Multiple a/c condenser question; adding 964 condenser

[DaveMcKenz]

Hi guys,
It's winter in Chicago, so I have a little tinkering in mind for my 3.2. I have a front condenser and a rear deck lid condenser. In general the condenser is supposed to take a pressurized gas and turn it into a liquid, I think. When you have two, or more condensers in series, I guess a gas and liquid mix is entering the second or third condenser. The output of each condenser is generally a smaller pipe than the inlet. On the stock front condenser the inlet and outlet are both #6.
I am thinking of adding a 964 condenser after the front condenser. It has #8 inlet and #6 outlet.
My question is can I make the front #6 condenser outlet go to the 964 #8 inlet? Fittings are available to do it. It may not be ideal, but I think might not be a big problem in terms of performance.
Any ideas appreciated.
Thanks,
Dave

[kuehl]

David,

I assume you are concerned with liquid refrigerant moving from a smaller diameter to a larger diameter might change state (liquid to gas)?

The 964/993 condenser/fan assembly was designed to be used 'alone'; provided you install it as intended. It takes quite a bit of hacking to place that unit properly in, say, the LH front fender. Why do you think you need twice (stock 911 + 964) the condenser function capacity?

[DaveMcKenz]

Hi Charlie
You know my a.c. works fine but I want more cooling on the hottest day. I found a used assembly and thought I'd make a poor man's Kuehl system.
Dave

[wwest]

The PRIMARY fault of the factory A/C system, as you have obviously determined, is inadequate refrigerant condensing capability/efficiency. But the focus on this can be narrowed even more tightly. The loss of condensing efficiency during low speed stop and go traffic, or any situation wherein the engine revs are kept consistently low.

Your car, assuming 84-89, has a feature unique to that model series. The cabin heating control module will automatically enable the cabin heater blower at full speed if the engine oil temperature rises about a specific level, and the roadspeed is consistently low.

There are 2 inputs to the cabin heat control module that used to trigger this function. 1, a speedometer input, 2, a thermostatic switch mounted on the engine oil cooler to detect engine oil temperature.

At this point you should take a break and read:

Pelican Technical Article: 911 Cooling Boost

Back?

Now, you could just remember to raise one of the cabin heat control levers ever so slightly to increase the low speed/RPM efficiency of engine cooling AND rear lid condensing efficiency.

Or you could automate this function. Add a trinary Pressure switch to the compressor high side and wire the third PS output between ground and the thermostatic switch input to the control module.

If you for some reason do not wish to use a trinary PS then "this" would alsol work.



Mounted on the compressor outflow pipe and insulated.

[DaveMcKenz]

Thanks Mr West
I have tried that mod with modest success but I want more.
Dave

[Discseven]

Dave... fun to see you in AC world now. Not sure what 964 looks like or challenges in making it fit. Can say I put CG's fender condenser in... very straight forward install.

You run R12 or 134?

[DaveMcKenz]

Hi Karl,
I am running R134 in a Retroaire system. It's "fine", but it does not have the cooling capacity of even a very basic modern car's a/c system. By this I mean, if I park it in the sun, and the interior temp goes to 120-130, the car never really becomes comfortable in traffic for my ride home. My 2001 Isuzu can cool down from those conditions in 5 minutes, no problem. I think it is heat exchanger capacity, and I am hoping I can solve it by creating a cross between the Griffiths system and a 964 system.
I sourced a used 964 condenser and fan assembly, which I hope to be able to cut down and mount in my left front wheel well in place of the windshield washer bottle. I will get a custom hose to put it in series with the existing condensers, rear and front. The 964 unit looks a lot like a Griffiths unit and is designed for the 964 LF wheel well.
I have about $300 invested in parts, and maybe some large unknown number of hours to develop the system. It's a hobby, so it's one of those challenges I kind of like.
Take care,
Dave

[kuehl]

David,

I fully understand/acknowledge your pursuit in this project. From time to time clients contact us for suggestions for improving upon either a competitor’s design which did not pan out, or they simply want to explore and have some fun.

As you know, in theory, the refrigerant hose sizes step down in size, from 12 or 10 to 8 down to 6 through the refrigerant cycle. On a stock factory system your suction side is 10, your compressor outlet is an 8 up to the stock deck lid condenser and forward to the front condenser. In design, if everything is running as planned (from gas to a liquid), the inlet and outlet of the front condenser is a 6 and remains so through the drier and up to the expansion valve (aka TXV, or TEV). So, to answer your initial question, you “normally” do not transition from a 6 back up to a larger 8. The reason, in theory, is the liquid refrigerant “could” change state, expanding to a gas; and in “theory” what would occur in your intended design is the 964 condenser assembly would need to change the state from gas back to liquid. This thought would seem to yield an all for naught exercise; no cost benefit in the added weight and complexity.

Has your suggested design been done before? Yes. With mixed results. Some DIY designers have contacted us on how to do exactly what you planned and some have said it works ‘ok’, others have struggled with pressures and temperatures issues.

Before you hack in a 964 system, and I suggest you search the forum here for what other’s have done; I have seen some installations that were ‘like factory’ and others that were simply backwards: meaning the fan was running in the wrong direction, another design had recycling air flow, and others I would not trust driving down the road (when it falls out it can hurt very much, either your car or to another vehicle behind you).

Since you goal is to improve upon the factory system, as well as the aftermarket upgrade you presently have, I would suggest, before you hack in the 964 into the car, you simply test the design outside of the car. However, to do this test you will need near like conditions you are attempting to over come “park it in the sun, and the interior temp goes to 120-130.” The best designer’s of vehicle systems, whether that be engine, suspension or sound systems, rely on past proven design concepts and they test their ‘new’ ideas prior to bringing them to the market. Your ‘dyno’ for the test will need to be a hot sunny day, just like you have described, where the vehicle is heat soaked.

The 964 condenser/fan assembly primarily functions well because of the massive 2 speed blower fan it has. Front ram air to the unit is limited. You can test your design, on hot day, by simply connecting present front condenser inlet hose to the 964 unit (cut off the #6 straight fitting and crimp on a 8 to 6 transition fitting). Make a hose for the 964's #6 outlet to the front condenser’s #6 inlet. For the 964's blower unit you can modify a simple circuit to test the 2 speed fan function, either powered by the vehicles battery or a stand alone 12vdc power system; relay and fuse as needed. Evacuate and charge based on P&T (pressures and temperatures), probably an initial 36 oz of R134a will be a good starting point; don’t forget to start with a new drier and add about 3 oz of refrigerant oil to make up for losses and increased system capacity. Run your tests and document your P&T at idle as well as vent temps. If you do get the gains you are after then you can permanently hack in the 964 assembly and create your circuit to turn on its blower motor; I’d suggest something simply such a 40 amp relay and proper fuse for the fan motor's amp draw, triggered when the front condenser blower motor is activated, and I’d simply use ‘full fan speed’ on the 964's condenser fan.

Assuming your design works for you, the next obstacle you will need to over come is the massive heat gain an 911 sees due to the fact there is so much glass and little insulation in the car. To overcome this you will need a higher capacity evaporator and greater air flow in the cockpit, the later two achieved simply with a higher speed evap fan motor and additional vents in the cockpit. Window tinting does help slow down energy coming through the glass, however once a vehicle has sat in the sun the btu's absorbed by the interior and body do not go away; the total AC system removes that. The quickest way to remove those hot day sat in the sun all day heat loads, initially, is to simply put down all the windows and drive for a few minutes. If it is 95F outside and 130F inside, mother nature has more power to remove the difference. Once the ambient and cockpit temps equalize you can then turn on that meat-freezer AC system and let it do its job.

Have fun, feel free to chat if needed, and Happy Holidays!

Griff

[DaveMcKenz]

Thanks, Griff.
I am not really going to break open my system until I solve the fan/coil install, and electrical control issues. I am leaning toward a single high speed fan unless my alternator won't handle it. I will then connect as you describe. I was considering the 964 after the front condenser, but I like yours better.
Dave

[wwest]

Much as I regret the recommendation, I suggest proper disposal (sell it, or..) of the 964 stuff and go with an aftermarket rear wheelwell mounted condenser/fan combination. FORWARD mounted rear wheelwell KIT.

Don't buy any other system upgrade before trying that one.

I'm assuming you have tinted the windows but are you aware that a 3M CLEAR plastic covering is available for the windshield that rejects IR?

[wwest]

Thread:

Zim Fender Condenser?


911 COOL Air Kit

[DaveMcKenz]

Originally Posted by wwest

Much as I regret the recommendation, I suggest proper disposal (sell it, or..) of the 964 stuff and go with an aftermarket rear wheelwell mounted condenser/fan combination. FORWARD mounted rear wheelwell KIT.

Don't buy any other system upgrade before trying that one.

I'm assuming you have tinted the windows but are you aware that a 3M CLEAR plastic covering is available for the windshield that rejects IR?

Thanks, Mr. West I do have window tint. The Zims unit looks about the same as the 964. I suspect the 964 is much more robust OEM quality as well. I think I could mount the 964 unit in front of the LR wheel or in front of the LF wheel as in the 964. Do you have any particular reason for favoring the Zims rather than the 964?
I don't really mind being an experimenter, if the lack of track record is the issue.
BTW if I had known about the Zims, I might have gone down that road.
Thanks,
Dave

[Uwon]

Dave, I think that you are on the right track with the 964 condenser. I'm by no means an expert with a/c's. However, about 2001, I installed a 964/993 condenser with fan in th left front fender of my '86 replacing the one in rear deck to make room for a huge intercooler. I retained the front lower condenser but did not bother to fix its fan when it went caput. I also added an enlarged centre vent under the centre console in place of the standard butterfly deflector. The system worked really well, and I am not exaggerating. I am essentially duplicating that setup in my current project except that I'm adding a Pro-Cooler as well. You can view my setup here starting with post #104.
Evolution of a Carrera RST
Hope this helps.
Good luck.
Johan

[wwest]

Originally Posted by DaveMcKenz

Thanks, Mr. West I do have window tint. The Zims unit looks about the same as the 964. I suspect the 964 is much more robust OEM quality as well. I think I could mount the 964 unit in front of the LR wheel or in front of the LF wheel as in the 964. Do you have any particular reason for favoring the Zims rather than the 964?
I don't really mind being an experimenter, if the lack of track record is the issue.
BTW if I had known about the Zims, I might have gone down that road.
Thanks,
Dave

Just the idea of buying a complete kit.....

Easier time of it...

[wwest]

Originally Posted by Uwon

Dave, I think that you are on the right track with the 964 condenser. I'm by no means an expert with a/c's. However, about 2001, I installed a 964/993 condenser with fan in th left front fender of my '86 replacing the one in rear deck to make room for a huge intercooler. I retained the front lower condenser but did not bother to fix its fan when it went caput. I also added an enlarged centre vent under the centre console in place of the standard butterfly deflector. The system worked really well, and I am not exaggerating. I am essentially duplicating that setup in my current project except that I'm adding a Pro-Cooler as well. You can view my setup here starting with post #104.
Evolution of a Carrera RST
Hope this helps.
Good luck.
Johan

Pro-cooler is truly snake oil...

About the only thing CG and I can agree on.

[DaveMcKenz]

Originally Posted by Uwon

Dave, I think that you are on the right track with the 964 condenser. I'm by no means an expert with a/c's. However, about 2001, I installed a 964/993 condenser with fan in th left front fender of my '86 replacing the one in rear deck to make room for a huge intercooler. I retained the front lower condenser but did not bother to fix its fan when it went caput. I also added an enlarged centre vent under the centre console in place of the standard butterfly deflector. The system worked really well, and I am not exaggerating. I am essentially duplicating that setup in my current project except that I'm adding a Pro-Cooler as well. You can view my setup here starting with post #104.
Evolution of a Carrera RST
Hope this helps.
Good luck.
Johan

Thanks, Johan. Your post was one of my main inspirations to move forward.
John

[wwest]

Speaking of experimenting.... a real KLUDGE!

The blower wheel falls short of matching the housing so that at higher revs the engine fan forced air volume can bypass the blower wheel.



This DIY mod results in more than doubling the cabin heat blower forced airflow.



More cooling air to the engine and no HUGE variation in cabin heat with gear changes.




Working on better, cleaner, implementation but for now....

[RSTarga]

Here is 964 codensor on a 911

[wwest]

Originally Posted by RSTarga

Here is 964 codensor on a 911

I'll still say that the LR front fender/fan kit is maybe 5X easier DIY install.

Are those wires to a thermostatic switch to run the fan "when" ?

[RSTarga]

As in the 964 the fan runs when ac is on. Eliminates rear condenser. Less weight at rear. Win,win solution. Also no engine heat.