Taguid

I would like to know if anyone besides Greg Brown has successfully added additional condenser capacity to your AUTO vehicle. If you did please add any comments that would assist. I am thinking of doing it myself but I would like input from the 928 brain trust. I would like to place it somewhere in the vicinity of where the cooling flaps used to reside. I have a 91 S4. TIA

SeanR

You'd be ahead of the game to add a 12" Spal pusher fan in front of your condenser and have it activate when the A/C button is pushed. Done it a few times and the hot soak issues are non-existent with it. You can get in on a hot day after the car has sat soaking up heat and in stop and go traffic the air flow is like your doing 70 on the highway.

FredR

An interesting project and something I planned attempting to the point I purchased a cooler unit with integral fan unit. I thought about placing this in the passsenger side front of the wheel well just behind the retracted headlamp.

The alternative I considered was to remove the transmission cooler and fit a full size manual tranny condenser because of the extra surface area and then use the auxiliary cooler for the ATF duty.

For sure the system is limited by condenser capacity as those with the rear cooler option should have figured out in warmer climes as switching it on immediately drops the temperature out of the main central vents.

In our summer season I tend to solve the problem by only taking the car out late afternoon or in the evening when it is a bit cooler.

A chap over here did the most lateral thing I have seen- he mounted the condenser at the rear of the car sort of integrating it into the bumperline. Although it did not look too good, it was not as bad as I thought it would look but interestingly it worked rather well. He integrated an air handling unit from a mini bus into the area in front of where the tool kit sits. He had no problems cooling the inside of the car although it tended to give him neck ache from blowing from behind!

GregBBRD

Of course, the obvious problem is by adding a fan to take away "heat soak" from the condenser, you are adding that additional heat to the radiator. This raises both the water and transmission temperates, which is not optimum on a hot day. My system "removes" 100 degrees of air temperature to the radiator on a 90 degree day....instead of adding heat!

When I make pieces, I generally have multiple goals in mind.....I try to always look at the "big picture". In this case, I wanted to increase condenser capacity, get a sold stream of liquid to both expansion valves, increase the cfm output of the front evaporator fan, and reduce the temperature of the air to the radiator.

My system does all of those things

I originally built and assembled this system to complement the "upgraded" 928's I'm always building. To have marginal A/C really limits the days one can use these cars! The system turned out to be a "loss leader"....an add on at the very end to make these cars better by a large factor.

For anyone doing this project themselves.....add up the costs of the pieces, before you start. While everyone thinks I'm getting rich off of these "inventions", the reality is that this particular product has a ~10% profit margin....not including the time it takes me to gather and assemble the parts.

My wife claims that if I added in my time, I'd be better off sending anyone that wants to buy a system $500 to just go away.

....And when I run out of the pieces I had fabricated to make up these systems, I will certainly "revisit" the economics of doing this.

FredR

Greg,

Had no idea you had worked this angle. Reading between the lines here does your system take the condenser duty away from the front of the radiator altogether? My experimentation sought to see if I could get the condenser duty accomplished out the way of the radiator air flow and thus leave the radiator well in control.

I kind of backed off after fitting a larger radiator and better fans etc but concluded that they did not do as much as I hoped they might in 44C/111 F typical summer heat over here. On a really hot day 49C/120 F the thing stays in the garage period. The test kit I purchased cost me about $400 and I got nowhere. I can visualise that two sets of the kit I purchased might work but just fitting it effectively and neatly would be quite a substantial effort. I got a quote from a local a/c shop to supply and fit the plumbing and that was going to cost about $500 and we have very cheap labour rates here. Thus a total system with no guarantees was going to cost about $1500.

I remain convinced that such a system would be a great benefit for those who run in hot climates as would some improvement to engine oil cooling.

traxtar928

I'm interested in this hot soak issue for the AC... my car's refrigerant is low, but heat soak after sitting in the hot Texas sun all day during work has been an issue since I moved here a few years ago. Any more details on the best fan to use? Attachment methods? Are there forum posts that detail it further?

I'm already running an aluminum radiator and the coolant temperature barely pushes past the first tick mark on the cluster gauge, so I think I'd be okay there.

GregBBRD

I retain the condenser in front of the radiator. The added condenser is a "stand alone" condenser from another vehicle, so it's heat transfer ability is quite large. There'a fan added to remove heat from this condenser.

Making changes to any vehicle can be a slippery slope. One change to one system can require changes to other systems.

The problem with any increased current draw (extra fans, larger fans), is that the stock 928 charging system is generally already over stressed (especially if modern stereos with high draw amplifiers are used, higher current draw headlights are used, larger fuel pumps are used, etc.

I made my higher output alternator because of this....again, I always look at the "big picture".

While not a requirement for my A/C system on a stock vehicle, if there are other higher current draw items added to the car, the voltage output at idle on a hot night, with everything on, can be near or even under 12 volts.

FredR

The unit purchased was rated at something like 17,000 BTu's and yet compact enough to fit in the front wheel arch.

My late S4 had an after market amplifier [big thing] and with the auxiliary a/c and headlamps on main beam at night it neede something like 3k rpm to break even. Took this up with Porsche and "they all do that" - urrgh!

Now that oil prices have forced me to be a "gentleman of leisure" maybe I will look into this a bit more.

My after market alloy radiator came without the ATF "cooling?" coil and thus rely on the external cooler only - did this after some list advice suggesting it would not be a problem- never been totally comfortable about this but I change the ATF at 30k km [approx 20k miles] to mitigate any potential half life degradation and during the first cycle regularly took some small samples to see if there were any negative signs. So far my ATF looks as clean as a whistle and no nasty burnt oil odours. Again less work for the radiator unless it also acts as a water bath to heat the ATF quicker in colder climates.

V2Rocket

I made a few bolt-in "parallel flow" condensers for 944s a while back. They make a nice improvement in cooling over stock-style serpentine if you are using R134.

I bought all my cores from this place - quick shipping, great prices. Buy the biggest condenser you can fit and make some easy mounting brackets...

https://nostalgicac.com/condensers/p...condenser.html

Speedtoys

When I do my radiator replacement..Hans's new fans go behind it, and a pair of good 10" SPALs will go out front of the condensor as well.

I wont hook them up this weekend, but soon there will be a relay allowing the head AC relay to not blow up..and I will use that to fire the fans.

Speedtoys

I would have suggested you can maybe get away W/O the external cooler, but not without the radiator cooler, which is many many times more efficient.

Speedtoys

"my car's refrigerant is low"

Is the larger problem really not the first problem you want to solve?

FredR

An interesting and understandable comment but somewhat flawed if I may politely disagree with your observation. The overall heat transfer coefficent for liquid/liquid cooling is much higher than a liquid/air cooler but that is not a measure of efficiency. What we are interested in is total heat transferred and that is impacted by driving force [temperature difference] and total surface area available for the heat transfer to take place.

In a stock radiator the ATF is on the hot side of the radiator so water coming from the engine is trying to cool the ATF. The laws of heat transfer determine that the temperature attained in a single pass cooler can only reach to 5 degrees C of the coolant temperature which is around the 100C mark and that means the ATF temperature out of the radiator would be in the region of 105 deg C and that is not cool enough so the radiator coil only would not seem to be an option or so I concluded.

Most engine oil coolers are external to the radiator and air cooled. Porsche changed ships mid life and by 1990 had the oil in that cooler under the radiator - why did they suddenly change? For the manual GTS they introduced an external cooler for the gearbox oil similar [identical?] to the auto tranny cooler.

I eventually reasoned out that the external cooler was the way to go but purchased another beefed up cooler should it prove to be needed. At the right temperatures ATF will last an awful long time before it oxidises but for every 20F [12C] increase in temperature its service life halves. I eventually managed to convince myself that if I limited my ATF service life to 30k km I should be safe. 10 years on I have not had an issue and hopefully that will remain the case but I remain a little concerned about it all despite my efforts and support from others.

After studying the system I wondered if the ATF running through the radiator tank was an attempt to heat it up quicker. In my environment I do not need to worry about the ATF being too cold.

Right or wrong it is an interesting subject matter for discussion

GregBBRD

The thermostat in a 928 opens about 3-4 needle widths before the white line at the 3/4 mark. Once the thermostat opens, the fans quickly follow. The temperature should hover approximately 2 needle widths below the 3/4 mark, up to the 3/4 mark.

If your temperature runs just beyond the first white mark, you should repair this issue, before you do anything, so you have realistic temperature information.

Either your gauge is radically out of calibration, or you have a bad thermostat...not a lot of other choices.

Taguid

Sounds like I'll need to add a front pusher fan along with the additional condenser and fan. I think I should be fine power wise since I just installed Greg's ultimate alternator.

Greg,
What size is the condenser that you were able to add and does installation require the removal of the passenger fender?