the ES-12a Industrial. No issues what so ever. I was thinking of adding the additional hole but after removing the bowtie, it was enough.

Again Congrats!

Thanks. I think the ES-12a has its own peculiarities (the pine fresh smell for example) but it seems to be effective, safer in some ways than R-12/R-134, and is reputed to be less leaky than the alternatives (larger molecules?). Congrats on your upgrade, too.

[EluxT]

A few years ago I bought the amazing Kuehl system from Griffiths for a '76 930. Three condensers. Air was 33 degrees coming from the stock vents on a hot day. Warning: not for the cheap of heart.

http://www.griffiths.com/porsche/ac/911ac/index.html

Elux
84 911
64 356

[Joeaksa]

Hey guys, bringing back an old thread. Several years on, how are you doing with the A/C systems? Have found a 993 condensor that I was going to add, and upgrade some of the other systems on the A/C but would appreciate some feedback on what you would or have changed.

This is going on a backdated 911.

Thx,

Joe A

[DRACO A5OG]

Still Good with my ES-12a, I have to keep turning it off because girlfriend states it is too cold now,

[Joeaksa]

Good to hear it. I have used ES as well and like it.

Thanks,

Joe A