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Still thinking method to make my M276 AC cooler by removing heat from heater core
Guys,
This applies to both M276 3.0TT or 3.5 NA for how the heater core is forever getting hot engine coolant flow.
When I just started my engine , ambient temp 30C ish and in my garage , the first 2-3 minutes is the best cooling my HVAC can give me, because the engine coolant is not hot enough to contaminate
my cool HVAC air.
M278 older version heater water valve can stop hot coolant from flowing to HVAC heater core.
The later version of the same heater valve, no more actual valve, so its like M276 free flowing hot coolant to heater core of HVAC.
To M276 3.5 NA owners, don't ever try to block coolant flow to HVAC heater core, as this will make coolant pump cavitate as there is no coolant to suck when thermostat is still closed or below 95C coolant temp.
M278 can have heater water valve and can stop coolant from flowing to HVAC heater core, is because there are still turbocharger cooling circuits which provides suction for coolant pump at all time like M276 3.0 TT.
M276 3.0 TT can be rigged like M278 with heater core coolant flow stop capability, but will be a DIY version.
This DIY version is what I been wanting to do, but still not sure how I can do it in a robust but elegant fashion.
M278 heater water valve is known to fail by cracking or the solenoid can pop out too.
Below is a cracked one, engine side. Below can also happen to M276 3.5NA or M276 3.0 TT when this V6 has age more and probably M276 3.0TT pipe's will fail first.
To date, in MBworld, I have not seen post on M276 3.5 NA and 3.0TT pipe cracked.....yet.
This plastic pipe is like a time-bomb and if I DIY my HVAC heater core to not flow hot coolant, I dare not do complete blockage like how M278 older version did.
The W211 get such a beautiful divert valve and a stop valve combo, this is the best option if can be done. But with those quick clips fitting and not simple hose barb, its a nightmare to modify a system to fit this nice diverter valve.
I have engine block coolant pressure sensor located exactly at the output of the fragile plastic pipe item no 3.
I been monitoring the pressure there at the #3 pipe outlet , at different stage of thermostat opening and RPM.
Pink rectangular zone is when the coolant is not yet at 95C or higher, meaning thermostat has not open yet and pressure can build up to 22 psi at #3 plastic pipe when I do WOT 6,000 RPM
Do remember, 22 psi is from an open flow to HVAC heater core, not a closed shut one. I wonder if I totally shut flow at #3 plastic pipe, how much more pressure can build* up there ? ( *when thermostat still closed )
Pink zone is car doing higher speed of 140 - 180 KM/H on average, hence coolant get cooled fast and plenty.
Green/Cyan zone is when the coolant has reached 95C or higher and thermostat opens, the pressure at #3 plastic pipe at WOT is only 8 PSI approx, because the bulk of the coolant flow is now heading to the radiator.
For the reason of pink zone, is my worry if I completely shut off coolant flow to heater core like how M278 was doing.,,, I fear the #3 pipe will crack. So I plan to use a DIY diverter hose with a Tee to prevent high pressure build up.
No matter how good the plastic air flow baffle in the W212 HVAC system is, the evaporator being so close to the heater core with minimum 85C at higher speed above 120KM/H and 95-100C at slower speed,
its a true waste of cooling power to be so close to something so powerfully HOT.
Where the hell is the logic here ? . Temperature in CELCIUS.
I need to scope the 12V coolant circulation pump of the heater core. Item #7 in my sketch.
If this 12V pump only run when HVAC control is set to HOT, I can then tag along its signal ( via relay ) to operate a 12V water/steam solenoid like below :
I hope the signal or power to the 12V coolant circulation pump of the heater core is not a PWM type. Its more of a hassle if PWM.
==================
Maybe I need to anticipate air bubbles from being created from HVAC heater core being sucked of coolant if there is only 1 of item 6 water solenoid.
Maybe I need to use 2 of item 6 water solenoid.
You are light years ahead fixing this new ridiculous problem we've found. I look forward to knowing you have the best A/C reworked with your sharp ingenuity.
PATH:
Your great analysis of the coolant path is key to what's possible to do without introducing new issues. I understand you are saying the engine pump relies on flow through heater core to prevent cavitation. We know that's the worst thing that can happen to pumps.
Does that mean we need a BYPASS circuit with a "Y" selector valve ?
CONTROL:
I try to be biased towards simplicity when possible. I think a manual coolant valve without any electric control would be suitable here. Two manual positions changeover: Winter or Summer.
CONNECTIONS:
I am all in for the old fashioned simple spring loaded hose clamps.
The MB push/lock hose connections need to be perfect or it will be a source of leak/air.
TEMPORARY:
For now, I have a plastic clamp on my heater core hose.
I hope we can improve our MB cooling to be as good as a basic Tercel.
I don't know. Looks to me like you the procedure is to cover some other problems, instead of addressing them.
I routinely drive in summer temperatures in 40-50C and my AC is freezing my elbows.
@S-Prihadi what temperature and flow (not pressure) in the coolant supply line to the heater core have you actually measured when in max cool (max A/C)?
@S-Prihadi Q: how low have you seen the AC temperature in the evaporator? is it to specifications?
You can do 2 measurements:
1 - MaxCool, @2000RPM, with heater valve as is (open)
2 - MaxCool, @2000RPM, with heater valve blocked (closed)
How low can you go a the evaporator before freezing it? is there any design room to go lower?
That will give you the maximum capacity of the system, it will never cool better unless you change a lot more parts.
The heater valve is supposed to help dry the cooled air, so if it is always open there is no control; therefore, there should be no need for a humidity sensor. Have you seen the humidity sensor in XEntry? how much humidity does it show?
One thing though, remember M276 3.0TT uses a different compressor than non-turbo W212, wonder if the difference is not only the clutch but also the cooling capacity . That could be the reason W212 AC experiences are model dependent ??
I don't know. Looks to me like you the procedure is to cover some other problems, instead of addressing them.
I routinely drive in summer temperatures in 40-50C and my AC is freezing my elbows.
K,
If your engine comes with heater core shut-off valve, you are gold and hence you HVAC is not heat contaminated by the heater core.
The OM651 has that valve. I do not know about your engine.
The M272, M278 older version, and M157 has the heater core shut off valve.
@S-Prihadi what temperature and flow (not pressure) in the coolant supply line to the heater core have you actually measured when in max cool (max A/C)?
The coolant to heater core, its temperature is the same as engine coolant general temperature.
The output port from engine block for coolant to heater core is the same main channel for coolant temp sensor.
I would not call my current situation a problem. My HVAC is still cool but I want it to be maximize without heat contamination from heater core.
If other engine variant get heater core coolant shut off valve, I would like the same luxury.
I do not yet have the actual coolant flow path 100% accurate schematic on M276 engine .
But one thing I do know, any cylinder furthest away from water pump almost always is hottest, say in inline 6 or a V12 engine.
M276 , the heater core gets coolant from Bank 2 and if there is no shut off valve, that means Bank 2 get less overall coolant flow compared to Bank 1,
because heater core takes some percentage of total flow.
In my yacht maintenance days, MAN V12 engine if pushed hard has this hot-spot weakness due to the way the coolant distribution is set up.
A few MAN V12 engine I seen has damaged that particular cylinder due to localized overheating.
This is a similar issue with MB OM606 inline 6 ( same as a v12 bank 1 or bank 2 ) in terms of localized hot spot for furthest away cylinder from coolant pump. http://www.superturbodiesel.com/std/...d.php?tid=6666
@S-Prihadi Q: how low have you seen the AC temperature in the evaporator? is it to specifications?
You can do 2 measurements:
1 - MaxCool, @2000RPM, with heater valve as is (open)
2 - MaxCool, @2000RPM, with heater valve blocked (closed)
How low can you go a the evaporator before freezing it? is there any design room to go lower?
That will give you the maximum capacity of the system, it will never cool better unless you change a lot more parts.
The heater valve is supposed to help dry the cooled air, so if it is always open there is no control; therefore, there should be no need for a humidity sensor. Have you seen the humidity sensor in XEntry? how much humidity does it show?
One thing though, remember M276 3.0TT uses a different compressor than non-turbo W212, wonder if the difference is not only the clutch but also the cooling capacity . That could be the reason W212 AC experiences are model dependent ??
I believed as per Xentry my EVAP is set at 2C. I will check again.
My last test on HVAC I do not have Xentry yet, it was iCarsoft. At that time I was applying heat shield to my HVAC refrigerant hoses.
I plan to do more HVAC test now that I know the system better and have Xentry.
I shall update
Your finding out some M276 engine variant feature normal coolant routing is very exciting news.
Thank you for sharing your heavy engine experience... now we want to increase the flow in bank2 instead of plugging it like stupid me. I like your point about heater core reducing the flow from bank2.
Imagine instead of sending hot coolant to the radiator, MB send it inside the cabin on selected models
Anywho I looked at my M276-NA today, apparently my heater clamp has fallen off already. Hopefully my bank2 head has not warped.
I remember Master Tasos pissed off at a car owner who had plugged his E63 heater core pipe 100% without any bypass. He simply said "that's not the way to do it". That sorts of prove hot climate UAE have heated air-con like we do... but not for long!
@S-Prihadi you want more cooling in the cabin, correct? You assume that ambient coolant circulation in the HVAC box maxes your “cooling” situation worse, correct?
More cooling = more hx from aircon system = more energy transfer = more power.
What you really want is an aftermarket modification to increase air conditioning performance. You want a “tuned” air conditioning system, using an engine performance analogy.
I offer that ambient engine coolant circulation should not be the focus. It is either immaterial (insignificant until you provide measurements otherwise) or not in your best interest to modify because it compromises the entire cooling system.
To get more aircon without modifying the coolant system, you need more heat transfer from the evaporator. Start with verifying evaporator efficiency. If the currently-installed evaporator output is not 100% vapor then the performance upgrade should be in the fan/warm air supply to the evaporator. This will extract all of the available hx the standard evaporator can deliver. No easy way to change the warm air inlet (return air from cabin) to the fan that I can think of.
If the evap is outputting 100% vapor then you can try to achieve more refrigerant flow. This could be done via different TXV or compressor but you might be limited by the pressure drops across evap and condenser. It’s a system.
Rather than go on the uncertain, time consuming and expensive journey above, you could look in EPC to see if Middle East countries of the same year as your vehicle offer different components for the aircon system. Look for different part numbers for condenser, TXV, compressor and evap. You want the “Saudi Arabia” aircon system.
The focus will ultimately arrive back at the evaporator, which as you know would be quite a project to change or modify. But you seem to enjoy challenges!
Anywho I looked at my M276-NA today, apparently my heater clamp has fallen off already. Hopefully my bank2 head has not warped.
So your heater pipe has no heater valve Cali ?
Clamp fell off but no leak yet right ?
I hope you have radiator tester. I got one from Aliexpress, not too bad but the one for Mercedes I need to modify a bit as the o-ring not so good and they made a mistake in installing another flat seal ...LOL
I hate the way MB does not show in real as-built coolant piping/flow schematic, even in WIS.
The way the parts are scattered all over the EPC is another headache.
In fact the WIS have a mistake on some hoses installed on my car for cooling system between the turbo return coolant and the heater core return coolant. My hose does not exist in the WIS for E400
I wonder in a model of M276 3.5 NA non turbo, if they do have heater shut off valve, there must be some sort of bypass hose to feed coolant pump suction side, otherwise where does the coolant pump get coolant when
thermostat is still closed shut ?
Too bad above can't withstand our coolant temp. Valve: Operating Temperature Range: -20°F to 250°F (-28°C to 121°C)
It need to be 150C rated as approx 136C is our 1.4 BAR coolant cap "burp & puke " temperature.
121C is my 3rd lap engine coolant temp, at my usual race/fun track
@S-Prihadi you want more cooling in the cabin, correct? You assume that ambient coolant circulation in the HVAC box maxes your “cooling” situation worse, correct?
More cooling = more hx from aircon system = more energy transfer = more power.
What you really want is an aftermarket modification to increase air conditioning performance. You want a “tuned” air conditioning system, using an engine performance analogy.
I offer that ambient engine coolant circulation should not be the focus. It is either immaterial (insignificant until you provide measurements otherwise) or not in your best interest to modify because it compromises the entire cooling system.
To get more aircon without modifying the coolant system, you need more heat transfer from the evaporator. Start with verifying evaporator efficiency. If the currently-installed evaporator output is not 100% vapor then the performance upgrade should be in the fan/warm air supply to the evaporator. This will extract all of the available hx the standard evaporator can deliver. No easy way to change the warm air inlet (return air from cabin) to the fan that I can think of.
If the evap is outputting 100% vapor then you can try to achieve more refrigerant flow. This could be done via different TXV or compressor but you might be limited by the pressure drops across evap and condenser. It’s a system.
Rather than go on the uncertain, time consuming and expensive journey above, you could look in EPC to see if Middle East countries of the same year as your vehicle offer different components for the aircon system. Look for different part numbers for condenser, TXV, compressor and evap. You want the “Saudi Arabia” aircon system.
The focus will ultimately arrive back at the evaporator, which as you know would be quite a project to change or modify. But you seem to enjoy challenges!
Good one, thank you .
I actually wanted to recover my R1234a so I can measure if indeed by weight it is to MB spec or not, with a good machine approved by MB. This is one parameter I must make sure to be within spec.
However, the machine does not have the optional refrigerant analyzer and I fear I may get unlucky when and if someone before me has a contaminated system.
So I decided for now, I got to wait.
As I said, this heater core DIY semi by-pass is also to gain more coolant flow to my Bank 2 , as side bonus from hoping to get the least heat contamination from heater core.
Let me device a good test to read all available perimeter I can read with the instruments I have at hand.
===================
I looked at my last tests where I got the evaporator temperature provided by the MB computer. 1st June 2021.
K,
If your engine comes with heater core shut-off valve, you are gold and hence you HVAC is not heat contaminated by the heater core.
The OM651 has that valve. I do not know about your engine.
The M272, M278 older version, and M157 has the heater core shut off valve.
I never had a need to dig the subject to this extend.
From about 20 MB we did own and who were often operated up to 120F/50C cooling was never a problem.
Fact is that I had to learn how to service AC "by a fire".
When I was learing mechanics in Poland, we never had AC in the country. So moving to California made the learning curve very urgent.
If you have XENTRY you can do a full aircon system diagnosis. If everything is nominal, the system is “working as designed” as the MB service department would say.
If XENTRY shows outlet air temp in the correct range, there may be limited or no additional performance possible.
In the end, the aircon system has the job to deliver target air temp together with target refrigerant temp and pressure. If these parameters are in spec, the car has done its job.
If you want something with more performance you would be asking for an upsized aircon system which means more airflow (fan power) and more refrigerant flow (compressor power) and more hx (evap power). The evap needs to be fed with more warm cabin (return) air to drive more refrigerant flow. But the system will not deliver more hx if the min evap temp is achieved.
@S-Prihadi , have you look at your AC pressures, both low and high side? The last picture with pressures at 10 bar, seems low to me with an ambient temperature of 34C. Wonder what the low-pressure side was at the time?
If the evaporator is already at 4C, the only room left is from 4 C->2 C, below that you will be looking for freezing outside the evaporator and blocking the airflow. Since @chassis opened the door for technicals, :
The evaporator should work as -> Heat removed from the air = Heat added to the refrigerant, the high-level parameters at that point are (not getting into the subtleties of how to compute the temperature changes)
Heat removed from the air = flow of air * air heat capacity * Temperature change of the air when crossing the evaporator= C_air * (T_air_hotside - T_air_coolside)
Heat added to the refrigerant = flow of refrigerant * refrigerant heat capacity * Temperature change of the refrigerant when crossing the evaporator = C_ref * (T_ref_hotside - T_ref_coolside)
Those parameters have limits based on physics, or the constrain of the system:
1 - 1st limit: the refrigerant cannot be hotter than the coolest air when leaving the evaporator
2 - 2nd limit: we cannot allow freezing of moisture in the evaporator, i.e. lowest temperature in the evaporator is limited by the freezing point of the water in the air
Equaling both formulas, and assuming an ideally perfectly working device (impossible) we can solve for the parameter of interest to you: T_air_coolside
As @chassis mentioned, you can adjust some of those parameters. For the T_air_coolside to get lower, you can only
1 - increase C_air (flow rate --> AC blower only since you cannot change thermodynamic properties of the air)
2 - increase C_ref (flow rate of refrigerant --> higher capacity compressor, and more or different refrigerant in the system which is not arbitrary since limited by volume and compressor design. Hope you get where this is going.
3 - lower the T_ref_coolside (TXV valve allowing a lower temperature due to the expansion of refrigerant w/o freezing in the evaporator, and/or cooling further in the condenser, i.e. increase the speed of the radiator fan/add another fan.
4 - Of course, the most difficult one is lowering T_air_hotside since you can only do that by moving to a cooler area (mountain or another country, Canada perhaps? )
All the above is a rough estimate. A real heat exchanger is never 100% efficient; therefore, refrigerant never reaches the lowest possible temperature (2nd law of thermodynamics); therefore, T_air_coolside will always be hotter than ideal given a fixed refrigerant, and compressor/system capacity.
@S-Prihadi , have you look at your AC pressures, both low and high side? The last picture with pressures at 10 bar, seems low to me with an ambient temperature of 34C. Wonder what the low-pressure side was at the time?
If the evaporator is already at 4C, the only room left is from 4 C->2 C, below that you will be looking for freezing outside the evaporator and blocking the airflow. Since @chassis opened the door for technicals, :
The evaporator should work as -> Heat removed from the air = Heat added to the refrigerant, the high-level parameters at that point are (not getting into the subtleties of how to compute the temperature changes)
Heat removed from the air = flow of air * air heat capacity * Temperature change of the air when crossing the evaporator= C_air * (T_air_hotside - T_air_coolside)
Heat added to the refrigerant = flow of refrigerant * refrigerant heat capacity * Temperature change of the refrigerant when crossing the evaporator = C_ref * (T_ref_hotside - T_ref_coolside)
Those parameters have limits based on physics, or the constrain of the system:
1 - 1st limit: the refrigerant cannot be hotter than the coolest air when leaving the evaporator
2 - 2nd limit: we cannot allow freezing of moisture in the evaporator, i.e. lowest temperature in the evaporator is limited by the freezing point of the water in the air
Equaling both formulas, and assuming an ideally perfectly working device (impossible) we can solve for the parameter of interest to you: T_air_coolside
As @chassis mentioned, you can adjust some of those parameters. For the T_air_coolside to get lower, you can only
1 - increase C_air (flow rate --> AC blower only since you cannot change thermodynamic properties of the air)
2 - increase C_ref (flow rate of refrigerant --> higher capacity compressor, and more or different refrigerant in the system which is not arbitrary since limited by volume and compressor design. Hope you get where this is going.
3 - lower the T_ref_coolside (TXV valve allowing a lower temperature due to the expansion of refrigerant w/o freezing in the evaporator.
All the above is a rough estimate. A real heat exchanger is never 100% efficient; therefore, refrigerant never reaches the lowest possible temperature (2nd law of thermodynamics); therefore, T_air_coolside will always be hotter than ideal given a fixed refrigerant, and compressor/system capacity.
^spot on^ can’t be said any better. Well done @juanmor40 !
Before I do the CHOKE ( use vice grip) the heater hose from engine Bank2 azz to HVAC heater core to study the difference , I looked at Xentry available real time data I can observe :
I was hoping to see PWM duty signal to the compressor and fan speed command to the fan.
Too bad fan speed data can not be read when I am in N22/7 HVAC module. Being a shared fanfor HVAC and engine cooling, MB need to do balancing act for its love of coolant temp target of 95-105C and HVAC would be a 2nd priority , I think.
The compressor duty cycle value 285 I marked red if can be translated to duty cycle....... it will be good, otherwise me need to scope/read it with a multimeter duty % menu.
This variable displacement compressor is not easy to see its pressure behavior, which is software based and not like a fixed displacement ON-OFF only compressor. To answer Juan question of low pressure/suction value on my compressor: I do not have the HVAC gauge/manifold to read LP pressure.
Evap is super clean. Air filter for blower is super clean. Condenser is super clean.
Assuming MB Indonesia done a good job and have vacuumed my HVAC system down to 500 microns of better and has charged it exact grams as per their spec aka my HVAC system is 100% OK,
now me have to look for any parameter in the coding which does not benefit me.
2 perimeters seemed to me as fuel efficiency priority and "noise" priority and not performance priority.
Mine is R134A.
Z04 code seems to be armored car or higher level protection car. More heat from machine gun ??
BELOW : Damn, my city traffic is LOUD, so what if the fan goes faster & louder ?
BELOW : MB code special parameters , because they know that the cooling capacity of the engine coolant system get reduced when heater core take a portion of the coolant flow instead of sending it to the radiator.
The powering up of this additional coolant pump is purely to increase coolant flow at heater core and not increase cooling capacity of radiator.
They should call it HEATER COOLANT PUMP and not additional coolant pump as though as it is for radiator cooling assist.
My naughty XENTRY Passthru can't change the coding/parameter............wont work , the ACCESS key is greyed out.
====
But my baby Launch Creader can !!!
NOPE, I have not change any of the parameters above.
Me want to do CHOKE that heater hose test first.
@S-Prihadi , noticed the [285] entry is 0, I take your AC was not running when you took the snapshot, correct? That entry is the "electric control valve" at the back of the compressor.
You can actuate the control directly from XEntry, from 0->100%, and you can measure your temperatures at the vents and see how it influences your cooling efficiency. I am no expert on these systems (or anything for that matter ), but I think the manifold gauges are mandatory to evaluate these variable displacement compressor AC systems. You do not want the low-pressure side to be "high" @50->70psi which seems to be a common occurrence, you wanted 30->40psi. Without that data point, I think you are driving blind. With the manifold, you can also "estimate" how fast the TXV valve is "relaxing" when you turn the AC off, i.e is it slow/fast to respond to changes.
Continue............
My naughty XENTRY Passthru can't change the coding/parameter............wont work , the ACCESS key is greyed out.
Surya, you may have to support the amazing source a bit longer. There is a way to activate the basic parameter changes using XEntry + Tactrix Passthru, or instead of using Tactrix Passthru using VCXDIag SE for Benz. It is not C4/C5, but it works. I guess that since you are getting the BenzNinja system, you will not need it anymore.
@S-Prihadi , noticed the [285] entry is 0, I take your AC was not running when you took the snapshot, correct? That entry is the "electric control valve" at the back of the compressor.
You can actuate the control directly from XEntry, from 0->100%, and you can measure your temperatures at the vents and see how it influences your cooling efficiency. I am no expert on these systems (or anything for that matter ), but I think the manifold gauges are mandatory to evaluate these variable displacement compressor AC systems. You do not want the low-pressure side to be "high" @50->70psi which seems to be a common occurrence, you wanted 30->40psi. Without that data point, I think you are driving blind. With the manifold, you can also "estimate" how fast the TXV valve is "relaxing" when you turn the AC off, i.e is it slow/fast to respond to changes.
Yes, engine is OFF when I read the parameters.
285 - the word POWER CONSUMPTION with A as unit, that is supposedly Amperage ........would not be duty cycle , unless Xentry uses 1.00 as 100% and give me 0.50 as 50% duty.
Yes, agree, I need to buy a pressure gauges. I will get two with shortest pipe to loose least gas. I am A/C fittings stupid
My vice grip is small, I can't completely shut the coolant flow to the heater core, but at least 80% blockage I think achieved.
AC turned ON only when idling speed has gone down to 700ish. This engine start is from COLD ( 29C ).
So the so called POWER CONSUMPTION of A9 compressor has a wrong unit of A ( Amperage ) but it seems it is relate-able to 100% duty. As 1.00 is the highest.
Pay attention to the yellow highlight, the DELTA value and the EVAP temp.
At minute 5 of 1st June 2021 and 4ish minute of today's test, the raised RPM for today was only 15 seconds duration ago towards 4mnt 29second..
Today with 80% choked heater core hose, albeit a 69C hot coolant flow will still happened and not completely stopped, the gain is so obvious.
In 2021, the evap can only remove 22.6C of heat in 5 minutes with heater hose totally open flow to heater core. Today 2023 the evap can remove 25C of heat while 30 seconds less time.
The air vent air flowing out temperature, in 2021 was 10.8C and in 2023-choked hose was cooler at 7.2C.
The delta was 6.1C vs 3.2C. This is so obvious the heater core heat contamination is a FACT.
Loosing 2021 vs 2023 : Loosing 2.9C of cool-ness for an air moving distance from EVAP to vent , a mere 20cm ish.....is A LOT of wasted energy from heater core heat contamination.
2021 heat lost for that short distance was 6.1C , 2023-choked hose heat lost only 3.2C.
My working room overall ambient temp I like if at 23C, if it get to be 26C, I freak out, its hot for me. 3C difference is gold, even 2C is valuable.
At the 8 minute ish HVAC run time, me raising RPM to 1,000ish for 3.5 minutes since 4ish minutes HVAC run time, have raised the coolant flow & pressure and it is so obvious I lost cool-ness
to 5C for evap to vent, also the engine coolant has reached 84C and that means the thermostat has not open to reduce Bank 2 azz pressure by diverting hot coolant to radiator.
So heater core get more hot 84C coolant flowing thru it.
Yes, 2023 my evap was cold at 4.3C but by the time the air has reached near the vent it is already heated up to 9.3C...damn heater core heat contamination at work... !!
=======================
Here is a unique finding.
I un-clipped the vice grip at camera clock 18:47. I let hot coolant flow better to heater core. Note : my camera clock is slower by near 4 minutes from the laptop clock.
I then turn ON the heater by setting temp to HIGH few minutes later.
Approx 10 minutes later, vent temperature already went up to 49.5C as highest and this is a recycle mode, not fresh air mode
So, even at HEATER mode, the HVAC compressor does not stop working.
Is the HVAC compressor still running because I did not DE-Actvate A/C button ?
Well, the A/C button is useless there because the computer does what the computer likes. Only total power OFF to HVAC computer and loose heat too, the most right button is POWER, there is no way I can kill the compressor.
By using fresh air or outside air, I can then add more heat to cabin because my outside air is hotter than interior air temp, also engine bay temp is hot when car is stationary for 20+ minutes.
Now watch what happen when I have "removed" partially the heat energy stored in the heater core by diverting/removing its heat to the cabin and then I set HVAC to COLD at 19:05
By 19:07 or within 2 minutes COLD setting running, the EVAP core goes down so fast to 3.2C and air vent temp coldest ever on record at 5.1C with only loss of 1.9C, because the heater core
heat energy at this particular time was already spent a great deal . So the WAS-hot-heater core as heat contamination is much reduced by 19:07 time.
So.......... this DIY heater core bypass project is worthy to continue
02-20-2023, 12:18 PM
. I wonder if I totally shut flow at #3 plastic pipe, how much more pressure can build* up there ? ( *when thermostat still closed )
. That could be the reason W212 AC experiences are model dependent ??
.
.
