Electric cooling fans

[Dr.Jeff]

I am still going through my notes from the recent SEMA Show, where I met with several key individuals and reviewed many products. One (of many) company and product lines that stood out to me is "GC Cooling" [gccooling.com]

A few years back, two engineers from SPAL decided to go off and build their own line of fans and related components. They have been in Europe for awhile and have finally established a US office. Their products are very well designed and made in Italy. The web site offers some helpful technical information to assist with designing an effective cooling fan set-up.

Talking to one of the engineers I was able to confirm some things I've always believed about electric fans:
The amount of air they move (eg. CFM) is related to the diameter, thickness, blade design, and speed...as one would expect. The work load needed to drive the fan (by the electric motor) is related the amount of draw. So a fan that moves more air requires more work from the motor and greater electrical load. Therefore looking at the electrical specs for voltage, amps, and watts (remember Ohm's Law?) will indicate something about the makers claims of CFM produced. Simply put, a small fan drawing a few amps cannot possibly move a ton of air. Unfortunately many fan makers like to highly exaggerate their claims about the CRM ratings.

GC also offers a nice fan controller. It uses its own temp sensor (installed in the engine) and starts the fan moving at half speed just before the engine reaches full operating temp. As the temp increases from there, the fan speed also increases. For a two fan installation, only one fan is utilized initially. The second fan comes on at full speed with the first one reaches a certain level. There is provision for a "AC" input as well. It is a very nice, solid, small package for a reasonable price. Something like this would replace the radiator mounted temp switch and offer much better temp control. I've used a similar product from a US fan maker but never liked its design or function. The GC unit has several design features that would be a great improvement.

 

[lookforjoe]

Sounds more like the setup used by many contemporary car makers, Volvo at least, based on my experience. Even 90’s Volvo’s had a ECU grounding circuit for the fan relay, that governed low and high speed fan circuits based on coolant temp at the engine, vs rad temp switches used in older cars.

Pretty sure my Honda setup has Efan control, I will be looking to implement that & ignore the rad switch. It’s really a poor design for a kid engine setup, since the rad temp on the outlet side is a poor reflection of engine temp, and not reactive enough to compensate until it’s already a problem.

With mods I’ve implemented, I find the coolant temp less prone to rapid rise over 190 in the heat soak situations that have always been problematic for me. The point being, if one can keep the coolant temp right at or slightly below 190, the potential for temp spikes seems to be drastically reduced.

 

[Dr.Jeff]

It is the same basic design as most moderns cars have (cooling fan module), as you say. By starting the fan earlier and at a reduced speed, you avoid the huge spike in current demand. And I totally agree it is much better to control the fans based on engine temp rather than radiator temp. One really nice feature this company offers is if you purchase one of their fans, you can get the control module built into the fan assembly, avoiding any external components. It is housed in a nice looking back plate on the fan motor.

 

[Dr.Jeff]

Huss, this got me thinking about temp sensor placements in general.

Just like having the rad fan sensor on the engine vs on the rad, it seems to me it would be a more accurate temp reading for the FI input to have the sensor directly on the head instead of on the T-stat housing. The temp at the head is more representative of the actual working temp than at the T-stat where the coolant is mixed. Fiat places the TTS and dash sender on the head, and there is a boss on the head where another sensor could be located, wonder why the FI sensor isn't there also. Any thoughts?

I guess this also relates to the other person's thread, looking for a T-stat housing.

 

[dcioccarelli]

Talking to one of the engineers I was able to confirm some things I've always believed about electric fans:
The amount of air they move (eg. CFM) is related to the diameter, thickness, blade design, and speed...as one would expect. The work load needed to drive the fan (by the electric motor) is related the amount of draw. So a fan that moves more air requires more work from the motor and greater electrical load. Therefore looking at the electrical specs for voltage, amps, and watts (remember Ohm's Law?) will indicate something about the makers claims of CFM produced. Simply put, a small fan drawing a few amps cannot possibly move a ton of air. Unfortunately many fan makers like to highly exaggerate their claims about the CRM ratings.

Hi Jeff,

I concur 100%. I bought some of the newer, slimline fans back in 2014 (like these) when I was installing my Bob G. aluminium radiator. They were certainly smaller and lighter than the stock fans and drew considerably less current. When the temperature got over a certain point, however (like being stopped in traffic after a long highway run) they simply couldn't bring the temperature down. I put the stock fans back on and they had no issues.

The fact of the matter is that there have been no recent advancements in electric motors (unlike with things like LED lighting vs. conventional) that make the newer ones considerably more efficient than older ones (I think the efficiency is always around 80%). The only areas where power is being lost (i.e. not being converted to rotational movement) is in heat, light or sound. Light and sound can be negated for an electric motor and I don't find the stock motors get overly hot. So essentially, any new, slimline fan that is not drawing as much current as the factory fans will also not be providing similar CFM rates (obviously I'm assuming similar blades and shrouds).

Cheers,
Dom.

 

[Dr.Jeff]

Well said Dom, same with the OEM fans on pretty much any vehicle. The motors are large, heavy, and draw a lot of current. The fan blades are also large and thick. And they really spin when they kick in. You mentioned sound, and indirectly that also plays a role; not in terms of the motor making noise, but in the larger volume of air being driven by the blades causing sound waves - you can really hear the rush of air when a good fan is working.

One electric motor design feature I have seen mentioned in recent years is "brushless" motors. Especially when a variable speed controller is used. I guess if the controller uses PWM technology, the brushless design works much more efficiently. Maybe someone can add some technical info on that (electronics really isn't my specialty).

Unfortunately there are a ton of inexpensive fans available. Although I really do not believe in the saying "you get what you pay for" (in too many cases price is inflated despite low quality/design), the good fans do tend to be rather costly. One of my X's came to me with a alum rad from one of our vendors, along with a pair of aftermarket fans sold as a package from that seller. They are worthless fans that don't move much air. I guess the improved efficiency of the rad may make it a bit less critical, if you happen to have conditions that do not require a big improvement in cooling system ability. But the reason for going to a aftermarket alum rad is typically the need for improved cooling. So to me it would seem prudent for the seller to include better fans.

 

[lookforjoe]

Dom's comments are making me think it would be worth re-installing the two factory fans ,if only to do a comparison of how long they cycle for to maintain proper temp. I never threw them out - I did cut the connectors off though, but that's not a big deal. I jsut felt that a setup with shrouding to funnel air would be better than the open housings these have, maybe that's not really true... I'll have to dig them out of the garage attic & check them out

 

[Dr.Jeff]

A shroud should help with any fans.
It would be interesting to find out the CFM rating for the stock fans and compare it to good aftermarket ones. There have been advancements in fan blade design. So the old stock ones may not necessarily be the best. We'd need to get more data to find out.