I just replaced the 5 blade fan with the 4 blade fan and it does move more air. Even thoug this is a subjective evaluation, when I removed my large M2 IC and had direct access to the fans there is NO argument for me that the drivers side (4 blades) pulls more air.
I measured the blades and the 4 blades fan at the widest portion measured 120 mm and 70 mm at the base. The 5 blades fan measured 92 mm and 55 mm respectively. The length (almost 4 inches), speed and pitch is the same for both.
So for exercise purposes only, lets say that in the 4 blades fan the total area is 4.7x2.8x4x4=210.6 inches to move air and the 5 blades fan is 3.6x2.1x4x5=151.2 inches. For the metrical sytem challenged 1 inch=25.4 mm
So there you have it, the 4 blade fan has to move more air than the 5 blade fan.
How much of a difference does this makes in degrees???? I don't know, it remains to be seen. I will report back as soon as I have any concrete numbers.

 

When you report, can you give some feel for how quickly you are able to pull heat out of the system? Say a general feel for degrees dropped for a given amount of time the fan is on. Would be nice to know...

 

I guess there's no truth to the stated theory that the reason there is a 4-blade fan is to eliminate resonation with the 5-blader when running at certain rpms (fan motor, not the engine)? No weird noises coming from the rad fans when running on high?

 

I will report of any strange resonating noises at high speed if I can pick on it.
This is still very subjective, unless there is an evident marked noise coming from the fans.

 

where did you pick up the fdans at?

josh

 

ordered from Malloy Mazda about $34 dollars

 

Personally, I think that theory is a figment of someone's overly active imagination, but I'll reserve final judgment until someone proves differently.

 

I actually think that the pitch of the fan blades is more important than the number of blades. Go check out some propeller driven airplanes or ship propellers. The pitch of the blade can be the difference between the blade pulling air or pushing it.

By the way the pitch is the rotation of the fan blades.

- Cody

 

Very true - - 1/4 mile speed boats only have 2 blades -- with INSANE pitch. But... In reference to cooling - the 25% increase in efficiency (maybe) does that simply mean that the fans need to work a few seconds longer to bring down the temperature appropriately? In which case does it matter. If the fans could not STABILIZE the temperature it might matter, but if their goal is simply to bring the temp from 95 to 94 would the extra air flow really matter??? I could see if I had to constantly manage my temperature to keep it at 80 it might matter but the few seconds of improved efficiency they are on likely doesn't matter.... In my most humble opinion...


Something else to chew on.. the 4 blade fan is less of an impediment for the airflow when the fans are not on.... Which is 90% of the time...

 

My mechanic has the 4 blade fans . I have been in this car for hours at a time, I have never heard any odd thumping fan resonation .The sound of the air flow is a little more than stock noise when standing out side the car . He paid $ 34 at the dealer 3 years ago .

 

there is a local guy out here that has had his fd setup with nothing but 4 blades for some time now. no noise what-so-ever. the noise thing is valid though. someone just over engineered it. you know how tires have off-set tread patterns? if you look at it, the "chunks" of rubber arent the same size. this brings that harmonic resonance down. cross drilled brake rotors?. . . the same thing. the holes are drilled in a fashion so that they are uneven to each other. this keeps that same noise to a minimal.


the thing to remember, though, is that harmonic resonance is a vibration. vibration makes noise. the vibrations could be so fast that your crude human ears cant hear it, but its actually vibrating the hell out of your ****. you know how old v8s had harmonic balancers on them? well, that keeps the engine from pulling itself apart.

i know that the blades on the fans are fine, though. its been done with much success. mine will be that way soon as well.

paul

 

duboisr and i are talking about the same guy. . . garfinkle. . . d-d-duuuuuuuuuuh!!!!

paul

 

Anyone know how much the 99+ upgraded fans are? I bet these can be ordered from Mazda, good chance they were used in another Mazda car.

 

The stock 93 -94 fans= one4 blade and one 5 blade . you go to the dealer and get one 4 blade fan and swap it for the 5 blade. Cost is $34 . The 99+ fans will cost more then that, For my info are they different ?