stock A/C performance - '87 3.2

[dw1]

I'm posting this to give people an idea of what a stock system converted to R-134a is capable of.

Earlier this week I carefully recharged the air conditioning system in my black/black '87 sunroof coupe. This included very long multiple vacuum cycles - which I highly recommend for our cars because of the tubing lengths.

The system is OEM, except for the barrier tubing from Griffiths Technical. The original Denso compressor was rebuilt a year or two ago with parts from Griffiths (and the extremely helpful input of Charlie Griffiths). Also, I replaced the expansion valve and added a PWM fan speed controller per the Pelican tech article - https://www.pelicanparts.com/techarticles/911_ac_switch/911_ac_switch.htm

Today being the hottest day of the year so far in my area, I decided to run a mid-day (early afternoon) test. The air temperature was 86°F, with a "feel like" temperature of 91°F and scattered clouds. Again, remember the car has a black interior & exterior. A T-type thermocouple was inserted into the center vent and used to acquire data during driving on local roads & highways.

I won't bore you with all of the 1 second interval data, but:
after 5 minutes of driving, vent temp.= 59.8°F
after 10 & 15 minutes of driving, 52.8°F
after 20 minutes of driving, 48.5°F

If I lived in a hotter climate or wanted to drive my car more in the hottest summer weather, I would DEFINITELY add some of Griffiths' options for improving the A/C, but for a stock system this is quite good, IMHO.

[Mixed76]

Good data point, thanks for taking the time to post

[Missed Approach]

Hi dw1- Here's my full 7-year writeup. I just ran the same test on July 2nd- (see post #17 with images)
The final additions were the new Barrier Hoses and Charlie's larger front condenser.
Outside temp 85F, heat-soaked interior to 105F, 38.8F after 15 minutes. Very pleased.

1986 A/C Repair and Overview

[GH85Carrera]

Back in 2004 my AC system was 100% stock. I had a planned trip to Ft. Worth in July, so I pulled a long vacuum, and recharged to optimum performance. It was great for night time or below 85 degrees in the day. Once it got above 85, it was useless, and I ended up just rolling the windows down when it was 100 degrees and in stop and go traffic. That is when I started my quest for great AC in my 911.

Many thousands of dollars in parts, and numerous conversations with Charlie Griffith, lots of dirty work replacing every rubber hose, and eventually every single part except the brackets, ducts and such, all that is left of the stock system is the front and rear condenser. I still use a factory stock style Nipopondenso compressor.

It simply works now. 107 degrees driving due west into the afternoon sun to Palm Springs, CA, it blew lots and lots of 37 degree air on me, and it was 100% comfortable until I opened the door of the car at the hotel to check in.

If you only rarely drive in 90+ heat, or just want to use the car on cooler days, the stock system is fine. If you want to take your wife on a road trip in summer heat, you will want the Mr. Ice project from Charlie.

In August, in Savannah, GA at lunch time, my wife actually asked me to turn the temp UP and she was cold. The heat index was 135 that day with 92 temps and 95% humidity.

[almostordinary]

Thanks for sharing the above experience!

My 87 coupe build was about ready to hit the road for its initial drive... nope. Motor has to come back out.

The misses and I just took her brand new Macan out for a drive up to Lake Arrowhead, and we both agreed, let's get the AC situated on the first phase of the build... which I was planning on holding off until next spring.

My plan:
- Use updated compressor I purchased
- Griffiths deck lid condensor (I have two and they are thrashed)
- All new lines
- New Drier
- I have read a bit about a "turbo" fan need to investigate a bit more.

Hoping to get this all put on the car in the coming weeks.

Can not wait to get this car on the road and miles under my belt.

-Ian

[tsuter]

You boys should really think about super parallel flow condensers on the rear deck.
That and a couple fans and you won't need any more condensers. Even for "red zone" cooling. Tube and Fin and Serpentine condensers are "old school" inefficient.
Cost maybe even less than $200 with the fans and way less plumbing.
https://www.ebay.com/itm/134442409777
For 911 w no turbo tail 12 x 28

Mines a massive 16 x 30...but I have more room in the tail:

[Nick Triesch]

I rebuilt much of my stock ac a few years ago . New dryer., expansion valve , rebuilt compressor, new o rings , thermostat switch . My car is black on black so at 85 outside is blows about 58 degrees. But blows a lot colder in the winter !!

[tsuter]

Originally Posted by Nick Triesch

I rebuilt much of my stock ac a few years ago . New dryer., expansion valve , rebuilt compressor, new o rings , thermostat switch . My car is black on black so at 85 outside is blows about 58 degrees. But blows a lot colder in the winter !!

Yikes!

[GH85Carrera]

Originally Posted by tsuter

You boys should really think about super parallel flow condensers on the rear deck.
That and a couple fans and you won't need any more condensers. Even for "red zone" cooling. Tube and Fin and Serpentine condensers are "old school" inefficient.
Cost maybe even less than $200 with the fans and way less plumbing.
https://www.ebay.com/itm/134442409777
For 911 w no turbo tail 12 x 28

Mines a massive 16 x 30...but I have more room in the tail:

I don't have, or want a tail on my car.

One of the biggest reasons for the fender condensers and not a large condenser under the decklid, the heat! When I added the two condensers in the fender, my engine temps went down, a significant amount. Instead of dumping the cabin heat via the condenser right into the engine cooling fan, it goes into the fender area, and away from the engine.

Driving 11 hours in 100+ degree heat, my oil temp stayed at 210 with the AC blowing 37 degree air all over me. The only time I saw higher temps was climbing up a long long mountain pass in 105 degree heat. It approached 230, but as soon as I crested the pass, it dropped to 210 very quickly.





Driving around in traffic in Roswell, I was staying cool, and the engine never went over 210.

[darrin]

Ian -- IMO, definitely worth considering both the Griffiths front condenser (as it provides more surface area than the stock) https://griffiths.com/product/911-930-kuehl-high-performance-front-cond/ and evaporator https://griffiths.com/porsche/air-conditioning/911-930/porsche-911-930-evaporators/ (ditto) -- My AC resurrection followed the same path you propose (though my original deck lid condenser was just fine), but also included these two. I'm VERY happy with the results and, 2 years post resurrection, my system continues to work as-completed using R-134. I'd considered adding a supplemental rear fender condenser during my resurrection, but since adding one would only require minimal additional work (installing the condenser, swapping a hose and another vacuum down/recharge), decided to control costs by omitting it from my scope of work. So far, no regrets

[tsuter]

Originally Posted by GH85Carrera

I don't have, or want a tail on my car.

One of the biggest reasons for the fender condensers and not a large condenser under the decklid, the heat! When I added the two condensers in the fender, my engine temps went down, a significant amount. Instead of dumping the cabin heat via the condenser right into the engine cooling fan, it goes into the fender area, and away from the engine.

Driving 11 hours in 100+ degree heat, my oil temp stayed at 210 with the AC blowing 37 degree air all over me. The only time I saw higher temps was climbing up a long long mountain pass in 105 degree heat. It approached 230, but as soon as I crested the pass, it dropped to 210 very quickly.


Driving around in traffic in Roswell, I was staying cool, and the engine never went over 210.

So you removed the rear condenser? Wow that's a first. I'm trying to find any auto manufacturer I can that does not put both the radiator and the AC condensers right in front of the engine block...or on top of it in the case of Porsche. They even put the Turbo IC and Condenser right on top....
I can't find anyone not doing that... and worried about "heat" on the engine....

Maybe you know some?

[Mixed76]

993 condenser is in the driver's front fender. 964 maybe same? Stock 993 system works mostly fine in Houston- slow to cool if the car is heat soaked but it does eventually get cool.

Later turbos put the intercoolers in the rear fenders, condensers fight for space up front with the radiators.

I.e., they're trying not to stack coolers one in front of the other in front of the engine.

Sent from my Pixel 7 using Tapatalk

[tsuter]

Originally Posted by Mixed76

993 condenser is in the driver's front fender. 964 maybe same? Stock 993 system works mostly fine in Houston- slow to cool if the car is heat soaked but it does eventually get cool.

Later turbos put the intercoolers in the rear fenders, condensers fight for space up front with the radiators.

I.e., they're trying not to stack coolers one in front of the other in front of the engine.

Sent from my Pixel 7 using Tapatalk

Nah...that's no good....

This is the best place for the condenser!

[GH85Carrera]

Originally Posted by tsuter

So you removed the rear condenser? Wow that's a first. I'm trying to find any auto manufacturer I can that does not put both the radiator and the AC condensers right in front of the engine block...or on top of it in the case of Porsche. They even put the Turbo IC and Condenser right on top....
I can't find anyone not doing that... and worried about "heat" on the engine....

Maybe you know some?

Nope, the factory original condenser is still in place back there, as is the factory stock front condenser. I just added the two in the driver's side rear fenders. They do most of the condensing work, and the fans on them blow a lot of heat away from the engine.

The biggest issue with the factory design, is not enough condenser capacity. So, yea, I have some heat from my condenser going into the engine, but not that much as the other three help out a lot.

[tsuter]

Well, that's good it still there. There is no reason to remove it. In automotive AC lingo there is this acronym called CTOA. The condensing temperature over the ambient.(CTOA) tells us how much hotter the condensing temperature is over the air temperature passing through the condenser. This should range between 7-8F and 30F depending on the efficiency of the condenser. The more efficient the condenser the higher the CTOA. Old 911 condensers not so efficient low CTOA.

Now mine is a very efficient super parallel 480 sq inches. The CTOA is around 30F. So if ambients are 105F I will measure and see a temperature on the condenser of as high as nearly 140F. Of course this is at the extreme of what we call "red zone" cooling. The condenser air temp is rarely above even 110-120.

Now as far as engine temps go they need to be and are far above 140F. In fact as the fan pulls air into the shroud it channels that air through a plastic duct into the "on engine" oil cooler to cool hot engine oil. The external thermostat then should be opening at 180F and sending oil now to the external cooler which of course is uninfluenced by the condenser at all.

The external oil cooler should be able to manage your oil temp at around the 180 to maybe 220 or maybe your external oil cooling needs to be looked at.

The only thing the condenser will do is possibly allow the engine oil to heat up to 140F faster than it may normally and maybe maybe allow the thermostat to open sooner but not at a higher temperature.

In any case it is certainly not deleterious to the operating temp of the engine and even serves to "cool" oil in the on engine oil cooler where the temperature is well above 140F and should be well above 140F.

Now I also have a turbo car so some other issues pop up but then you have a turbo tail as well which offers some fun AC prospects.

For straight forward NA 911s, a rear condenser will not make your engine oil overheat. The bump from ambients is not even 30F. Those old condensers like your will never see a CTOA of 30F.

So I'm glad you did not remove your rear condenser. And the point of my post was not for you to yank out your four condensers as you are happy with them and your system and they are what is called a "sunk cost".

But for others, who have not gone down this expensive route, they should take a look at modernizing their rear condenser into a super parallel flow. with fans. In this manner they may well be able to avoid all the issues of 2-3-4 condensers and use just one. A major savings in cost as well as plumbing.

[tsuter]

I really like this setup here. From a Nissan Altima. If my fans go out I will likely look at this. They didn't have these when I built mine.

Marry this up with a nice parallel flow rear condenser for your 911 like in the pics I posted above....and it would not be your condenser's fault if you can't cool.



Add $150 for the condenser....nice!

[tsuter]

And to wrap this a bit after updating your evaporator/blower assembly, I would look at adding additional under dash plenums off the "bow tie". See red circles in the pic below.
Can't hurt to distribute that air a little better.

I do not sell product....or represent sellers who sell product.....

[wazzz]

Originally Posted by tsuter

I really like this setup here. From a Nissan Altima. If my fans go out I will likely look at this. They didn't have these when I built mine.

Marry this up with a nice parallel flow rear condenser for your 911 like in the pics I posted above....and it would not be your condenser's fault if you can't cool.



Add $150 for the condenser....nice!

Interesting and a cheap solution. But I wonder if these are pushers or pullers. They look like pushers (not sure though). This type of blades is made for CW or CCW but not both. So they wouldn't suit your setup if they are pushers.

[tsuter]

Originally Posted by wazzz

Interesting and a cheap solution. But I wonder if these are pushers or pullers. They look like pushers (not sure though). This type of blades is made for CW or CCW but not both. So they wouldn't suit your setup if they are pushers.

Could be...not sure...if I have to do research and do design I'll need to charge you a design fee and get an NDA...

[wazzz]

Ok let's do that.

I just realized I need pushers anyway, because the only place where this double fan would fit is inside my whale tail, so that would be above the condenser.

Not enough space inside, because of the 3.2 intake, airbox and heater piping.