Sanden 4440 install

[L31MaxExpress]

And later:


So that puts you at a total of 11oz (volume) of oil for your 68oz (weight) R134a system, if my math is correct.

Correct. I have never changed the oil amount switching to a different refrigerant either.

Is your objective to charge the system with the same volume of refrigerant?

As I know you know, but which some readers may not have recognized, is that the system can only accommodate a certain volume of refrigerant; that is one consideration in the “refrigerant substitution” game.

The density of R134a is 4.25 kg/m³.

That of R152a is 2.7 kg/m³.

So I might assume one would substitute ~40oz of R152a for 64oz of R134a, i.e., scaled by the ratio of their densities.

Comments? I’m learning here, not pontificating.

Next, I assume the orifice tube is selected to provide a similar product for the "mass flow" * "heat of vaporization". I suppose this is practically the same as saying "select the orifice tube to achieve the proper vent temperature" under similar conditions.

Then, the compressor volume per revolution relationship comes into play, but I’ll save that thought.

Note: It may appear I’m mixing-up my dimensions here by scaling the oz (weight) of refrigerant using densities given in terms of kg/m³, but that’s not the case; by dividing one density by the other, the result is a dimensionless scalar. So, the resulting refrigerant amount is still oz (weight).

No my objective is to get the system to a point where it has the proper superheat returning to the compressor without getting liquid back to the compressor. I ended up slightly past the point where the suction line returning to the compressor starts approaching the temperature of the inlet of the evaporator. Properly charged you want to stop right when the suction line is about 3-5° warmer than the evaporator inlet. I was at about 6-8° and thought I could get them closer when I was charging and added another 2-3 ounces and all it did was raise both the suction and discharge pressures and warm up the inlet and outlet to the evaporator.

 

[L31MaxExpress]

Since I am working on wiring the fan into a relay to control via the PCM as an auxiliary fan and a few other things tonight. Took a few pictures. Its close but with a rigid mounting setup it is no closer than the electric on my Pathfinder.

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There is the sanden.

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I am re-installing my cruise control as this thing wants to roll 90 with ease.

 

[1998_K1500_Sub]

There is the sanden.

I had forgotten you used the Sanden #4261 which has the smaller (~112mm) pulley. I know that it’s spec’d for the Express.

I used that #4261 on my Suburban L31 to provide increased AC pumping volume vs. engine RPM. Typically GMT400 L31s use the #4440, which has the larger OE-sized (~132mm) pulley.

My L31’s crank pulley is 8”. I wonder if the Express L31 uses a smaller one.

 

[1998_K1500_Sub]

My objective is to get the system to a point where it has the proper superheat returning to the compressor without getting liquid back to the compressor. I ended up slightly past the point where the suction line returning to the compressor starts approaching the temperature of the inlet of the evaporator. Properly charged you want to stop right when the suction line is about 3-5° warmer than the evaporator inlet. I was at about 6-8° and thought I could get them closer when I was charging and added another 2-3 ounces and all it did was raise both the suction and discharge pressures and warm up the inlet and outlet to the evaporator.

Noted. In terms of “charge ounces”, as long as you didn’t exceed the number I qouted earlier (which you didn’t) you’re OK from a “system volume limitation” perspective.

I understand your perspective on superheat as well. Could you have instead tweaked the superheat with a different orifice tube (mass flow)? If so, which method is more optimal (ignoring the work involved with swapping orifice tubes)?

 

[L31MaxExpress]

I had forgotten you used the Sanden #4261 which has the smaller (~112mm) pulley. I know that it’s spec’d for the Express.

I used that #4261 on my Suburban L31 to provide increased AC pumping volume vs. engine RPM. Typically GMT400 L31s use the #4440, which has the larger OE-sized (~132mm) pulley.

My L31’s crank pulley is 8”. I wonder if the Express L31 uses a smaller one.

Factory pulley was 8" on the van. My March crank pulley is 6". So 25% underdriven on the compressor and p/s pump. The march water pump pulley is slightly larger than stock and calculates to 33% underdriven. The alternator pulley shipped is for stock ratio on it. The underdrive pulleys work really well in my setup. With the loose 2,800 rpm stall converter, I idle the engine at 850 with the a/c on. The stock L31 would have to idle at 637.5 rpm to equal the compressor speed my van has at idle. IIRC the stock L31 idles like 550 rpm. Off-idle my rpm rises and stays a bit higher than a normal L31 with the converter slip.

 

[L31MaxExpress]

Noted. In terms of “charge ounces”, as long as you didn’t exceed the number I qouted earlier (which you didn’t) you’re OK from a “system volume limitation” perspective.

I understand your perspective on superheat as well. Could you have instead tweaked the superheat with a different orifice tube (mass flow)? If so, which method is more optimal (ignoring the work involved with swapping orifice tubes)?

I believe you will transfer more heat with a higher pressure differential with a smaller orifice. The condensing pressure and thus temperature will be higher and the smaller orifice will allow the refrigerant to cool more in the condenser. If the refrigerant is not cooled well it turns into almost a foam going through the orifice. The froathy foam does not do a good job cooling. The smaller orifice will also reduce the suction side pressure and lower the refrigerant in the evaporators boiling point. Its a bit of a balance though. What helps at idle, does not necessarily help at highway speed. I have tried every orifice from 0.071 to 0.057 in this. The best balanced on both R134a and R152a has been the Red 0.062 Ford. Which is why I chose to try the variable orifice. It closes off to a smaller opening at idle and only opens fully if the head pressure rises excessively. On the highway when pressures drop it opens up to allow more mass flow.

 

[L31MaxExpress]

I started a new thread on the Duramax blade but since we were talking ac performance, will share it here too. So I did a thing last night while I still had this apart. I trimmed the Duramax fan blades to clear the 01-02 shroud, bolted it up to the 2007 TBSS severe duty thermal clutch I had on it before and spun it on the water pump. Still clears with virtually the same clearence. It will definately move some air now especially when the PCM calls for the auxiliary electric fan to be on.

Will let you guys know what it does for refrigerant pressures, vent temps, and engine temp later this afternoon when it gets hot. Think they are calling for it to be 104F this afternoon.

Used the first trimmed blade as a template. Sharp scissors cut through the blade material like a hot knife through butter.

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[L31MaxExpress]

Results are in, posted them in the duramax blade post in more detail. But with the 16" electric fan running, after 10 minutes idling in 102°F it was down to 38° in the center vent and 40°F out the far left vent. A/C pressures were 255 and 39. Van was an igloo at that point, switched the 16" fan off. The pressures slowly increased to 275 and about 43. The center vent rose to 45°F and the left vent about 46-47°F. That is still 10°F or more better than the stock van did with R134a, vent temps would have been around 60°F with the stock fan, stock condensor, stock compressor and R134s. I turned the fan back on, idled it up to 1,350 rpm and after 5 minutes the center vent had dropped to 36°F at which point the compressor cycled. Pressures where about 250 and 30 when I looked a minute or so after the compressor cycled and the low side was slowly decreasing. I think it is cycling at about 26 psi.

Left vent after 10 minutes with the 16" fan on.

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AC pressures with the fan on

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Center vent after 10 minutes with the fan off.

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Pressures after 10 minutes with the fan off. Electric puller is knocking 20 psi off the head pressure and a few psi off the suction pressure.

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I will also add, I have yet to re-install the accumulator blanket so it is just soaking up engine compartment heat. I tore the old one trying to remove it and have a new one on order. Last time I replaced the missing blanket the temps dropped 2-3°F at the vents and it knocked about 2-3 psi off the low side reading and about 8-10 off the high side. I think I can get it to idle at around 35-36°F out of the vents.

 

[1998_K1500_Sub]

@L31MaxExpress, you do good work.

 

[L31MaxExpress]

After I finished messing around on the van, jumped in the 2011 Pathfinder that was sitting in the shade to drive home. After 20 minutes of actual driving, it was down to this when I parked in my driveway. Properly charged R134a system with a heavy duty fan clutch. It also has a factory electric puller, where I got the idea to add the one on the Van. Performance is typical of a dual evaporator R134a system. On the highway it will get into the 30s, cruising around at low rpm in stop and go driving it struggles. Just a comparison point of R134a vs R152a in a similar system. Its not apples to apples but a valid comparison as they were both dual evaporator OE R134a systems.

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