Chrisbert

The reason that line is ice cold is because it is after the evaporater.

The compressor "compresses" the refrigerant. The refrigerant is hot at this point due to compression. It runs into the evaporater via the expansion valve. Expanding gases become colder. The fan blows air across the cold coils in the evaporater and it comes out the vents. It runs from the evaporator back to the compressor in lines that are ice cold to the touch where it starts over again.

Thus, I never tried the mod when we originally talked about it. Maybe though, this is keeping the refrigerant at a temperature that makes the compressor run a more efficient duty cycle?

juikster

the reason you want to wrap the line leaving the evaporator is because the refrigerant that has left the evaporator has changed from liquid to a gaseous state and any more heat added to the suction line to the compressor causes the gas to gain heat from engine compartment which is unfavorable(superheated gas)
which screws up the efficiency of the cooling system and its that extra added heat that will have to be removed by the condenser coil up front...So a good wrap of insulation to this suction line is important........

Chrisbert

So if the refrigerant in its gaseous state enters the compressor at a lower temperature it will make life easier for the compressor. Less on/off constantly...

Gonna have to try it.

StealthTL

iTrader: (1)

I wouldn't bother even wrapping it.

That pipe is not a factor in how cold your a/c is going to be. You will notice that all the peeps who replied said it "felt colder" or "seems better", there are zero measured differences -
Does it get to 44*F before cutting out?
Does the compressor cycle every 23 seconds instead of every 52?
Is the outlet air temp colder at idle?
...and by how much?

Pure placebo effect/conventional wisdom - "It must be colder, because I insulated the 'frosty' pipe"

That pipe goes from the evaporator to the compressor, if it is 'frosty' it means you didn't put enough cabin air over the coils, and you are wasting cooling. From there it goes thru the comp, then the drier and the condensor. Now it is hopefully back at ambient temp, ready to re-expand and do its refrigeration thing again.

The two feet of insulation on the evap outlet is irrelevant.

Sorry, but save your cash.

S

Brice-RX8

Also, in the summer time when you have it on max A/C the compressor is going to basically run non stop anyway, it will not cycle on and off nearly as much as when the temp is cooler and you don't have it on max A/C, if your system is cycling on and off really fast every couple of seconds at idle then you have problem with the system like low refrigerant

lethologica

I might not be looking at the same line, but in my car that tube is pretty hot, and I haven't used my AC yet. But I've touched it while changing my oil filter, if you are reaching for it from the drivers side it would touch your right side of your right arm. Is this the same tube?

TeamRX8

iTrader: (25)

they sell a special wrap with clamps just for hoses and pipes

http://www.thermotec.com/products/full/11600/11600.html

but I have to question it's effectiveness too

Razz1

Yes, it's the same tube and it does get very hot.

The A/C is colder but it will still cycle.

Now mine goes from super cold to warm and the cycles are much shorter.

Before it was: a little cold to hot and consistently cycled back and forth.

Go to: http://www.porterfield-brakes.com/

Zaku-8

what other things can be done to the A/C?

also, is refrigerant level something that has to be checked now and then? Ever since it got warm my A/C doesnt seem as effective as it used to be.

Razz1

duh......?

It's an inherrant problem. Even the 05's aren't fixed yet.

TeamRX8

iTrader: (25)

there'a TSB for faulty AC amplifier, should be factory corrected on later production vehicles though. I think there's another TSB/flash update that delays the AC cutoff rpm point so it doesn't kick off so easily during semi-spirited driving (what most RX-8 owners would call normal)

fwiw, if it was as easy as insulating a hose don't you think the manufacturer would be aware of this? They aren't that stupid you know.

rx8gurl

hi, i really want to try this mod. Can anyone tell me where and what product exactly would tackle this mod. Thanks

TeamRX8

iTrader: (25)

would suggest an introductory course in how an A/C system works so you can make the informed decision

http://www.familycar.com/Classroom/ac1.htm

as someone so aptly put it, "insulating the frosty pipe", has no bearing on how cold the air blows out the vent

fwiw the "frosty pipe" is the return line, not the supply line, too funny :D

Blue87Sport

This is an interesting thread. One one hand you have the skeptics saying "insulating the frosty pipe is a waste of time". On the other hand you have folks saying that reducing heat absorption in the system will increase effectiveness. Neither side has any direct evidence one way or the other.

Not being an HVAC expert, I'm just think this through out loud and have a couple of questions. Some people say the return pipe gets very hot and others describe it as "frosty". Am I correct to assume that it gets frosty when the AC is on and gets hot (due to high ambient under-hood temps) when the AC is off? If that is the case, then I think it is safe to assume that the (uninsulated) pipe will aborb heat, thus increasing the temp and pressure of the refrigerant gas inside.

So what is the effect of this increase on the system? Does the compressor increase the pressure by X psi? If so, then the warmer return line will result in a hotter than normal output from the compressor. Or does the compressor run enough to produce a target psi? In this case, the higher input pressure just lets the compressor do less work, perhaps decreasing its duty cycle.

Assume that the added heat of the return pipe carries through to the compressor so the temp going into the condensor is higher. At a given airflow, a hotter condensor will shed more heat than a cooler one. Whether it sheds enough heat to compensate for a higher incoming refrigerant temp is unknown. So will mod have any effect on the temperature of the refrigerant entering the evaporator? If it does, then the evaporator has the potential to absorb more heat from the cabin. Of course, whether the design can achieve this potential depends on the heat exchange properties of the evaporator such as its size and airflow and how it is controlled by the AC system.

In my mind, there are two many variables to be able to analytically say whether this would work or not. It ultimately boils down (a little AC humor there) to whether this mod impacts the temp of the refrigerant entering the evaporator.

I guess the only way to know is a controlled experiment. Measure the vent air temperature before and after the mod trying to keep other factors such as outside temperature, driving speed, starting cabin and engine temp the same. Anyone up to the challenge?

jaguargod

So following that line of logic, factory installed protection for the oil coolers and a/c condenser must be really difficult for the manufacturer to envision and engineer. Otherwise they would surely have made them standard issue by now, right?.

Nubo

I think the system is capable of more BTUs, but is being restricted from doing so. I noticed this the other day, doing the 4000-rpm shutdown procedure after briefly moving the car. I decided to hit the AC button. Since I was now in the garage (door open of course) it was fairly easy to hear the AC clutch engage and I also noticed a decrease to about 3600 rpm, holding the pedal position steady.

But, the compressor clutch did not stay engaged for long. The vent air began the familiar "cycling" behavior -- cool/lukewarm/cool/etc... And everytime it cycled was exactly timed with the AC compressor engaging and disengaging.

It seems to me that a good deal of the problem is related to the duty cycle being imposed on the compressor. This is part of what the upgraded "amplifier" seemed to address (in addition to enforcing recirculate-mode). But the success of the new amplifier is less than stellar by most accounts on this forum. My unit is past the VIN target for the TSB so I don't know if my cycling is more or less than what a unit with a newer amplifier experiences.

Why would the compressor duty-cycle be "detuned", so to speak? I can think of a few possible reasons

1) to aid with an already-disappointing fuel economy
2) prolong the life of the compressor
3) mitigate the heat load on the radiator
4) keep the evaporator coils from icing up

Of those, I speculate that #1 may have been the biggest driver. #4 is always important, but I don't have any idea how close or far away from an icing problem we are -- that is, how much could the duty cycle be increased before it becomes a concern?

I think my next bit of research is going to be wiring an LED into the AC-clutch circuit so I can see on my dash when the unit is operating and when it's not. I'd like to get some accurate measurements of the actual duty cycles and compare that to times when the AC seems to be doing ok and when it seems to be particularly anemic.

My end-goal in this is to see if there is any cheap and reasonable way to increase the compressor's duty cycle to a point where the driver is not constantly aware of the weak AC.

ezrider55

I moded mine with grey foam pipe cover from Low's. I had new AC Amp already installed for months. With new AC Amp air was cool. Wtih pipe cover it is cold. :D My .02 cents worth.

TeamRX8

iTrader: (25)

I ran an FD with exposed coolers for years and never had a problem, that said anything can damage your car at any time. You don't have a cowcatcher to avoid gatorbacks too do you? I had a bolt kick up and bust the windshield of my company car. Should they also supply a windshield screen?

FWIW, I live in TX and my A/C will freeze me out, I generally like it colder than anyone else I know

Razz1

So, why do other manufacturers cover the A/C line?

Believe me it works. It's not a complete fix, but helps. Helps enough that the A/C is more than tolerable. Add the AMP and it's better yet.

This is the order in which I repaired the A/C problem. Like I said id cycles less frequently and the air is colder.

Vaillant

What we need is someone to measure the air temp before and after the mod. Quantitative evidence. Who wants to volunteer?

~ Matt

r042wal

I wrapped mine in 1/2" foam used for insulating copper pipes. I then wrapped foil tape around the foam, the same foil tape used to seal heating ducts.

I mentioned this mod to one of the technicians when I was at the dealership buying oil last week. He said that he *could see* how this could make an improvement.


Unfortunately, we are in the middle of a heat wave in Ontario and it is too hot to go outside this weekend to see how well it works :-)

bxb40

I just did the insulation mod. I used glass fiber insulating band (4" wide) and wrapped it double layer. Then on top, aluminum body fixing tape (4" wide) in sections around the pipe turns, and length-wise on the strainght portions. Both were purchased from Auto Zone - nothing special. Looks kinda fine - obviously not something to rave about, but it ain't all that ugly either.
The AC worked just fine at 92F we have now in NJ (read on the car sensor). I already have the updated amplifier installed as well. Short of checking the level of the refrigerant - maybe is on the low side? - and tinting windows, there is nothing else to be done about the AC on this car...
So, instead of talking up and down and theoretise on the benefits of insulating that pipe - interested people should just do it ($10 in parts, 30 min installation).
As for the skeptics, no need to discourage people! Let them do it - what's to lose?!? I just don't get it....

therm8

And besides, I'm thinking of going on an intake insulating frenzy from the airbox to the engine and saying "**** off" to heat soak, because of this thread :p

krwkenny

They use this same theory on housing A/C. Check some of your lines at home for insulation.

wedge357

Got mine done today using 1/2" foam copper insulation tube bought from Home Depot. The foam tube is split on one side with adhesive strips to close together, costs $6. I used aluminum tape ($2) and taped it lengthwise covering the foam surface except where the foam is split. I pulled the tube over the a/c piping, pressed the adhesive ends together, covered the remainder with some more aluminum tape then tiewrap ($2/10 tiewraps) the whole thing down. Total cost for the mod: $10.