Electric vs stock fan. Which is better?
 

O I am trying to decide to go to an electric fan or stock fan on my 88 rx7. Is there any noticeable difference between the two cooling wise?

Too many variables to answer definitively, but in general, no.
Sufficient airflow is sufficient airflow, the radiator doesn't care how the air is provided.

That said, I much prefer electric fans, for a variety of reasons.

And what are those reasons?

I hate electric fans.
You lose the "tool tray" on the car.Otherwise known as the stock rad shroud.

For this solution you get a Electric fan with shroud(like a Merc Villager fan),a new alternator and a corsport front rad panel.

So I assume it doesn't matter what fan you put in there? I already have a new alternator on there with a double pulley too.

It's really personal preference. The biggest pro for an electric fan is a cleaner looking engine bay/easier access to the engine.

If going electric I believe it's said you want something that flows atleast 2800 cfm or better.

Do some research on it.

If you go electric,then try to simplify things and get a fan setup that will pretty well fit the Rad and you do not have to make any shrouding for it.
I opted for the Merc Villager fan and you just cut a small piece and Bob is your uncle.Installed with some L brackets.
A Fiero Fan(V6) is good and also the Taurus Efan or Lincoln I have heard is good too.

BUT there is nothing wrong with a Good Operational Stock Fan,so really it is your decision on what you do.
The Efan cleans up the engine bay a bit,that is about it.Makes things a little more visible.

I don't mind my stock fan, the only reason I would go electric is to free up some space.

I never priced a stock fan clutch, but maybe I would consider switching if it was a very pricey item

Free up space for what?
Switching to an efan left a giant gaping hole in front of my engine, space that I've filled with, ahh...well, nothing.

So far unmentioned, the best and most useful attribute of the electric fan is the ability to accurately control its operation.
The stock fan is a dumb, brute force solution to providing airflow, it has only the most general idea of what the coolant is actually doing.
A well set up fan control circuit will respond much more quickly and effectively to temp variation than the thermoclutch ever could.

After five years of efan operation I'm also prepared to say that you DO get a net horsepower gain using an efan...the whole "Increased draw on the alternator offsets the mechanical drag of the thermofan" argument is bullshit because it ignores the fact that the efan is hardly ever on.
There is always parasitic drag from the thermoclutch, it never disengages and free spins. The efan is only on for brief periods under normal circumstances.

Last summer I took a road trip and during the entire 3300 miles the fan came on twice, for a total of less than 15 minutes.
During the winter, as long as ambient is under @50°, even city driving doesn't trigger the fan. I check mine periodically just to make sure it still works because I don't think it has triggered on in months.
The FC is my only car and a daily driver, BTW.

I would ignore the "extra room" and "extra power" arguments as mere distractions, the real reason to use an efan is the more precise control it gives you over the cooling system, a critical component in the rotary package.

It is worth noting that even Aaron Cake, author of the cited "Myth" article, uses electric fans on his projects.
So there.

Mazdatrix lists it for $246, Rock Auto doesn't list it at all.

stock fan for stock car cant be beat, for modified car it cant be beat

control what? the thermostat controls the temperature the fan just keeps it in check

a properly operating stock set up is very hard to beat and keeps the car running very cool even on hot days , in traffic with the AC going I rarely seen 190 degrees

And how many people are spending $250 to ensure they have " a properly operating stock fan"?
How many 25 year old thermoclutches still work at spec?

What do you mean "control what"?
You control the amount of time the fan is on, obviously.

first off- If his fan is still working he should leave it alone

I dont see the need to control how long the fan is on, all the FCs I had with stock fans kept the car right in the 180-190 degree range keeping it simple is really nice sometimes

As owner of the nicest FC I know of your opinion must be respected, so I guess we'll just agree to disagree on this one.

I see no advantage to the stock fan other than it's already there.

if not operating- yes make a change, if its working keep it simple and dont touch it

sound good?

Sure it does.
To be fair though, that doesn't seem to be the approach you took with your car.

If your clutch fan can't be stopped by a single finger (wear thick gloves if testing this!) while the engine is running, the clutch is sticking. In which case yes, it is wasting a little power.

The clutch fan is only creating any significant load when the temperature dictates, just like the e-fan.

Weird. Every RX-7 car I've ever tuned will constantly toggle the e-fan during city and low speed driving. It's all datalogged.

Good bloody luck fitting large turbos, intercooler piping, air filter and associated upgrade parts with the stock mechanical fan. :)

Also note that I tried for a year to use a SPAL FAN-PWM to bring the gradual clutch-fan behavior to my on-off e-fan. Ultimately I gave up because the SPAL FAN-PWM sucks rancid donkey balls. But on my Cosmo, I used two smaller e-fans and have them programmed in stages to provide more linear temperature control vs. on-off. E-fans were used on the Cosmo due to space concerns and because A/C is installed.

I reject the "power consumption" argument as specious anyway, hardly significant either way except to note that the thermoclutch ALWAYS loads the engine because it never decouples.



Although I have an optimal setup for cooling- no AC and a NA engine- I'd credit my car's behavior more directly to the trigger temps of the fan.
My LOW speed (this is an 18" Lincoln fan, BTW) doesn't toggle on till 195° and I can sit for quite a while before hitting that point.


I never found more sophisticated control to be necessary.
Although my setup is hooked to the ECU and activates the BAC when the fan comes on, I usually can't tell if the fan is on till I see the VDO water temp gauge plummet. There isn't much noise or noticeable effect when it triggers.
I don't believe it has EVER gotten hot enough to switch to HIGH, which in my case is 210°.

Except that when the fan is idle, it's only spinning due to the slight friction of the bearings in the fan clutch. Romp the throttle and the engine speed increases while the fan freewheels unless the temperature is past the clutch engagement point. A properly working fan clutch is not a power drain in anything but a minuscule amount. Certainly well within a non-lab dyno's margin of error.

Though this is a wide assed guess, an idling air pump probably takes more engine power to turn than an idling clutch fan.

The way I see it, either fan will do the job just fine. Except that it's so easy for people to screw up an e-fan install that most are best served just keeping the stock clutch fan. I have had arguments with people installing e-fans because they say the fans I am recommending are "huge" and "bigger then ma' V8!". Then they come to me with overheating cars and I say "Yep, told you".

That's a pretty light load, and a higher trigger temp than I would be comfortable with in a modified turbo car, but I can see how in this case assuming a properly functioning rad, the fan doesn't trigger very often. It would annoy the hell out of me seeing the temp gauge wag up and down, and that's a much higher temp than Mazda runs the engine at.

More and more OEMs these days are PWM'ing their e-fans to act like clutch fans. More stable temperature control, and an electrical load that can be gradually increased and tailored to the cooling needs of the engine. All translates to better mileage and a smoother experience for the driver. People like to complain about OEMs but the fact is that they are now selling cars with 150K+ warranties, which are so refined that if the FC was produced today, it would be regarded as junk.

No, it isn't.
The FD for instance, doesn't trigger low speed fannage till 221°.

Everyone should remove the stock fan because it sucks. If you add an electric fan, you gain like 20HP. Also, ditch the thermowax because it adds heat to the intake, robbing you of at least 15HP! All stock equipment on this car is bad!

I love the smell of hyperbole in the morning.

Sadly, there are people who wouldn't quite understand that level of sarcasm and hyperbole.

SOLD

Thank you sir for the clarity and reason enough to purchase one. I always thought to myself, the stock one does JUST fine, can't argue that. BUT, E fan looks so CLEAN. I have only had one REAL concern about efans, that is the hint of it going out. With fan clutch I hear it, can spin it, and you can see it go out with the way the temp reads and car runs.

Your comment of consistancy makes total sense. Who doesn't want accuracy? And the benefit of much easier access to work on the car.

Thank you.

Free up space for more options of radiator, oil, and and intercooler mounting. But true, anyone looking for bolt in upgrades won't ever need that space open.

Monopoly money?

Sorry, I own a rotary bruva .. lol

Yes, it is. Stock thermostat temp is 82 (or is that 84?) degrees. With the stock fan, that's about where the FC runs.

Did you really just invoke the FD, possibly the worlds most unreliable vehicle (for reasons thoroughly related to heat), as an example of how things should be set up?! :D The same car that Mazda had to issue a cooling system recall for so that the fans continued to run after the car was shut off, to avoid boiling the coolant? Didn't that same recall also drastically lower the turn on temp for the fans?

The FSM states that the FC thermostat BEGINS to open at 180° and is FULLY open at 203°.
I would contest the idea the Mazda intended normal operating temp to be UNDER the fully open thermostat temp and that 195° is dangerously high.

I'll defer to your greater experience though and accept that maybe my particular car is an outlier/freak.

Yup, I did.
Funny how Mazda screwed up and did exactly the same thing on the RX8, eh?

Should I run Regular Oil with a Stock fan,...Or Synthetic with an Electric Fan?:scratch:

Funny you should mention that.
I found that after installing the efan, my car required no oil at all.

Didn't think that was significant or I'd have brought it up sooner.

premix it brah

I usually drain my fan clutch and mix 2 stroke and synthetic oil, the filler is at the top.

I'm jk, oil has nothing to do with fans

Unless you're Lexus.

Clokker vs Aaron Cake in a debate about cooling, with reference to the FD...:ttiwwp:

Aaron is correct about how the clutch fan works. To put it in easier terms, think of the clutch inside the fan as a Torque Converter from an Automatic Transmission. Yes, it IS spinning at all times, but can easily be stopped with a single finger just like how the brakes on a car will stop the car at a red light.

As far as proper operating temperature is concerned, I'm agreeing with Aaron 99% on it. A stock S4NA's A/C fan switch triggers at 195 degrees (TII is 207 degrees), while the thermostat is open at 180 degrees. Before my 20B Conversion, I was running with a Taurus fan & Alt, triggered via the 195 degree thermoswitch. Although I did not have an external temperature gauge in an otherwise bone-stock car, the car never seemed to overheat IIRC. A modified turbo car is an entirely different story though...

Per the S4 FSM, the thermostat for both NA & TIIs begins opening between 80.5 degrees Celsius (176.7 Fahrenheit) and 83.5 Celsius (182.3 Fahrenheit) and is fully open at 95 degrees Celsius (203 Fahrenheit). The FD's thermostat is identical in this manner.

Most of us know that the FD's cooling system is essentially the gold standard for how NOT to do things. It is simply insufficient for the heat being generated and trying to cover for it with the fans just didn't work. For evidence of heat-induced failure, one needs not look further than the turbo control solenoids.

Aaron, could you please recommend a suitable activation temperature for an Electric Fan? I believe you state in your E-Fan Article that the thermoswitch should not fight the thermostat. Considering that FD owners benefit quite a bit from using a S5T2 fan thermoswitch, I think it would be to everyone's interest to know what is reasonable for their fans to come on at.

Per the FD's FSM, the fan thermoswitch should read as follows:
214 degrees: 0.5 ohms Max
226 degrees: 1 Mohm minimum

Although I'm not a fan of ECU-Controlled fans, I do see the merit in accurate, predictable control. But at the same time, it is not the end-all, be-all answer for everyone. My preference is to have a thermoswitch with a manual override switch in parallel. If I need to override the normal operation for any reason, I can force the fan on. Otherwise, it is controlled by the thermoswitch(s).

When I have time to translate the JC Cosmo's FSM, I'll report back with my findings. In 13B-RE form, it is essentially a FD with a FC radiator and clutch fan, so it should be quite interesting what Mazda states its thermostat and A/C fan switch should trigger at...

I am eagerly awaiting Aarons answer to your question akagis. If it where me, I'd set the fan to turn on at the halfway point between thermostat starting to open and thermostat fully open (which is about 87-90*C)

yes do, the 3 rotor has a very interesting setup.

its got two thermostats, one 92c, and one 82c. the 82c thermostat has an ECU controlled vacuum valve to turn it on and off. since its ECU controlled, there are 7 conditions where it operates, coolant temp, a/c on or off...

then it has a mechanical clutch fan, like the FC, although its bigger. in a ducted shroud.

then it also has an ECU triggered electric fan.

the RX8 also had plenty of coolant seal failures with the same engine sealing configuration as the 12A and early 13B, which almost never blew out the coolant seals and ran about 20F cooler. those early engines also used.... a mechanical fan.

hotter engine temps may help with efficiency but it also hurts reliability and adds to the "hot start" variable. when talking expansion and contraction, more is not better.

to the efan debate, i hate efans. at least i hate AFTERMARKET efans, the controllers which are saving your engine are usually unreliable and turn on erratically unless you set one up properly with a probe INSIDE the coolant flow ON the engine.

ecu controlled e-fan all the way.. mine never turns on unless sitting in traffic. I have it set to turn on 195F, off at 190F

Datalogs here are the key. A standalone equipped car running on the highway (so we're ignoring fans here) will run around 84 degrees with a stock thermostat. Give or take a degree or two of course. As logged.

Important to remember it is the thermostat which sets the temperature of the car, not the fan. The fan is just there to pull air when there isn't enough natural airflow. Which is why most new cars are also switching their fans based on speed and temperature.

An interesting experiment for people is to disable their e-fan then get the car to about 200F or so. Then turn on the e-fan (leave it on!) and immediately go onto the highway. The car likely won't cool down very well as the fan is a restriction. Turn off the fan and the temperature drops like a stone.

I typically set the fan-on point to 195 (F) and the off point to 188 (F). Staged fans are a bit different. Typically one fan will be set to come on at 190 (and with the A/C) and off around 186. Depends on the car though. If it cycles too much that can be adjusted.

The goal is to keep appropriate airflow through the rad to keep the temperature stable. Makes it much easier to tune.

Unless it's a stupid Microtech which only allows you to set the fan-on point (it cuts the fan off 5 degrees below) and only then in 2 degree settings. So I set it to 90C.

Thermoswitches drift and fail, and as a mechanical device, will wear our. Plus this causes all kinds of silliness when you want the ECU to control the fan, such as an A/C situation. And it means that you can't easily cut the fan at speed, which hurts cooling.

Just a few days ago when I said my fan triggered at 195°, you responded:
It would seem we both consider 195° a safe temp for low speed fan operation.

You are absolutely correct about the fan on/highway test, the fan is a hindrance when the incoming airspeed is higher than the fan's suckage (*technical term*). That's why it's nice to have air relief flaps in the shroud as they mitigate this effect.

This phenomenon would also seem to be a strike against the stock mechanical fan, the shroud has no reliefs and (unlike an efan) the blades are never idle.

Just sayin.

I like the way you approach it Aaron. To end the whole Thermoswitch Vs ECU Trigger debate, let's approach it this way:

If you have an unused output on your Haltech/Microtech/Megasquirt/Etc ECU, use it for the fan as Aaron Cake suggested. This method allows the ECU to override the activation temperature based on road speed, A/C activation or other conditions based on its software settings.

If you're using a stock ECU or don't have an extra output on your EMS, using a thermoswitch in the temperature range Aaron recommended will do the job. Doing it this way means the ECU CANNOT interrupt the fan's behavior based on road speed, A/C, etc.

I prefer to have some redundancy built into the circuit, hence why I suggest a Manual Override Switch wired in parallel to the Fan Trigger. One can consider it an onboard diagnostic mode that's available to the driver at any time.

It is my mistake. I got a bit confused because the US uses Fahrenheit, unlike the rest of the world which properly uses Celsius.

Doing the mental conversion caused me to think 195F is hotter than it is. I've tried in later posts to translate into Fahrenheit for non-standard US readers.

The clutch fan freewheels. It's speed achieves equilibrium with the incoming air. In the same sense, the oncoming air cools the fan clutch which will disengage the fan once up to speed.

This is why I have always felt just fine using the Perma-cool "finger chopper" though many may not or don't like it due to it's lack of a shroud or ducting. At highway speeds there is nothing to interfere with airflow. This is where most of my driving is so it's a good fit. It is set up with a thermoswitch. Highest my temps have got was acouple of years ago I got stuck in traffic in Huntsville, Alabama in July( near 100F temp and they peaked close to 230F. I think it was more the radiator was maxed(stock size copper/brass replacment) than the fan being insufficent. I am going to intentionally go get in traffic on a hot day this summer to see how the Godspeed I just got does.

As to the original question I like the E-fan. Makes working on the front of the engine much easier. My clutch fan died years ago so I switched. Only wish I had my autometer gauge when it was functioning. As to the pros and cons to cooling I'll let you guys continue to hash it out.

As to the FD not kicking the fan on till 220. That is crazy on Mazdas part. No wonder they had so many problems. I start to worry if my temps reach 220 in traffic.

I didn't realize anyone was even having that debate.

I wish I could find the source because I swear I've read that the thermoclutch operates in the 30-80% lock up range. It never fully disengages nor does it ever fully lock.
No matter, the differences would be trivial and hardly relevant in the real world.

ill sound like a broken record and say again when its a NA car, especially with no AC its a much easier chore keeping the car cool


adding to what aaron said about electric fans on the highway- The design of the shroud plays a large part. I had a custom shroud that covered the entire radiator, so the only air that could pass through it had to come through the fan- this ran warmer on the highway.
I switched to a taurus set up, which the shroud doesnt cover the entire radiator- I feel this helped keep the car cooler on the highway. I keep meaning to install one or two of those rubber flaps in the shroud I feel they can only help things.

http://www.submariner.org/thepno95/P...or%20flaps.jpg

http://www.mgexp.com/phile/1/206789/...aust_Flaps.jpg

Just a thought. A mechanical fan spins more stuff than an electric fan and with the battery in the loop, wouldn't that help performance? Not spinning more stuff? Inertia?

A manual fan override is a handy thing to have when you are at the track. Just make sure to run appropriately heavy wire (12 gauge) to an appropriately heavy duty switch, assuming you are bypassing the fan relay completely (which is good redundancy).

There are many adjustable thermo switches made by Derail and the other vendors. Just avoid the cheap little mechanical silver type with a probe that sticks into the rad. In my experience they are unreliable and hard to set to any consistent temperature. The best types use a standard CLT (GM typically) which screws into the water jacket (drill and tap the water pump housing).

I also agree with flapped shrouds. If possible, it's the way to go.

If someone is curious as to how I would set up a cooling system, then Episode 27 of my Cosmo covers exactly that. Fan stuff is near the end where I install a Derale dual fan assembly with aluminum shroud, pressure release flaps and properly wire it up to EMS (MS3-Pro) outputs.

I've consulted the FSM several times during this discussion and have a question for the thermoclutch fan advocates...

There is absolutely zero specific information about the specs or a test process for the thermoclutch in the FSM.
"Push fan with finger and feel for resistance" is as technical as it gets.

Unlike most other consumable parts on the car, I doubt people have been regularly replacing their thermoclutches, so chances are excellent that yours is a pretty old example.
Given that the fan is a pretty important component in a very critical system, short of buying a brand new thermoclutch, how can you feel comfortable depending on a part you can't test?

Put a heat gun it, low setting, and see if it grabs.