MyE28.com

Well, with a 104 degree day yesterday and a heat index of 112 I am no longer willing to tolerate mediocre AC performance. My system is currently convereted and charged with R134a. The compressor is healthy. On a nice 80-90 degree day the AC is decent if not downright cold in the morning. However once it gets hot, its hopeless. Having read posts by El Guappo and JBort, I have contemplated changing the condesner to a parallel flow unit as well as charging the system with R12a instead of going back to R134a.
I would like to know if one was to change to r12a, would the upgraded condenser be absolutely necessary?
Would just charging the system with r12a give me me performance close the that of a stock r12 system?
If the upgraded condenser is required to ensure cold vent temps in all conditions, do I need two units as in JBorts car, or will one unit be sufficient and more effective than the stocker?
If upgrading condensers, is there going to be significant difference in vent temps between r12a and r134a?
I basically want the system to perform as well or better than the stock system did when it was charged with r12. While this is a tall order I know it can be done and I am willing to do what it takes to make it happen as if it doesn't improve, the car basically won't get driven during summer months.

Well speaking as someone who has messed about with r12a (in JBorts driveway with his gauges) I am coming to the conclusion that its just not worth the trouble.

I am going to do the dual parallel flow condensers but go ahead and run r134, and it will be plenty cold enough. The ease of buying the 134, its easier to work with, and just plain less guesswork. The shop where I had the custom power steering hose made for the ex's Touring will also do AC lines, and each crimp is only $2. Big winnar. So after I buy all the line, I will cut off the end pieces at the yard (for the BMW ends) buy the new ends for the probably American sized condenser fittings, and have all the pieces mocked and marked. Get them all crimped, fit it all together, fill, adn enjoy the Sacramento summer in relative cool...

I hope...Sometime after 5erFest....

Jay3

When you say r12a isn't worth the trouble, what do you mean? Is it an issue of getting the charge amount correct or something else because it doesn't seem that much is involved in replacing 134a with the r12a.
I do like the idea though of the dual condensers with 134a and not have to worry about sourcing the r12a or any long term issues. I guess I just want to make sure that the effort will be rewarded with air that is cold from the vents no matter the outside temp and whether I am moving or not. On a 100deg day 50+ degree vent temps just don't cut it.

134a very cool!
See it "live" at 5er fest 2008 8)

you should take your car to a local A/c repair shop (or buddy) and have them hook up a set of gauges to see where your pressures are at once everything is warmed up. maybe there is a cooling issue with the aux fan?

alijonny wrote:you should take your car to a local A/c repair shop (or buddy) and have them hook up a set of gauges to see where your pressures are at once everything is warmed up. maybe there is a cooling issue with the aux fan?

I have all of my own equipment and the pressures are good as is the aux fan. I am convinced that the stock condenser just isn't up to the task of trasferring enough heat away from the refrigerant, which in this case is the less efficient 134a. Cooling a car when its 100+ deg outside and 50-60% RH is a challenge. It seems the solution here is more condenser!

Its been proveon that the old style tube and fin condensers are FAR less efficient and in NO WAY suited to r134a operation. r134a almost REQUIRES a parallel flow condenser. What JBort has going there is pure AC pr0n. And yeah, its plenty cold too...maybe there will be some booby chicks there to 'demonstrate' the cold temps?

I have not seen the distribution point though to separate the flows to the 2 condensers.

Jay3

JBort wrote:
134a very cool!
See it "live" at 5er fest 2008 8)

WTF!!! I heard about 2 condensers and figured it would be 2 small ones side by side, but 2 back to back with a small fan? WTF! I suppose what works is what counts, but I'm still shaking my head.

Of course I've been finding out for years, just when I think I know it all, I don't.

Mike W. wrote: WTF!!! I heard about 2 condensers and figured it would be 2 small ones side by side, but 2 back to back with a small fan? WTF! I suppose what works is what counts, but I'm still shaking my head.

Mike, that fan is full-sized from a Mercedes and puts out plenty of CFM. It's also on an override switch so I can have "full airflow" anytime! 8)

(I'll show ya at 'da 'fest)

Jbort, what size condensers are those in your car? Did you order them from Arizona Mobile Air? Also, I can't quite tell from the picutre but are the condensers mounted in series or parallel? If they are in series does the compressor outlet enter the front or rear condenser first? Do you feel that the second condenser is absolutely necessary? At the end of the day results are what matters and if your setup works well, then it is worth replicating in my car as I am done with mediocre performance.

I'm running R134 in the E24 with all other stock components, save for the conversion to a Sanden style compressor, and it gets damn cold. Granted, it does have the dual AC system, but I think that even with the front only it would freeze me out...

From realoem it appears that the e24 does have a different condenser from the e28, and the late e24 has a different one still. It could be that it is a bit larger than the e24 unit and takes to r134a better than the e28 condenser. Who knows...

Big Bronze Rim wrote:From realoem it appears that the e24 does have a different condenser from the e28, and the late e24 has a different one still. It could be that it is a bit larger than the e24 unit and takes to r134a better than the e28 condenser. Who knows...

E24's do have a much larger condenser, more like the same size as in E23's.

Well it looks like I will be upgrading to a single parallel flow condenser which is slightly larget than the OE unit. I had a huge find yesterday at PNP. I was scouring the yard for good finds and I find a 535i that looks as if it had recently had it's AC system professionally converted to 134a. The car was hit in the rear and the AC parts couldn't have been more than a few months old. It had custom hoses and a super sweet PF condenser that already had custom brackets made up to mount it to the car as well as mounts for the aux fan. I grabbed everything and am pretty excited that this may make for some exceptional AC in the car this summer. Hopefully I will find some time this weekend to get it all installed and get the system charged up. I will report back with my findings.

earlier e28's had a larger condenser

Update! -
This last weekend the condenser was installed, leak checked and the system charged with R12a (I used Redtek 12a). Yesterday was the first time driving the car with the new parts. I must say I am very pleased with the performance of the system. In the morning(80F ambient) I saw vent temps dipping down to around 36F. In the evening with ambient temps hovering around 98-99 on the drive home, with the car moving the vent temps were around 39F and about slowly climbing to45-46 with the car barely moving in stop and go traffic. It pulls back down almost immediately once RPM or road speed increase. I find this quite acceptable and it will be even better once the car is tinted. I will finally be able to actually enjoy driving this car in the summer!

Big Bronze Rim wrote:In the evening with ambient temps hovering around 98-99 on the drive home, with the car moving the vent temps were around 39F and about slowly climbing to45-46 with the car barely moving in stop and go traffic.

I know 134a systems require a higher air flow across the condensor; probably true with the less-efficient r12a. I installed an aux fan from a Mercedes and wired it for a high speed bypass which I activate while idling. Makes a difference. Thanks for your update! 8)

JBort wrote:

Big Bronze Rim wrote:In the evening with ambient temps hovering around 98-99 on the drive home, with the car moving the vent temps were around 39F and about slowly climbing to45-46 with the car barely moving in stop and go traffic.

I know 134a systems require a higher air flow across the condensor; probably true with the less-efficient r12a. I installed an aux fan from a Mercedes and wired it for a high speed bypass which I activate while idling. Makes a difference. Thanks for your update! 8)

I was under the impression from looking at the vapor pressure curves for the hydrocarbon refrigerants like 12a, that they are much more efficient than r134a. They are very similar to r12, but have a temperature glide, which r12 does not. My high side readings were a LOT lower than 134a for a given ambient temp. The compressor also seems that it is consuming less shaft power. I am using a stock BMW aux fan on the condenser but I may upgrade to a better fan. JBort, it was your setup that prompted me to go the parallel flow condenser route and I am very glad I did.

Im planning to modify my AC in 2 of my cars since i live here in "warm" Arizona. I bought Freeze 12 for one of my cars and Im going to purchase a cross flow condensor. Im not familiar with R-12a. I have a license to buy r-12 but as you know its a pain in the a** to find. As far as tinted windows are concerned, Im going to use heat rejection film. You can use it without tinting and it will block heat as well as UV light much better than plain dark limo tint of ordinary film. Some of the aftermarket cooling fans are unbelievable these days in the amount of air they can pull (or push). Im sure they can draw the amps though.

Bimmerman wrote:Im planning to modify my AC in 2 of my cars since i live here in "warm" Arizona. I bought Freeze 12 for one of my cars and Im going to purchase a cross flow condensor. Im not familiar with R-12a. I have a license to buy r-12 but as you know its a pain in the a** to find. As far as tinted windows are concerned, Im going to use heat rejection film. You can use it without tinting and it will block heat as well as UV light much better than plain dark limo tint of ordinary film. Some of the aftermarket cooling fans are unbelievable these days in the amount of air they can pull (or push). Im sure they can draw the amps though.

I definitely want to use a tint that has good rejection properties but don't mind a bit of tint as I think it looks good on a white car. R12a/HC12a (amongst other trade names like Redtek, Duracool, Envirocool) are hydrocarbon based. I think the blends are slightly different but are basically the same thing. It can be put into either r134a or r12 systems, meaning that if the system is r12, it does not need the oil to be changed or barrier hoses installed. It also requires no liscense to buy. I may try out an e39 condenser fan that I have access to or I may buy a Spal fan and use that in place of my old tech aux fan.

JBort wrote:
134a very cool!
See it "live" at 5er fest 2008 8)

ok, i feel like the slow kid here but I know little of this. So to improve my AC, should I get a larger condenser, or should I just run 2 stock ones?

also, do I run them in series or parallel? if in parallel, how do I split the charge?

From what ive been told you need a better condensor than one you would use for r-12. You must use a cross flow or parallel condensor in which the flow is simuliar to a turbo intercooler. meaning the opening where the refrigerant enters the condensor branshes off into multiple paths to reach the other side of the condensor buy which time its given off all its heat, then exits the con. simplistic explanation

k, can i nab one of these from a junkyard car of any variety/ethnicity? or do i have to go buy one aftermarket?

Brad got lucky finding a recently converted 535i with the parallel-flow condensor that fits!
Aftermarket PF Condensors can be found here: http://www.ackits.com/c/Parallel/Parall ... minum.html
If you have access to Freon R12, there is no better substitiute. Period.
If you deceide to convert to 134a or 12a, you will need an upgraded condensor (as Bimmernman has stated) to be efficient.
BTW, my "dual parallel flow condensors" is admitted overkill! I had a friend who wanted to try this as an experiment, and he had the equipment to build any barrier-hose! The 134a refrigerent runs thru these in series; rear first then front!

JBort wrote:Brad got lucky finding a recently converted 535i with the parallel-flow condensor that fits!
Aftermarket PF Condensors can be found here: http://www.ackits.com/c/Parallel/Parall ... minum.html
If you have access to Freon R12, there is no better substitiute. Period.
If you deceide to convert to 134a or 12a, you will need an upgraded condensor (as Bimmernman has stated) to be efficient.
BTW, my "dual parallel flow condensors" is admitted overkill! I had a friend who wanted to try this as an experiment, and he had the equipment to build any barrier-hose! The 134a refrigerent runs thru these in series; rear first then front!

JBort is correct. There is no better refrigerant than r12, but in lieu of r12, I think r12a is a better choice than r134a. However, r12a is theoretically illegal and some may be comfortable with the fact that it is in fact a flammable hydrocarbon.
And I did get really lucky finding what I did in the junkyard. Looking at the Ackits.com website, the closest match to the one I found would be the 14"x19.5" unit (for all I know that is the same unit, it just doesn't have a picture). It fits great in the car. I will try to get some pics of mine mounted up.