How can anyone boost his car's A/C EFFICIENCY?
🤔

(Any well working factory condition W212 and siblings with clean filter - All OEM working parts)

 

me waiting for the tips.....

 

How does typical A/C system work:
Compressor
Condenser - Fan
TxValve aperture
Evaporator -blower

A refrigerant gas (R141 aka. "freon") gets compressed into a hot liquid that's cooled in the front condenser then evaporated to absorb some heat from the cabin thereby returning to a lower gas pressure to be cycled through again.


mighty TXV

Everyone still on-board... so far so good??


Outside engine bay is really baking hot @200°+F while inside driver is trying to keep his electrolytes around 69°F...
All the heat absorbed inside the cabin comes out up front in the condenser rad to handicap the engine's own radiator cooling.

Engine would keeps getting hotter in the city back to back traffic... but Benz engineers added a PWM multi-speed fan that the ECU controls for the occupants own comfort.


So how could anyone make this A/C loop more efficient without replacing any parts or messing with the refrigerant ?
?
🧐

 

Let me try some, based on what I know about HVAC

01. Cold is the absence of energy.

02. We use energy to remove those "warm" temperature/energy, using the compressor as heat pump.

03. Expansion and compression, based on air. Compress fast = hot. Release fast ( decompression ) = cool
#3 I understand very well because I maintain dive compressors and to produce EN12021 clean super dry air ( mine is targeted to be -48C dew point air dryness), I must understand #3 and its media filters.

04. So pick up heat from inside car cabin via air>>> via the evaporator and discharge the heat outside to the condensor via air to ambient air. Hence condensor is always in front or the most forward cooling radiator in the car.
#04 deal with thermal transfer.

05. Humidity has a play in this. The more humid the ambient RH is , the more energy needed to cool the air.
Humidity is also sensed by us, since moist air doesn't feel as cool as dry air of same temperature.
Water vapor in air aka RH I know quite well, again the dive compressor air production is as dry as 0.2% ish.

06. The freon charateristic I never really study it. So I am blind about it.

 

Clean the condensor coil up front.

or

Move north where it is cold.

 

There is an error in the write up you have. The refrigerant DOES NOT get compressed into hot liquid. It gets compressed to a hot high pressure gas, which then condensed to liquid in front of the car inside the condenser that gets cooled by air flow.

How to make this system more efficient would be to make sure the compressor, condenser, expansion valve, evaporator and all piping is dimensioned correctly.

Also, need to keep cabin air filter clean so that you get proper air flow thru the evaporator coil so all cooling is taken from the coil. Cabin air filter needs to be good quality filter so the evaporator coil stays clean. This is the same thing as it is in a normal house A/C system.

MB engineers probably did the best job for engineering the system components. The only place you probably could help is to insulate the piping where you see the piping under the hood.

Especially any part of the piping you can see sweating will pull heat from the hot environment under the hood as that is where the temperature difference between piping and surrounding space is the greatest, but insulating also piping returning from the evaporator could help as if temperature under the hood is higher than gas returning from evaporator then that piping part will also pull heat into the gas that adds to what the condenser in front must do. But this efficiency improvement would not be that big of a deal. If it was, those return lines would have been insulated by some car maker already.

I haven’t looked at any of the A/C piping in my car yet so I don’t know how well MB did the piping insulation. I would assume line from expansion valve is well insulated so there should be no sweating piping visible, but I don’t know.

 

Yep, you pretty much got it! I used to be totally out of my league in the A/C chapter until a did a lil study & hands-on.

Our w212 is fitted with a nice HEAT EXCHANGER that helps recycle the energy left in the cool vapors back into the incoming warm liquid. It's not that I care to save two drops of gas but when a system is pushed to its limits the efficiency should be considered.

What got me dealing with my Air-Con is the day I drove my new E350 to a 110°F climate. The car with all its fancy HVAC controller, sensors, fan, blower, zones flaps could hardly cool the cabin at all.... useless! I thought how ridiculous this thing can not perform well above 90F weather.

I had to go drink my Starbucks tea walking around air-conditioned HomeDepot. So I thought lets try something new today...


classic pipe sleeve tube


aluminum faced foam wrap $3


(FYI: wrap packaging)


crafty Sunday: HE wrap job

Coming out of Home Depot a bit cooled down, I started covering my heat exchanger to prevent external heat transfer. That instantly made the A/C 40% better but still not arctic cold... I'd realized the A/C in my Benz was far from perfect and could easily be improved.

I have been to enough tropical places in Southeast Asia to witness how excellent the A/C can be out there when it is a serious commodity. So I did my due diligence with the Internet. I have learned some ropes from A/C pros, line set tools, maintenance, pag oil...
All this lead me to further tweaking in the same direction.

 

Once I saw what wrapping the heat exchanger did, I wonder how it was possible.... So I decided to experiment with wrapping the section between the condenser outlet to the heat exchanger inlet.

It turns out, this is the section that makes the greatest temperature improvement because it is 100% exposed to high engine heat (unlike the HE which is mounted in a sealed compartment near the brakes master cylinder).


pipe wrap up front section

How can that be...?
Instead of cooling the condensed gas down to ambient (80...110F) and then letting it get reheated around the engine bay (250F) then cooled again through heat exchanger (80F). Wrapping the up front section guarantees you are keeping your liquid gas as cool as it got upfront before cooling it further through the heat exchanger.

Limiting the absorption of under hood heat, improves the overall cooling efficiency to deliver seriously frigid A/C vents.

RATIONALIZATION :
My high pressure pipe wrap made it obvious to me that more calories can be absorbed with a cooler fluid. Seems obvious afterwards, right?

Bingo! Try it out...
It works very well on any vehicle with A/C, especially those without HExchanger where the temps near firewall are as high as it come... 300F: big deal!
It makes an old healthy A/C perform like a champ better than new.

With these pipes insulated, you'll notice that city traffic lights won't quickly affect your A/C temperature even though compressor is spinning slowly at near idle rpm.


my imperfect enhancement 🙂

Compressor pipes...Nop:
The two sections of pipes that are to be left alone are those surrounding the compressor. The Incoming gas needs to be expanded warm for winter defrost and the Outgoing pipe is super heated by the 200Psi pressure.

This begs the question...:
WHY DO THINK BENZ ONLY DID A PARTIAL HE WRAP??

TIPs:
Do not try to band or puncture your A/C pipes whem wrapping them. They are quite fragile and use tiny O-Rings under pressure (60....200psi)

Any systems that sees zero pressure will need to get evacuated with a vacuum pump before refill.

If an A/C system keeps leaking after being refiled, test your Schrader valves for slow leak!

It's easier to have an imperfect wrap job than to disassemble the conduites for a perfect wrap unless old system needs service.

You can apply the same principles to your home refrigerator for faster less frequent runs - Exactly same benefits x 24/7.

Any cool thoughts??

 

Right, the one difference I see between home and car is the absence of a high heat 250F source to offset the condenser cooling.

In home the line-set pipes traveling side by side all the way are a sort of practical HEAT EXCHANGER. In that regard Benz car give us this "free" extra efficiency.

It's not like I wanted to pimp my $70k ride but it not cooling me under 110F heat was my direct call for action.

I let you imagine the face of the stealer adviser asking me "what happened here?" looking at my funky wraps - My car, my way. 🧐

 

Ok, so essentially up in previous posts, I showed how I wrapped my high pressure line to keep it near ambient temperature until inside the cabin.


SIMPLIFICATION:
Ignore for a minute that A/C is about compressing "R12/141/freon" gas.... The technology helps move heat.

Imagine that we have a heat pump that is simply moving calories. We have the ability to move heat from inside and reject it at the front of the car (just like electricity is used to move energy). I tested that preserving the ability to absorb heat is essential.

With car A/C we are using pressure to move heat. Gaining heat involves wasting pressure unnecessarily. Doing this Inside the cabin is good but inside the engine bay is a pure waste.

When moving calories the key is too have as few calories leaks as possible. Don't let the engine bay calories leak back into the high line.
PIPE WRAP.!!

What have you got to loose:
$5... try it out✌️

 

You are spot on: the cooling done with the condenser fan at the very front ahead of all the engine heat, should best be preserved.

When the engine heat is allowed to get right back into the high line, we have lost that cooling.

It then becomes much harder to pick up cabin heat with a 250F fluid.
A 90F fluid is more efficient to picking more heat during evaporation phase.

All this rhetoric seems pointless until you try wraping said pipes to quickly figure reality - Any car or GMC truck too!

With 80F ambient, the improvement may not be obvious because the HVAC module regulates working temperatures.
When you reach closer to 95...100..110F... then top efficiency becomes an obvious big deal to drive.

 

what you're saying stands right, I know we are moving heat with pressure, not with fluid temperature.

What I've tested above is: "we can move more heat with a cool (high pressure) fluid than with a hot one" ✌️

For a $5 roll of soft wrap, try it and explain why it works... without over thinking.

I believe one of the A/C basic is the refrigerant Temperature and Pressure are directly linked, right?

What happens when the high side line absorbs engine heat?? Then why cooling ability goes down??

 

I used to think like and it made perfect sense, specially in home HVAC. Then I realised that theory did not entirely stand. With cars I was never impressed with cooling performance above 95+ heat.

Have you ever noticed how your A/C air temp climbs up at a long traffic light (ECO OFF!) add a hot car to the front blowing its hot air at you on a 95F day... still good air temps???

if not don't sweat it.. be curious try my $5 wrap!
✌️

 

To me that is spectacular, how do you achieve that? 👏

I'd really like to learn how to get closer to that performance. What did you do to make up for loses? 🤔

 

Florida high humidity that's serious heat ... like dry Sonora desert heat in AZ.
I am sure you've seen miracle A/C booster shots, any thruth in those claims?

 

Awesome thread, thanks for your contributions

 

I totally agree, we are on the same page.
Besides I said to specifically leave the low side return alone to let it fully expand just like you mention.
Compressor is for 100% gas vapor and not a liquid pump.

I wrote to leave both sides of the comoressor alone and specially not wrapped in case people feel more wrap is better.... no-no!

My topic here is to prevent the pressure line from absorbing high engine heat on the way from front to firewall.

 

That may be the case. What you're gona say once you try it out 😃

You spotted the HEAT EXCHANGER, right...
Why is MB usig that?
What purpose does it serve?
Why uneeded for the past 40 years?

My wraping plays along with the HE job making liquid side cooler.

 

It did not escape you the "heat exchanger" is made of both lines traveling together to exchange calories?

My gosl is not to deal with suction it's about shielding the liquid line from engine heat.

From the point between the compressor to where the HE starts, the suction line is untouched. Besides the heat added into the succion line helps it right along to completely expand, which is a good thing - So far from a problem here.
good ?

 

All along I said to just try, it was nearly free , no need to over think but hey no problem....
let me ask you why Germans waited so long to use a heat exchanger, it was not needed for long...

Personally I don't use this sort of logic to fix problems. Real hands-on "Trial and error" leads to practical solutions much faster than saying 'it's that way because that's how they do it" - Are you serious??

Wrap it up!
In mild weather (70..85) when the system has enough cooling power the difference can go unnoticed, unless at long hot traffic stops.
The difference only becomes obvious in the upper temperatures (95...110) when this A/C system becomes borderline useless.

That's when the insulated liquid line makes difference.
I'd say it brings a good 25% more cooling that is lost to inefficiencies when summer heat climbs.

I have done this mod on both of my cars: frigid consistent A/C temps.

When you know what to expect, results are obvious, no need to split hair or be afraid of change for 1/2 a pack of wrapper -

Easy did it...👏

 

​​​​​​PLEASE UNSUBCRIBE FROM THIS THREAD - GO BACK TO YOUR COMFORT ZONE.
I DONT NEED YOUR ABUSIVE DRUNKEN INSULTS.
SPEND YOUR TIME IN BETTER WAYS.

 

All I know is my STOCK 2015 E400 AC works down here in South Mississippi on the gulf coast where it is Hot and muggy..
AC works great - Even sitting still...

I am not sure but does MB use a VARIABLE COMPRESSOR? Like my Volvo does.

Makes for a most efficient system because the Compressor adjusts its displacement to match the heat removal load required.
New Fancy home AC (& Heat pumps which is an AC that runs in Reverse) have this feature as do Mini-splits aka ductless.
All about efficiency these type can get 24-42 SEER Cooling Effiency ratings.
SO you are most comfy...in your house these super efficiency systems adjust compressor size and run time along with exterior condensor fan speed ain inside evap fan speed.
Since there are a lot of variable in how much cooling an AC system can produce.

FYI: In the USA units for AC cooling is BTU/hr ...

Now Your wrapping of the lines with insulation will technically help....
but how much is very very tiny amount and probably not worth the time effort and later mess as this stuff deteriorates and makes a mess which it will.

Example: Say your car produces 2 tons cooling this afternoon = 24,000 BTU/HR..
Insulating your underhood 2-3ft long line set would maybe add 5 btu/hr more cooling....
which means it can change the temp of 5 lbs of water 1F in 1 hour @ Sea Level as ambient pressure has an effect

YOu would be better off Changing air filter
Clean exterior of condensor of all the dead bugs to increase heat transfer.
And like wise clean evaporator inside car.

MAke sure duct work in cabin is sealed and HEater core is sealed up in box so AC cooled air does not run across the always hot heater core.

Best advice get ventilated seats to blow air on your back and thighs...


Man this brings me back to College and Thermo, where we learned AC systems and how they work.
All those gas laws... Yuck....

Hope I helped more then hurt