HuggyBear

i see how to's and such out on the net, but no real explanation on what exactly the benefits are. can anyone help me out?

looking for the benefits and HP results if anyone knows them. im deciding whether its worth the effort or not over the winter.

thanks

TriangleMan

I've done this mod myself, so here's the quick and dirty

Advantages:
No big fan for your engine to have to turn, more hp.
Fan clutches wear out quick on high-revving rotary. One fan clutch is $125.
Ability to turn on fan while engine is off.

Disadvantages:
Electric fan can kill your alternator, especially if you have a big stereo.
Have to dig under hood to turn on/off (Unless you wire in a switch under your dash or something that interrupts the current.

Lemme know any questions you have.

Aaron Cake

iTrader: (1)

It's not so much an increase in HP that results, but better throttle response. The extra HP is used by the alternator to provide the current to drive the fan.

There is one disadvantage though. If you cooling system is not running perfectly, the electric fan may cause your car to run hot.

SureShot

Pro: The electric fan really opens up the space. Throttle response is much better.
Con: Like Aaron says, your cooling system must be already in good shape.
Note: The rorary engine creates much heat. Anything less than a Flexalite Black Magic will not pull enough air. The fan has a thermostat to turn it on as needed.

LLADNAR

well some of the problem is that the thermostat that activates the fan does not kick it on when the A/C is on. that is where you can have some problems,,because the A/C gets very hot

turboren

A/C? Who needs A/C?

I used a stock Fiero fan & shroud with an Imperial adjustable thermostat with great results. Adjustability is a plus. No overheats, but I have no A/C parts in the engine bay anymore.

Ren

Bruceman

iTrader: (5)

Pros:
No more noise like an aircraft prop from under the hood
Now you can here the wankel music
Engine warms up much quicker because no air gets drawn through the radiator and over the engine on bitter cold mornings

Cons:
None

tIIforever

how hard was it to get the fiero fan in there and is there any way too rig the fan to turn on when the ac goes on.

NathanRX7

I have to disgree with you there. I went to the junk yard, found a stock electric fan in a Ford, proceeded to see how it's size compared with the radiator in one of the FCs in the junk yard, then bought it for $20. It works great.

fuzzi

What kinda ford did you get the electric fan offa ?? I hear that people have had good results with those .. was it a taurus or something... I was thinking of doing something similar to my car....

NathanRX7

One of the big pieces of junk. A Taurus, Crown Victoria, or maybe a Thunder Chicken.

Aaron Cake

iTrader: (1)

It's worth mentioning that the fan from a 4cyl Pontiac 6000 pulls a LOT of air, and is available for next to nothing. I used one of these fans in a hovercraft project, and it was able to float about 100 LBS. Not sure if it's enough airflow for a rotary though...

2kwik4u

I am currently running the Taurus Fan (out of model with 3.8L engine) in my S10 pickup with Excellent results. It keeps the tmp at about 180 with a 210 thremostat ( temp climbs to 210 then drops again as soon as thermo opens), But I plan on swapping it over to my Rx-7 this weekend. I will post results!! The hardest part is getting the wiring right!!!

TriangleMan

I disagree with that too, my fan is the $65 electric fan from discount auto parts and if i let it sit there and idle, it will turn back off because it cools so well.

Bambam7

I would definately recommend using an electric fan.
It clears up a LOT of space under the hood
You get to see the cool aluminum rad...
The engine revs quicker- and seems a little smoother at high RPMS's
I have a perma-cool, about 70 bucks at Ramchargers. that blows a HELL of a lot of air- It didn't come with a shroud, so it's a finger-chopper, the shroud also increases the efficiency quite a bit- so that'll come next.
I am using a thermostatic controller- sticks into the rad fins. Turns the fan on automatically.
Something you must do if you have A/C- splice the A/C compressor clutch signal wire into the relay for the fan. That way, when the A/C goes on, you don't overpressurize, and blow off all of your freon. The A/C will also work better with a cooler condensor.

turboren

My car is in SC right now, and I'm in Iceland, so I'm going off memory. I spent a lot of time designing it, though, and installed it about six months ago, so it's still pretty fresh in my mind. Unfortunatley, I didn't take any pictures, so I'll have to describe the installation as best I can.

When looking for suitable electric fans, I spent a lot of time in bone yards and catalogs. The two fans that I finally decided to try were the fan from a 3.8 Taurus, and the one from the Fiero. My choices were based on flow characteristics, shroud area, fan size, number of blades, blade design, and original application design intent.

The Fiero has a very large (16") single plastic fan with GM's famous offset 5-blade design. It has a ring surrounding the outside edges of the blades. This gives the fan stability at high speeds, and aids in cooling ability by redusing pumping losses at the ends of the blades. It also has an open cage, meaning less restriction to flow (just keep hands/tools/rags/etc out of the blades). The offset 5-blade design allows less restriction to flow across the radiator when the fan is not running. It also has a nice wide enclosed shroud to allow more of the radiator's tubes to be cooled by the pull of the fan. The shroud isn't big enough to cause serious loss of cooling flow at speed, though, due to the size of the fan.

The Taurus has a slightly smaller (15.5", I think) plastic fan. It has more blades (9 or 10), and they are curved as opposed to the Fiero's basically straight blades. Like the Fiero, it has the ring around the outside edge of the blades to improve flow. It, too, has a shroud large enough to cover most of the
radiator. In addition, it was designed to cool a transverse-mounted 3.8L V6 in a relatively cramped engine bay, which is never an easy task. Based on this alone I could have chosen the Taurus fan and probably had good results.

The main reason I didn't use the Taurus fan was because I knew the fan would not be running all the time. When not running, the Taurus fan has more stuff in the way to impede flow. It has twice as many blades, and they are relatively closely spaced. The cage that supports the motor is like that of a desk-top fan: many intersecting supports, designed to keep dumb-*** Taurus owners from reaching into the fan while the engine's warm enough to cause it to turn on (I bet I can grab it while it's turnin, hyuk, hyuk...). And the shroud doesn't have as much of an open design as the Fiero does, making it something of an air brake when the car picks up speed.

turboren

The Fiero fan and integral shroud actually fit (barely) right in between the upper and lower end tanks. The shroud covers all but like three or four rows of tubes on the radiator, as the RX-7 radiator is a little wider. I secured the shroud to the radiator end tanks using heavy-duty (150 lb) zip-ties, which I ran through the tube fins at the top and bottom. It took two per corner, one to run over the tank, and one through the fins (keeping it as straight as possible), for a total of eight. Be sure you run the ties this way, as if you try to run the ones through fins in an arc, you will bend and possibly break fins. The ties, when installed, should resemble something like a horseshoe around the tanks, with a failry straight tie connecting both ends. During the installation process, I bent (slightly) a whole row of fins, as, like I said, it doesn't cover the entire width of the RX-7 radiator. This won't hurt anything as long as you don't bend too many, and there wouldn't be much flow here anyway, since edge of the shroud blocks it off. You want to try to keep the ends of the shroud off of the tubes, if possible. I have one side kind of resting on one row of tubes. I keep an eye on it. No leaks from vibration yet, and I honestly don't think it will cause chaffing of the tube because it's well secured. You may wish to file down the edges of the shroud to make the whole thing fit flat.

The fan thermostat I used was a universal type from Imperial that I bought from a local Advance Auto. Hayden and a few others make these also. Fan turn-on is adjustable (via a rotating **** on top of the controller, which, annoyingly, has no indicating marks) from like 160-230 deg F. The sensor is a gas/liquid filled bulb that feeds a signal to the electrical control. Increasing temperature causes the fluid in the sensor to boil, increasing the pressure in the line from the bulb to the controller, which causes a set of points to close, allowing electricity to flow to the fan.

I mounted the controller to the fenderwell in front of the left strut tower. Be careful when unrolling and routing the sensor and line, as the line is very thin and will break if handled roughly. If you break the line, the controller is no good. I ran the line from the fenderwell, around the front of the battery, along the top of the upper radiator end tank, and down into the shroud.

I installed the sensor with a pair of zip-ties through the radiator fins, under the fan shroud, as close as possible to the outside edge of the shroud. This keeps the air flowing across the sensor somewhat enclosed, allowing it to get a good representative sample. While it could be argued that installing the sensor in this manner would give it a false cool-off signal from the rotating fan, it should be noted that the fan is working to pull air across the radiator, and not push it through. Some eddies will of course come off the blades, but the vast majority of the air flowing across the sensor is heated air coming from the tubes and fins of the radiator. Not nearly as accurate as using a water-temperature sensor, but it works very well and was easy to do.

I wired the controller directly to battey voltage using a 10 AWG blade-type, weatherproof fuse holder with a 20A fuse. (I had this fuse holder left over from a project at work, but I think you can find them at Radio Shack or any good car audio shop. Don't go with less than 12 AWG, though, as the fan's current pull will overheat anything less.) I tied this fuse-holder wire to the engine fuse block, Main (80A) fuse, protected side, with a crimp-on ring terminal. This allows the fan to run after the car is turned off, as needed. Be careful using this method, though, as keeping the controller set too low may drain the battery. I haven't had this happen, but it is important to remember that a fan large enough to cool the rotary pulls some major juice, usually in the neighborhood of 15-19A. A weak battery won't take this too many times (without the alternator running) before it keels over.

When I got the fan from the donor Fiero, I cut the wires as far into the harness as I felt necessary. I think I got about three feet of wire from it. This allows me to use the stock GM connector, so if I ever have to replace the motor, I can just plug 'n' play. I usually try not to cut wires or hoses in the junk yard, because I hate it when someone does that to me (trashes a good wiring harness in the interest of time) but I wanted a "factory" look. I even got the plastic conduit to keep it low-key.

There are two wires coming off the fan. You need to find which way the wires go to make the fan pull, BEFORE you wire it in. Reversing the wires will make the fan run backward and try to push air out the front of the car. Not good for cooling, especially when running down the highway. Anyway, I hooked them up so that the positive lead (when in puller mode) ran to the controller. The negative lead I ran to ground out on the frame at the base of the controller, via ring terminal and castellated lock washer.

turboren

Auto tranny cars and TII's do have a circuit for running a small auxiliary fan, which comes on when the A/C is on, and also when the coolant reaches a certain temperature. The circuit includes a temperature sensor (in the coolant thermostat housing), relay (behind the front bumper cover), controller (under the passenger's right footwell kick panel), and dedicated fuse (in the interior fuse block). While I initially thought of using this circuit (car used to be A/T), the wiring is designed for a 5A max load, and I figured it would be way too much trouble to rewire the entire circuit. It would make for a flawless, factory-looking installation, though, if you were stealthy enough to get all the wires back in their harnesses properly. You would have to use a heavier-duty relay, though. The 30A A/C relay from another car could be used.

If you want to run A/C (as I said, mine had none of the A/C parts in front of the firewall), There are several ways you can do it. Probably the simplest is to just use the fan setup as I just described. I don't know how well this will work, though, as the condenser will not have a fan running all the time it has the compressor senging gas through it. It SHOULD get hot enough to trigger the fan thermo sensor, but it might not. This would seriously decrease the A/C's cooling capacity, and would be especially likely in stop-and-go traffic. It wouldn't necessarily damage anything, but your A/C wouldn't work very well until you got going.

Another option is to use the fan and control circuit from a TII or A/T car. Either should be a plug and play deal; all the wires are already there, you just need the components. Since you have your own thermostatic controller, you can get away with not using that, although I think you have to ground out the connector for the thermo-switch. Try it both ways and see which way works. By not using the thermo-switch, you save yourself from having to use the coolant thermostat housing from the A/T or TII donor car. This will allow you to have a fan that comes on with the A/C as needed, which will pull less current than the large radiator fan. It may still turn it on, though, if the heat from the condenser is enough to cause the radiator fan sensor to turn the fan on. Thankfully, the condenser fan is only an extra 5 amps max, but that may still be enough to cause the alternator to be under strain at idle, especially with the lights on, and if you have a high-powered stereo system. Keep an eye on your voltmeter.

The third, and probably most complicated option, is to figure out a way to have the radiator fan serve dual duty as a condenser fan. You would definitely need either one 30A relay, which received signals from both the fan controller and the A/C switch, or a seperate 30A relay for each, wired in parallel, so that either or both would turn it on. This could probably be done using the signal from auxiliary fan controller to the aux fan relay. Wiring wouldn't be overly difficult, but would be more involved than anything mentioned thus far.


Whew! I think that about covers it. If anything else comes to me that hasn't already in the three plus hours I've been working on this, I'll let you know. Any questions, feel free to e-mail me.

Ren
very tired
turboren@yahoo.com

turboren

P.S. If you think this is a worthwhile bit of info, please recommend it be flagged for archiving. I spent an awful lot of time on this and don't really feel like typing it again.

Thanks,

Ren

RX-7Impreza

Ren,

You are a true car guy. thanks for the incredible amount of info.

does anyone know if an auxiliary water temperature sensor can be installed into the radiator itself so that a more accurate switch it would be nice if one could fit into the air bleed hole on the left side of the radiator.

i will look into it and report what i find

Thanks again,
Justin

turboren

"does anyone know if an auxiliary water temperature sensor can be installed into the radiator itself so that a more accurate switch it would be nice if one could fit into the air bleed hole on the left side of the radiator. "

You could use the temp sensor and coolant thermostat housing from an TII or A/T car. I don't know what temp it turns on at (contacts close), though.

You could use the temp sensor with a 30A relay like this:

Run a control power wire to the relay's solenoid magnet from either switched or battery power, depending on whether you want the fan to run with the car off or not (I recommend yes). The ground side of the solenoid's magnet goes to the temp sensor. If the temp sensor has one blade (I think it does), this should be enough. If it has two blades, you'll have to run a jumper wire from the other blade to ground somewhere.

After determining the direction of fan rotation, ground the negative lead to the frame. The hot lead will come from the switched part of the solenoid. The input to the the solenoid switch should be connected to a voltage source using a 20A or 25A fuse. You could wire this section up as I did in my installation. Make sure to use at least 12AWG wire.

Your options for A/C fan operation would now be limited to either the aux fan or the A/C relay. If using the A/C relay, wire it in parallel with the temp sensor relay. Alternately, you can use a relay with two parallel input sources, and have either the A/C switch or the A/C compressor clutch magnet line provide the second relay solenoid magnet circuit completion path. (Crystal clear, right? )

I know I said the thermo bulb method isn't very accurate. Let me clarify this. Since the sensor doesn't sit in the water, it doesn't specifically monitor water temperature, and in theory will not react as quickly to temperature changes. It does, however, monitor the temperature of the air surrounding the radiator, and, since it is in contact with the tubes themselves, it also monitors the temperature of the tubes. Aluminum and brass are both excellent conductors of heat, so the temp on the outside of the tubes is very close to the temp inside the tubes.

In practice, the thermo bulb method works very well, mainly because the system is adjustable. If, for example, the thermo bulb operating temperature was set to 180°F, it might not actually come on until the water temp reached 185° or 190°. Since the thermo bulb fan controller is adjustable, you can set it to come on at any temperature you want (well, within its design parameters anyway). I have it set now so that it never gets above slightly below half on the stock temp gauge. I would guess this equates to somewhere between 185° and 195°.

Ren

LLADNAR

you could buy a coolant temp sensor from jegs for 16.99

and you could get a 2 speed fan and wire one speed to the coolant temp sensor and one to the a/c,,that should solve all the problems

turboren

"and you could get a 2 speed fan and wire one speed to the coolant temp sensor and one to the a/c,,that should solve all the problems"

Yeah, that would work too. The problem is finding one with a shroud that will fit the 7's radiator. A shroud is important to prevent uneven cooling while the fan is running. It does provide somewhat of a flow restriction when the fan isn't running, though.

I saw a shroud mod suggested in Car Craft or Hot Rod. They cut out sections of the shroud and used spring-loaded hinges to reattach the sections. The spring held the newly-formed "flaps" closed while the fan was running. When the fan stopped, the flaps would open if the vehicle speed was high enough, reducing aerodynamic drag on the car and allowing more airflow through the radiator. Obviously, the springs weren't very strong.

Ren

LLADNAR

hey that is a pretty good idea,,never thought of that

Pinfield357

will doing this mod make the motor run hotter or cooler? also r all the fans the same from the 4cyl 6cyl and 8cyl fiero's?