ABC's of 80's A/C and Cooling - Part 1

[SUMOTOY]

ABC's of 80's A/C and Cooling Part I (7/8) temp data

90 F ambient
94 FZJ80 supercharged
10in flat bladed pusher fan
A/C recently fully serviced, new expansion valve and dryer
Raytek 750F IR temp gun
stopwatch
For all tests climate control fan on low, fresh air intake only (no recirc), truck fully hot at idle. Hood closed other than to read underhood and sight glass temps

Ok laddies, a bunch of data I have to sort through, and pressures are the real test IMO (and a bit easier to observe and log) but some of the highlights

VENT TEMPS
Method: IR temp gun scanning for lowest possible reading on DS Vent.
Lowest temp reading: No Fan = 57.5F
Lowest temp reading: Aux Fan = 46.2F

Comments: Average temp differential as compressor cycled was ~12degrees F

CONDENSER TEMPS:
Method: IR Temp gun scanning sight glass area for lowest possible reading
Lowest Temp Reading: No Fan = 149
Lowest Temp Reading: Aux Fan = 135F
Comments: Tough to get consistent temps here, with compressor cycles and hood popping to measure. The Average temp differential was 10degrees. No fan resulted in highest temps 170F, With fan high temp was 155. I think the reason to use pressure guages is valid, because the pressure is more stable.

A/C on to A/C off - TIME TO 115F (relay - off)
With Aux Fan connected = ~2min
Without Aux Fan = ~2:30

Comments: I believe this to be a good indicator that the fan does good things, but airflow in the engine bay sucks. I confirmed this by taking readings of the air filter box. With Fan 194F, Without Fan 180F. More airflow through the radiator makes for good a/c performance, but not necessarily engine performance. I also note that my switch was +5-8 degrees in terms of accuracy (read: relay shutoff 115-123F)

CONCLUSIONS - TEMP BASED
A/C mod works at idle speeds. Expect a reduction in vent temps over time. I did notice that if I just hooked the aux fan back up while the A/C was on, the temps didn't come down. This makes me think that keeping that fan on while the A/C is on (not just compressor) is key to maximizing the effectiveness of the cooling mod.

I also believe that trapped air prevents this mod from becoming more effective. I saw some dramatic increases in underhood temps, so we really need to get that heat out of the hood. I suspect that a 12 in fan wouldn't have yielded any better numbers because of this. Some open hood data might help here too.

Without hood vents, I believe the aux fan works like a capacitor, it will increase the time to A/C heat soak, but elimination of it would require venting the increased underhood air. I also suspect those without superchargers should realize a better benefit than I did, since I have a convection oven right where I'm blowing hot air from my aux fan.

Other Misc data. Trans got hot, as in 200F hot, with very little exchange thru the cooler at idle (maybe 10 degrees). This adding some heat soak to the whole experiment.

Fan placement. I suspect that the aux fan is probably causing the engine fan to uncouple, a bit of a tradeoff, better condenser cooling with less radiator cooling. so I doubt any massive increase will be seen without a coolant controlled fan, another reason to go electric IMO. I measured temps in the engine fan thermostat of 211 degrees peak 200 average at idle. That seems high to me for a low load situation, and deserves more data collection. I'm convinced that the fan thermos are failing from high heat in the core.

That's about the jixt of it until I can put this thing on the guages.

HTH

Scott Justusson
QSHIPQ Performance Tuning
Chicago
94 FZJ80

 

[landtank]

It was on recirc with all the windows open and the front doors open as well..

I measured the vent temps with a digital thermometer held against the vents.

How much more accurate do you need?


I remembered tghe ambient temp wrong, it was 84*, editted above post.

 

[Tools R Us]

I got a couple of wireless weather stations with remote probes, playing with placement to temporarily install them on the truck to collect data. Yesterday I made a run to a foundry to deliver tools and recorded the highest temp so far, 128.2 measured with a probe on the left mirror in the shade! No wonder I was sweating loading those tools.

In heavy traffic on surface streets ~35 mph it read 116, at stoplights in full traffic (3 or 4 cars wide ~10 deep) it was 119. On the freeway in full traffic (4 to 6 lanes packed going ~65) it read 118. Back on the surface streets near the shop 114. I failed to bring the vent probe, the indoor module is on the console top in the shade and once it stabilized it stayed between 80-84 the whole trip with the A/C running full bore, auto, recirculate.

Today I made a little trip to the dentist, with the vent probe. I left at 10:30AM mostly highway with light traffic, outside 100-104, vent 52-49, cabin 82-77, the last mile was rural surface street, the fan dropped down a speed, but the clutch didn't cycle. On the way back, 1:00PM mostly light traffic, one short section of wall to wall 4 lane ~60mph traffic, outside 106-114, vent 52-56, cabin 82-84 and the A/C ran full bore.

The big thing that was reinforced was, what a big difference in microclimates there are in an urban environment.

My cooling system and A/C is stock, the only change is a blue hub with 40K on it.

 

[Cattledog]

I still see shared information as difficult to compare without complete data. Good start ST.

Humidity, atmospheric temperature, AC settings, AC system leaks/condition, radiator condition and modification, will all have and impact on the amount of energy the system can remove from the cabin. I am interested in humidity because the thermal conductivity of the air changes from 0 % humidity to 100%.

Testing on a rainy days could work well for consistancy. Without a standardized testing proceedure and calibrated equipment, information will be difficult to compare.

This is asking alot. But, I would like to see the pressure readings on the high and low side of the AC system, time to AC cycling, AC Settings(follow factory manual testing proceedure in test in the shade), relitive humidity, atmospheric temperature, and a consistent condensor temperature testing spot. Also including any information on the current state of the cooling system would be usesful. I.E. new/modified clutch, rad flush, welded shut coolant lines. Testing done before and after the addition of the aux fan. Then repeat the tests a couple of times. I know all of this is a pipe dream... I think sumotoy's post has most of that info.

If this mod works, the data will prove it quickly.

 

[SUMOTOY]

Baselines and comparos - Temps

I propose that we get some baseline established, so we can actually compare apples to apples.

For starters in terms of the Vent temps (Vt) everyone is looking for.
- 15minute full heat soaked engine and bay, A/C on during this
soak phase
- Cimate control on center vent
- Climate control fan position 1 (low)
- Climate control set at "Fresh Air" position (no recirc)
- Ambient temp recorded
- Truck at normal idle speed/s
- Truck parked in full sun
- A/C mods/service
- Fan/clutch replacement
- (Aux Fan size and placement and method of activation)

Then:
Best temp reading off of drivers side vent. I say 'best', because with my Raytek I got a few and chose the lowest recorded, and happy to compare the best anyone's probe can find.

Not sure we are ready to move on to cabin temps yet. When we are, a set placement of temp readings might be in order. I like back of rear headrest, since it's impossible to "optimize" airflow in the test.

Scott Justusson

 

[Cattledog]

- Truck parked in full sun

Prefer shade, The suns intensity can vary greatly from location (AZ vs VT) and time of day (8 am vs 2 pm). Interior color could also effect the cabin temp in direct sunlight. My guess is being in the shade is the same everywhere regardless of the interior color.

 

[SUMOTOY]

I still see shared information as difficult to compare without complete data. Good start ST.

Humidity, atmospheric temperature, AC settings, AC system leaks/condition, radiator condition and modification, will all have and impact on the amount of energy the system can remove from the cabin. I am interested in humidity because the thermal conductivity of the air changes from 0 % humidity to 100%.

Testing on a rainy days could work well for consistancy. Without a standardized testing proceedure and calibrated equipment, information will be difficult to compare.

This is asking alot. But, I would like to see the pressure readings on the high and low side of the AC system, time to AC cycling, AC Settings(follow factory manual testing proceedure in test in the shade), relitive humidity, atmospheric temperature, and a consistent condensor temperature testing spot. Also including any information on the current state of the cooling system would be usesful. I.E. new/modified clutch, rad flush, welded shut coolant lines. Testing done before and after the addition of the aux fan. Then repeat the tests a couple of times. I know all of this is a pipe dream... I think sumotoy's post has most of that info.

If this mod works, the data will prove it quickly.

Good luck sir. I'd like to 'just' do pressure tests, cuz I can table what the temps are, and my temps were much tougher to isolate and repeat (BTW, I did 10-12 repeats of each cycle - that took a couple hours easy). But very few have pressure measure ability - even a shop guy when it's summer season... Remember too, condenser temp isn't really a valid comparo, you are really looking for temp at the pressure switch or sight glass, since that's what the FSM considers the high pressure measure. That measure also accounts for radiator efficiency, backpressure (remember I'm shroudless and clipped on the engine fan), trans cooler heat soak, the sum of which goes by the high pressure switch and sight glass...

Remember too CD, temps are valid, you just have to define them clearly, they give you the pressure. Humidity is a variable, but on a fresh system, it's a negligible one, it's no different in my mind to air or moisture content in an older serviced truck. Find your lowest Vent temp (Vt) or find your lowest high pressure side temp (HPt), it'll be tough to fudge either one if you have the baseline defined.

I had extensive training in TQM, testing and quality controls in my former plastics blow molding life. CD, this is a crude test, but we have a couple of FSM targetted temps and pressures that should give us some freedom to have less than optimal methodology and conditions.

After a lot of running around in 90 degree heat today with my aux fan spinning away, my subjective eval is that this is a great mod for city driving. My truck was downright COLD today, and it didn't matter if I was stopped at a light or lugging around at 20mph. I left the fan on low, the CC on fresh air, and it was downright chilly.

What might be something better to consider is a stop and go test. The before and after aux fan appears to be much more dramatic. Again, I see that aux fan as a capacitor, it puts the condensor at optimal temps at low speeds, then stopped, it gives a pretty long reserve of low pressure (temps) of the condenser. Really makes me think hard about those hood vents, but I'd like to get more data first.

I might also like to point out on the Spal site I posted to TRU, their comment about 35mph being the point at which a fan becomes less efficient to ram air. I have some Range Rover documentation that's at 45mph for their boxes. But that becomes a significant piece of information when we think about 'bigger', our tight fan shrouds (er, not me I gots none), and hot high speed runs. Could we have a fan actually hindering proper cooling? Given my 24 foot camping trailer experience in 100 degree heat, I sure think so...

Lots of food for thought. All numbers and comments welcome. I'm keeping my aux fan, it appears to work, exactly where I need it to most.

Cheers

Scott Justusson
94 FZJ80 Supercharged and aux fanned
Chicago

 

[SUMOTOY]

Prefer shade, The suns intensity can vary greatly from location (AZ vs VT) and time of day (8 am vs 2 pm). Interior color could also effect the cabin temp in direct sunlight. My guess is being in the shade is the same everywhere regardless of the interior color.

Vent temp (Vt) is not Cabin temp (Ct) - yet. I don't think you could put the cabin temp variable matrix together on a supercray. Regarding sun, I like the ability to keep everything as hot as possible at idle, but 90 in the sun or 90 in the shade could be a notation. Remember no recirc, you are taking hot air from in front of the windshield.

Then again, I burnt the back of my neck this morning, so maybe everything just feels cooler...

SJ

 

[97 FZJ80]

Relative humidity is also a major factor in determining vent temperature. The same AC system performing in different RH environments, a higher RH would result in a lower VT.

 

[SUMOTOY]

Relative humidity is also a major factor in determining vent temperature. The same AC system performing in different RH environments, a higher RH would result in a lower VT.

Maybe. A data point to consider. I figure at the temperature differentials we are speaking of, it's not going to be enough of a variable to be a 'factor'. And in fact, higher humidity will cause the thermister to cycle more, most likely negating that 'efficiency'. Spraying water or methanol on the condenser? Ok that's cheating... Again, I'm looking at all ways anyone could stack the deck, just give the lowest vent temp. If I was living where it was dry, and wanted to tilt the deck in my favor (RH equivelency factor), I'd use IDougs excellent suggestion to soak the crap out of the radiator and condenser with simple green. Optimize the heat exchangers.

Cleaning out the fins of the under dash heat exchanger with a toothbrush also helps. Mine was full of small leaves and dog hair from the PO.

Again, we need numbers. We can do a lot of 'splainin after we have them.

Scott Justusson

 

[Dusty]

I did notice that if I just hooked the aux fan back up while the A/C was on, the temps didn't come down. This makes me think that keeping that fan on while the A/C is on (not just compressor) is key to maximizing the effectiveness of the cooling mod.

Scott I need you to clarify. so are you saying that the condensor fan mod test shows that the fan does not lower vent temps if the fan is turned on after the ac has been running? if that be true I cant see how your results can be valid because if you repeated the tests multiple times you would have been turning the fan on and off. So...if what you said above is true the vent temps would not fall when you turned the fan back on after being off. Perhaps I'm not getting something. could you clarify.

 

[SUMOTOY]

Scott I need you to clarify. so are you saying that the condensor fan mod test shows that the fan does not lower vent temps if the fan is turned on after the ac has been running? if that be true I cant see how your results can be valid because if you repeated the tests multiple times you would have been turning the fan on and off. So...if what you said above is true the vent temps would not fall when you turned the fan back on after being off. Perhaps I'm not getting something. could you clarify.

I did the test two ways. I left the truck running without the fan + A/C, and then just hook the fan back up + A/C. Read: I didn't allow the condenser to return to 115F. When I did that, I got a very slow (if any) reduction in Condenser temps (measured at the sight glass). My goal in doing this was to present a difference between wiring with A/C on vs wiring with Compressor. I believe if I waited forever or longer it would have dropped the temps.

However, when I returned the condenser to 115 between each test, I found the temp rose and stabilized per my report. Again, thinking of the fan mod as a capacitor, I would expect this behavior in the measures. Once the A/C condenser is hot, the added fan cooling was slower than my patience.

HTH

Scott Justusson

 

[Tools R Us]

I did the test two ways. I left the truck running without the fan + A/C, and then just hook the fan back up + A/C. Read: I didn't allow the condenser to return to 115F. When I did that, I got a very slow (if any) reduction in Condenser temps (measured at the sight glass). My goal in doing this was to present a difference between wiring with A/C on vs wiring with Compressor. I believe if I waited forever or longer it would have dropped the temps.

However, when I returned the condenser to 115 between each test, I found the temp rose and stabilized per my report. Again, thinking of the fan mod as a capacitor, I would expect this behavior in the measures. Once the A/C condenser is hot, the added fan cooling was slower than my patience.

HTH

Scott Justusson

Your slow temp response can probably be traced to two things. First by not running a fan shroud, your not getting, even, strong airflow through the condenser and your data doesn't apply to most of us that have them. Second the small fan is only cooling a spot on the condenser, it's like the difference between holding an ice cube against it or hitting the whole surface with the water hose.

IIRC the condenser has ~550 inches of line in it. The heat transfer takes place overtime as the fluid flows through the cooled line. Any part of the condenser that isn't getting good airflow, the line in that area isn't cooling and acts like any other line in the truck, effectively making the condenser smaller. A larger diameter fan spreads the cooling over much more line greatly enhancing the cooling efficiency. On Rob's truck with the 14" fan, the difference is quickly noticeable in gauge reading and vent temp when the fan is switched on and off.

 

[re_guderian]

Just doing some rough calcs on area's of coverage by the fans (assuming a 5" motor diameter for both), gives the 14" fan >2x the area of coverage with airflow.

 

[SUMOTOY]

Your slow temp response can probably be traced to two things. First by not running a fan shroud, your not getting, even, strong airflow through the condenser and your data doesn't apply to most of us that have them. Second the small fan is only cooling a spot on the condenser, it's like the difference between holding an ice cube against it or hitting the whole surface with the water hose.

Could be a fan shroud problem, could be the massively clipped blades on my fan I noted, could be the plethora of clipped and welded radiator cores too. The main reason I just ditched waiting for it, didn't care for the purposes of my data. The 'constant' was only condenser temp start point in each test of 115degrees. Could be that once the condenser is soaked, it needs some massive heat exchange because of a wide variety of variables. Regarding fan size, it really depends. The picture you attached has a curved blade design. That means it's less efficient all else being equal.

IIRC the condenser has ~550 inches of line in it. The heat transfer takes place overtime as the fluid flows through the cooled line. Any part of the condenser that isn't getting good airflow, the line in that area isn't cooling and acts like any other line in the truck, effectively making the condenser smaller. A larger diameter fan spreads the cooling over much more line greatly enhancing the cooling efficiency. On Rob's truck with the 14" fan, the difference is quickly noticeable in gauge reading and vent temp when the fan is switched on and off.

I don't believe that's well stated, and not true as stated. I think a better summary would be an aux fan has the potential to make an effectively larger condenser.

Example: A 10 in fan on a 550in condenser makes it effectively a 600in line condenser, and a 14 inch fan makes it effectively a 640in line condenser

(Actually we should be using an area comparison - but temps and pressures would suffice). I say "potential' because higher pressure thru the radiator means higher pressure behind the radiator. In my experience you have a tough time realizing that potential without a corresponding drop in downstream radiator pressure (Ram Air theory has two pressure zones: High Pressure Zone - in front of condenser and Low Pressure Zone - engine bay). The higher the pressure differential ratio the more effective the airflow, the more heat exchange all else being equal. (Read: Hood Vents)

I'm only giving my data as the fan is installed in my truck. No shroud, and clipped engine fan blades, and clipped radiator core, and is part of that data. I look at it this way, if I can see improvement with the subpar low speed cooling system in my truck, with a handy 10 in flat blade fan, those with anything better, get *more*. I also know after 40mph, I have more flow thru my condenser and radiator than those running 'better' low speed systems.

Hence my propensity to go after electric fans 1 in front for the condenser, 2 behind the radiator for the radiator. When they aren't needed for low speed cooling, they aren't hindering airflow either. Then to realize all that extra cooling potential, reduce the low pressuere zone (Pl) in my ram air system.

Right now, the 10in fan makes a measureable difference in my truck. Better or worse than any other? Don't know, haven't seen that data yet. If your friend put a flat blade 14in fan on the front of his truck, he would increase his fan efficiency. Might help, might not.

Scott Justusson

 

[Tools R Us]

...If your friend put a flat blade 14in fan on the front of his truck, he would increase his fan efficiency. Might help, might not.

Scott Justusson

I will get right on that, maybe Derale will send him just the blade so he doesn't have to buy a whole fan? Let's see I will tell him, Scott said if you buy a 1100 cfm fan that pulls more amps to replace your perfectly good 1350 cfm fan it will increase your efficiency? Now my brother isn't the sharpest crayon when it comes to car work, but somehow I don't think that will fly with even him? He also doesn't like doing car work for the fun of it, his cooling system works well, so we can probably talk him into a clutch valve tweak and adding a bit of thicker fluid to increase it's performance. But changing a fan for the fun of it when he has axle kits, 4.88 gears and a winch sitting here and a rear bumper on order needing to be installed isn't going to happen, he will have to suffer with the non Scott approved fan.

 

[cary]

I probably shouldn't open my mouth, but theory or not, I am guessing that Tools R' Us living in Chandler Arizona (where today it is 115F) probably has a clue on what actually works and doesn't work for keeping cars from overheating.

Personally, I think in a climate like his, a pusher fan is a great idea, here it is 107F right now and even with a new radiator and new fan clutch, I am seeing temps in bumper-bumper traffic of 210f. It is clear if there is any issue with the stock LC system it is airflow at idle and low speed.

 

[landtank]

All I want to know is....who gave this bickering, argumentative thread a 5 star rating?

 

[SUMOTOY]

Ram Air

Kevin:
As is the way with 'forums', lacking technical information and getting corrected on mindsets tends to result in rather unnecessary posts of personal nature. There is no question you have a mindset on this issue, and several others, not sure why. I have a lot of questions, and a lot of documentation, and a lot of data from my business of building high performance automobiles for street and track. I don't ram it, I am happy to share it.

I can use this experience to look at an 80 and see several areas where it lacks documented improved engineering design. I can present data supporting using the smallest pusher fan to accomplish the task of what I considered minimal additional cooling necessary AT the condenser.

Part of that documentation would include that larger pusher fans can be more efficient at low speeds. However, part of that documentaion also advises that too big a pusher fan can also decrease high speed airflow through the condenser and radiator core. Knowing that, I chose to mount my 10in fan as low as possible, much of it out of direct airflow (over half of it is below my TJM). I also am quite pleased that my fan appeared to provide the extra 'capacitor' effect on my condenser temps. I have no interest in cooling my radiator with it, since pusher fans are usually 20%+ less efficient that puller type fans.

Bigger is better is something I never subscribe to. I subscribe to measures, temps and reviewing documentation. SAE has done a lot of work on radiator efficiency, airflow, and electric fans. There are several accepted knowns in theory and design that prevent me from accepting many of the bigger is better, and existing design arguments I find on this forum.

I thoroughly enjoy tweeking with my automotive toys to make them better, using my paid job experience to help me address these tweeks. In Heat Management, I am very well versed and seasoned. I'm no expert, I AM a performance guy in evaluating claims and engineering to automobiles.

I am also quite used to mindsets. It's part of taking the 'bull' by the horns, and systematically breaking down misconceptions and quantifying claims in comparable terms. And I thoroughly enjoy getting tweeked for being a technonerd, because I can laugh at myself and the tweek quite easily. I'm a ex rallyist, ex showroom stock driver, autocrosser, rallycrosser, Steamboat Ice track eventmaster, marque driving instructor, and avid offroader. So, I don't sit behind my desk or put things together without testing. Please don't let me frustrate you Kevin, I'm after something good for our trucks. And since Toyotas aren't my business, I can share my information, education and practical engineering without worrying about who bought and paid for it.

I have a propensity to work with those that have little patience and make blanket statements quite contrary to accepted theory and practice. That would include you Kevin, and I don't judge you for it. I only ask that you present data or facts to bust my chops, because the cynical part really detracts from acquiring good data and evaluation. I like to get baselines on operation, need and possible solutions.

I'd also be happy to take any discussion off line for those less high profile, and have already. And Kevin, you can also take this off line at any time. I don't need to save face, and I'm on a task with a LOT of information and BTDT experience.

Peace Kevin, please feel no obligation to delete your last post.

Scott Justusson

 

[SUMOTOY]

Aux Fan Wiring Options

Several folks have installed aux fans in front of the radiator. Those that have, please post the method of activation relay location, etc. Dan are you manual activation only?

Scott Justusson