Not sure if this has been posted in the past (searched and found nothing on it).
Here is the long and short of it. The stock FD cooling fan system pulls a lot of air, more than any after market fans of the same size. However, there is an interesting fact about them that allows for more cooling capacity. The two fans are distinctly different. The passenger side hase a fan with 5 blades where as the driver side has 4 blades. Each blade on the four blade fan is wider and has more pitch and depth than the 5 blade. The result is more air flow created by the 4 blade fan than the 5 blade (the difference is quite obvious when you put your hands on the back of the fan). So here is the idea, replace the 5 blade with the four blade (~$37.00 from Mazda) and increase the total air flow throught the radiator.
Side note, the reason for the 5 blade and less air flow was due to the location of the stock airbox. Most of us do not have stock airboxes anymore so it is not longer an issue. I will have mine installed next wednsday, I'll report back on the water temperature differences.

 

No beef with your theory but like any theory, there has to be peer reviewed:


Just b/c one has 4 blades with greater pitch does not mean that it pulls more than a 5 blades with less pitch. You can design a 3 blade to flow the same as 4 blade. The only limitation being the stall speed of the 3 blade.

I would be more convinced if there is some way of showing air flow rate. Another way to show it may be to hook up an ammeter to see how much ampereage the 4 blade is pulling versus the 5 blades.

Just my 2 cents.

 

I thought the different fans were so there wouldn't be weird harmonics or loud noise caused when both fans were running at the same time. Anyone know?

Wade

 

Yeah, it's cause of constructive interference with the noise put off by the fans. When the two sound front's meet, at the certain wavelengths they reinforce each other making it louder... It's how you create "beats". Take two tuning forks that have similar wave length (eg 2Λ and a 3Λ ).

 

pomanferrari, what theory? I stated a fact, it is as simple as putting your hand next to the fan and feel the difference in the air flow. As I stated in the original post, the difference is quite noticeable.

Rikki, I think I need to clarify the reasons. If you have no cooling problems to begin with, then no, you will not notice any cooling differences. At most your fan will disengage more often (since it is temperature controlled). Looking at you setup, you still have the ic in the stock mounting position, and there is no airflow changes to the radiator. But if you have a fmic like a lot of us do, there is a problem with the amount of airflow being restricted by the ic. This is especially true if you did not change the geometry of the stock radiator (some people stand the stock radiator up parallel to and immediately behind the ic, this allows for all of the air flow, eventhough restricted, to flow perpendicularly throught the radiator). For those who have not done the radiator mounting mod, overheating is a problem at high speeds because the airflow after the fmic is simply not enough to sufficiently cool the water. My redesigned belly pan in combination with the fan blade change should be sufficient to increase the airflow back to or exceed the stock design, and resolve the over heating problem.

 

let us know how it turns out trex

 

The reason raised by Wade makes sense.

As to your fact to support your premise... I have a story to tell ya. I got written up by a cop, on a horse no less, for doing 65 in a 45 zone. Went to the judge who asked the cop how he was able to come up with such precise number. The cop said, it's a fact based on his own two eyeballs and 20 years of experience as a cop. So I asked the cop, you're on a horse that is moving at a trot, you're bouncing up and down and you can gauge my speed? The judge laughed and threw the case out.

What's my point? I don't trust subjective perceptions, e.g. like a butt dyno number. I don't dispute your "FACT" because I can not disprove your subjective belief. I'm just disputing your premise for the difference in blades.

 

Update on the 4 blade fan mod. After replacing the fan blade, there are no harmonic noises, none. I have a variable temperature fan control that is adjustable, with the stock fan configuration, at the lowest setting (sitting in traffic with 100 deg F ambient temp) the best water temp is 185 F. With the twin 4 blade in the same condition, the water temp is at 170 F. Pictures to follow soon.

 

bump....

 

Just get the upgraded 99+ cooling fans , Mazda added extra blades to both fans for more airflow.

 

Not sure what the "99 fans" look like or where you can get it from, but as I posted before, more blades doesn't necessarily mean more air flow. Given two blades with the SAME pitch and depth, more blade will produce slightly higher airflow, but if they have the same pitch and the depth as the 5 blade stockers then definitely no. Besides, it only costs about 37 bucks to do this mod, hard to beat.

 

sounds like its working out for you trexthe3rd, but i know for a FACT, from mazda, that the different blades are to "reduce" noise by sending out different frequencies. anyway, good luck...like i said, its great that ur not noticing any wierd beating noises coming from the front bumper.

 

There have been thousand of volumes of technical papers written about propellers, and that is what we are talking about here. And no one, except a highly skilled aeronautical engineer, is qualified to pass judgement on whether or not this mod works.

Don't let the bastards grind you down. Anyone who even tries new mods is OK in my book, no matter how wierd or apparently worthless. Go for it.
Measure it. Guess all you want. Just DO IT and don't let anyone **** with you. It's FUN.

Sometimes, seat of the pants "feel" is better than any analytical description, and when it comes down to it that is the basis of many engineering decisions/applications.

Mazda's engineers were pretty damn smart in my book, but they also brought us some losers like exploding AST tanks, pre-cats, overly complicated turbo systems, etc.

I'll bet they had **** eating grins on for a week when the first FD3S was publicly unveiled........