Installed Griffiths rear decklid condensor

[mnmasotto]

I had previously installed a Rennaire A/C system with the desert duty front condensor. The only thing I left out was the Procooler. I used a standard Porsche dryer instead. Don't ask why, my mechanic did this without my knowledge.

I stayed with R12 and measured the vent temps vs. outside temps on multiple occassions. With SoCal temps of 90 degrees or greater I never recorded a vent temp less than 52 degrees. With outiside ambient temps between 80-90 degrees I recorded vent temps as low as 46 degrees.

I recently replaced my factory Porsche rear decklid condensor (two row) with a new Griffiths rear condensor(three row). The fit and finish of the unit was excellent. The system was then recharged with R12 to the same high and low side temps by the same A/C shop. The shop said my system was only a few ounces low.

When I picked up the car the outside ambient temperature was 91 degrees. My vent temps stayed a 39-40 degrees the entire trip home. I had one measurement of 42 degrees when I was stuck in stop and go traffic for a short period.

I used a standard rod type? temperatue gauge which was stuck in the vent throughout the tests. The accuracy of this $10 gauge was confirmed with a $75 laser temp gauge.

[richde]

as long as you used the same measuring device..the actual accuracy doesn't matter, it's the consistency. It showed a definite improvement.

This makes me feel better about pulling my complete A/C system since I don't need it now in this mild climate. It will all need to be replaced when I move to Nevada anyways.

[Barrpete]

Wow, your mechanic didn't do you any favors by not installing the Procooler. I have the same Rennaire setup with the Procooler running 134a and can get in the low 50's when its 108 out in stop and go traffic.

When ambient temps are in the 80-90 range its upper 30s.

[mthomas58]

Originally Posted by mnmasotto

I had previously installed a Rennaire A/C system with the desert duty front condensor. The only thing I left out was the Procooler. I used a standard Porsche dryer instead. Don't ask why, my mechanic did this without my knowledge.

I stayed with R12 and measured the vent temps vs. outside temps on multiple occassions. With SoCal temps of 90 degrees or greater I never recorded a vent temp less than 52 degrees. With outiside ambient temps between 80-90 degrees I recorded vent temps as low as 46 degrees.

I recently replaced my factory Porsche rear decklid condensor (two row) with a new Griffiths rear condensor(three row). The fit and finish of the unit was excellent. The system was then recharged with R12 to the same high and low side temps by the same A/C shop. The shop said my system was only a few ounces low.

When I picked up the car the outside ambient temperature was 91 degrees. My vent temps stayed a 39-40 degrees the entire trip home. I had one measurement of 42 degrees when I was stuck in stop and go traffic for a short period.

I used a standard rod type? temperatue gauge which was stuck in the vent throughout the tests. The accuracy of this $10 gauge was confirmed with a $75 laser temp gauge.

Can't believe that changing out your old rear deck condenser would have had that much of an impact in reducing vent temps unless it had some blockages. Sounds like recharging with the proper amount of refridgerant was the real driver here. In any event, congrats on the results.

[JeremyD]

Did you change the evaporator? the old evaporators are pretty darn inefficient.

[mnmasotto]

Yes, I previously installed an entire Rennaire system sans Procooler. My mechanic left it out, don't ask me why. I am using a stock Porsche dryer. I though about spending the money to have it put in but the A/C works so well now it would be a waist of time. I wish I could upgrade the fan at the evaporator, I think that is the only weaak link.

P.S. my car is a 1987 Carrera 3.2

[mthomas58]

Originally Posted by mnmasotto

I wish I could upgrade the fan at the evaporator, I think that is the only weaak link.

P.S. my car is a 1987 Carrera 3.2

I'm pretty sure this can be done by backdating only your evap box cover/and fan assembly to a pre-1987 unit that will accept the fan motor upgrade. That's what I plan on doing (someday)

[JFairman]

The procooler doesn't remove heat from your system... not one little degree.
Think about it... It is a heat exchanger but it doesn't exchange any heat out of the AC system into the air like a condensor does.

All it does is move some heat from the high side refrigerent and transfer it to the low side refrigerent. That is not desireable because it makes the compressor run hotter.
The somewhat cool regrigerent gas coming out of the evaporator going back to the suction side of the compressor is the only thing that cools the compressor and keeps it from overheating and shortening it's service life.

I have tried 2 procoolers and compared the results to other 911/930 AC systems using a much less expensive and better looking, better fitting griffiths reciever dryer and in my opinion, and most AC shops, a regular reciever dryer works better and is simpler.
Also, the regular receiver dryer has more room for dessicant and charcoal inside it than the double wall procooler so it does a better job of filtering and removing moisture from the refrigerent.

The procooler requires 3 more hoses to work and will be in the way of bigger tires on a full lock left turn.
The idea of a subcooler has been around for a long time and if it was really a good idea all AC systems would use one.

[mthomas58]

Originally Posted by JFairman

The idea of a subcooler has been around for a long time and if it was really a good idea all AC systems would use one.

My 2 cents:

1) Subcoolers do work. As to how much is controversial for sure. As far as increasing the operating temp of the compressor to the point of premature failure, I've seen no proof of this (not say there is no proof, I've just not seen any and I am by no means an expert - but Jim Sims is and he is a proponent of subcoolers)

2) Every component or upgraded component in the A/C system provides an incremental benefit. When you are working with the sub-optimal design of our 911 system - every little bit helps.

3) The reason all A/C systems don't use them is that modern A/C systems are designed with sufficient condenser capacity, RAM air flow, evap capacity and fan air flow that they are not needed. A procooler would be redundant in a modern system.

[Zeke]

mnmassoto, I thought you had a fender condenser.

[JFairman]

Originally Posted by mthomas58

My 2 cents:

1) Subcoolers do work. As to how much is controsversial for sure. As far as increasing the operating temp of the compressor to the point of premature failure, I've seen no proof of this (not say there is no proof, I've just not seen any and I am by no means an expert - but Jim Sims is and he is a proponent of subcoolers)

2) Every component or upgraded component in the A/C system provides an incremental benefit. When you are working with the sub-optimal design of our 911 system - every little bit helps.

3) The reason all A/C systems don't use them is that modern A/C systems are designed with sufficient condenser capacity, RAM air flow, evap capacity and fan air flow that they are not needed. A procooler would be redundant in a modern system.

I experimented and worked on my 930's AC all last summer and I learned alot.
Spent over $2000 in parts alone and went through 2-30lbs bottles of R134 doing it.
Been there done that so I have some experience with all this stuff now.

If the compressor is running hotter because the suction line refrigerent is at a higher temperature from a subcooler transferring high side refrigerent heat over to it, than it's internal wear parts and seals are not going to last as long.

If you really want to make the 911 AC system cool better this is the lowest cost and most effective upgrade you can make along with new barrier hoses.
http://www.***********/cgi/sh000001.pl?REFPAGE=http%3a%2f%2fwww%2eallzim%2eco m%2facatalog%2f&WD=conditioner%20air&PN=911_COOL_Kit%2ehtml%23a911_2e573_2eADD_2eCOOL#a 911_2e573_2eADD_2eCOOL

I installed one of these last summer along with the rennaire kit and it installs perfectly and works great.
If you like the procooler, thats great.
For the money it cost and the extra hoses you'll need to install it, you can do alot better by adding condensor area with a 10" fan like the above kit in the left rear fender well.
And, 18" wheels with 225x40 tires on the front of a 930 will rub a procooler on a full left turn while going over the bump turning into a driveway because it's twice as thick as a griffiths or OEM receiver/dryer.

Here's a pic of my procooler installed.

[Jim Sims]

Subcoolers work; they are an old concept - they were in my mechanical engineering thermodynamics text 30 years ago. They use the evaporation of any liquid refrigerant that exhausts the evaporator and the exhausting cold gaseous refrigerant to precool the incoming hot liquid refrigerant. There is liquid refrigerant at the exit of evaporator due to the fact that evaporators and the throttling of the expansion devices are not perfect and ideal for all conditions. They haven't been used much in automotive applications simply on the basis of economy: in the past the fuel saved wasn't worth the additional manufacturing and installation cost. Subcoolors are now being built integrally into the condensers of some automotive air conditioning systems. I expect more of this (in addition to using the A/C system as a heat pump by adding a four way valve for winter operation) as hybrid and electric vehicles begin to proliferate. Cheers, Jim

[crustychief]

I don't know anything except that my procooler works. Actually MTHOMAS58's thread about his install is what made me decide to install my own A/C and it works really good out here in San Diego.

[mnmasotto]

Milt,
If you are refering to the aluminum unit in the front of my drivers side front fender, well that is a auxillary oil cooler. I had purchased a 993 condensor to go in the drivers side rear fender but was not sure how well it would fit and did not want to spend too much money in fabrication costs.

I talked with the gentleman at Grifiths and asked why he does not offer a procooler? He said flat out "they do not work". I too have a degree in Mechanical Engineering and I am not sure of the theory and physics behind a procooler. It is true that you are not exchanging any heat to the outside environment.

However, I do respect the experience and knowledge of those who work in the field on a daily basis, so I will have to defer to them.

JFAIRMAN Could you please post some photos of your rear fender condensor?

[JFairman]

I just went out and snapped a few pics of the Zims LR fender condensor.
With the car on the ground and wheel installed it's kinda hard to see but I think you can get the idea.

I had a better picture of it with the wheel removed but can't find it right now.
Thats a 10" fan that came in the kit on the condensor.
This Zims kit uses a much bigger condensor than the more expensive Griffiths kit.
It also comes with the aluminum tire splash gaurd pre cut and installed on the condensor with stainless steel hardware.
There is about 2" clearance from the 315x30/18 tire to the splash gaurd back there.

I put another 10" puller fan on the origonal tail condensor and there is a 2" thick rennaire "desert duty" serpentine condensor in the front with rennaire's serpentine evaporator in the smuggler box.
I wrapped the evaporator box with the thermal wrap.

The origonal Nippondenso compressor and mount is better quality than the Sanden from my experience too.
My first Sanden 507 was dead on arrival... it wouldn't make pressure, and the replacement one they sent me has a clutch that makes strange grinding noises when it disengages after only 2 months of use, but still works for now...

On a 930 you have to grind a little metal off a corner of the stock magnesium intake manifold to make clearance for one of the back cover bolt heads on the Sanden 507. Thats not too big deal though, you can't see it once the compressor is in place.

The fender condensor with fan, and the 10" fan on the origonal 930 tail condensor are the 2 things that helped give me cold AC the most.

hope this helps..

[mnmasotto]

JFAIRMAN,
Thanks for the photos! I was not aware this condensor went in the front of the wheel well. Do you have to remove the condensor to re-index the torsion bar? I noticed you have Sway-a-way adjustable spring plates. Do you also have polybronze bushings in the rear? If so, do they make noise when you push up and down on the back of the car or when driving at low speed over bumps? Trying to get the noise out of my suspension has proven to be a very difficult task indeed.

[JFairman]

You're welcome.
The condensor in this kit is 12.5" wide and 18" tall so it goes up in there as far as possible and gives the most condensor area possible in that location. The 10" fan moves some air too.
Kit comes with relay, wire, hardware, hose, and do it yourself fittings with hose clamps. I used 2 hose clamps tight on each connection when I used those. Crimp on connectors are better of course, but then thats more money... The clamps are working fine.

I indexed the torsion bars to give me some adjustment range on the springplates when I installed them so you would have to remove the condensor to go in there again. With the adjustable springplates there is no reason to index the spring plates again for my use.
The control arm bushings are the origonal rubber ones and I put plenty of molybdenum grease on the large red urethane bushings in the spring plate kit when I installed it.
There are no have no squeaks in the car. Just the Sanden AC compressor clutch grinds and chatters when it disengages. Maybe there is a way to fix or adjust that.. don't know yet.

3 days ago I used the AC, now I'm enjoying using the heat here