Would like to replace the dual fans

If I could figure out a way to use the Volvo/Ford assembly off my C30, I would do it. Just too tall :( Since it would be tied to the EMS in my case, the fan runs at variable speed (beyond the two basic hi/low) to maintain proper coolant temp based on engine temp, not rad temp. The feed & ground wires are substantial gauge - compared to the stock or generic fans.

Have you tried using the controller with the existing fans? There is little reason a PWM controller couldn’t pulse the existing fans.
 
Have you tried using the controller with the existing fans? There is little reason a PWM controller couldn’t pulse the existing fans.

I haven't. I'm using aftermarket fans with the shroud I made & I never did make the vent flaps, so I plan on removing the rad/shroud when I drop the drivetrain to clean all that up. I'm going to use the lower temp fan switch, but also use the EMS ground , which may modulate fan speed anyway, vs. the on/off stock setup. Basically, I'll have two methods of fan control.
 
the fan runs at variable speed (beyond the two basic hi/low) to maintain proper coolant temp based on engine temp
Spal and another fan company showed the same design at a trade show about a year or so ago; continuously variable speed controlled by a module to regulate the fan output based on engine temp. Expensive but a great idea.
 
Have you tried using the controller with the existing fans? There is little reason a PWM controller couldn’t pulse the existing fans.
That would be interesting. If it works it might be a more affordable approach at this, depending on the availability/cost of the module. But I imagine several cars have this sort of thing these days, so perhaps a module could be sourced inexpensively at wrecking yards.
 
I'm running two stock fans through the stock 16-amp fuse, and it hasn't blown yet.

I measured the current draw of the stock fan - the inrush current peaks my 20A linear power supply (peak current duration is pretty short, but the data logger of the power supply picked it up, next I'll put it on the scope).

I don't have all the currents available to share at the moment, but I tested at 9V, 12V, 13.5V, and 14.4V (14V) The original harness limits the voltage at the fan - best option is to wire a relay and a fused feed off the battery. There is a noticeable improvement in fan speed - judging from the change in sound. I didn't measure the RPM, my tachometer can't be found at the moment!! I installed a relay on my car, and the fan has never sounded healthier! (albeit, it is LOUDDDDD!!)

Ideally the voltage at the fan is 14V (ideally the voltage is this high at the fan, unfortunately it's far less with the stock harness - I've measured as low as 10V with the alternator putting out 13.5V at idle) - one fan with application static pressure using a 17 tube 3-core rad measures 15.3A with the power supply set at 14.4V! - It is pulling a LOT of air. My next step is to try and measure air flow in CFM. At 13V, the current dropped to 13.66. Lower voltage, the current draw is less - but so is the amount of air its pulling. Lowering the supply voltage "sounds" very different.

I imagine the stock fan pulls a lot of air and does a good job of keeping the car cool in traffic - but it is annoyingly LOUD! In my opinion, best choice of fans is BLDC (brushless DC) - but they're pricey (Spal offers them) but they'd be the most efficient.

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Stock late model fan is just over 2 kg = 4.409 lbs - earlier units had a plastic shroud/frame.

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I measured the current draw of the stock fan - the inrush current peaks my 20A linear power supply (peak current duration is pretty short, but the data logger of the power supply picked it up, next I'll put it on the scope).

I don't have all the currents available to share at the moment, but I tested at 9V, 12V, 13.5V, and 14.4V (14V) The original harness limits the voltage at the fan - best option is to wire a relay and a fused feed off the battery. There is a noticeable improvement in fan speed - judging from the change in sound. I didn't measure the RPM, my tachometer can't be found at the moment!! I installed a relay on my car, and the fan has never sounded healthier! (albeit, it is LOUDDDDD!!)

Ideally the voltage at the fan is 14V (ideally the voltage is this high at the fan, unfortunately it's far less with the stock harness - I've measured as low as 10V with the alternator putting out 13.5V at idle) - one fan with application static pressure using a 17 tube 3-core rad measures 15.3A with the power supply set at 14.4V! - It is pulling a LOT of air. My next step is to try and measure air flow in CFM. At 13V, the current dropped to 13.66. Lower voltage, the current draw is less - but so is the amount of air its pulling. Lowering the supply voltage "sounds" very different.

I imagine the stock fan pulls a lot of air and does a good job of keeping the car cool in traffic - but it is annoyingly LOUD! In my opinion, best choice of fans is BLDC (brushless DC) - but they're pricey (Spal offers them) but they'd be the most efficient.

View attachment 52979


View attachment 52981

Stock late model fan is just over 2 kg = 4.409 lbs - earlier units had a plastic shroud/frame.

View attachment 52982
Excellent research Myron!!! Very well done with proper testing, I love it. 😊👏🏆

Fans do have a very high but very brief initial spike. Since a fuse is relatively slow burn it doesn't blow despite the draw being more than the fuse rating for that instant. Modern fans are available with a module that ramps up the initial speed just enough to reduce that initial spike significantly. They also have the added benefit of being able to vary their speed to match the need (i.e. temperature control).

Couldn't agree more, the current is limited with the stock wire harness.

I think efficiency is the key. While the stock fan may draw a lot of air, it is doing it inefficiently. That results in more electrical demand and more noise. You can get the same or more flow from a aftermarket fan (as you suggest) with much less draw and noise. And it will be much lighter.
 
We need weight in the nose…

Yes lighter is better, less wieght, less horsepower needed to sate the savage right foot…
 
This is as easy as gets. Get any dual spped fan without a controller. Wire it to ignition as pictured, or wire directly to 12v. If direct to 12V the fans will continue to run until the radiator has cooled down. You can also use the cooling down stage stage to put a fan in the engine compartment to remove radiant heat. Done this on many cars. 928's, Boxster and currently doing it to a Cayman and will also do it to my X1/9.

For the 928 I used a large single dual speed fan from a 2004 Ford Falcon. I removed the factory shroud with a Dremel and then mounted it in the original 928 shroud. The 928 was an 86 model that used an engine fan. Noisy and just not that efficient. The new fan worked flawlessly in South Australian 42c summer days.
 

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