Get a PWM fan controller. It will make a huge difference.

Pardon Our Interruption...

 

I have a Davies Craig controller that cycles my fans like on new cars by using a thermostat that I set the on/off temps.

 

That’s actually one of the reasons I like the factory electric fans, they are durable, efficient and quiet. I have a 90’s V8 T Bird 2 speed fan on mine and you can hear it outside, but not inside. Granted, my car is not super quiet, but the fan is not loud at all.

 

Agree, mine are aftermarket, but inside I sure can't hear them, and outside just a little bit.
Now with the car off...still not very loud IMO... think of the old box fan on high ?

Number of blades and blade pitch will make a difference. I think that's why Spall ? went to those curved blades ?

 

Curved fan blades are quieter than straight fan blades.
An axial fan with straight blades is more efficient than one with curved blades.
Turbulence of the air going through the radiator fins causes noise.
Sound deadener placed under the hood will help get rid of some of the noise.

 

I'm still finishing up some stuff before I'm back on the road but I'm using the Northern PWM fan controller Don pointed out. I guess it runs the fans at 2-speeds, a low speed where you can't even hear them and a high-speed where with the hood up you definitely hear them. IIRC, Carl designed the circuit to run at 50% and 100%. In my setup, I'm using a dual 12" setup repurposed out of a Ford SVT Contour, and these 6-bladed fans have the curved, scythe style blades. I have an underhood sound pad, so I'm hoping that the 100% speed is tolerable if and when its needed. I've only run the motor a couple of 20-30 minute warm up sessions, the fans go on at low speed at 180-ish, and kick into high speed at around 195°. I just added the NIOSH DB meter App on my iPhone and will check the sound eventually. My BBC with solid lifters is pretty noisy under the hood as it is, so it'll be interesting see what the DB readings are.

Mike

 

This is not accurate. PWM gives continuously variable fan speed from 0 to 100%. The 50% is when the AC commands the fan on to maintain system pressure.

Don

 

I run a DCC PWM fan controller and 4th gen fans in my 77 and I almost never hear them running

 

I second this! I have a DCC controlling my two fans and they are very quiet. Been using this setup for the last two years and it works perfect. It is nice to be comfortable driving in 90's F in stop and go traffic and not worry about over heating or that loud fan noise we are all used to. The PWM controllers act like a soft start also so the amp load on the electrical is MUCH smoother and significantly lowers the spike relay type controllers have.

 

One thing I've been wondering about... with a 180° thermostat and a 180° triggered set of fans... I'm wondering if the fans will run unnecessarily? Time will tell, but perhaps the 195° sensor might be better suited? Anyone else running the 180° sensor with a 180° thermostat?

 

I have a sensor that has the low speed come on at 80* c (176* f) and a 180* T stat in mine and don’t have issues with the fan running excessively. I think it would depend on location also, mine is in the front of the intake by the water neck.
Mine has been like that a few years and no issues.

 

From what I understand, Carl designed this particular PWM system with a variable or progressive circuit that will go from 0 rpm to full speed as temperature hits the 180 mark and continues to rise. I think it also is designed to come on at 50% speed whenever the AC is engaged. The way I have mine setup, I wired in a very low draw LED indicator on my dash that will come on whenever the fans are on. I did it because I wanted to know for sure that the fans were working. My intention is to wire in a toggle switch on the dash to shut the indicator off if I find it annoying.

In this picture you can see my three LED indicators, the eBrake is on (lower left) and the car is running and so we're the fans (about 195 degrees). The Ignition On LED is only on when the key is in the ON position and the motor is NOT running.

Mike

 

The DCC PWM controller I am using for controlling my fans is set to hold the temperature it is set at (190 in my case). Thus the speed of the fans is completely variable depending on the thermocouple signal it gets. It does however like Mike (57vette) indicated have the ability to turn on the fans when wired to receive a signal from the A/C.

To better understand how PWM's work read this. It is very helpful. How PWM's work

PS - I use a PWM to control my fuel pump to maintain the desired fuel pressure. Nice as this means the fuel is only being pumped enough to provide the pressure needed. No more, no less. Which means less power under normal driving, thus less wasted energy pumping fuel unnecessarily (i.e.- heating the fuel and using amps)

 

Carl emailed me last night and explained the 180/180 scenario. He noted that the outlet temperature is always going to be cooler than the coolant coming through the thermostat neck. So the placement of the temperature sensor next to the outlet neck will control the fan(s).

"The temperature at the bottom/outlet of the radiator will be cooler than the inlet. Hence the engine temperature will be higher than 180* (usually 185-190*) before the fans kick on. This needs to happen so that the thermostat is fully open before the fan comes on. Once the car is moving the air forced through the radiator will take over for the fan."

He also added this tidbit:

"If you ever want to "see" what's going on just run some speaker-size wire into the cabin of car. One attached to the ground lug on the controller, the other to the fan lug. The cabin-side attaches to an incandescent light bulb (something with a filament/not LED). Once the fan starts coming on the light will be dim and ramp up with intensity as the controller speeds up. Once you're comfortable with what's going on the wires/light can be removed."

I'm missing a couple of clamps on the expansion tank that are due today, so if I get them installed I can re-burp the system for the last time and then take the car out for a ride and see how everything works. I know its only 16# of pressure, but I didn't want to have the hose popping off at the radiator neck or at the expansion tank and dumping coolant all over.

Mike