Are two smaller fans better then one?

[vetteboy86]

I have to do a senior project for school, and was wandering if two smaller fans were better then one big fan? I know that it was during the C4 years that there was a switch from a single fan set up to a dual fan setup. What was the primary reason for this, it must be better for cooling right? Well on a side note, they must be better then the older belt driven ones? Does anyone think that because the electric fans were introduced for the C4, that it has a big effect on saving power and mpg of the engine?

Thanks for everyone's thoughts

Craig

 

[jmccloud]

Two fans

Yes, two small fans are usually better than one big one. That is - when the surface area that they cover is larger than the single big one. This is true when the area is markedly rectangular rather than square (like a Corvette radiator that is much wider than it is tall). This is the same reason that 4 valves per cyl. perform better than two, more area.
And yes, the electric fans 'save' a lot of energy. I have a '66 with a 327 and belt driven fan. When that fan is working (it has a thermostatic oil type clutch), it's like cutting off two or four cylinders. An electric fan can draw its surge from the battery that may be charged by the belt driven alternator. Eventually a similar amount of work will be done but over a longer period of time.
Also, the electric fans offer a lot more control. For example, a powered fan usually reduces air flow above about 50 mph. The electric fan is much easier to disengage than the belt driven one. And one of two fans may be activated to attain slight cooling when needed, avoiding socking the engine with a load of too cold fluid if one big fan were activated.

 

[Ken]

It all has to do with radiator size, shape and surface area, as well as the fan's capability to move air. Then you have electrical concerns to keep in mind...

 

[G Winter]

A couple things to add. Removing the fan from the water pump also saves on water pumps. Not nearly so hard on the bearings.
Noise is also a factor , overall I believe it is quieter with the electric fans.
On an olds tornado I changed to electric fan and on average gained 1 mile per gal .


A little side note. When changing to an electric fan , you must use a relay. Wiring directly into the ignition circuit will turn the coasting fan into a generator keeping the engine running for up to 15 seconds after tuning off the ignition.

 

[WhalePirot]

The fan is not needed above about 40 mph, I believe. Later ECMs cut all power to the fans above 50, I think.

Before electric fans, we used variable 'flex' fans, fiberglass fans, etc. to cut the power drained from the engine by the belt driven fans.

I was told that my stock '84 fan would cool a 700 hp engine, so I cannot explain why two fans were used in later years. I still use that fan with the modified cooling components, with fine effect, though my 406 is a bit shy of that power level .

As Ken mentioned, proper radiator and thermostat choice, shrouding, cleanliness and proper coolant flow all combine, and must be balanced, to ensure proper engine cooling.

In another thread, I explained how my engine still ran hot, with the 'super' radiator and water pump, until I changed thermostat BRANDS. For all I know, I could still have nearly a grand in my pocket, if I understood proper coolant flow first; not just believing the 'sellers' at BeCool (who also claimed I needed their expensive fan).

"The answer to nearly every WHY question is..........money." --- Me, 2003