There's no guarantee that spinning the '99 fan blades faster will increase cfm, because the design of the blades plays a huge role in how efficient they are at their designed max speed. Think back to my analogy about the WWII propeller-driven planes; if simply increasing the number of blades increased the "propeller's" power, then all the aircraft designers would've had to do was make props with as many blades as they could cram onto the prop. On the same token, modern propeller blades don't remain in the exact same position as their speed increases; they actually rotate to change the airflow over the blades to make them more efficient at the rpm they're running at.

Your point regarding the '99 fan assembly's lower current draw is definitely a benefit, however. But is it worth the money and trouble?

 

If somebody sends me a set of fans I will test them and do a write up complete with water temps in different situations such as A/C on or off, highway cruising with and withough A/C, and city stop and go traffic with and without A/C What could be better for testing cooling system changes than summer in Phoenix?

 

Tom93R1---We already have a list of people getting the fans to test, Im having a little trouble getting the 7 blade one right now, hopefully in a few days. Thanks for the offer though.

 

Does anyone have specs for the volume (cfm) that each fan is supposed to move at a given rpm? There are two speeds per fan, if memory serves, which is why there are four fan relays. I guess that would result in eight separate rpm/cfm ratings.

'93-'95 4-blade - half speed rpm/cfm, full speed rpm/cfm
'93-'95 5-blade - half speed rpm/cfm, full speed rpm/cfm

'99-up 5-blade - half speed rpm/cfm, full speed rpm/cfm
'99-up 7-blade - half speed rpm/cfm, full speed rpm/cfm

 

Hey Jim, I believe the fans have 3 speed settings(low, med, high) with the 4th relay(A/C) turning the fans on by one level if activated. I tested it using the power FC and datalogit with the car off by changing the degree settings.

 

Really? I could have sworn that the wiring schematic for the fans showed two power leads per fan, one per relay, but it's been awhile since I've looked at it. I'll have to dig out my shop manual.

 

we are still waiting on actual data too

 

It is 3 speed, and both fans operate in sync so there are no combination there.

 

I'm starting the car like ... tomorrow morning. I SWEAR I'll start getting some data! lol

 

I guess I should have specified that I was not talking about how the stock ECU controls the fans...

Each fan has two relays for two possible speeds, "high" and "low". If you're wiring up your own system like I am, you can combine them in any configuration you want. You can trigger all four relays at once, two relays each in two stages, or one at a time in four separate stages, if you wanted to.

 

I agree 100% with Kento.

Generally speaking, the more blades the more CFM, along with much more quiet operation. Each set of fixed fan blades is optimally designed to deliver maximum efficiency at a DEFINED RPM. There is quite a bit of voodoo still associated with pitch, curvature, flex, etc.
It remains one of the most complicated problems to solve in all of aviation engineering - that's why designers are constantly tweeking propellers and wings on airplanes. Improving efficiency even 1% has dramatic effects.

In your set up there will be more "resistance" to the additional blades, (not to mention the added rotational mass - which is significant) which will tend to make the 93 - 95 spec fan motor "work" harder. You will be slowing down the motor, making it run much hotter and consequently shorten it's life. Mazda needed to change the motors along with the fan blades to compensate for this. The amp rating of the motor has nothing to do with it's peak torque, which is really the most important factor.

My bet is that without the new 99 J-spec fan motors you are not pushing any more CFM, and will likely burn out your motors much more rapidly then if left alone.

You need to focus on getting more fresh air into and out of the engine room quickly if you want to improve radiator efficiency. It's garbage in, garbage out. Always has been, always will be.

But hey - thanks for trying! A big "attaboy" for something new. Why not?

And an additional tip: Clean the dust and grime off of your existing OEM blades (especially the leading edges) and put a couple of coats of wax on them before reinstalling - you'll instantly get a HUGE increase in CFM.

Vee vant to keep zee air attached to zee surface.

 

I doubt that there is that significant an increase in the mass of the new fan blades, so I'm not sure what you're basing this assumption on, except the "if it ain't broke, don't fix it" principle.

OK, you lost me there... GIGO is a phrase usually only applied to computers, not airflow.

 

FWIW, my 1995 shop manual shows three fan speeds, two "low", and one "high".

"Coolant Fan Relay No.1" is activated by pressing the A/C button on the HVAC, sending power through the yellow/white wire to each fan motor, completing the circuit with the black wire on each motor which is always grounded. Both fans, "low" speed.

If the Water Thermoswitch is closed, the "Coolant Fan Relay No. 3" is activated, providing ground to the blue/orange wire to each fan motor. The ECM activates "Cooland Fan Relay No. 2" and "Coolant Fan Relay No. 4" when coolant temperature reaches a certain temperature, sending power to the white wire to each fan motor, completing the circuit with the blue/orange ground wire. Both fans, "low" speed.

The combination of the two circuits would result in a "double dose" of power to each fan motor, resulting in both fans, "high" speed, unless I'm mistaken.

The reason that I said four speeds is because there are two power leads to each motor. For someone who is adapting the fans to a different application, the fans could be controlled at high or low speed independently.

 

Hard to say which one flows greater CFMs.

It's like saying what has greater impact?

A Semi-automatic .50 caliber or a fully automatic 9mm?

One has less blades, but they are wider.

The other set has more blades, but less surface area per blade.

If the blade surface area were equal then it would be safe to assume that the one with greater units of blades would cut the cake.....

 

OK. Still no results from the testers, or did the 7 blades ones not come in yet?

 

You're forgetting the pitch of the blades...

 

Well, I haven't been able to really do any hard testing.. Still working out the bugs from my rebuild/single conversion. I couldn't get the temp over 160 at idle with them off so far.. so I didn't really get to see how well they cool..

 

Lets see if I can do this right:

Wiring diagram section B-2, page Z-42 or thereabouts.

Fan relays No. 2 and No. 4 are activated via the ECU, which is in turn "notified" of the coolant temperature by the thermosensor in the back of the thermostat housing, just above the thermoswitch, which is mentioned below. When the ECU sees a temp of 221 F, it activates relays 2 & 4, which ground the red with yellow stripe and white wires to fans 1 and 2, respectively, yielding a "low" speed. If the cooling system recall has been performed, when the electrical load sensor senses a load, the temp is reduced to 208 F that the ECU activates relays 2 & 4. If the recall has not been performed, the E/L sensor effects the operation of relay 3, described below.

Next, relay No. 3 is activated by the thermoswitch (black connector under the thermosensor on the thermostat housing) at 226 F. This grounds the blue with orange stripe wire on both cooling fans, yielding a "medium" speed. Thus, to get medium speed, relays 3, 2 & 4 must all be switched, grounding the blue with orange stripe wires to both fans, and the red with yellow stripe and white wire to fans 1 & 2 respectively.

Finally, relay No. 1 is activated by the A/C system WHEN it is running. If the A/C is switched on, but the A/C is not actively cooling (really, the clutch on the pump is not engaged), then relay 1 is not switched. Relay 1 grounds the yellow with white wire to both fans, yeilding a medium speed if only relays 2 & 4 are activated, and a high speed if relays 3, 2, & 4 are all activated (think arizona desert driving).

I'm pretty sure that covers it.

 

spurvo,

You are right.

Was that in response to me not having data due to the low temps?

I could manually trip the fans to either setting if I wanted, I just thought it was funny that for 25-30 minutes at idle the car never went over ~160. Not sure if that's good or bad though..

 

Nah, I was just schooling Jim!


HAHAHAHAHAHAHA!!!one!! Like I could EVAR do such a thing!! I was just clarifying the fan operations. As far as which set up will work better to cool the car, I guess I think that if you need to change the fan blades to get the car cooled down, you are already in trouble with respect to temp control. Stock fans work great, especially with manual control over their operation. At highway speeds, shouldn't need fans to stay cool. Obviously, heat extraction post shut down would be better, as would even more efficient extraction from the turbo area, a better manifold design, more room in the compartment, and on and on.

I wish my car would stay at ~160F while idleing. Actually, not, as peak power occurs at 190 to 200 F, but that's a different issue. Mine goes to the thermostat 180 F, stays there for about 10 minutes tops, then climbs as the radiator stops being able to absorb the heat. Fans come on when they should, temp goes down to 190F, they shut off, it rests at 190 for about 30 seconds, then climbs again, more or less like it's supposed to.

Unless I turn on the fans the MOMENT the temp gets over 190-ish, cause I'm all **** and stuff...

Hey, my 1000th post!

 

Not true, at least not on my car. After I eliminated the A/C system completely, including all the underdash hardware, I could still force my fan(s) on by pushing the A/C button in.

It's irrelevant anyway, since I no longer have a Mazda ECU or the four fan relays, and my reference to "4 speeds" were the four power leads to the fans (2 per fan) which can be configured any way I want.

 

Hmmm... production changes rear their heads. Mine only goes to high when the A/C gets cold. Voodoo...

Jeez I hate to pick, but my fans have 4 wires each, one with white, yellow/white, blue/orange, and black, the other red/yellow, yellow/white, blue/orange, and black.

Wait, you have '95, no? Hmmm....

 

Two power leads and two ground leads per motor, hence 4 "speeds". High and low on each of 2 fans. Obviously there are more combinations possible with 2 fans, but each fan has 2 speeds.

Yes, hence the reference to my 1995 shop manual...

 

Would someone please tell me how much of a difference changing to the 4 blade fan makes in temp?

 

do we know if the 5/7 blade fans work better or not yet?