RotorMotor

iTrader: (5)

im looking into options to modify/improve cooling of the stock fans, and id like input.

as it stands now, i have an FC thermosensor (thanks to dale clarks recomendation... same as the miata thermo sensor). this should turn the fans on much earlier... however (as i understand it) the fans will only operate on MEDIUM when this is activated @ 190F. from the 4 possible relays... #2 and 4, are controlled by the computer, #3 is controlled by the thermo-switch, and #1 is controlled by the heater control unit (when you press the AC button).

and here is my understanding of the fan operation:
OFF - no relays
LOW - when relays #2 and #4 are active
MED - when relays #2 and #4 are active PLUS EITHER #3 OR #1
HIGH - when ALL relays are active (computer turns on #2 & #4, thermoswitch reaches activation temp. which turns on #3, and AC is engaged and running which turns on #1)

before i go any further into asking questions/posing solutions, i would appreciate it if someone could verify the information i just listed. also, some questions that i had to clarify things before i go further were:
1) what sensor is the computer using to decide when to turn on relays #2 and #4?
2) what temprature would that be?
3) since that temp. is most likely higher than my new 190F thermosensor, how will the fans function if the thermo sensor relay (#3) is tripped BEFORE the computer copntroled relays (#2 and #4).... will i still get a fan level of MEDIUM??
4) since there are 2 fans... when are the individual fans turning on and iff in relation to the various levels?? (im assuming that there are 2 relays per fan... one for LOW, and on for MEDIUM... and when both are active you get that particular fan spinning on HIGH???)

thanks for bearing with me... after i understand this setup then ill start asking my REAL questions... but first things first -heath

RotorMotor

iTrader: (5)

so no one knows one in the 3rd gen section knows how the fans work? ha! this forum is going downhill fast... where did all the knowledgeable people go? it seems that people are more interested in talking about side skirts and rear wings than actual technical info... go figure.

anyway, Mahjik... could you please move this thread to the advanced section?? thank you

HDP

iTrader: (2)

Probably spending Easter with their families...

Mahjik

iTrader: (1)

There is no more advanced section, it's back to being archives only.

Kento

Thank you. That might be a logical assumption.

You could always do your own research if you're so impatient...
http://www.scuderiaciriani.com/rx7/fan_mod.html

Kento

Also, the fan motors are wired in parallel, so they work together, not individually...

Check page F-144 of your FSM for additional info.

RotorMotor

iTrader: (5)

im not impatient.... ive just been noticing the forum "declining" recently in regard to usefull info. i do realize that people are with their families.

as far as the scuderiaciriani website... thats (and another 3 independent websites were where i got the previous info... although i still dont understand 100%)

TT_Rex_7

I would like to know the questions that you have. I would also like to know more details about how the fans work, and might get my answers from the questions that you have.

-Alex

Mahjik

iTrader: (1)

The ECU uses water temp as well as ELU (electrical load). This is why you can trick the fans on by turning on the parking lights.

221F stock (without electrical load). I believe around 215F with electrical load.

The ECU doesn't really know if the fans are running or not. It just triggers the relays. As far as anyone knows, there is no feedback that ECU reads from the relays so it won't care if the relay is already on or not.

As mentioned, the fans are wired in parallel.

jeremyb

I've had the fan that can be seen on... and the a/c fan off before.

RotorMotor

iTrader: (5)

and it uses which sensor to decide this? (reason being, im trying to track down why my fans are acting strange... and im starting w/ the thermosensor as a few things point to that.. but it could be other stuff)

so what that translates to is (if im understanding this correctly)... if you buy a 190F thermosensor, you will only activate relay #3 @ 190F(one of the fans on low or Med)... then once temps reach 221 the ecu will basically turn that fan on high, and ther other on low (by activating relays #2 and #4)??

is there a way to modify the sensor that the ECU reads to defermine temp?? although tricking the ECU into thinking the car is running hotter than it really is may have some adverse affects on how the ECU adjusts mixture etc.

one last question that i had was in regards to the 4/5 blade fans. i know the black 99 spec fans are 5/7 (but no one seems to have any data on whether they aid in cooling or not). anyway... i was wondering if anyone knew the reason for the staggered fans, and if switching the 4 blade to another 5 blade would be of any advantage?? thanks, heath

HDP

iTrader: (2)

If you have a PFC, I think fan speeds/temps can be adjusted with the Datalogit.

I remember reading a thread on that exact subject. I'm not sure which section it was in, but it went into detail about it... search

Kento

Uh...we're referring to the fact that the radiator fan system has two fan motors, which are wired in parallel, not that the A/C fan in-cabin is tied to their operation (which I guess is what you're referring to).

zullo

The question, at least for me, is - if the thermoswitch is only triggering medium speed fan operation at 190, is there a straightforward way to force high speed operation?

If this is what the "fan mod" is all about, just point me that direction and I'll study up on it. My impression has been that I didn't need that mod with a lower temp thermoswitch.

Mahjik

iTrader: (1)

The thermoswitch is used to turn the fans on at 221F. Anything else is going to use the coolant temp sensor and the electrical load unit.



What exactly is the problem you have with your fans?



Aside from the thermoswitch (and the parking light trick), there is no real good way to "trick" ECU for fan control without directly manipulating the relays.

Yes, that would be bad as other things also run off the thermosensors (on the stock ECU).

Staggering the fans is to eliminate any harmonic pulses two of the same fans could create. I don't know if you've ever been in a room with two large spinning fans, but they can produce a numbing pulsating sound.

People have switched and used two of the same fans and never noticed anything like that, but their exhaust systems probably drown out any noise the fans would make. In stock form, the noise must have been present for Mazda to use the staggered fans.

As for data on the '99 Spec fans; the only data is that they don't draw as much current. Honestly, if different fans are going to be difference between keeping your car from overheating, then you have bigger problems than just fans.

Mahjik

iTrader: (1)

Yep, you can force the fans on HIGH:

http://rx7.voodoobox.net/howto/fanswitch/fanswitch.html

The lower temp thermoswitch allow the fans to come on sooner, per stock ECU control. It's a good mod as it doesn't require any intervention by the driver (you don't have to remember to hit a switch). Since you have the PFC, the thermoswitch is useless. You can control the fans via the datalogic.

zullo

Don't have Datalogit

I'll have to move it higher up the $list

Kento

It should be noted here that if your car has had the fan wiring update done, the voodoobox fan switch mod may not work with medium or high fan speed settings due to the difference in relay wiring, both color coding and routing.

HDP

iTrader: (2)

What wiring update?

KevinK2

In most cases, miata type switch will give med speed (ac off) at about 210F. Also in those cases, grounding the "mod" switch instantly turned on the fans.

In a few cases with the fan control module added to the ecu by the factory recall, grounding the test wire did not instantly turn on the fans unless the 221F relays were closed per the ecu thermosensor, or mabe unless x minutes expired after grounding the switch. med speed fans required that fans already be at low (ac off).

Simple test is if with ign on, ac off, grounding the test wire turns on the fans with engine cold. Then the med speed trigger (miata switch) does not rely on the 221F trigger before kicking the fans on med speed.

To R-Motor, Med speed is plenty to cool a healthy FD in traffic, etc. Pull AC relay or fuse to run high speed fans, with usual fan mods.

Kento

26. FUEL LEAKAGE RECALL - ENGINE FIRES
CAMPAIGN #60504

The problem is that fuel lines become brittle because of excessive
engine compartment temperatures. Eventually, they leak fuel and the
car catches fire. The recall involves replacing the fuel lines with
a different material and adding a fan control relay which runs the
cooling fan for 10 minutes after the engine is shut off.

Mazda Motor Corporation will notify all subject vehicle owners by letter
and will install an additional control unit for the electric cooling fans.
The fans activate after the engine is turned off when the coolant
exceeds a specified temperature. Mazda will also replace the fuel hoses
with modified hoses in all these vehicles without charge.

Affects:
All 1993 RX-7 models manufactured beginning December 1, 1991
and 1994 RX-7 models manufactured through September, 1994.

VINs affected:
JM1FD33**P0200001 - JM1FD33**R0303550

Total number of affected vehicles: 13,400
Repair Time: 3.8 hours

Install Part Nos.
N3A1-18-SE0 Fan Control Kit
N3A1-13-S70 Fuel Hose Kit

HDP

iTrader: (2)

The little black box connected to the side of the stock ECU?

Mahjik

iTrader: (1)

Well, IMO, the PFC is really a pointless mod without getting everything. Once you have the datalogic, you can set your fans to come on at any point you see fit. That will render any sensor the stock ECU uses to turn on the fans pretty much useless (aside from the coolant temp).

Mahjik

iTrader: (1)

This was my case. It made the "quick fan mod" useless for me. I opted for the Miata Thermoswitch and was very happy with it.

Kento

Yes, that's part of the recall, what they refer to as the "additional control unit for the electric cooling fans".