Better AC with different size pulley?

[L31MaxExpress]

Actually, I am not sure about the heater question. I have often wondered just how much the heater figures in to things. In overheat emergencies, which happen all too often during a life in the desert, we always turned the heater on high to try to suck some extra heat out of the motor.

In this case, it is a moot point, as I have the heater on a manual on/off valve. I do not want that hot water sitting in my A/C box.

What do I want? We really do have 125+ degree days here. Lots of them. Sometimes 115+ in the middle of the night. Manufacturer's extreme conditions testing ground is near here for a reason. Our cooling systems must be Super Duty +++. This is a stock engine-- no performance improvements such as headers or high compression that would complicate cooling.

I want enough cooling performance that it will sit at a long stoplight, and never go above the thermostat rating temp, with the A/C on and 120 degrees ambient temp.

It's not impossible; the cop cars idle for days without a "China Syndrome"!!

I am looking at handheld anemometers to check airflow. As I mentioned, there is room in my fan shroud for a larger diameter fan. How critical is that fit?? Could this be my problem?? Again, once traffic starts rolling, it cools right back down, but it's at 200+ and climbing at the stop.

Thanks,
Vettepilot

If your truck is a Vortec with a spin on fan clutch should be relatively easy to use the Duramax blade. GM 1580690 on the Hayden 2851 clutch. I ended up having to trim a bit of the blade length to fit in the fan shroud of my Express van. It has not been a problem. I followed the contour of the blade, marked the distance I needed to trim, IIRC it was 5/8" or so, then trimmed the first blade. I used the trimmed off piece as a templete to mark the rest of the blades. A sharp pair of scissors or tin snips will go right through the plastic blade. Even with the blades trimmed a bit, the Duramax fan has a lot more surface area and pitch than the 11-bladed tow package fan.

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[1998_K1500_Sub]

In this case, it is a moot point, as I have the heater on a manual on/off valve. I do not want that hot water sitting in my A/C box.

Good!

I want enough cooling performance that it will sit at a long stoplight, and never go above the thermostat rating temp, with the A/C on and 120 degrees ambient temp.

It's not impossible; the cop cars idle for days without a "China Syndrome"!!

Random thoughts I have (as I tap on my phone):

An engine at 200F is not “hot”.

At 15PSI pressure a 50/50 mix boils at 268F.

Reflecting on the “cop cars”:

On my 1998 L31, the ECU will take remedial action by disabling the AC when coolant temps exceed a threshold of ~124C (256F), as a means of mitigating high engine temps. Evidently GM thinks that’s appropriate. That’s almost 100F higher that 160F.

So the cop cars, if similar mitigation steps are used, benefit from a LOT of temp rise across the radiator to shed heat, as compared to your objective of 160F.

I don’t know what GM’s “cop” option provides in terms of radiator airflow but I’m sure it’s an engineered solution.

To mitigate recirculation of hot air, GM may have also provisioned the “cops” with additional air baffles.

For reference, OE aux cooling fan option on the 1997 L31 appears to enable at 225F.

Your goal of maintaining engine temps anywhere near 160F while stationary sounds aggressive. GM seems to take a relatively relaxed approach.

I would be interested to see what the temp is behind the AC condenser / into the radiator in your target conditions with your current radiator fan.

The more air you can move at idle, the more efficient your AC will be, and the closer you’ll get to your 160F objective.

Please keep us updated as this effort pans out

 

[JohnZ71]

If your truck is a Vortec with a spin on fan clutch should be relatively easy to use the Duramax blade. GM 1580690 on the Hayden 2851 clutch. I ended up having to trim a bit of the blade length to fit in the fan shroud of my Express van. It has not been a problem. I followed the contour of the blade, marked the distance I needed to trim, IIRC it was 5/8" or so, then trimmed the first blade. I used the trimmed off piece as a templete to mark the rest of the blades. A sharp pair of scissors or tin snips will go right through the plastic blade. Even with the blades trimmed a bit, the Duramax fan has a lot more surface area and pitch than the 11-bladed tow package fan.

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i have GOT to do this. I'm with Vettepilot, i want the most extreme cooling system. Beyond overkill. i don't care if i end up getting 9mpg, i want it to stay cool and the AC Freezing.

 

[1998_K1500_Sub]

i want ... the AC Freezing.

Dual AC condensers were installed by @Wildblue19 on a GMT400, here:

https://www.gmt400.com/threads/88-94-5-7-suburban-a-c-diagnosis-and-tuning.59125/post-1408382

(and dual compressors as well, for a dual evap system)

@L31MaxExpress has also experimented with alternative refrigerants and reported his results on GMT400; search for “R152”.

IIRC he's even experimented with dual condensers in series; if not, I'm pretty sure he's talked about it.

 

[L31MaxExpress]

I tried another trick this evening. I swapped the blower wheel for a metal wheel with thinner vanes and more opening between the vanes. It made a slight improvement in the output. By slight it did see 14.8 mph before the blower/alternator heated up and settled down around 14.0 mph continuous. That is about 1/2 mph improvement. You would think after all these years the aftermarket would offer a higher rpm blower motor capable of moving more airflow. Next step is going to be to tape up the ducting. I feel that is going to make the biggest improvement, especially blocking that vent next to the engine cover pointing nowhere off.

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[KansasOBS]

Interesting to see the speeds, and fan testing. I will say the new gmt400 that I was like "wow, this ac sucks" was a suburban. Rode a lot in a gmt400 panel van that was new also, it didn't do terribly bad. No windows, maybe that helped to an extent, but it was still a bare metal box.

Its been a few years now, but I used to design/build/fly fpv freestyle drones. All this talk about motor RPM got me thinking. Person could probably just gut out the center of a junk fan, for the flange. Or even lay one out in CAD, and have it cut out of carbon fiber, by some places that do such, for not a lot of money. Grab an ESC, and a brushless BLDC (3 phase) motor. Mount it up. Replace the guts of the fan speed knob with a pot, connect that to the ESC, and have a really strong variable blower.

Would also allow a person to ditch the resistor pack.

I would say I could design and build, but not sure its worth it. Doubt many of you would want to get into the gutting of heater controls. A know could be added elsewhere, but that's kinda meh.

 

[1998_K1500_Sub]

All this talk about motor RPM got me thinking.

Mebbe…

- take an existing fan,

- apply +14V, +15V, …, +++

- measure the airflow with each voltage increment to learn what is attainable within the physical limitations of the fan housing and air handler

Just don’t burn up the fan motor in the process.

I’d love to see the numbers.




Later, if warranted, give thought to an improved-design motor / PWM / IBGT / VFD / multiphase solution.

 

[Vettepilot]

Yeah, the high temps modern engines run at are ridiculous, bad for power, detonation resistance and longevity, and none of my engines are ever going to run that hot---> never!! They only run them that hot for smog purposes anyway. Yes, I understand that anti-freeze plus pressure raise the boiling point. Doesn't matter, I will never run mine that hot, it's ridiculous.

Thanks for the fan advice, but I don't like and don't run clutch fans.

Yeah, on the HVAC airflow, we need a higher KV motor. We have the amps...

We need someone to pull theirs, one that's in good shape, and tach it at 12.5 volts so we can figure out the stock KV, then just search out a replacement motor with a higher KV. Might take a little adapting, but we can do that...

Vettepilot

 

[L31MaxExpress]

Forgot to post this one. That is a GMT400 pusher fan with the shorter bracket flipped upside down and the longer mount legs bent to hold the fan in the desired location. They work fairly well.

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[1998_K1500_Sub]

You earlier cited the cop cars as an example:

“It's not impossible; the cop cars idle for days without a ‘China Syndrome’!!”

yet you don’t like their method:

Yeah, the high temps modern engines run at are ridiculous

Ok then, show us the cooling fan solution(s) you craft that finally satisfy your objective. I’m interested.

I’ll offer to help. Tell me how much heat you need to sink per unit time (BTU, kW), the ambient air temp and coolant temp (you’re set on 160F) and I’ll tell you the minimum CFM it’ll take to do the job.


On the topic of blower motors:

We need someone to pull theirs, one that's in good shape, and tach it at 12.5 volts so we can figure out the stock KV,

“KV”?

“kW” probably…

Measuring the voltage and current is easy-peasy, multiply them and their product is the applied power (W). Maybe @L31MaxExpress will oblige if we ask nicely.

“Tach it” - do you need the RPM? Can do, with a ‘scope.