Selecting an electric radiator fan - PeachParts Mercedes-Benz Forum

martureo · #1 07-06-2016, 01:10 PM

I'm well under way on my 603 powered s123 project. Finally selected a radiator and mounted it. Now I'm onto getting an electric fan.

Pertinent information:

This will be a pusher fan, there is less than 3 inches between the radiator and the front of the engine.
There will be an a/c condensor (yet to be chosen) in front of the radiator
I'm not going to modify the car body

I'm using the Nissens radiator for a 87 300TD. Cooling area dimensions are 24 x 18 inches --> 432 in^2

It seems that the consensus is that you want 70% of your cooling surface to be covered by a fan or shroud. This is going to be a pusher, so a shroud doesn't really help (as it would block air traveling through by motion of the vehicle).

So that's 302.4 in^2 that I need covered.

I've done a little math to try to figure out what I could get on the surface of the radiator and what would each setup cover.

2 x 10in fans
78.5 x 2 = 157 in^2

2 x 12in fans
113 x 2 = 226 in^2

1 x 16 in fans
201 in^2

I don't think I can get anything bigger than a pair of 12in fans or a single 16 in fan in front of the radiator/condenser (things start getting in the way).

Additionally I've read that a pusher fan is 15% less efficient than the same fan mounted as a puller.

So I'm left asking the question, is that enough cooling or should I be worried/looking for another option.

leathermang · #2 07-06-2016, 01:17 PM

I do not believe that the same fan mounted as a puller is more efficient than as a PUSHER.....
it comes down to the seal between what needs air going across it....and the fan...
if pulling... then once past the radiator....
the space between the radiator and the condensor is seldom sealed.. and air is a liquid... following the path of least resistance....

So I vote for pusher in front of a condensor.. the engine fan will be helping on the other side in that case...

There is a high performance Italian fan which has been suggested and used by people here in the forum in the past...

https://www.summitracing.com/search/product-line/spal-electric-fans

Mxfrank · #3 07-06-2016, 03:25 PM

The problem with this problem is that you haven't given enough information. How thick will the condenser be? Will there be a rear mounted fan as well? What engine are you trying to cool?

If you need to squeeze a fan AND a condenser into less than three inches, you have no options. The thickness of the motor is proportional to the power of the fan...if the motor is too weak, airflow will suffer and coverage won't matter.

martureo · #4 07-06-2016, 04:31 PM

I'll help you out.

Quote:

Originally Posted by Mxfrank

The problem with this problem is that you haven't given enough information. How thick will the condenser be? Will there be a rear mounted fan as well?

Quote:

Originally Posted by martureo

This will be a pusher fan

No, there is only a pusher fan.

Quote:

What engine are you trying to cool?

Quote:

Originally Posted by martureo

...my 603 powered s123 project.

Quote:

If you need to squeeze a fan AND a condenser into less than three inches, you have no options. The thickness of the motor is proportional to the power of the fan...if the motor is too weak, airflow will suffer and coverage won't matter.

I have room in front of the radiator for a condenser and fan setup. I have already described the size of the fans I can fit there.

leathermang · #5 07-06-2016, 04:34 PM

Did you check out the Spal url I listed ?

Mxfrank · #6 07-06-2016, 05:24 PM

Ok, I'll give this one more try. There's no difference in coverage area between 2-12" and 1-16" fan. The reason is that the motor occupies about 12 sq in in the center of each fan. Since these fans will be flush mounted, that area represents dead air. So the effective coverage area is just about the same for both choices. The only variable you need to worry about is airflow. The fan's airflow will be a function of how powerful the motor is, the more powerful the motor, the thicker the fan will be. And that's the problem. If you can find a 1" condenser, that leaves you just 2" for the fan. And there won't be many choices in that thickness. you'll probably find you get around 1000 CFM in free air, which is low for this engine.

martureo · #7 07-06-2016, 08:20 PM

Quote:

Originally Posted by leathermang

Did you check out the Spal url I listed ?

I have. I've also seen a few others out there from flex-a-lite, Mishimoto and Derale.

I've been trying to do this by the numbers and get it right the first time. I just can't see how I'm supposed to get 70% coverage.

martureo · #8 07-06-2016, 08:24 PM

Quote:

Originally Posted by Mxfrank

Ok, I'll give this one more try. There's no difference in coverage area between 2-12" and 1-16" fan. The reason is that the motor occupies about 12 sq in in the center of each fan. Since these fans will be flush mounted, that area represents dead air. So the effective coverage area is just about the same for both choices. The only variable you need to worry about is airflow. The fan's airflow will be a function of how powerful the motor is, the more powerful the motor, the thicker the fan will be. And that's the problem. If you can find a 1" condenser, that leaves you just 2" for the fan. And there won't be many choices in that thickness. you'll probably find you get around 1000 CFM in free air, which is low for this engine.

Let's clear something up for the third time. There will not be anything between the radiator and the engine. This means that the 3" I mentioned is insignificant as it was a measurement between the engine and radiator.

16" is the largest single fan unit I can find. And I have found units which advertise a flow of 2400 CFM.

I can, and intend on mounting the condenser as flush to the radiator as possible. I still need to choose a condenser and was looking on this site for suggestions.

ROLLGUY · #9 07-06-2016, 08:44 PM

I happened upon this thread, after just about ten minutes ago talking to a friend about his bragging on the A/C system (Sanden 7 cyl. with a 16X20 PF condenser and 16" high CFM pusher fan) in his 300TD. He was traveling from Las Vegas to So. Cal, and stopped in Baker CA, and parked under a shade tree near the "Worlds Tallest Thermometer " to take a nap. He put the seat back and slept while idling, and the A/C full blast. He woke up a few hours later practically frozen inside the cabin of his wagon. He looked up at the thermometer and it read 106 degrees. The moral of this story is that (in my opinion) the cooling fan made all the difference in helping the A/C keep the cabin cool. Yes the parallel flow condenser helps, and yes the Sanden helps, but I think the biggest contributor is the fan. I don't have the manufacturer or specs of the fan (I plan to post the info on my Sanden thread when I get it), but it is the largest and thinnest fan with the most CFM he could find. The PF condenser is the best one available as well. Yes this application is in a 123 with a 617, but I think it should work the same in your project.

leathermang · #10 07-06-2016, 08:53 PM

Quote:

Originally Posted by ROLLGUY

...... The moral of this story is that (in my opinion) the cooling fan made all the difference in helping the A/C keep the cabin cool. Yes the parallel flow condenser helps, and yes the Sanden helps, but I think the biggest contributor is the fan. ....

THE bottle neck of ANY AC system is Air across the condensor... if that is substandard nothing else can make up the difference...

hope you post the specific brand and model ... a picture would be nice too if you can get it...

ROLLGUY · #11 07-06-2016, 08:57 PM

Quote:

Originally Posted by leathermang

THE bottle neck of ANY AC system is Air across the condensor... if that is substandard nothing else can make up the difference...

hope you post the specific brand and model ... a picture would be nice too if you can get it...

I know I have a photo somewhere, but can't find it. I do know that the frame is red plastic. It comes shipped as a puller fan, but turning over the fan blade makes it a pusher.

funola · #12 07-06-2016, 09:35 PM

"This will be a pusher fan, there is less than 3 inches between the radiator and the front of the engine."

Is the viscous fan still there or not?

martureo · #13 07-06-2016, 09:39 PM

Quote:

Originally Posted by funola

"This will be a pusher fan, there is less than 3 inches between the radiator and the front of the engine."

Is the viscous fan still there or not?

No. The 3 inches is between the radiator and the pulley on the water pump. I'm going to be moving the engine back at least an inch, but even then its too tight for my comfort.

ROLLGUY · #14 07-06-2016, 09:48 PM

Quote:

Originally Posted by martureo

No. The 3 inches is between the radiator and the pulley on the water pump. I'm going to be moving the engine back at least an inch, but even then its too tight for my comfort.

If there is no engine driven fan, then the radiator can be fairly close to the pulleys. If you are planning to put a fan between the radiator and pulleys, (I can only assume you are NOT putting a fan there, as you have stated the fan needs to be a pusher), then it needs to be a "puller". If you are putting a fan between the rad and engine, then I am totally confused.....Rich

funola · #15 07-06-2016, 09:52 PM

I think he is saying the pusher fan in front of the condenser will be the only fan, since there is no room for a puller fan between radiator and engine.