Installing A/C in an Early S30

[Xnke]

Ok, I am going to chronicle my experiences installing an A/C unit pieced together from junkyard parts, and a Vintage Air evaporator unit. You won't save a TON of money, but it IS less expensive than buying the whole system outright, and you can get BETTER performance.

 

My Z is a '72 S30, so it has the least amount of room under the dash and infront of the radiator to mount parts.

 

First up, the Condenser Coil. I used one from a Mazda 626:

 

 

The aluminum lines need to be re-bent, and this is a real job. Use a GOOD tubing bender, go gently and easily, and be careful. Aluminum tube likes to collapse, and you DON'T want to put any stress on the brazed joins where the tubing meets the end-tanks of the core.

 

To mount the condenser, it has rubber feet on the bottom of the tanks, like newer style radiators. You will need to drill two 5/8" holes in the lower core support, to let the rubber feet sit down in. I am probably going to end up notching my front core support to set my condenser down a little lower, but this is not required on the Later S30's with the lowered core support.

 

 

a few aluminum brackets later for the top mounts, and waaaa-laaa! it's in.

 

 

See how nice the high side line of the condenser matches up with the compressor location?

 

 

Compressor: I used a new SD508 clone, mounted to a ZX compressor bracket. The idler pully needs to be moved rearward 1/8" for use with the stock 2-row L24 damper, and the idler pully bracket has a steel boss on it that needs to be removed to fit the compressor in the correct location. Both of these modifications involve cutting and welding the steel idler pully bracket. No need to drill/grind/weld the aluminum casting. A few bits of 5/16" all-thread and a short piece of 3/4" angle steel, with thick washers welded into place, are next up and are also, pretty simple. Or you could just use the original ZX air conditioning compressor.

 

 

Next up on the list of parts is to buy the evaporator unit, and get it installed in the car.

[zgeezer]

Ok, I am going to chronicle my experiences installing an A/C unit pieced together from junkyard parts, and a Vintage Air evaporator unit. You won't save a TON of money, but it IS less expensive than buying the whole system outright, and you can get BETTER performance.

 

My Z is a '72 S30, so it has the least amount of room under the dash and infront of the radiator to mount parts.

 

First up, the Condenser Coil. I used one from a Mazda 626:

 

 

The aluminum lines need to be re-bent, and this is a real job. Use a GOOD tubing bender, go gently and easily, and be careful. Aluminum tube likes to collapse, and you DON'T want to put any stress on the brazed joins where the tubing meets the end-tanks of the core.

 

To mount the condenser, it has rubber feet on the bottom of the tanks, like newer style radiators. You will need to drill two 5/8" holes in the lower core support, to let the rubber feet sit down in. I am probably going to end up notching my front core support to set my condenser down a little lower, but this is not required on the Later S30's with the lowered core support.

 

 

a few aluminum brackets later for the top mounts, and waaaa-laaa! it's in.

 

 

See how nice the high side line of the condenser matches up with the compressor location?

 

 

Compressor: I used a new SD508 clone, mounted to a ZX compressor bracket. The idler pully needs to be moved rearward 1/8" for use with the stock 2-row L24 damper, and the idler pully bracket has a steel boss on it that needs to be removed to fit the compressor in the correct location. Both of these modifications involve cutting and welding the steel idler pully bracket. No need to drill/grind/weld the aluminum casting. A few bits of 5/16" all-thread and a short piece of 3/4" angle steel, with thick washers welded into place, are next up and are also, pretty simple. Or you could just use the original ZX air conditioning compressor.

 

 

Next up on the list of parts is to buy the evaporator unit, and get it installed in the car.

 

I wonder why you used the Mazda condenser, when the condenser from a 280 (and perhaps the 280zx) is a straight on bolt in. The high and low pressure lines line up with the compressor located on the driver's side and the unit bolts on to the front using the same bolts that mount the radiator. Unlike most add on a/c for the early s30s the 280 unit is full size.

 

I have photos of the unit on my series 1: look at my album on this forum under zgeezer.

 

I am looking forward to seeing how you mount the Vintage a/c. That is on my long list of things to do.

 

By the way your work is nice.

 

G

[Xnke]

The Mazda condenser is a MUCH MUCH MUCH more efficient design than the 280Z condenser. It is a parallel flow condenser, built similar to an intercooler. It is also actually a little bigger than the 280Z condenser, which is what is called a tube-and-fin serpentine condenser.

 

I had both condensers available to me, and the Mazda unit is not only newer, more efficient, less restrictive to the air passing through it, and bigger, but it's also about 3lbs lighter, to boot.

 

 

PS...PLEASE don't quote big posts complete with photos...

Edited July 3, 2010 by Xnke

[Tony D]

What's 'inefficient' about the aftermarket condenser or the 280Z or 280ZX condenser?

 

Most issues with aftermarket S30 air are due to air leaks bypassing the evaporator, not system component sizing. Actually almost all the components are grossly oversized in the old S30 systems.

 

Yes, even with R134 in there.

[Xnke]

The condensers that are commonly fitted to the S30's are effective, yes, but not even close to the level of the newer designs available. Would you run a turbocharger intercooler designed like the S30 condenser? No, of course not, because there are more effective designs available. The condenser in an A/C system is the same thing, a charge cooler located after a compressor. As I said, the Mazda condenser I chose to use is more effective, has a greater capacity, and I was able to fit it in space available. Not to mention it is lighter weight, and offers less restriction to airflow than the old tube-and-fin type.

 

Also, the S30 is not the most ideal situation for climate control...lots of window area, and little to no insulation, except what you install after you pull out all the old thin rotted stuff and replace it.

 

Another issue for me is the flow through the core...I will eventually have a turbocharged engine with intercooler infront of this, and then the radiator is behind this. They will all be ducted together, with a fan shroud, but that is a LOT of flow restriction possible!

 

This is why I chose this core over the old style core.

[Tony D]

'Xnke'

The condensers that are commonly fitted to the S30's are effective, yes, but not even close to the level of the newer designs available. Would you run a turbocharger intercooler designed like the S30 condenser?

This isn't an intercooler is it?

No, of course not, because there are more effective designs available. The condenser in an A/C system is the same thing, a charge cooler located after a compressor.

And if the current item does the job, what do you expect to gain from 'more efficient' units? Overcooling? Unless you have seen evidence of the prior system not making capacity, 'upgrading' is a theoretical crapshoot based more in 'well lets do it anyway just because' than logical thought or engineering.

As I said, the Mazda condenser I chose to use is more effective, has a greater capacity, and I was able to fit it in space available. Not to mention it is lighter weight, and offers less restriction to airflow than the old tube-and-fin type.

There, a scintilla of some cogent thought arises: possibly lighter weight (whatever that difference makes) and possibly less restriction to airflow. Marginal reasons to upgrade, but possibly worth it. Possibly. If the original wasn't performing. The original performs---that you don't have one makes this an acceptable choice in your application, but don't get people thinking there is anything wrong with the original components. They are more than up to the task at hand. As I originally stated, the problems with the Aftermarket systems generally stem from improper installation and air leaks than undersized components, they are grossly oversized matter of fact! Going in the opposite vein---would you install a GTR 500HP capable Intercooler on your stock ZXT? Well, sadly to say with this 'more efficient thinking' vein...it's possible you would---and reap no advantage from it. Planning on driving in mudcaked ralleyes with the A/C on? Then I guess that may pay off for you!

 

Also, the S30 is not the most ideal situation for climate control...lots of window area, and little to no insulation, except what you install after you pull out all the old thin rotted stuff and replace it.

No worse than a Geo Metro---look at component sizing on it and realize how terrible OVERSIZED the original 70's era stuff was! The condenser core was good enough for a MUCH larger car, as was the Evaporator---matter of fact, that same evaporator was used in ARA's kit for Chevy Full Size behind the dash setups! This doesn't mean the components are undersized for an S30 due to 'not ideal situations' but again, most shortfalls in these early systems are due to poor installation and leaks in airpath, NOT components being undersized! They are grossly OVERSIZED as a matter of fact.

 

Another issue for me is the flow through the core...I will eventually have a turbocharged engine with intercooler infront of this, and then the radiator is behind this. They will all be ducted together, with a fan shroud, but that is a LOT of flow restriction possible!

Then proper airflow management will be necessary on the Condenser as well as the evaporator. Making it "bigger and more efficient" is a ham-handed way of getting around proper airflow management. It may work, but don't give the impression there is anything wrong with the original stuff supplied with the ARA or Frigi-King kits. If they worked fine for countless thousands of miles in my turbo car without an issue, methinks you are going into 'overkill mode' out of some misguided notion that there is something wrong with the components as sourced originally. There is not. People apply patches and fixes to something which is poorly designed or not understood. They proclaim victory over a problem which didn't exist. I can see not having a condenser and then saying "this one will work" but having an original ARA or Frigi-King condenser in-hand, I would be sorely tempted to 'forego' your 'upgrade' simply because it's unrequired even for the application you state. It's plenty oversized. Now, if you got one which was HALF the square footage so airflow over the radiator was only HALF restricted---you might have something there. But as it is you have effectively restricted flow through the whole radiator, with the same realitve delta T across the device---so what have you gained? Nothing, in reality. And in terms of system efficiency??? There is no free ride in thermodynamics. That you didn't have one, and found this one fits is the biggest justification for using this part. Don't think you have gained anything in 'efficiency'.

[calpoly-z]

I will be watching this post closely.

 

Moved down to Laredo, TX for work after finishing up school and it is HOT down here. The car is all but undrivable for most of the year without A/C. So I guess that means I need to get something installed, and it needs be a very good system to deal with 110+ degrees PLUS humidity from time to time.

 

I've got a few other things that need done on the car before I worry too much about this, but it would be real nice to have a solid, functioning HVAC system when I finally do get her back on the road.

[Tony D]

A common misconception is that Humidity adds somehow to the loading of the A/C system: it does not. COOLING is the only thing A/C has to do, dehumidification automatically takes place during this process. It's why evaporators can't run any colder than 35F...any colder and the copious condensate that forms rapidly turns to a big block of ice and renders the cooler ineffective. 'More is not necessarily better' is the watchword.

 

If anybody has ever taken a car into the SoCal or Southeastern Desert areas they will have experienced the worst thermal loading possible. Humidity removal is a secondary byproduct of the cooling process. All you need to insure is you have a proper condensate tray and adequately designed drain tube from the evaporator housing.

 

If you time the compressor cycling, and monitor the head pressure (and know what you are looking at) you can gauge how efficient each portion of the system is doing it's job. That a compressor cycles on and off signifies you have 'excess capacity'---you will notice nowadays the A/C tends to cycle ON a lot more than OFF when it's hot out. You will also notice cooling efficiency goes up when the car is moving forward rather than when standing still at idle. All signs that the components are progressively getting smaller, and working harder. Yes they are more 'efficient' but they are also working at 100% capacity far longer. The net result is that any deficiency at all in the system will result in marked decrease in the cooling capacity and a miserable cabin environment.

 

In the old days, the systems were so grossly oversized it wasn't funny. I could make condensate appear on the windshield, side windows, and hatch glass in my 75 Fairlady Z with the stock Nissan In-Dash air. I actually had to turn the adjustment knob down because it would literally get meat-locker cold inside sitting in the sun parked with the engine at controlled idle (the vacuum dashpot kicking up idle when the compressor kicked on).

 

The 75-78 systems were better than the ARA and Frigi-King simply because they were a blow-through evaporator core and less susceptible to leak dilution of the cold air. But the JDM system in the Fairladys sent to Tropical Climates with the little knob way up under the dash...AMAZING! And yes, it used the 'old style' flat copper tube and fin condenser... The size of the components in the ARA and Frigi-Kings was oversized because of the draw-through aspect of the evaporator. Blow through that puppy instead and you will get a meat locker inside the car it's so oversized!

 

There are tag-on under-dash units that will fit under the glove box. Give those a serious look---I can remember FOG coming out of them they were so cold! And since they usually have dual fans and can get decent air-exchange in the cabin (plus be mounted anywhere) they work exceedingly well.

 

Everybody gets stuck on the paradigm of an A/C system having to blow from the front of the car through the stock registers. The under-dash units work great and will cool the interior just as well. EVEN BETTER you can place them BETWEEN THE SEATBACKS blowing FORWARD and get a very efficient cooling without having knee clearance or fusebox (260 or 280Z) issues. This is where the Toyota 2000GT had it's aftermarket A/C pod... Worked great!

[Xnke]

Uh, I do belive I stated I DO have an original 280Z condenser, but that's a non-issue. I've got my reasons for running the Mazda unit, so I'll run it. (another reason I'm using it: I have been talking with the good folks at VA for a while about this...they are recommending using the parallel flow condenser for a lot more reasons than I am.)

 

Anyway, Placed the order for the plumbing parts, and some pre-swaged aluminum hardlines.

 

I ordered:

 

1 90* -10 beadlock O-ring (condenser high side)

1 90* -10 beadlock Flare (compressor high side)

1 foot -10 barrier hose (compressor to condendser high side)

 

1 48" -6 pre-swaged aluminum hardline (drier to firewall)

1 straight -6 bulkhead fitting (firewall)

2 90* -6 beadlock O-ring (evaporator fittings)

2 foot -6 barrier hose (evaporator feed)

 

1 72" -8 pre-swaged aluminum hardline (firewall to compressor low side)

3 90* -8 beadlock O-ring (evaporator fittings and compressor low side)

1 90* -8 bulkhead fitting (firewall)

3 foot -8 barrier hose (evaporator return and compressor low side to hardline)

1 90* -8 beadlock flare (compressor low side)

 

Also ordered a standard drier, with -6 fittings in and out and a high/low pressure switch.

[Tony D]

The whole crux is the following statement:

" and you can get BETTER performance."

 

Simply state your quantifiable goals. If the stock system, or even an aftermarket system delivers 37 degrees center-register what more 'improvement' do you plan on getting? How do you plan to quantify a contention that it will be 'better' performance.

 

The condenser core may well be more 'efficient' but it's heat rejection will be identical in terms of BTU's as the previous unit. It's based on load on the refrigerant system. What have you done to 'improve' that? You have added 'margin' on the liquid side...was it needed?

 

If the original systems were incapable of producing 37 degrees center register (the industry standard) then I would say someone aiming to improve and give 'better' performance would be a simple, straightforward matter.

 

But since the original systems when properly installed and maintained GIVE the benchmark...exactly what are your goals to meet in order to quantify 'better'?

 

I see the possible improvements are in airflow and air-exchange within the cabin (not anything related to the refrigerant side, but the ventilation-fan side). Both OEM and aftermarket systems have responded to massive increases in flow across the evaporator core with MORE 37 degree center register airflows---meaning the components have ample reserve capacity.

 

I am just getting at your contention you are going to make a system 'better' yet have offered nothing more than 'you can get these parts easier' or 'possibly cheaper'---but that doens't go towards improving the systems performance.

 

If you are going to tell us you are going to make a good functioning system 'better' then you need to tell me at least what your empirical goals and benchmarks are for an impartial review.

 

If you start with a car misfiring with fouled plugs on three of six cylinders, are new spark plugs, or different spark plugs 'making it better'?

 

If the plugs are fouling from bad rings and oil depositions, is the replacement of hotter range plugs an improvement and 'making it better'?

 

In both cases I would say it's not, it's simply a normal maintenance procedure, or band-aiding another situation undiagnosed by someone.

 

So goes it with 'improvement' of the A/C system. There are touted 'efficiency improvements' for this component or that...but if the stock system was amply capable of cooling the cabin easily (when functioning properly) how are you quantifying 'make it better'?

 

Or are you simply putting in hotter plugs?

Edited July 4, 2010 by Tony D

[Xnke]

It is a better system for a modern installation. It takes less power to drive the compressor to produce the same amount of cooling, it offers less restriction to the airflow through the core, it offers less restriction to the refrigerant flowing through the core, it produces with the same 37 degree center vent temperatures with higher airflow through the evaporator core, allowing hot, outside air to be drawn through the core in a non-recirculating fashion to be cooled to the same temps as the recirculated air. Yes, I will be running both vented and recirculated air with my install. It also does not use the draw-through system of the old dealer-installed aftermarket air conditioning, which while it may have worked, did not work as well or as reliably as a differently designed blow-through system.

 

It also matches with the evaporator system that I am using, and is recommended by that company. The original system in good repair, used with the design-specified R12 refrigerant, can perform very well. I have a complete Late S30 system that I could use. You know as well as I know, that the early S30 dash in a USDM will NOT allow the later USDM S30 air handling system to fit correctly. I would have to change the dash and console to a 1974-1978, which I am not willing to do. I am choosing to NOT use 35 year old components when I can take advantage of 35 years of automotive air conditioning technology advances, AND design my system from the start to run with R134A. For the same size evaporator, R134A requires a condenser with approximately 30% higher capacity than an equivalent R12 system. R134A just doesn't have the specific heat of R12, and the systems are designed and optimized differently.

 

I'm not saying, at any point, that this system is the ONLY way to do it. I am saying that I am using these parts, for these reasons, and that's it. If you don't like it, TonyD, then you don't like it. Do it your way, which works too.

 

I'll dig up my references and PM them to you, Tony, complete with maths, after I have the system installed and can take good measurements. After it's installed and running, I'll actually be (In theory, I'm still looking at the math for this part) able to measure the efficiency, and (In theory) calculate the power usage, and, with a little handwaving, estimate shaft-horsepower needed to run the system.

Edited July 5, 2010 by Xnke

[Tony D]

Using superheat and various other measurements this can be done. Measuring cycle time under standard conditions (say before/after) and charting heat removal in the cabin is also a rough measure of efficency increase.

 

I was involved at Parker-Hannifin in testing HVAC systems in Ford Vehicles and am suspect of most claims of 'improvement'---yes even of older stuff. Your comment of 30% larger R134 Condensers is about right, but the 'old' condenser was about 50% oversized to begin with which is what I was getting at, if you propose the new condenser returns this same margin using R134A---while technically an 'improvement' it still falls within the original parameter of a 50% margin.

 

Excess margin which usually isn't used.

 

I'm not saying I don't like it, I'm asking what the proof will be that you will end up with anything quantifiably 'better' as you claim. My contention has been that likely you will at BEST equal the original system performance.

 

I've been down this road, remember I mentioned Geo Metro earlier? Look at the compressor on that baby. About the size of a Z's AIR pump. Matter of fact, it mounts nicely there....

 

Relative heat loading and greenhouse similar....

 

Powered by a 1.0 three cylinder so HVAC system must be superefficient....

 

Lot of work, got the same relative results as with the 'old tech'---it's where my statement that 'newer usually just means smaller with less margin and working harder all the time'

 

Really, you want the best thing for your efficiency? Ditch that huge Sanden style compressor, go get one off a Geo Metro, and get an Accumulator/Dryer fabbed that is HUGE---say 12oz or 24 oz. This will give you sufficient liquid side reserve to let that little Metro compressor cycle on and off when under full head load in the cabin. Storage means less horsepower is required during transients.

 

Otherwise, BTU's in and BTU's out won't change. Compare a York to a Sanden, yep more efficient. But if you already had an aftermarket with a Sanden... you're going to be hard pressed to show an 'efficiency increase'...

 

35 years of HVAC hasn't changed much. I've been doing it about that long now and the automotive stuff is really simple compared with the industrial stuff out there. It's FO system in most cases! You can change that... but is the added complexity and service hassles that may be encountered worth it?

 

I'm just asking questions, send the maths along, it's interesting experiment but measurable differences will in the end (I'm betting) will be nil. (Airflow across the exchangers will increase...but BTUs are BTUs and that is what will impact your radiator as much as airflow!) I'm interested to watch, but you made a STATEMENT instead of an "I hope to" so whenever someone states 'this is better' I have to ask why they are saying that. RIght now there is no proof. It's a hypothesis, not something that can be stated factually. I look forward to the progress, but until then it's all conjecture. All the best calculations in the world make something look great until you put it on the test bench and get sorely disapointed. Lets at least get to that point before making statements that it's better. That is what I was getting at.

 

Remember, I NEVER said I didn't like it. I just didn't like the statement that it was better without any proof of that fact.

[zgeezer]

OK, here's what I glean from this thread and my own knowledge that I can put to use for my AC conversion.

 

1. The 280 A/C condenser [Cu not Al] is a bolt in, is more than adequate, and can be rotated to match a compressor mounted on either side of the motor.

 

2. For the severely space challenged look at a Geo A/C compressor [Thanks a bunch for this tip] and

 

3 Consider installation of the evaporator behind the seats.

 

I'm not a HVAC expert, but Cu not only conducts electricity better than Al, but it also transfers heat faster.. quite a bit faster. Al is lighter.

 

G

[ozzzzz]

Tony D I must applaud your use of emperical. Just the other day I was trying to use it in a sentence. I gave up after a couple trys. You crack me up. Most entertaining though.

[Tony D]

I encourage xnke's experiment, I don't know where it got misinterpreted that I didn't like it, I just wanted to make sure we could get quantifiable results.

As you gleaned from some of the writing, when I had a non-travel job I could do 'experiments'... One of which was fitting the larger parts of a complete Geo Metro HVAC system into an S30 under the premise that it was the most compact and efficient modern unit available which would have similar greenhouse cooling requirements and internal volumes.

I couldn't instrument well enough for my satisfaction (not enough probes available to me after I left the analytical place I was working) to quantify if the result was worth it. I basically was driving a 240 with no dashboard and Geo Vents taped and angle-ironed aroudn the front of the dash. To my subjective appraisal of the change it seemed to get colder than an ARA/Frigiking, but by no means was it as cold as my 75 Fairlady Z with the JDM cooler in it. That got me thinking further.... and you know where that leads.

 

It was a LOT of work, and to get the geo stuff, small as it was, into even a stock 240 or 280 dashboard (you CAN fit the evap into the stock place for the early S30--it WAS available with factory in-dash air in JDM!) for a more efficient blow-through setup...in the end what I found was even utilizing the stock components (be they 260/280 in-dash or ARA-FrigiKing under-dash) the KEY was a blower that gave sufficient air exchange.

 

Almost above all else, THIS SINGLE POINT made the BIGGEST DIFFERENCE in cool down times, and the ability of a passenger or driver to 'feel cool'... IMO the 280 and 240 fans are not up to the circulation job. Marginal at best. The JDM cooler for the tropics had a considerably different flow system in it and I wish to hell I had photos of the setup as it looks a lot like the modern stuff. Like I said, I had to 'dial it down' to keep from freezing inside the car in 33C Tropical Humidity. It seemed to have a bigger fan, but likely it was just a 280Z style blower.

 

I went through a lot of work, determined I was going to reinvent the wheel with the Geo System in the car, but really it felt no better than the ARA it replaced. I just didn't feel like I wanted to continue and hack up behind my dashboard on an early S30 dash to accomodate the geo parts, or adapt the geo evap to a configuration that would fit as a slip-in sort of conversion in a 240 setup.

 

Really, the 240 in-dash setup was very similar to the 260/280 setups, the evap was in the exact same place. The vacuum diaphragms are unobtainium, so venting would have to be either manual wires or something you make on your own. The new electromagnetic heater control valve Vintage Air makes gives interesting possibilites with linear pots for actuation if you want to retain the stock 'lever look'... but it's a thankless task IMO.

 

Like I said, my ARA keeps the interior of my car at 70 F going 110mph on a 103F day with 85% R/H and I don't think I can ask for much more than that. I guess you could get it to 65 and that would be an 'improvement' but how much work will someone have to do to get that 'improvement'? Is this the point of 'diminishing returns' at some point? That is where I got with the Geo Metro project.

 

Hell, the back axle from that damn donor car is STILL in the back yard!

[ozzzzz]

I encourage xnke's experiment, I don't know where it got misinterpreted that I didn't like it, I just wanted to make sure we could get quantifiable results.

As you gleaned from some of the writing, when I had a non-travel job I could do 'experiments'... One of which was fitting the larger parts of a complete Geo Metro HVAC system into an S30 under the premise that it was the most compact and efficient modern unit available which would have similar greenhouse cooling requirements and internal volumes.

I couldn't instrument well enough for my satisfaction (not enough probes available to me after I left the analytical place I was working) to quantify if the result was worth it. I basically was driving a 240 with no dashboard and Geo Vents taped and angle-ironed aroudn the front of the dash. To my subjective appraisal of the change it seemed to get colder than an ARA/Frigiking, but by no means was it as cold as my 75 Fairlady Z with the JDM cooler in it. That got me thinking further.... and you know where that leads.

 

It was a LOT of work, and to get the geo stuff, small as it was, into even a stock 240 or 280 dashboard (you CAN fit the evap into the stock place for the early S30--it WAS available with factory in-dash air in JDM!) for a more efficient blow-through setup...in the end what I found was even utilizing the stock components (be they 260/280 in-dash or ARA-FrigiKing under-dash) the KEY was a blower that gave sufficient air exchange.

 

Almost above all else, THIS SINGLE POINT made the BIGGEST DIFFERENCE in cool down times, and the ability of a passenger or driver to 'feel cool'... IMO the 280 and 240 fans are not up to the circulation job. Marginal at best. The JDM cooler for the tropics had a considerably different flow system in it and I wish to hell I had photos of the setup as it looks a lot like the modern stuff. Like I said, I had to 'dial it down' to keep from freezing inside the car in 33C Tropical Humidity. It seemed to have a bigger fan, but likely it was just a 280Z style blower.

 

I went through a lot of work, determined I was going to reinvent the wheel with the Geo System in the car, but really it felt no better than the ARA it replaced. I just didn't feel like I wanted to continue and hack up behind my dashboard on an early S30 dash to accomodate the geo parts, or adapt the geo evap to a configuration that would fit as a slip-in sort of conversion in a 240 setup.

 

Really, the 240 in-dash setup was very similar to the 260/280 setups, the evap was in the exact same place. The vacuum diaphragms are unobtainium, so venting would have to be either manual wires or something you make on your own. The new electromagnetic heater control valve Vintage Air makes gives interesting possibilites with linear pots for actuation if you want to retain the stock 'lever look'... but it's a thankless task IMO.

 

Like I said, my ARA keeps the interior of my car at 70 F going 110mph on a 103F day with 85% R/H and I don't think I can ask for much more than that. I guess you could get it to 65 and that would be an 'improvement' but how much work will someone have to do to get that 'improvement'? Is this the point of 'diminishing returns' at some point? That is where I got with the Geo Metro project.

 

Hell, the back axle from that damn donor car is STILL in the back yard!

 

I did not get the impression you were against what he was doing or not like it. Just giving him a hard time in a rather long winded way.I have used the word unobtainium before. You crack me up. Good for a laugh I always liked it when people charged a/c units until they got beer can cold on the suction line myself. That one cracks me up too.

[Tony D]

I dont think I was giving him a hard time, either. People thinking this have obviously never underwent peer review in college. That's not giving people a hard time, it's inquiring if they thought out their hypothesis and it's end result.

 

On the face of it, the claim of 'taking less horsepower to drive the compressor' for instance... You have a set BTU load in, a set BTU load to reject, and you must compress X gas to X pressure to get the expansion required. He's using a large sanden compressor. Sure it's 'more efficient' than a york, but not much if any different than standard sandens from the 70's. The work needed to compress the gas and expand it will be the SAME based on BTU input. He's palaying with ideal gas laws, and compression physics. Using the same style compressor, 'efficiency' I'm laying money will be a wash. They don't sell lysholm screw compressors for AC service in Automotive Applications, nor do they sell Centrifugals, so the largest possible efficiency gains in the biggest power user (the compressor) are ruled out. Most people put sandens on their york AC systems long ago when the originals crapped a seal. That's when they converted to R134A as well. I know that's when I did it. The sanden is quieter, and makes more CFM than the york, but the york never needed an idle speed dashpot to keep the car from stalling at hot idle either...

 

So yeah, it's more 'efficient' but that means it's pumping more. And in most cases the difference between a 1 cylinder, 2 cylinder, or 7 cylinder reciprocating compressor is the smoothness of delivery and less pulsation. That's about it. Drive horsepower remains the same as they are one-step compression machines, not multi-staged. That means similar efficiencies in compression.

 

These are physical laws. You have to be pretty sneaky to get them to bend on a shoestring budget. It's coming down to semantics as usual. An 'airflow increase' may be a goal, but if the airflow is now 15 F hotter than a lower flow with a lower temperature....is there and improvement.

 

There's no free ride... It will just take some time to confirm this. Buy a Kestrel and take good measurements. Static pressure stations underhood will help as well. Like I said, 'been there, done that, interested to see the result but suspect I already know it!'

 

[Xnke]

Hey, I'm not taking too much offense at this; I just see Tony get all over folks about just about any field of work in the Z's and it does irritate me at times; the downfall of a text-based information exchange. I can't always tell when he's being snarky, or if he's forcing me to proove my point. (yes, I realize that it's a two-way street.)

 

I was hoping to hear about that JDM evaporator system a little...hoping to coax some info out of Wiki. I knew it would fit in the early S30 dash, but I don't have one, and have a pretty low chance of getting one.

 

On the face of it, the claim of 'taking less horsepower to drive the compressor' for instance... You have a set BTU load in, a set BTU load to reject, and you must compress X gas to X pressure to get the expansion required. He's using a large sanden compressor. Sure it's 'more efficient' than a york, but not much if any different than standard sandens from the 70's. The work needed to compress the gas and expand it will be the SAME based on BTU input

 

Yes, BUT you are also moving more CFM of refrigerant, with a greater condenser area, and less restriction to flow: less head pressure is required from the compressor, and while you are still going to be changing state, you are not spending as much energy heating and cooling...rather than the fluid being heated to 150F hot side, and 32F cold side, you're seeing the fluid heated to 100F hot side, and 35F cold side...which is plenty, and takes less energy input to do. You still have the high side and low side, but instead of 280PSI high, you are down to around 150PSI or so being required for proper exchange. BTU's are BTU's, You're exactly right on that point. (mostly pulled those numbers out of my butt...but they are not too far out of line. You get the idea.)

 

Really, I would LOVE to have a variable displacement compressor to work with...Set up a controller to aim for temperature or pressure targets, and minimize the overshoot on the high-temp/low-temp. Maybe after I have a working and tested system. The other way to go is to use a variable expansion valve...which is where I'm starting. The variable valve's range is limited, however. Also, variable displacement compressors are generally more expensive and a bigger a pain in the ass to keep running correctly compared to the more reliable fixed displacement types.

 

These are physical laws. You have to be pretty sneaky to get them to bend on a shoestring budget. It's coming down to semantics as usual. An 'airflow increase' may be a goal, but if the airflow is now 15 F hotter than a lower flow with a lower temperature....is there and improvement

 

Again, you're missing a point...the condenser (Ideally) WON'T have to dissipate as much excess heat, because it won't be working as hard. An airflow increase WON'T be raising the temperature of the airflow through the condenser...think about it. One CFM of air through a given heat exchanger can carry away X amount of energy with Y temperature increase. Let the energy be fixed, and let two CFM's of air flow through the exchanger: The temperature of the air flowing through the heat exchanger will drop. More airflow, at the same energy, results in lower air temperatures through the exchanger. I won't say the temperature will half, because it won't...nothing is perfect, and I don't have enough data to figure out what percentage of half would occur.

 

So, let's combine those two thoughts:

 

Less head pressure means lower upper temperature: The condenser is cooler for the same volume of refrigerant being condensed; ideally we would only have to deal with the heat of evaporation, and no more.

 

More condenser capacity: the refrigerant is giving up the heat of evaporation to a larger volume of air, resulting in an overall lowering of air temperature through the condenser. This doesn't have to mean that we're not exchanging the same amount of energy!

 

Now, before you attempt to shoot down the "lower head pressure" argument (It's the weakest point I've made, so far)

 

In any heat exchange system like this, we want as much of the high pressure side to be the same pressure as we can get, and we want it to be no higher than we really need. If the compressor can flow more CFM than the condenser can, then the pressure in the segment from the compressor to the condenser is higher than the segment from the condenser to the orifice. We are wasting energy in compressing the working fluid to a higher pressure, and thus a higher temperature, just to ensure we have proper pressures present at the orifice.

 

If I get around to taking the hood back off the car (won't happen for a bit because I'm still doing bodywork on it for at least two more weeks) I'll try to show the difference in the two condensers a little better. I'm also going to be ducting them together, and sealing off the remaining holes in the core support to try and reap some aero benefit as well, and I think that having the radiator and condenser closer to the same size will help keep both heat exchange systems taking advantage of the ducting, instead of just one.

[Tony D]

Xnke, what you are missing in your assumptions is that a 'more efficient cooler' somehow will change the BTU's that need to be rejected. It won't.

And the compression required (lower head pressure or not) will still be the same.

 

It's why I said the work done is the same. I'm not going to get into polytropic head calculations, but you aren't changing anything, the cabin will still have X BTU's to remove, and the condenser will still have X BTU's to reject. If you have a bigger condenser, this doens't make that any different. You may be exchanging them quicker, but you still have to compress and cool again to remove it.

 

You are confusing excess capacity with efficiency.

 

You touched on the ONLY thing that would really make a difference: A Variable Displacement Compressor.

 

In fact, operating a compressor at the lowest possible head pressure CONTINUOUSLY is the most effective and efficient way to operate this system. The FO system would work, with the evaporator core temperature controlling a varialbe unloading piston (or various other capacity control scheme on the compressor) to keep it loaded 100% and ONLY compressing what it NEEDS to compress to accomplish the BTU rejection/adsorption in the system. In this case the accumulator would act to dampen transients. This is how larger industrial systems with complex PLC control schemes work. FAR more space required than available in the engine bay!

 

This is why I chose the Geo Metro Compressor---it would be operating near capacity all the time---it's the SMALLEST compressor that will accomplish the job. And THAT leads to EFFICIENCY.

 

Making cores flow better, increasing their heat rejection only allows them to be SMALLER to do the same job. If you OVERSIZE THEM then you loose that efficiency as you now have unrequired system volume, blah blah blah...

 

I just spent three days programming a system integrator that allows 3 500HP variable displacement compressors track a dynamic plant load---each compressor having approximately 35% turndown, and each compressor supposedly having a 50% total load capacity. System pressure was designed to be X kPa, and I successfully tuned the system to run a X-250kPa much to the System Engineer's Consternation. He too believed he needed large storage, but if the control system is good enough and can respond quickly there is no need for any overshoot, or undershoot, and reservior (accumulator) capacity just becomes a luxury. This setting saved this plan ungodly amounts of Kw. I do this stuff every day and have a pretty good handle on system dynamics. The exchangers don't change the BTU's in or rejected. And ultimately THAT determines comrpessor size.

 

IMO, with the compressor you have you are solidly in 1970's technology by oversizing the compressor by a factor of about 3X. This is terribly inefficient.

 

Exchanger modifications will allow you to exchange BTU's but the medium to exchange these BTUs must be compressed and expanded to do this function. You will overcompress, then depend on accumulator volume to dampen them. If you want EFFICIENCY, any engineer will tell you go with the SMALLEST possible compressor and ADD CAPTIVE VOLUME (capacitance).

 

The COMPRESSOR is the key to the efficiency equation. Anything else is window dressing, it is at the change-of-state portion of the equation, and this is a zero-sum game. BTU's in and BTU's out. The energy used comes from compression to ENABLE change of state. You need to get efficiency out of the compressor.

[Xnke]

Well, the compressor I have is what will get used, for now. It may last a long time, it may last six months; we'll see.

 

I am gonna hit the junkyard in a few weeks again; I'll take a look at any variable displacement compressors I find and see if anything would fit up nicely. Tony makes good points; but I still think I can get a measurable improvement with what I have now. Eventually the variable displacement/fixed orifice system will get switched out.

 

More emails back and forth from VA and myself; I'm looking into smaller compressors with the same footprint as my current SD-508. There are several, and I could trade for an SD-503 or SD-505, however I'd have to modify the clutch a little. VA thinks that going to a variable displacement system would be a bad idea; but then again they sell variable-orifice systems.