AC install

[wwest]

Originally Posted by kuehl

Actually it was Dr. Weston (Newark, NJ) whom developed the light bulb and it was Edison whom had the saavy PR. Then again Edison spent years infatuated with the plant life of Ft. Meyers for a filament while Weston solved the problem.

Good to know...


No thinking about it. This forum is about air cooled cars with limited front end room for naturally forced air or fan assisted condensers. And, fans running after the engine is turned off on a 996/997 or other "marque"

were not intended to reduce a/c system pressures.

And you can be sure of that, how? Technical white paper, read the minds of design engineers? Since most cars use Stacked condensor/radiator assemblies the need to cool one results in cooling the other, plus alleviating the radient heating effects on the condensor from the NEARBY radiator.

The refrigerant return line in my '92 LS400 ran across the front of the frame at the bottom of the radiator and would often have 1/8 to 1/4 inch of rhime ice after a long drive due to the upstream actions of the EPR. My '95 has that return line routed across the fire wall behind the engine and with the EPR downstream near the driver's side fender well.

Why the change...? Find ANYTHING published by Toyota or Lexus to explain...NO.

But with a mear pitance of A/C knowledge one can easily deduce that the early design could quite possibly be prone to compressor slugging and subsequent failure. Whereas the later design uses, quite obviously, the engine/exhaust heat to complete the conversion of liquid refrigerant to a gaseous state prior to reaching the EPR.

Marques? Is this a Hemmings publication?

The rate of loss is relative to the amount of surface area. 911's have more a/c surface area because of the larger volume of hose; hence barrier hose reduces the permeation rate.

But again, you are avoiding the actual question. By your own statements Porsche's have 4 times as much permeable non-barrier hose area as do most cars of the same era. Shouldn't that mean, assuming non-barrier hoses were/are the problem just as you surmise, an 8 year leak/refill cycle for all those other marques?

1) The low and high a/c side system pressures equalize to the static level, rather quickly.

But again, not so "quickly" should the evaporator already be at 32F and with the TXV fully closed.

If you doubt that connect a service gauge set and watch.

I did exactly that. Well, not exactly, I only monitored low side pressure. A search will find my statements of the time but I do remember that it was easily long enough for the heat rising from a HOT engine to have an effect.

The high side will drop from 350 down to the relative static psi based on the ambient temperature (refer to a refrigerant chart) and the low side rises to the same.

But, yet again, not if the TXV just happens to be closed at the time...unless the compressor valves are faulty and allow reverse flow.

2) Amazingly the engine's heat dissipated up through the condenser does not raise the system pressures.

Then why is it that YOU insist that the engine lid be closed during maintenance procedures or tests of this type. If, with no engine fan to force flow through the rear lid condensor, the atmosphere itself would result in an inordinate rise in system pressures, why not?

If you feel strongly about your hypothesis you have been tossing in every a/c related thread here in the forums then maybe you can take the conjecture to a higher level (no pun) and present a video for us.

I have an inate faith in the knowledge and intelligence of our audience to know which statements are based on truth, logic, or experience. Since you seem to be the only one making illogical statesments may I suggest you run the trial.

No. The pressure does not rise. We have been working on 911's a/c systems since 1984. We use 3 different designs of service gauges, 3 different manufacturer's. Some of analog and some are digital, one has recording. They gauges don't lie.

The result is always the same: turn off the a/c and the high side drops and low side rises and typically with 15 minutes or so both pressures are at a static psi relative to the type of refrigerant and the outside ambient temperature; look at a refrigerant pressure chart.

Simple test for you. Attach the guages, close the lid, run the car on a dyno long enough that the oil cooling valve opens fully. Turn the A/C on, but with the evaporator[ blower fuse removed. Now, when the compressor first cycles off due to the evaporator thermostat at full tilt (no fair using the high pressure compressor cutoff switch) simply switch the engine off.

You can think and conjecture what ever you wish however facts are facts.
Once again. Make us video of your rising pressure concept.

Logic indicates a video is only needed for non-logically thinking naysayers and I would need certification to a serious level of the video to convince them/you. On the other hand if YOU produced the video....??

[SilberUrS6]

Originally Posted by kuehl

You can think and conjecture what ever you wish however facts are facts.
Once again. Make us video of your rising pressure concept.

Griff, you can never reason with an inductive thinker. He already has the answer - he will search around for data to support his conclusion, and ignore data that does not fit the conclusion. Science and scientific thinking is anathema to his sort. No matter how many times you present facts, he will ignore the ones that don't fit the "proper" conclusion. Like the incorrect calculation he makes on hose length. Hose length is a linear function. But working fluid loss from a non-barrier hose depends on surface area - a squared function of length. This is a fundamental mistake he makes every time the subject comes up. That and the very logical mistake of no looking at solutions adapted by the community: if additional condenser fans actually worked, people wouldn't go to the huge amount of trouble to improve system components. Let's not even discuss the expense - compared to the time and effort required to install system components like barrier hose, the expense is almost (!) trivial.

[SilberUrS6]

Originally Posted by wwest

I have an inate faith in the knowledge and intelligence of our audience to know which statements are based on truth, logic, or experience. Since you seem to be the only one making illogical statesments may I suggest you run the trial.

LOL, the irony is astounding.

[wwest]

Kuehl, question and answer time.

Truth or not?

1. When the engine is shut down the refrigerant compression stops as does airflow cooling of the rear lid condensor.

2. When the engine is shut down the high side pressure might be at a maximum, (350PSI according to you).

3. When the engine is shut down, ignition switch completely off, the evaporator might be at 32F with the TXV fully closed.

4. When the engine is shut down it might be fully heated due to the OAT and a period of HARD running.

5. In the above case, 4, the resulting convection and radient heat flow from a HOT engine would result in the average, high/low side equalized, refrigerant pressure rise.

[wwest]

Originally Posted by SilberUrS6

Griff, you can never reason with an inductive thinker. He already has the answer - he will search around for data to support his conclusion,

and ignore data that does not fit the conclusion.

Have any of us seen any "data" coming from Kuehl. Only statements based on his never having seen it happen therefore it doesn't happen.

Science and scientific thinking is anathema to his sort.

(***1)The last I knew "science" would indicate that when heat is applied to a liquid it will increase in volume, or in the alternative, pressure will rise, should the container be restrictive. If enough heat is applied the liquid state will convert to gaseous thereby resulting in a much greater rise in pressure, again, assuming a restrictive "container".

Anyone wish to step up and dispute that statement?

No matter how many times you present facts,

Kuehl, by his own admission, is open to FACTS to prove his lack of knowledge or experience in the specific area of discussion. Kuehl admits that he has no FACTUAL data nor any experience that proves or disproves my statements that under certain conditions, commonly encountered conditions, the high side pressure will rise above the system design limits.

he will ignore the ones that don't fit the "proper" conclusion. Like the incorrect calculation he makes on hose length.

Hose length is a linear function. But working fluid loss from a non-barrier hose depends on surface area - a squared function of length.

Okay, so both Kuehl and I improperly used length. But the base foundation holds, why aren't water cooled engined cars of the same era plagued with A/C refrigerant leakage. I just sold our '92 LS400 and the one and only time the A/C was serviced was to convert it to R134a. Our '95 LS400, 270K miles, has NEVER had the A/C serviced.

This is a fundamental mistake he makes every time the subject comes up.

Where, what, do you find as a fundamental mistake in the fourth paragraph (***1) above, on which my entire conjecture is based?

That and the very logical mistake of no looking at solutions adapted by the community:

Your statement here is just plain completely wrong, on more than one occassion I have given credit where credit is due, Kuehl will bare me out on this one. What I have questioned is the relative value, $$ wise, of "other" solutions

if additional condenser fans actually worked,

A search, easily done for anyone wishing the TRUTH, would discover a few instances wherein the additional rear lid cooling fan(s) do work. Porsche itself, with the front condensor fan, is a perfect example. Also, haven't I seen other posts wherein additional or improved fans were used at the front?

people wouldn't go to the huge amount of trouble to improve system components.

Maybe you need to look into this "huge amount of trouble" in a historical sense. Look, again, at the technological level of the blower/fan Porsche used for the front condensor. When was it that these modern day radiator cooling fans became readily available in the marketplace and cost effectively so. I suspect, strongly so, that had these technology advanced fans been available at the time, mid-seventies, say, Porsche would have used them for additional cooling of the rear lid condensor instead of the horribly inefficient front condensor/fan combination


Let's not even discuss the expense

Sure, let's IGNORE the 900 lb elephant...!!

- compared to the time and effort required to install system components like barrier hose, the expense is almost (!) trivial.

So, who is it that still states, with reasonable crediabilty, that replacing those supposedly non-barrier hoses is still thought to be required. Might have a simple binary compressor control switch plus an after-run rear lid condensor cooling fan using a trinary switch have done the trick? Or maybe even an after-run period for the front condensor cooling fan based on a trinary switch?

....

[Arne2]

As someone who has no dog in the hunt (I don't really need A/C in Western Oregon), can I make a suggestion that might help keep every A/C related thread on Pelican from going rogue?

wwest - perhaps you should create a blog or personal web page somewhere to itemize in detail your thoughts, opinions and position on this topic, with whatever documentation you feel is necessary. Then all you'd need to do is post a link to that page in any thread where you felt it was appropriate. Maybe that could end all the back and forth arguments in all these threads. After all, Griff has is commercial webpage to make his views known, so perhaps you need to find someplace of your own, rather than cluttering every single A/C thread here.

Just a thought...

[wwest]

Originally Posted by Arne2

As someone who has no dog in the hunt (I don't really need A/C in Western Oregon), can I make a suggestion that might help keep every A/C related thread on Pelican from going rogue?

wwest - perhaps you should create a blog or personal web page somewhere to itemize in detail your thoughts, opinions and position on this topic,

with whatever documentation you feel is necessary.

I will readity admit that I would much rather rely on the common sense, "Horse Sense" as my mother would say, of the reader to separate fact from fiction. A lot more fun, also.

Then all you'd need to do is post a link to that page in any thread where you felt it was appropriate. Maybe that could end all the back and forth arguments in all these threads. After all, Griff has is commercial webpage to make his views known, so perhaps you need to find someplace of your own, rather than cluttering every single A/C thread here.

Just a thought...

The problem is that the to and fro of "these" discussions are much more educational overall in my opinion than would be a "white paper" from either Kuehl or myself.

Right or wrong, EVERYONE gets to step in and express an opinion or theory.

"Crowd" intelligence and/or experience can be a real asset.

[wwest]

Puzzling..

Since everyone seems to acknowledge that a blower fan moving airflow over a condensor, or an oil cooler, in a wheelwell, mostly "hidden" from natural airflow, is helpful it makes it rather hard to see the naysayer arguments against a fan moving more airflow over the rear lid condensor as valid.

[kuehl]

2) Amazingly the engine's heat dissipated up through the condenser does not raise the system pressures. Then why is it that YOU insist that the engine lid be closed during maintenance procedures or tests of this type. If, with no engine fan to force flow through the rear lid condensor, the atmosphere itself would result in an inordinate rise in system pressures, why not?

I don't "insist". The 911 rear deck lid condenser is designed to have air moving through it, pulled from the engine cooling fan. If you want to 'test' the system you have to do so with the engine deck lid down gently resting on the ac services hoses.

Originally Posted by wwest

Kuehl, question and answer time.

Truth or not?

1. When the engine is shut down the refrigerant compression stops as does airflow cooling of the rear lid condensor.

2. When the engine is shut down the high side pressure might be at a maximum, (350PSI according to you).

3. When the engine is shut down, ignition switch completely off, the evaporator might be at 32F with the TXV fully closed.

4. When the engine is shut down it might be fully heated due to the OAT and a period of HARD running.

5. In the above case, 4, the resulting convection and radiant t heat flow from a HOT engine would result in the average, high/low side equalized, refrigerant pressure rise.

1. Partially True. Convection from rising heat from engine pulls air from underside head cooling fins up through deck lid..... but that does not raise a/c pressures.
2. Maybe. It could be anywhere, on the average, depending upon the ambient temperature, from 180-350 psi. Not according to me, according to the way it is. ... lol.
3. Not true. As soon as you turn off the compressor the evap coil temp rises
simply do to the nature of physics of molecules in our world... hot always moves to cold. Since there is a great mass of hotter molecules surrounding the coil the coil absorbs the heat and its mass temp rises. And by the way, the TEV/TXV never closes all the way. You cant test that for yourself if you wish.
4. Has nothing to do with the fact of how the ac system operates or why your system on your car leaks.
5. Not true. When the a/c system shuts down (the compressor stops pumping) the low side and high side equalize because of the TEV ... the liquid refrigerant moves through the TEV and expands into the low side.

DECK LID CONDENSER COOLING FANS?

The Engine’s Cooling Fan
The rear deck lid condenser removes heat absorbed by the refrigerant (in the evaporator process) via the engine cooling fan.
The 911 engine’s cooling fan pulls an average of 1335 liters per second at 6100 rpms. Actual volume varies depending upon the year; there are many quotes and charts. So lets keep it simple and say 1335 ls is fair.

Since most comparisons in air movement with fans are in CFM lets do the conversion:
(1335 per second) X (60 seconds in a minute) = 80,100 liters per minute.
Then convert the liters to cubic feet, (80,100) x (0.03531467) = 2828 cubic feet per minute. So the average 911 engines cooling fan has the propensity to move 2828 cfm at 6100 rpms.
Assuming this is linear we can further say:
0 rpm = 0 cfm
1525 rpm = 707 cfm
3050 rpm = 1414 cfm
6100 rpm = 2828 cfm
or simply 46 cfm per rpm
And let's assume at idle of 850 rpm, the cfm is equal to 391 cfm (850 x .46).


What Could You Put Under the Deck Lid Condenser
The typical 911 condenser is 9"x27.5" of effective area, or 247.5" sq in.
Ideally the largest diameter pancake electric motor puller fan you can mount under the condenser is a 9" nominal. The inexpensive red colored fans posted in the thread boast a CFM of 1730 (we will assume at 0 static pressure) and consume 12 amps each? I’m going to shoot from the hip here and I will say BS. After testing dozens cheap and inexpensive fans over the years, and knowing that many Ebay seller’s claims or test data can inaccurate (for many reasons), I would want to ‘see this for myself’ as they say. So lets take a reputable fan company such as Spal and exam their PN 30100442; a 9" puller that moves 649 cfm at 0 static and draws a 6.1 amps at 13 volts. under 0 static pressure. So at “idle”, you could have an electric cooling fan pulling 60% (engine fan 391 cfm/ electric fan 649 cfm) more air !

How Effective Could Electric Fans Be?
Any given fan never pulls across the entire deck lid condenser. Effectively 1 fan does not pull a 9" of diameter, or 63.6 sq in, across the surface because the fan’s motor area is typically 4.375", or 15 sq in (no fan blades), so the effective surface the fan works on the condenser is 48.6 sq. in each. Let's multiply that by 2 fans for 97" nominal sq in of working area, or 39% of the condenser area. At idle, if you have a 60% increase in air volume working on only 39% of the condenser area, the net effect might be .... .60 X .39 = 23% in total improvement for that condenser... at idle. And then you have to wonder if the engine’s cooling fan will allow that 23% increase in air move through it? Well all calculations thus far have been with a foundation of 0 static pressure. So we will have to think about it. And, in the world of AC, a 23% increase in air flow, at 0 static, usually does not mean your vent temps will drop by 23%... that is another set of equations.

At Idle
“At Idle”. For some drivers, ‘at idle’, might mean sitting in the car after a long day of work, waiting and hoping the vent temps will get cool quickly. “At idle” could also mean coming to traffic light or a stop sign. So how may driving hours do you do in a given day? How many minutes of your average trip or joy ride are really at idle? That varies for most however lets assume you are taking a 60 minute drive. Is 10 minutes fair to say? I’d say on the extreme maybe “yes”. So if you want a possible 23% increase at best in rear deck lid condenser cooling performance, at idle, maybe you might try to Spal Fans. But then again... read on.

Above Idle, The Real Ride Losses
Above idle... what most of us spend doing, say driving around town between 25-40 mph, what are our engine RPMS’? For me it is usually above 2000 rpms for sure. Looking back at our estimate of engine cooling fan speed cfm’s we calculated that then engine cooling fan is likely moving .46 cfm for each rpm. So 2000 x .46 = 920 cfm moving through the engine deck lid without add on electric cooling fans. The add on electric cooling fans, at best, could move 649 cfm. That is less than the engine’s cooling fans! So what happens? Dam it!
That’s right, Dam It happens. Those electric cooling fans are now blocking or damming the work of the engine's cooling fan. Not by 100% though, but enough to cause a reduction of air pulled in by engine cooling fan. How much? We know the 2 electric cooling motor housings total 15 sq. in. . The 2 sets of motor blades account for an approximate 45 sq in. So in total 15+45 = 60 square inches of direct blow through blockage potential. The deck lid condenser is 247 square inches. 247-60 = 187". So there is a loss of 24% of your deck lid condenser working area, (187 / 247 = .757) = 24%, when you attach two 9"fans ...when ever your engine rpms are above ? .... 649 cfm/.49 = 1324 rpms !

The Choice is Always Yours!
A) Do not add cooling fans to the deck lid condenser, and simply realize that an increase in engine rpms above idle allows the engine cooling fan to pull more air through the condenser, as well the compressor pushes more refrigerant through the system.
B) Add cooling fans to the deck lid condenser, and when ever you take a drive, your deck lid condenser will be working 24% less efficient for most of your driving time.
C) Add cooling fans to the deck lid condenser, and just sit in your car, in your driveway,
and keep the idle below 1324 rpms, realizing that you at least accomplished something for the moment.

And, as always, everyone, including Wwest, are welcome to comment on the simple math, or provide their own math equations, estimates, data, or whatever floats your boat.



Johann.. sorry i got carried away from your thread's question, however I'd prefer the readers have facts rather than fiction to read here.

[SilberUrS6]

Originally Posted by wwest

Puzzling..

Since everyone seems to acknowledge that a blower fan moving airflow over a condensor, or an oil cooler, in a wheelwell, mostly "hidden" from natural airflow, is helpful it makes it rather hard to see the naysayer arguments against a fan moving more airflow over the rear lid condensor as valid.

LOGIC FAIL.

The system, as stock from PAG, is acknowledged by most folks as barely adequate. Having experienced a stock system in E. WA during the summer, I can tell you that "barely adequate" on a 105-degree summer day in a black, heat-soaked interior would be a euphemism for "not in any way adequate". Yes, 70-degree air will come out of the vents, eventually. And a delta of 35 degrees from ambient isn't too bad. But it doesn't keep up with the IR input from all the greenhouse:interior volume ratio. Now, having laid that groundwork, moving air over the condensors is great. Moving more air over more condenser area is even better. But *even at 60mph for extended time*, the stock system has trouble keeping up with cooling requirements in 105-degree OAT conditions. In this situation, your idea of decklid fans has no bearing - the engine fan is moving more air than your fans can. In fact, your decklid fans might be cause air restriction at that point. Not good for my motor, never mind my AC. The front condenser is getting about as good airflow as it's going to get.

So, what will help here? Not your decklid fans. The plain fact is that system capacity for cooling the interior volume of the car is maxed out. Improving the condensing and evaporator capacity can help. Now, here's where you normally change the subject to stop-and-go traffic. And for a Seattle summer (I am a West Side native - grew up in the Skagit Valley), in stop and go traffic, a 35-degree delta might be just fine to cool the interior of the car. After all, summer temps rarely get above 85 degrees in the Puget Sound region. Yes, they do climb higher, but that's not a regular occurance. Just like I've seen 105+ degrees over here. More often, we're in the 95-100 region in July and August.

Airflow over the condensing surfaces is ONE aspect of evaluating the system. Yes, everyone who has two brain cells to rub together agrees with that. But you treat it as though it is the only thing that matters, and ignore everything else. From the evaluation of the availble data, it is my belief that cabin airflow and evaporator capacity are the limiting factors in creating a large temp delta between the interior and exterior of the car.

[SilberUrS6]

Originally Posted by wwest

The problem is that the to and fro of "these" discussions are much more educational overall in my opinion than would be a "white paper" from either Kuehl or myself.

"Educational", yes. In a way that clarifies the AC situation in aircooled Porsche automobiles?

Hardly. Assertions from emotion (horse sense) are not substitutes for facts. Facts trump any amount of "common sense", because so often "common sense" is really code words for "cultural myth". Assemble facts. Come to conclusion. (P.S. don't exclude any facts from your conclusions, and don't include "wrong facts" to support your conclusion.)

[wwest]

Originally Posted by kuehl

1. True.

2. Maybe. It could be anywhere, on the average, depending upon the ambient temperature, from 180-350 psi. Not according to me, according to the way it is. ... lol.

Since the question was "might be" I'll take your answer as "TRUE".

3. Not true. As soon as you turn off the compressor the evap coil temp begins to rise, rises
simply do to the nature of physics of molecules in our world... hot always moves to cold.

A few minutes ago I opened the door to the freezer compartment of my frig, how long might you think it will take for the freezer compartment's atmospheric and "radient" temperature to rise even 5 degrees with the open door but no forced air movement? With the A/C evaporator and surrround, already chilled to freezing and no source of air flow my bet is that it would take longer to get that 5 degree rise vs my frig. And then there are those that claim they adjust the thermostatic control swiitch to only turn off the compressor at ~28F...

Looks like your BIAS against actual factual information might be showing up.

Since there is a great mass of hotter molecules surrounding the coil the coil absorbs the heat

So, just where did you come by those hotter molecules? Transmutation?

and its mass temp rises.

And by the way, the TEV/TXV never closes all the way. You cant test that for yourself if you wish.

I did, and while the issue of fully closed or no was inconclusive the evidence indicated that it was well enough closed that it took a significant period(***1) of time for the high and low side pressures to equalize. ***1 Clearly long enough for the rising engine heat to have an effect on the high side pressure. Even if the TXV is open to entry of liquid refrigerant into the evaporator core wherefrom is the heat to come to convert the state to gaseous if that core is already at 32F..?

4. Has nothing to do with the fact of how the ac system operates or why your system on your car leaks.

It was a "true or not" question. Your bias is showing yet again, save the editorilizing for later.


5. Not true.

How can that be? You are on record as saying that the OAT, atmospheric OAT, will have a positive effect on refrigerant pressure. You have said that the equalized pressure will be higher as a function of rising OAT. Or did I get that wrong?

When the a/c system shuts down (the compressor stops pumping) the low side and high side equalize because of the TEV ... the liquid refrigerant moves through the TEV and expands into the low side.

I most whole-heartedly agree. But the base question is how fast will that happen given the circumstance of a fully chilled evaporatior and evaporator "surround"? AND is that enough time to drive the high side pressure well above an initial 350PSI assuming the engine was HOT.

DECK LID CONDENSER COOLING FANS?
The Engine’s Cooling Fan
The rear deck lid condenser removes heat absorbed by the refrigerant (in the evaporator process) via the engine cooling fan.
The 911 engine’s cooling fan pulls an average of 1335 liters per second at 6100 rpms. Actual volume varies depending upon the year; there are many quotes and charts. So lets keep it simple and say 1335 ls is fair.

Since most comparisons in air movement with fans are in CFM lets do the conversion:
(1335 per second) X (60 seconds in a minute) = 80,100 liters per minute.
Then convert the liters to cubic feet, (80,100) x (0.03531467) = 2828 cubic feet per minute. So the average 911 engines cooling fan has the propensity to move 2828 cfm at 6100 rpms.
Assuming this is linear we can further say:
0 rpm = 0 cfm
1525 rpm = 707 cfm
3050 rpm = 1414 cfm
6100 rpm = 2828 cfm
or simply 46 cfm per rpm
And let's assume at idle of 850 rpm, the cfm is equal to 391 cfm (850 x .46).


What Could You Put Under the Deck Lid Condenser
The typical 911 condenser is 9"x27.5" of effective area, or 247.5" sq in.
Ideally the largest diameter pancake electric motor puller fan you can mount under the condenser is a 9" nominal.

"ideally...9" nominal...." Simply not true, even with the "useless" overlap the two 12 inch fans move a lot more airflow through the rear lid condensor than did the fans sized not to overlap the condensor size. Think of the useful CSA of the 12 inch fans vs the CSA of the 9" fans.

The inexpensive red colored fans posted in the thread boast a CFM of 1730 (we will assume at 0 static pressure) and consume 12 amps each?

I’m going to shoot from the hip here and I will say BS.

That's quite CLEARLY NOT what we're here for.

After testing dozens cheap and inexpensive fans over the years, and knowing that many Ebay seller’s claims or test data can inaccurate (for many reasons), I would want to ‘see this for myself’ as they say. So lets take a reputable fan company such as Spal and exam their PN 30100442; a 9" puller that moves 649 cfm at 0 static and draws a 6.1 amps at 13 volts. under 0 static pressure. So at “idle”, you could have an electric cooling fan pulling 60% (engine fan 391 cfm/ electric fan 649 cfm) more air !

There you gio again, who would use 9" fans when 12" will do so much better?


How Effective Could Electric Fans Be?
Any given fan never pulls across the entire deck lid condenser.

I can take pictures of the engine driven fan and SHROUD in my '94 F/awd Ford Aerostar if you like.

Effectively 1 fan does not pull a 9" of diameter, or 63.6 sq in, across the surface because the fan’s motor area is typically 4.375", or 15 sq in (no fan blades), so the effective surface the fan works on the condenser is 48.6 sq. in each. Let's multiply that by 2 fans for 97" nominal sq in of working area, or 39% of the condenser area. At idle, if you have a 60% increase in air volume working on only 39% of the condenser area, the net effect might be .... .60 X .39 =

23% in total improvement for that condenser... at idle.

And how can you or I say that isn't just enough? Then consider the useful CSA of two 12 inch fans....

And then you have to wonder if the engine’s cooling fan will allow that 23% increase in air move through it?

My Kestrel model 4000 (NKHOME.com) airflow rate/speed meter indicates that it does, and more.

Well all calculations thus far have been with a foundation of 0 static pressure. So we will have to think about it. And, in the world of AC, a 23% increase in air flow, at 0 static, usually does not mean your vent temps will drop by 23%... that is another set of equations.

We are not discussing vent temps, at least not directly

At Idle
“At Idle”. For some drivers, ‘at idle’, might mean sitting in the car after a long day of work, waiting and hoping the vent temps will get cool quickly.... read on.

Why not just narrow the field to drivers that could use more A/C capability than the factory system will supply, isn't that YOUR venue?

Above Idle, The Real Ride Losses
Above idle... what most of us spend doing, say driving around town between 25-40 mph, what are our engine RPMS’?

Then might I say that YOUR products are not appropriate for the most of us..?

That’s right, Dam It happens. Those electric cooling fans are now blocking or damming the work of the engine's cooling fan.

NOT so, just simply not so. With elevated engien RPM those condensor cooling fans might be acting as light duty power generators thereby removing some of the load of the alternator on the engine. Sorta balances things out, maybe. Unlike the issue of the engine fan blocking the fan forced airflow (it doesn't) the fans are free to turn faster and faster as engine RPM rises, abet with a slight load due to acting as generatiors.

Not by 100% though, but enough to cause a reduction of air pulled in by engine cooling fan.

Have to test that one, but instinctively I think not.

How much? We know the 2 electric cooling motor housings total 15 sq. in. . The 2 sets of motor blades account for an approximate 45 sq in. So in total 15+45 = 60 square inches of direct blow through blockage potential. The deck lid condenser is 247 square inches. 247-60 = 187". So there is a loss of 24% of your deck lid condenser working area, (187 / 247 = .757) = 24%, when you attach two 9"fans ...when ever your engine rpms are above ? .... 649 cfm/.49 = 1324 rpms !

The Choice is Always Yours!

A) Do not add cooling fans to the deck lid condenser, and simply realize that an increase in engine rpms above idle allows the engine cooling fan to pull more air through the condenser, as well the compressor pushes more refrigerant through the system.

Hell yes, by aall means for those of you stuck in rush hour stop and go traffic, TX in August, or even Olive Branch MS, be sure and pay close attention, religiously so, to keeping that engine RPM well elevated.

B) Add cooling fans to the deck lid condenser, and when ever you take a drive, your deck lid condenser will be working 24% less efficient for most of your driving time.

More guess work..!

C) Add cooling fans to the deck lid condenser, and just sit in your car, in your driveway,
and keep the idle below 1324 rpms, realizing that you at least accomplished something for the moment.

Why go this far off point, pulling my leg?

And, as always, everyone, including Wwest, are welcome to comment on the simple math, or provide their own math equations, estimates, data, or whatever floats your boat.

Johann.. sorry i got carried away from your thread's question, however I'd prefer the readers have facts rather than fiction to read here.

...

[brads911sc]

LOL

Seems to me that once again you have been caught making it up as you go, are unwilling to prove it with real data and therefore give us these incoherent statements. Kuehl has pages and pages of graphs, data and very little of what he says is conjecture... it is the person challenging the proof that must provide the new proof... LOL

Originally Posted by wwest

Logic indicates a video is only needed for non-logically thinking naysayers and I would need certification to a serious level of the video to convince them/you. On the other hand if YOU produced the video....??

[brads911sc]

Well Said,

Logic is a funny thing... those who do not have any, can not understand it.

Originally Posted by SilberUrS6

LOGIC FAIL.

The system, as stock from PAG, is acknowledged by most folks as barely adequate. Having experienced a stock system in E. WA during the summer, I can tell you that "barely adequate" on a 105-degree summer day in a black, heat-soaked interior would be a euphemism for "not in any way adequate". Yes, 70-degree air will come out of the vents, eventually. And a delta of 35 degrees from ambient isn't too bad. But it doesn't keep up with the IR input from all the greenhouse:interior volume ratio. Now, having laid that groundwork, moving air over the condensors is great. Moving more air over more condenser area is even better. But *even at 60mph for extended time*, the stock system has trouble keeping up with cooling requirements in 105-degree OAT conditions. In this situation, your idea of decklid fans has no bearing - the engine fan is moving more air than your fans can. In fact, your decklid fans might be cause air restriction at that point. Not good for my motor, never mind my AC. The front condenser is getting about as good airflow as it's going to get.

So, what will help here? Not your decklid fans. The plain fact is that system capacity for cooling the interior volume of the car is maxed out. Improving the condensing and evaporator capacity can help. Now, here's where you normally change the subject to stop-and-go traffic. And for a Seattle summer (I am a West Side native - grew up in the Skagit Valley), in stop and go traffic, a 35-degree delta might be just fine to cool the interior of the car. After all, summer temps rarely get above 85 degrees in the Puget Sound region. Yes, they do climb higher, but that's not a regular occurance. Just like I've seen 105+ degrees over here. More often, we're in the 95-100 region in July and August.

Airflow over the condensing surfaces is ONE aspect of evaluating the system. Yes, everyone who has two brain cells to rub together agrees with that. But you treat it as though it is the only thing that matters, and ignore everything else. From the evaluation of the availble data, it is my belief that cabin airflow and evaporator capacity are the limiting factors in creating a large temp delta between the interior and exterior of the car.

[Arne2]

Originally Posted by wwest

The problem is that the to and fro of "these" discussions are much more educational overall in my opinion than would be a "white paper" from either Kuehl or myself.

That's your opinion. But in my experience people will learn from these "white papers" a lot quicker than they will trying to extract data from all of the venom you bring.

I'm done here. This is yet another A/C thread that is no longer useful, the signal-to-noise ratio has gotten too high.

[brads911sc]

No one said it couldn't be part of the solution. I have a fender condenser with a fan. It really does exactly what you say.

The issue is that the airflow over the deck condensor is only 10% of the shortcoming of the 911 AC system. At any RPM over 1700 or so its not doing anything... It also raises engine temps beyond 9 oclock. there are quite a few of us that have tried it. Finally, when doing the tradeoff with engine temps and the improvement its not there.. because you haven't addressed most of the underlying issues.

If I am driving along at 80 mph, at 3000 rpm, pressures correct, and im still sweating, then adding fans is immaterial. if i can update components and increase capacity with additional condensers, better evaps and more air volume and have temps where I do not sweat, then I would think that proves that while the fan may marginally assist at idle, it is only part of the equation. The fan is secondary...

Your argument is not really logical.

Originally Posted by wwest

Puzzling..

Since everyone seems to acknowledge that a blower fan moving airflow over a condensor, or an oil cooler, in a wheelwell, mostly "hidden" from natural airflow, is helpful it makes it rather hard to see the naysayer arguments against a fan moving more airflow over the rear lid condensor as valid.

[dshepp806]

I think you mean the S/N ratio has become too LOW (i.e., "more noise than signal).

Best!

Doyle

[wwest]

Originally Posted by brads911sc

LOL

Seems to me that once again you have been caught making it up as you go, are unwilling to prove it with real data and therefore give us these incoherent statements.

Kuehl has pages and pages of graphs, data

While I have not seen any of those I have little doubt that they exist, but they would pertain, clearly pertain, only to the improvement gained via the use of his own, expensive, products.

and very little of what he says is conjecture...

One only need to read a few of his opposition posts to determine that insofar as adding two 12 inch radiator cooling fans to help cooling the rear lid condensor all he has is bad, misleading math, and pure conjecture.

Qute clearly Kuehl has no actual facts, actual use or trials to negate my position regarding the use of rear lid condensor cooling fans. And why is that one might ask? Should Kuehl do a trial based on actual use and that trial prove my case then the viability of his entire product set goes out the window.

So, obviously, Kuehl is much better off spending his time blowing smoke for those willing to listen.

it is the person challenging the proof

I have challenged no proof, nor data, that improvements based on Kuehl's product set are valid.

that must provide the new proof... LOL

Sorry, I have nothing that needs proving, either you understand the logic, and yes, science, behind my theory are you accept Kuehl's conjecture that it can't possibly work.

Meanwhile I'll continue to use my 90K mile F/awd 2001 RX300 as a daily driver, depending fully and sometimes solely (speed = 0) on its ELECTRIC radiator fan for extracting HEAT from both the engine radiator and A/C condensor.

[nettles503]

I'm so glad I removed my A/C.

Sent from my DROID BIONIC using Tapatalk 2

[wwest]

Originally Posted by SilberUrS6

LOGIC FAIL.

The system, as stock from PAG, is acknowledged by most folks as barely adequate. Having experienced a stock system in E. WA during the summer, I can tell you that "barely adequate" on a 105-degree summer day in a black, heat-soaked interior would be a euphemism for "not in any way adequate".

May I ask to what, which, are you making this comparison? And what is your expection of the time period it would take for ANY A/C system to cool down such an interior of that ilk and in those conditions. I have NEVER purchased a vehicle with a dark or black interior for the very reasons you are encountering. I'm not even sure an LS400 set at maximum cooling but with a black interior would satisfy my wife's idea of a quick cabin cooldown after setting out in the hot sun for a few hours.

Yes, 70-degree air will come out of the vents, eventually. And a delta of 35 degrees from ambient isn't too bad. But it doesn't keep up with the IR input from all the greenhouse:interior volume ratio.

There is NO system in existence that can combat the effects of bright sunlight shining directly on our body coming through an untinted window. Other than window tint that is one you simply must learn to live with.

Now, having laid that groundwork, moving air over the condensors is great. Moving more air over more condenser area is even better.

But *even at 60mph for extended time*, the stock system has trouble keeping up with cooling requirements in 105-degree OAT conditions.

That statement puzzles me greatly. Even prior to the fan modifications neither my 78 Targa (Memphis, even) nor my 88 Carrera had any problem maintaining the cabin comfort level "at speed".

But, first and foremost, is the lack of A/C capability really your "base" problem?? In my case during a recent drive to/from central MT in those (same?) 105F conditions I had more of a problem with the evaporator freezing up at high altitude than I did with keeping the cabin, and my wife, cooled. My '88 (Diamond Blue in/out) does have window tint that helps.

If your evaporator cannot be sustained at or very near 32F then you need to look elsewhere for a problem. If it can be sustained at 32F then you need to consider window tinting and maybe some roof and door insulation. I suppose some would say that increasing the evaporator airflow might be of help. While that would likely be true for initial cabin cooldown (keep in mind that the evaporator needs to remain at 32F even at these times) having system airflow that high and even cjust coolish can be pretty discomforting within a relative short period, let alone an 8-10 hour drive.

In this situation, your idea of decklid fans has no bearing - the engine fan is moving more air than your fans can. In fact, your decklid fans might be cause air restriction at that point.

Not very likely but I will soon test that point.

Not good for my motor, never mind my AC. The front condenser is getting about as good airflow as it's going to get.

So, what will help here? Not your decklid fans. The plain fact is that system capacity for cooling the interior volume of the car is maxed out. Improving the condensing and evaporator capacity can help.

Again, not if the evaporator is already being sustained at 32F. If it isn't, especially once the cabin has cooled down to a comfortable level, then yes, you need to figure out how to add cooling capability.

Now, here's where you normally change the subject to stop-and-go traffic.

Yes, but always with regard to the climate in TX, TN, Ar, or MS.

And for a Seattle summer (I am a West Side native - grew up in the Skagit Valley), in stop and go traffic, a 35-degree delta might be just fine to cool the interior of the car. After all, summer temps rarely get above 85 degrees in the Puget Sound region. Yes, they do climb higher, but that's not a regular occurance. Just like I've seen 105+ degrees over here. More often, we're in the 95-100 region in July and August.

Airflow over the condensing surfaces is ONE aspect of evaluating the system. Yes, everyone who has two brain cells to rub together agrees with that. But you treat it as though it is the only thing that matters, and ignore everything else. From the evaluation of the availble data, it is my belief that cabin airflow and evaporator capacity are the limiting factors in creating a large temp delta between the interior and exterior of the car.

The only true, real, evaluation of the system performance involves two desparate circumstances. One, Initial cabin cooldown, and two, sustaining the cabin cooldown but with a relatively LOW blower speed.

If you have a BLACK/dark interior, no window tint, and have done nothing to insulate the car otherwise from heat intrusion or cooling out-welling then I truly feel for you.

There is something about the human comfort equation that you may not be aware. Once your dark interior is heat soaked the adverse radient heating effects on your body will endure, adding seriosuly to your feeling of discomfort, untill those surrounding surfaces are also adequately cooled down. So, your A/C might be perfectly adequate in keeping the cabin "atmosphere", air, at a reasonable comfort level, but due to the radient heating effects from your surround you still feel discomforted.