Radiator Electric Cooling Fans

[Dr.Jeff]

In another (related) thread we've been talking about radiators. It reminded me of a great family company in SoCal (Mattson Custom Radiator in the City of Stanton) that has been building custom radiators, as well as all related aspects, for decades. It was started by the grandfather (Jack Mattson) way back in the 50's or 60's and is now run by the grandson. All three generations are named Jack so it gets confusing, but the dad (Jack 2) of the current owner (Jack 3) was one of the nicest guys I've met in the automotive industry. He earned the nickname "fan man" because electric fans was his thing. He had what I believe to be the first rights to sell Spal products in this region. They have been a staple at the Pomona and Long Beach car swap meets for as long as I can remember.

I had a long conversation with Jack 2 at one of the swap meets once and he told me the following basic rules to mounting fans on radiators. I took notes as he talked and I've rewritten it a few times over the years so I won't lose it:

1) For a "puller" fan mounted behind the radiator, put the front edge of the fan blade 5/8" to 3/4" from the radiator core surface.
2) For a "pusher" fan mounted in front of the radiator, put the trailing edge of a straight blade fan 1/4" from the surface of the core (due to the lack of a shroud, see #3).
3) Always use a fan shroud on a rear mounted "puller" fan. Never use a shroud on a front mounted "pusher" fan. Add air bypass doors to the fan shroud in areas where the fan does not cover the core. This allows air to flow past the shroud when the fan isn't running.
4) If AC is installed mount the condenser 1/2" in front of the radiator core (surface to surface gap).
5) Never use those "through the core" zip-tie mounts to install a fan on a radiator.
6) Use a fan control temp switch slightly higher than the thermostat rating.
7) He preferred circuit breakers over fuses. And for a two fan setup he used two relays, but both can be controlled by one temp switch.
8) Use the thickest (vs "slim") fan that will fit.
9) The size and number of fans is different with puller and pusher setups:
9a) For a puller installation use a fan or fans that cover as much of the core as possible. Even if part of the fan's blades extend beyond the edges of the core in one dimension. The extra overlap of fan can be covered by a small shroud to prevent sucking air from around the rad.
9b) For a pusher installation do not allow the fan's blades to extend beyond the edges of the core. Even if that means some core area is not covered.
9c) Therefore the number and size of fan(s) will depend on achieving these criteria (9a and 9b) more than anything else. In the event that either one or two fans will result in the same coverage, then one fan is better than two. (I don't recall why).

Bear in mind the majority of applications they see are things like muscle cars, hotrods, custom builds, etc. A Fiat X1/9 cooling system certainly isn't one of those, but I imagine all of the same principle rules should apply.

We'll add more posts about fan CFM ratings, controller principles, brands, sizes, etc.

 

[Dr.Jeff]

Perhaps before this thread gets too far it might be useful to set some parameters for the nature of the discussion. As much as possible I'd prefer if we can limit it to only the fans and not the rest of the cooling system. There are certainly a lot of areas where the X's cooling system could be addressed further, but let's talk about them elsewhere for the sake of keeping things on track.

Likewise I'd prefer to avoid any discussions on whether or not the X's cooling system needs any improvements. That is not the point here. The hope is to explore options, investigate questions, and consider new ideas for the interest of those so inclined. If you are not one of those people then please start your own thread.

I appreciate the cooperation and look forward to hearing ideas and learning more.

 

[Dr.Jeff]

In the other thread about radiator airflow there were some good comments made regarding the cooling fans. Here are just a couple examples.

@kmead stated: "Having better fans, more fans and better control of any fans would be a benefit without doubt. I believe someone here did use some simple instrumentation to document the air volume from the existing fans versus some no name brand fans and the existing Fiat fans although not as efficient electrically were superior to the aftermarket fans. Particularly for those who live in a brutally hot climate. Starting the fans at a lower radiator temperature would assist in the system not becoming heat soaked as quickly if at all which is what we are ultimately seeing when our car’s temperature starts to climb."

@Jonohhh mentioned a PID fan control. I'm sure he has discussed it more in his thread on cooling system design. I have not reviewed all of that thread yet so hopefully he can add the relevant info here about using a PID to control cooling fans.

There are other great posts, if I missed any of interest please feel free to add.

 

[Dr.Jeff]

As was noted in Karl's comment (quoted in post #3), many aftermarket fans go not have much of a CFM rating. The blade and motor design does not pull much air. Typically the way around this was like the stock factory fan, a hefty blade design with a huge motor to drive it. But this also means it has a huge amperage draw. Particularly on startup to bring that big blade into motion.

One feature available on newer fan designs is use of a brushless motor. That offers several benefits, including no sparks, no startup surge in amperage draw, and variable speed operation. With controllers to complement the variable speed feature the fan will only draw as much air as is needed to maintain the target temperature. Likewise it will ramp up the fan speed on startup to eliminate the normal power surge that fans have. These make it possible for the fan to have a higher CFM flow capability (e.g. blade design) but without the drawback usually associated with it (namely amperage load).

Given the nature of the Fiat X's electrical system this can be a big plus, even for a stock replacement fan.

Here is some info on the Spal brushless fans:

Publish Online

indd.adobe.com

 

[NEG]

I thought the OEM fan motors where already brushless

 

[Dr.Jeff]

In fan design the motor - as discussed in the prior post - is not the most important factor. The design if the actual blades can make a big difference in the volume of air (CFM) it moves. Typically there are three basic types; straight, curved or "S", and wide or "paddle" (which can be curved or straight). There are others but these are what I most often see offered in the aftermarket.

Lots of additional little factors go into the design, like the pitch and cross-section profile among others. Therefore just looking at the overall size (outside diameter) does not tell much about the efficiency. But for a given blade design at a given speed a larger diameter will move more air. And rotation speed of the blade isn't as straightforward as it may seem either; faster does not always mean better. In fact a good blade design will work better at lower speeds than a mediocre design at higher speeds. A really big blade can move a ton of air even when barely moving (see Karls reference to "Big Ass Fans").

As far as I understand, each of the three general types of fan blades have some characteristic features. The straight blade allows the slimmest profile and decent CFM but at the cost of increased noise. The curved blade is much quieter and can offer similar CFM but in a medium profile. While the wide paddle will give the highest CFM but is by far the thickest profile and usually the noisiest. A combination of styles, like a curved wide paddle vs a straight wide paddle, will be a compromise of those functions. For comparison sake the stock fans on the X are a wide straight paddle.

To help put things into perspective, looking at some spec sheets from a leading maker of fans I see the following comparison. Both are 11" diameter (as would be utilized on the X), with similar motor designs. The slim profile straight blade fan has a CFM rating of 800 with a depth of 2" and draws 7 amps. The thick profile wide paddle fan has a CFM of 1200 with 3.5" depth and draws 12 amps. Both were measured using the same test criteria. That's a 50% increase in air volume for the thicker one. Unfortunately the info I looked at did not give the noise dB levels, but I can say from experience the second design is a lot louder.

All of these design features, including the motor and the blade, will differ from one manufacturer to another. As will the price. So it isn't fair to say a aftermarket fan is less efficient than the stock fan - it depends. I don't recall seeing any specs for the stock fan's CFM but it would be interesting to compare that with some aftermarket options.

 

[Dr.Jeff]

I thought the OEM fan motors where already brushless

My comments pertain to aftermarket fans. However I seriously doubt the stock fans from the 1970's Fiat design are brushless. The technology for brushless DC motors only came into existence in the late 60's. And they weren't widely used in the automotive industry until much later. So it is not likely Fiat paid the money for such a new technology when they were to be used as a steady state motor on a low priced vehicle. But it would be interesting if that was the case. It could allow for a continuously variable function with a solid state controller.

 

[NEG]

Yes, good point.

 

[Stuartc]

The std fans are infact very good even though there seems to be a propensity of people to change them out.
The straight edge heavy pitch moves a lot of air. Downside to straight edge fan is they are noisier and while a lot of contemporary fan/cars have curved blades these are quieter at the expense of air volume.
If there’s any deficiency to point to
Of the OEM fans is the motor which is a “brush type”. If a can find a “brushless” motor to replace the “brush type” that’s what I’ll be doing in the future.
The only other area is in operation which is either on or off.
I have added fan resistors (Fiat Panda) to the low side of the motors and 2 temp radiator sensor (Fiat Ducato) in conjunction with a “Trinary” switch on the receiver/dryer which gives the std fans 2 speeds low/high depending on demands.
I’ve also added a Fiat Fan Switch in the dash switch cluster that has RGB led and indicates blue for low speed, red for high speed and green for dash illumination but that’s another topic

 

[Kurt]

I’m sure those original fans are heavy as crap too

 

[Dr.Jeff]

I’m sure those original fans are heavy as crap too

They are. The other drawback, in addition to the high dB's and weight, is they suck a lot of current compared to more modern fan motors. But I agree with "Stuartc" they do move a lot of air.

I don't recall ever any seeing the CFM rating mentioned for the stock fans?

 

[Jonohhh]

A while back, I got uh "gifted..." a set of SPAL VA14-AP7/C34S 7.5in pusher fans, but looking at the design the area for passive airflow is indeed very small. While 7.5in is a bit smaller than desirable, it would work.

They pull between a little over 10A each, and are rated at 348cfm.

Most definitely not ideal for the application, but it highlights one issue with the smaller range of "modular" fans from aftermarket companies like SPAL and others:

The fan motor is huge in diameter, much like what you'd find on the larger 15+ inch fans, and because of this there is very little area for air to actually flow. Not so much of an issue when the fan is operating, but most definitely quite restrictive for passive airflow:

 

[Dr.Jeff]

They pull between a little over 10A each

Is that the actual draw or the recommended rating for the fuse? For fan motors in general the initial start up has a very brief spike (unless they are brushless motors) but then it settles down to much less.
The fuse for each stock fan is 16 amp. While that is likely higher than the normal load, the stock motors do draw a lot of current.

Those might be a bit too small for the X. That's not a huge amount of CFM due to the small diameter.

 

[Bjorn Nilson]

When I bought the aluminum radiator I also replaced the stock single fan with two Biltema fans (like Harbour Freight here). I have no idea how much they flow but they are much more efficient than the stock fan and very low weight. I have SPAL fans for oil and injector cooling but decided to try these very cheap (25 USD each) fans to save some money. I am using the stock relay and fuse without issues. They are 80W each so they draw 13,3A.

One reason for their high efficiency could be that dual fans cover most of the radiator area compared to a single fan:

 

[lookforjoe]

I'm currently using 12" FFD 1600cfm rated fans

As with everything else, I can't say these make any difference to maintaining coolant temp, since I changed to the VW regulating switch at the same time, and tipped the rad so they point downward more than stock. They do function as expected.

One thing, with many aftermarket fans, the wire gauge is laughable for the claimed amperage. Look at the gauge of any OEM fan motor, even the PWM versions. If I could fit a Volvo (Bosch) fan I would have. They move substantially more air than any of these - found this when looking at the PWM controller links

 

[Ulix]

It just happens that an engineer in the geman X-forum took on the topic of fans.
He compared the stock fan to two Spal models, Spal VA07-AP12/C-58A and Spal VA02-AP70/LL-52A.
He mounted them to a used rad and a recored one with a more open core.
He used an air flow meter at different points, from the center out to the edge and compared.

His findings were interesting. The Spal units were quieter and used less power, but the stock fan actually cooled the best!
His recommendation is to stick with the stock fan if it is in good condition.
I like that. The engineers back then weren't stupid and not all components used in our cars seem to be old italian junk made from used tin cans.

Kühler Tuning - X1-9 Forum

 

[Bjorn Nilson]

It would be interesting to compare the flow from TWO modern fans that together draws 10-15A, and a single 10A stock fan.
It would also be interesting to know how much airflow they block when NOT running.
If we study "airflow per ampere" I am almost sure the modern fan will win.

 

[Ulix]

Björn, have you considered going to an electric water pump?
I think your car out of everyone here would benefit most from that change.

Considering that all evidence points to the fact that (given a rad in good condition), the water pump is by far the "weakest link" in the cooling system, I think you would see a huge benefit to your cooling situation.

 

[lookforjoe]

It just happens that an engineer in the geman X-forum took on the topic of fans.
He compared the stock fan to two Spal models, Spal VA07-AP12/C-58A and Spal VA02-AP70/LL-52A.
He mounted them to a used rad and a recored one with a more open core.
He used an air flow meter at different points, from the center out to the edge and compared.

His findings were interesting. The Spal units were quieter and used less power, but the stock fan actually cooled the best!
His recommendation is to stick with the stock fan if it is in good condition.
I like that. The engineers back then weren't stupid and not all components used in our cars seem to be old italian junk made from used tin cans.

Kühler Tuning - X1-9 Forum

Interesting! For posterity, if you are a member there, can you download & add the test page here? I tried to copy & save as images to no avail.

 

[Dr.Jeff]

It just happens that an engineer in the geman X-forum took on the topic of fans.
He compared the stock fan to two Spal models, Spal VA07-AP12/C-58A and Spal VA02-AP70/LL-52A.
He mounted them to a used rad and a recored one with a more open core.
He used an air flow meter at different points, from the center out to the edge and compared.

His findings were interesting. The Spal units were quieter and used less power, but the stock fan actually cooled the best!
His recommendation is to stick with the stock fan if it is in good condition.
I like that. The engineers back then weren't stupid and not all components used in our cars seem to be old italian junk made from used tin cans.

Kühler Tuning - X1-9 Forum

This is great, an actual test. Thanks to Ulix for sharing it.

I'm curious. If I understand correctly, he describes testing two styles of stock fans; one with the metal ring around the fan blade, and one with I believe is a plastic shroud. I don't recall ever seeing a stock fan with a plastic shroud? Or am I misunderstanding things? EDIT: I see the pics at the bottom of his page. I've never seen that other style of stock fan with something of a shroud. Although it really isn't a full shroud so it doesn't surprise me it did not help. He found the other one (with only a metal ring) to work better overall.

He makes another good point. Due to the heavy electrical load the stock fans have, the car's electrical system might actually allow less voltage to the fan motors if it cannot carry the current sufficiently (hope I stated that correctly). In other words, there may not be sufficient electrical power to allow the stock fans to perform at their maximal level, as in his tests with a really robust external power supply. As he stated, less voltage causes the fan speed to slow and therefore draw significantly less air. But I'm not necessarily saying that is the case, only a possibility....especially on cars with the typical electrical issues.

Other good points are the huge difference in noise levels, and the possibility that the old stock fans may not be in top working order (I know I have some that are noticably less effective than others).