aftermarket fans (not electric)

I have been watching all the threads about installing electric fans and I understand why it can be a good idea. This got me to looking at my stock set-up and noticed that the clutch covers a large part of the inner fan blades.I thought if a person replaced that set-up with a fan like a flex-a-lite ,100% of the blades would be pulling air plus not slipping on the clutch.Then I noticed that there aren't any 15 inch fans like that for a serpentine belt. Does anybody know of one or tried this just to see if there was a difference good or bad ? It looks like a 16 inch might squeeze in there but it would be close.

NOISE! it will sound like a freaking jet turbine under your hood all the time! Yank the stock mech fan off, find another electric fan with cowl, trim and fab a bit, wire in it and your done! Takes just a few hours, but very do-able.

I'm working on a solution to eliminate the OEMR fan clutch (for various reasons - mainly; for people like me who are tired of changing the thing, and rock-crawlers who run at low speeds and for whom heat is the enemy...)

Pretty much anything you can bolt to that fan clutch will have the clutch hub problem - even though the clutch hub is smaller than the "effective fan hub" (central area of ZERO blade pitch) and therefore isn't a problem.

However, look around here for people who have lost engine mount cushions, and had the fan clutch hub mill out a nice round hole in the radiator.

I'm sort of at a standstill right now - I'm still catching up from recent events (cf. my "What I got for Christmas" thread) and while I've got the first design finished, I haven't been able to prototype it just yet.

My solution is intended to use the OEMR attaching hardware and fan blade for simplicity, but figure it being about 1/3 as wide, and eliminating the entire clutch assembly forward of the current location of the fan plane. The fan will NOT be relocated as a result.

5-90

A permanently engaged manual fan would definitely create some noise, not to mention increasing winter warm-up times. Of course an electric fan without the benefit of a thermostat would do the same. Just depends on what floats your Jeep.

I am looking hard at electric fans but am thinking along the lines of 5-90 , if I keep the mechanical , that clutch has to go.
Why would eliminating the fan clutch lengthen my warm-up time ?

Because the fan speed would always equal the engine speed. The clutch that normally is there is thermostatically controlled, free wheeling when cold engaged when hot.

I did a dual e-fan a couple years ago and my Jeep warms up quick in the winter because the temp sensor in the radiator keeps the fans off until warmed coolant is finally circulating through the radiator. Then using PWM it gradually increases the speed of the fans to keep the temperature at a fairly constant rate.

On one hand you have simplicity with a mechanical fan, but the flexibility of the e-fan setup can outweigh some of the reliability vulnerabilities it gives up.

Correct. That, and even at full lockup, I'm told that the mechanical fan only runs about 80% of the pully speed - so you'd note longer cool-downs as well.

I'd not think it would affect warm-up overmuch - because the thermostat still stays shut until it hits 180*F or 195*F (depending on what you've got.) Besides, it's still only a real issue with OBD - because the system keeps track of warmup time. The HEGO sensor warmup isn't an issue, because it's heated (the "H" in "HEGO" - Heated Exhuast Gas Oxygen.)

The noise issue would probably be minimal, if you've opened up your exhaust anyhow. While it will certainly be noisier (although I've not determined how much just yet,) the mechanical fan is always running at some speed, and is making noise anyhow. I'd not think "Jet Engine" (I don't have enough material for a report yet,) but the air mover will certainly make some sort of noise. Then again, we all like a little engine noise, don't we? Otherwise, we'd alldrive a Lexus or some damn thing (and I don't know about the rest of you, but I know that I like a little engine noise! Gear drives are even better...)

One thing I'm certain to do while running a proto cycle on this thing is to take a "before" and "after" recording on my rig, and I'll post those on the site as well - and let you make your own decision. Probably from the driver's seat and near the front bumper, for comparison.

5-90

The fan speed is directly tied to the size of the pulley being used. Larger diameter, slower it turns. Smaller the diameter and the faster she spins. Just like over/under driving a waterpump or alternator.

The other minus of mechanical, which impacts a smaller percentage of owners, is the inability to disable the fan when fording deep water.

Extended warm up times will be more exaggerated in colder climes.

I am aware of that - and I may design overdrive/underdrive pullys as well, but I doubt it much.

However, what I was referring to was the inherent "slippage" of a viscous coupling - since it's not mechanical, it's just about NEVER going to be truly 1:1.

I also haven't been able to address the need to ford (just yet) with a mechanical - either I'll have to design a much stronger knuckle (the current design calls for 6061-T6 as a compromise between machinability, material cost, and durability) or I'll have to come up with some way to make an electromagnetic clutch happen in there - I haven't decided. Considering that a stronger knuckle transfers the failure point from the clutch to the idler pully bearings, I'll probably have to come up with some sort of clutch (which will likely go from 80% at full coupling to, perhaps, 95-98% - much better.)

5-90

Correcting my statement as I thought you were referring to a fan that was permanently engaged, not something with some sort of variable coupling.

Water probably isn't as common by you as it is by me. So I could see that not being a high priority. The fan blades are where the stress is going to be in that situation and I am sure they could be made strong enough to resist failure in a water crossing.

Good luck with it.

You have not even thought of the extra HP loss and fuel consumption due to always pulling a fan permanently? Also the flexi fans are shocking for a 4wd. The whole design principle is wrong for one. They are designed to flatten the blades the high the RPM to save some HP and fuel. That works fine in theory on a car when the engine speed is high, so is the road speed and hence more air pressure help the air through the radiator. But on a 4wd in low range you have a high revving engine pulling you through deep mud or up a long hill etc and the fan then flattens it's blades and you have less air flow when you need it the most! They also have a very nasty habit of letting blades go as well!!

Gojeep , I have thought of the milage and horsepower but was willing to give some up in return for better cooling. The high RPM's and slower moving I hadn't thought of . OK , that idea just bit it .
Back to the thinking board , just seems there has to be a way to improve the stock fan design without going electric.

Ridr said:

Gojeep , I have thought of the milage and horsepower but was willing to give some up in return for better cooling. The high RPM's and slower moving I hadn't thought of . OK , that idea just bit it .
Back to the thinking board , just seems there has to be a way to improve the stock fan design without going electric.

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You can just use a fan from any car in say the 70's as their fan blades did not flatten. It was mainly the after market ones that did to increase HP at high revs. You can just mount the existing fan straight to the flange with some adaption too. I have heard of some how fixing the viscous coupling so it will only drive full time without slippage so try pulling that apart to see how they do it.

I’ve been using a 16” reverse rotation flex fan in my XJ for the last 2 years. It fits, but you have to be real careful with the spacer – a 1/8” makes a difference. I don’t remember exactly what length spacer I used, but if anyone needs it I can go measure it later. The “jet engine” sound is complete BS. It’s no louder than the factory clutch fan that was on there originally. It does a much better job at cooling the engine and warm up time does takes a little longer. I’ve done several water crossings and it’s not a problem. The blades simply flatten out, much like they do at high RPM. The blades are no more prone to coming apart than any other mechanical fan. As for the fan not pulling max air at high RPM in 4 Lo, that may be a potential theoretical problem. I regularly take my Jeep 4 wheeling and it has never been an actual problem in real life. I suppose if you were stuck in a mud pit and stood on the throttle for 15 or 20 minutes with out moving the Jeep it may be possible to over heat it. At that point you have much bigger issues, like how do you plan on getting home. As for gas mileage, I can’t really say one way or the other. It didn’t seem to improve or reduce my mileage. It has helped keep my Jeep running cooler and I’d do it again with out reservation.

double post

We ran a stainless steel flex fan( no clutch) on a 1977 GMC Jimmy for years (38 mudders,worn out ,3.07 gears) on NC beaches,deep sand, NC summer temps, worked great never any heating problem. Also had a 1976 GMC truck had the clutch fan pined( drilled thee holes through clutch used bolts with nylocks ) never a problem. Good Luck

voudoux said:

We ran a stainless steel flex fan( no clutch) on a 1977 GMC Jimmy for years (38 mudders,worn out ,3.07 gears) on NC beaches,deep sand, NC summer temps, worked great never any heating problem. Also had a 1976 GMC truck had the clutch fan pined( drilled thee holes through clutch used bolts with nylocks ) never a problem. Good Luck

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He's had 10 years to figure it out so I think he's good ;-)

I was recently on another forum (HDTalking) that would warn you if you were bringing up a thread from the dead. I wonder vBulliten has that setting.

Lol. I played with flex fans.

In low range you overheat. The fan flattens out but you don't have enough vehicle speed to get adequate airflow.

Don't understand the 10 year comment, back to the fans. Where would you be turning the engine high enough for a long enough time to cause it to heat? Just curious. I very rarely used low range in the sand, no mater how loose . Never turned the engine very high so the fan feathering never was a issue. Have a 2011 wrangler that you need to run in low to so all the computer controls( most of them) are cut off. Would go fine in high but the computer takes over ,traction control etc and its bogs down. I all depends on what and where you use your Jeep .Thanks