rotordave

iTrader: (1)

I hope I'm not out of line posting this long after the fact, but...

I found a thorough discussion on fan clutches/e-fans here:

The Myth of the Electric Fan

The conclusion seems to be that you should only switch to an e-fan if you want more space in the engine bay.

rotordave

iTrader: (1)

Oops, I found it is already linked to in this thread:

https://www.rx7club.com/1st-generation-specific-1979-1985-18/e-fan-fan-clutch-atf-other-myths-exposed-620821/#post6610439




Anyway, I would like to buy a new fan clutch but when I called hte local auto parts store they couldn't tell me which model to get. All I have is this list of Dayco items:

http://www.dayco.com.au/products.aspx?G=1785&P=1518

I did find this thread while searching, closest I could get to finding out the specs of the fan clutch:
https://www.rx7club.com/1st-generation-specific-1979-1985-18/help-how-put-stock-fan-back-537657/#post5623186

kenn_chan

thats arron cakes page, and while he can be quite knowledgable in some areas he is often full of himself also. we had a very short non productive discussion on this some time ago, where he tried to empirically state that it freed up no more than 1~2 HP.

the gist of my argument was that rotating mass is rotating mass and any reduction is gong to cause ans increase in HP hense acceleration, and also that his assumptions were based on the newer type mechanical fans that use a more efficient blade design. I have personally recorded up to 12 HP increase on an ENGINE dyno, now this is were we got into the argument, because he felt that the roller dyno was more accurate, I feel that the engine dyno is more accurate because it does not mask other parasitic losses therefore the individual items can be more accurately accounted for. he then went into the whole alternator is useing more electricty blah blah blah, but that as has already been pointed out is only when the car is sitting in heavy traffic, anything above 25~30 MPH and you have more airflow across the radiator then you will ever get with any fan.

any ways sorry for the rant.

kenn

Jeezus

iTrader: (4)

I love my e-fan. 2nd gear definitely feels more rev happy to say the least.

ray green

iTrader: (14)

Three more arguments against efans:

1. Switching to an efan costs time and money. Keeping your stock fan is free.

2. Most things that change the original stock configuration of your FB are going to reduce it's resale value, including efans. These "mods" will generally be perceived as molestations by a prospective buyer. Think about it, would you prefer an unmolested well kept stock FB or one that has been modded and driven more aggressively?

3. And no, there is no evidence that efans produce more horsepower or cool better (they don't). It's just that if you own an efan you THINK they produce more horsepower and cool better (just like I think my red leather seats are more classy and more comfortable).

But Stu is right, if you put one in you might enjoy the placebo effect.

dj55b

iTrader: (2)

https://www.rx7club.com/naturally-aspirated-performance-forum-220/simple-gain-suggestions-n-owners-715386/

Have a look in this thread. The guy has dyno proof that he gained 12rwhp just from the efan mod. Rob from rotary shack says it can rob even more on a hotter day. Also another guy will be doing some more car testing with a customers car to validate some more with dyno proof again.

Jeezus

iTrader: (4)

Sorry Ray, but I beg to differ. Having a 79 and an 82 with stock clutch fans, then going with an E-Fan really made 2nd gear easier to pull through. Just think: the clutch fan is attached to the engine. The engine spins more as you rev more, and spins the fan as a side effect. Now, having removed the fan from being engine driven to being non-engine driven, you elimenate the fact that the enging has to go through the air drag of the clutch fan, vs the non-engine drag of the E-fan. Electric motors produce the most torque at 0 RPM. When you transfer the energy required for the engine to turn the fan to an engine not turning the fan, you get your stock HP back. Not trying to say that an E-Fan with VTEC stickers will give you HP, but having an E-fan vs non-efan is a considerable difference.


If it really matters, I still have the stock clutch here, minus the fan blades. If someone would ship me the blades, I can get a dyno of Stock VS E-Fan to settle it lol.


But in all seriousness, E-fan made my 2nd gear (atleast noticably) pull faster.

Jeezus

iTrader: (4)

And to add to my post above... If you take a stock 30 or 23lb flywheel, and replace it with a lighter weight 18 (iirc) RB flywheel, or maybe even a 9lb flywheel, does your engine rev faster?




Now imagine if you remove the weight from the front end, IE the clutch fan, PLUS removing the drag created by the fans pulling the air backwards.


Now, I do agree on one thing. Stock fans are more reliable, as in if my E-fan quits, the car will begin to overheat vs the car still staying cool because the clutch locked up. That is why I am paranoid and watch all my gauges every 2 minutes

ray green

iTrader: (14)

Yeah but can your efan do this?:

http://youtube.com/watch?v=Oi7BANPkh-Y

Jeezus

iTrader: (4)

Nope... Sam cut his fingers just INSTALLING his... lol


But here is an old vid of it starting first time in the day, cold start.

http://www.youtube.com/watch?v=E6yxbdQAZmk

dj55b

iTrader: (2)

What does this have to do with anything? Have you looked at the thread that I posted?

Will your Clutch fan stop when doing speeds of about 30+ mph when the air ramming into the radiator is more than sufficient to cool it down? That alone is usable HP when racing.

trochoid

iTrader: (6)

Empirical observation is no substitute for scientific testing. What does that mean? It means seat of the pants/bench racing is no substitute for controlled and reproducible scientific testing.

When all of you who've posted empirical opinions realize this, the discussion will be over until someone does controled, scientific dyno testing that yields results that others can test for and confirm using the same parameters of testing. Providing that the original parameters and proceedures are scientifically valid to begin with.

Do the above paragraphs sound intelligent, believeable, are you convinced about the truthfulness what I said? Probably. But the real question is, is it true and how can one confirm or dispute it? If my statements are believeable and you are convinced, then it must be true, right? I'll let each of you decide for yourselves whether my statements are true or not.

All of the above long winded and big worded statements and questions are to make a simple point. No matter how many opinions are espoused from observations, the hp answer cannot be difinitively known unless one dyno tests for comparison between the stock fan and an electric fan.

And I guarantee that even with indisputable results, no matter which way it goes, some will still argue their point.

Jobro

iTrader: (2)

An E-Fan won't make your engine make more horsepower.
An E-Fan won't cool better than a properly running clutch fan
An E-Fan will put an extra 10+ Amps load on your alternator.

But a correctly setup E-Fan with appropriate switching settings will only come on to prevent the engine from overheating. The stock mechanical fan WILL be an UNNESSESSARY parasitic loss in any case other than car traveling below about 20kph.

I feel is is appropriate to state that turning that mechanical fan when the engine is spinning at 3000-8500rpm could be wasting a fair whack of power that an electric fan won't be.

Blah blah the load on the alternator is just the same/worse than the load caused by the fan is COMPLETE BULLSHIT, the E-Fan (when properly setup) will only come on when the coolant is around 93degC or 200degF, which will never happen with the vehicle coasting, the electrical load increase will only be at idle, for part of a minute, when sitting in traffic for multiple minutes.

Even the dyno test is an unreasonable situation to test the improvements caused by the electric fan, because its benefits are reduced by the fact that there is no road speed induced airflow cooling the radiator/engine.

A good test would be just getting a g-tech or one of the more sophisticated things, and going for a run in gear and testing 40-70mph times with and without the clutch fan installed. Pretty soon you will see whether there is much to be had, it won't be much most likely. But I'm sure there will be some merit.

dj55b

iTrader: (2)

^ But if you can see a HP increase even with the fan on on a dyno, what will that tell you on the street when its offf? More HP.

sgieldon

Not to make this thread go on any further & a bit off the original ?
79-81 used the Short under Radiator Oil Cooler setup.
The Stock Fan Blades are Straight.
82-85 Fan Blades are slightly Curved.

Which style Fan Blades do you Guru's think will Push more Air?
I run the early style setup in my 84 and am using the Straight Blades.
My temp stays @ 179 most of the time unless I drive it Hard on a Hot Day = 185 to 190.
No cooling issues, just curious!
I have 5 complete Clutch Fans 50/50 early and later model setups in the garage that are about to be tossed.
Sorry about the Thread Jacking.
sgieldon
steve

Jeff20B

iTrader: (13)

Oh great. Another synthetic vs mineral oil debate.

I like to use a clutch fan where possible. Where it is impossible, I'll grudgingly use an electric fan like in the MG, baja etc.

glewsRx

iTrader: (1)

Jeff chimes in. I'm with him.

ray green

iTrader: (14)

"Will your Clutch fan stop when doing speeds of about 30+ mph when the air ramming into the radiator is more than sufficient to cool it down? That alone is usable HP when racing."

Fan clutches are essentially free wheeling except when extra cooling is needed, usually only when stuck in traffic. My stock cooling system works very efficiently, so there is almost never a time it needs to engage the fan for that extra air flow, even when sitting in traffic.

So no, properly functioning fan clutches don't sap any horsepower, except on real hot days when you are sitting in traffic and not going anywhere anyway.

I have to agree with Jobro on this one:

"An E-Fan won't make your engine make more horsepower."
"An E-Fan won't cool better than a properly running clutch fan"
"An E-Fan will put an extra 10+ Amps load on your alternator."

Jeff20B

iTrader: (13)

When some e-fans first turn on they can spike at 20+ amps. Of course it depends on the motor and whether it has a PCM soft start or just a simple relay. A simple relay will cause a sharp spike.

John64

Just upgrade your alternator!

1983GSP

when the fan clutch is engaged, you ''feel'' a big difference on my 83. when its not engaged you dont notice it. when i first start it in the morning and hold it at about 2000 rpms you hear the fan churning like hell, then as it disengages the rpms pick up approx 300 rpms. so i have to back off the throttle to keep it at 2000 rpms. does the mechanical fan cause drag on a rotary? of course, when it is engaged. when its not engaged, i dont think you would be able to tell a difference.


ive owned multiple sbc's with the ol' flex fan. then i put an e-fan on and ive never went back. why? you felt a noticeable difference between a flex fan and an e- fan. and when i took my multiple sbc's to the track, i picked up almost a tenth by switching to an e-fan. do e-fans work? yes. would a clutch fan have worked as well? probably. if my fan clutch goes out on my fb im going to an e-fan for the sole purpose of cooling when i want to, like after a hard run, or between rounds of a footbrake shootout.

Jeff20B

iTrader: (13)

When mechanical fans go into freewheeling mode, you can easily stop them with your finger and even spin them backwards. Be careful if you attempt this on your own car with your own fingers!

This freewheel mode takes no power from the engine and is less of an air restriction than a typical e-fan mounted to the radiator. So in this way, a clutch fan is far superior to an e-fan. Just something to consider if you're thinking of doing an e-fan.

mar3

iTrader: (8)

When all of you who've posted empirical opinions realize this, the discussion will be over until someone does controled, scientific dyno testing that yields results that others can test for and confirm using the same parameters of testing. Providing that the original parameters and proceedures are scientifically valid to begin with.

Although not as scientific as if Bell Labs had conducted the experiment, Car Craft has, in fact, done this very experiment on back-to-back-to-back tests on the same chassis dyno, same car, same day and saw more and more rwhp as they started from stock and progressed in 4 steps to end up with the E-fan...and rwhp is what makes you go. We are all awaiting Feb 2nd to see what the next back-to-back dyno test comes up with in the other thread.


This freewheel mode takes no power from the engine...

Scientifically impossible...I'm sure you meant, "takes almost no power", which may or may not be true...we'll find out on dyno day.

ray green

iTrader: (14)

"Just upgrade your alternator!"

If you upgrade your alternator (higher amps, I presume) you will put more drag on the engine and reduce effective HP output. In other words, grasshoppers, you don't get something for nothing, as Mar3 correctly points out.

The fan clutch is so popular because it has been found to be the most efficient method for air control over a wide range of driving conditions. A junk yard taurus fan just can't compete with the Mazda engineers.

trochoid

iTrader: (6)

Jeff, I have to disagree on a couple points. An electric fan, correctly hooked up with a thermoswitch will freewheel when not in use. It, however, usually stops unless there is enough air, (velocity), coming through the radiator to spin it. The clutch fans don't stop, even when freewheeling because the viscous fluid never fully disengages. This is why Ray can reach in and stop his in his vid. The engine and belts are still turning the fan, through the viscous liquid. The parasitic loss is miniscule compared to when the fan is fully engaged.

If someone could figure out the wiring, relays, etc., a freewheeling e-fan that's spinning going down the highway could be converted into a low amp output alternator.