Clutch Fan vs Electric Fan

[Mattchou]

Is there any HP gain,MPG gain etc by convertering a clutch fan to an electric fan on a car/truck.
There is a topic on this running at another forum which has mostly speculation so I'd like to have a defenative answere if anybody know it.
Thanks,
Matt

 

[moribundman]

You can't gain hp, but you may loose less hp by converting from a viscous clutch-driven fan to an electric fan -- however, the electricity that the electric fan consumes must come from somewhere, which is of course the alternator. An electric fan will put more strain on the alternator. An electric fan may be of advantage if you need to squeeze the least bit available power from your engine. In my opinion, it's not worth replacing a simple and reliable clutch-driven fan in exchange for a more failure-prone and only marginally more efficient electric fan -- unless the viscous clutch needs to be replaced, which can be costly. An electric fan conversion may also make sense if you want to be able to control fan speed, because you could install two thermo switches for low and high fan speed settings.

 

[eljefino]

I think it's a great idea, mostly because I almost never get stuck in traffic long enough to need my electric fan in my transverse-engined cars.

Even my truck, a dodge dakota, has a k-car 2.5 that's normally transverse, installed longitudinally. Rather than mess with the belts and computer they just stuck an electric fan in there.

Plus I hate the "school bus roar" a clutch fan makes on a cold morning before the goo loosens up. I think the things are dinosaurs unless you're in desert country and always need a fan blowing over the ac condensor. I see you're in Florida so the answer may not be as cut and dry for you. You could probably get a pusher fan cheaply enough at a junkyard that mounts in front of the rad and conduct your own experiments WRT heat, power and mileage.

 

[Pablo]

As Mori wrote. It's not really going to buy you anything in "extra HP". But as el Jefe wrote - fans are sorta dinosaur like and electric fans are quieter and have millions of miles of experience. I never had one fail.

I did the conversion on my high mileage Volvo 240 turbo. The viscous clutch was shot and I figured on a turbo 4 - the less direct drag on the engine the better. I always had a healthy battery and had just replaced the alternator.

I had a variable 'stat switch. Seemed to work great. The thing rarely if ever came on during the cold winter months - so right there it was better than spinning the fan clutch. In the hot months - it came on and cooled fine when idling after a little "boost exploration".

I had a nice relay with high power right off the main + bus from the battery, and the controlling power was switched 1+ (didn't need full ignition on to work, just key in and one click)

I was lucky as my radiator upper and lower brackets held the Mr. Gasket fan perfectly after drilling four holes. I wouldn't trust those through the fin straps.

 

[jmacmaster]

I have a 2003 Ford Ranger with the 3.0 liter V6 Vulcan engine. This engine's been around since about 1986 and only produces about 154 hp. I'm on 3 Ranger owner websites and on all 3 websites the owners of the 3.0 liter V6 Ranger are constantly discussing how to increase hp and torque. MANY of them have switched to an electric fan. The consensus of opinion, some of that opinion backed up by dyno tests, is that the e-fan will give you little, if any, more hp and/or torque and is not worth the money. And remember, the fan isn't running all the time, so IF you get any gain, its only when the fan is running.

 

[H2GURU]

I think the electric fan may work out for you as with the pricier ones you can actually program them to run for a specified time after a long run in order to aid in cool-down.

 

[Gary Allan]

The whole energy equation comes down to duty cycle. On my mom's Citation ...the OEM rad was shot. Replaced it with one 50% thicker. The fan went from running over a minute at idle to 15 seconds (no, I didn't use a stop watch). Now back load that tidbit into how often you may or may not need your fan spinning 24/7 with the clutch. You can "cheat" in terms of total saved hp in terms of alt drag vs. hp lost with direct mechanical loss. It's not a zero sum gain.

The only draw back is the air conditioning. It always wants to turn the fan on ..even if you're going 60 mph. I haven't managed to overcome that challenge in any reliable manner (visions of micro-switches that react to flaps that open @ a certain mph)

 

[moribundman]

It also depends on the whole setup. For example, my car has a viscous clutch-driven fan for the radiator and an additional electric fan for the AC condenser. I really wouldn't want two electric fans. Over the past 155k miles, the electric fan failed twice: once because of a loose wire and once because of a defective thermo switch. The viscous clutch has so far worked reliably without any problems.

 

[Gary Allan]

One of the few features (aside from the splendid fuel economy) of my Pukeout 504 diesel wagon was the mechanically driven fan (it also had an auxillary electric fan) that had what appeared to be something not unlike an ac compressor clutch. It just didn't lock up unless it got juice from some source (I'll assume a thermal switch in the engine's water jacket).

 

[moribundman]

The viscous clutch in my A4 engages and disengages the fan, depending on the air temperature behind the radiator. The clutch contains a bimetal valve, two chambers, a drive disc (Don't know proper technical term) and the viscous fluid.

 

[Gary Allan]

The disadvantage to that is that it draws power when it can't do any good. For example ... when you're going down the road at 75mph in 90F weather. The air coming across the rad may be hot enough to engage the clutch ..but there's no practical advantage to have it working at that time. This is another advantage of the electric fan that's engine temp actuated (pcm/ecm whatever). It doesn't care what temp is coming across the rad.

 

[moribundman]

I'll have to stick my head under the hood while driving to check when exactly the fan is running. I do notice when the electric auxiliary fan kicks in, which is only after driving the car hard, or when idling a few minutes in very hot weather.

 

[tdi-rick]

Quote:

---

The disadvantage to that is that it draws power when it can't do any good. For example ... when you're going down the road at 75mph in 90F weather. The air coming across the rad may be hot enough to engage the clutch ..but there's no practical advantage to have it working at that time. This is another advantage of the electric fan that's engine temp actuated (pcm/ecm whatever). It doesn't care what temp is coming across the rad.

---

Not always Gary.
I've come across several vehicles where it appears that ram air at speed isn't enough to overcome the poor under bonnet air flow. The (viscous) fan is needed to actually push/evacuate this high pressure air from the underbonnet area to allow adequate flow through the radiator, and I'm talking of vehicle speeds above 80 km/h, and admittedly high load and ambient.
One vehicle, Nissan's Patrol with the TD42T turbo diesel is a known overheater when towing and the 'fix' is to slightly overfill the fan clutch to engage the fan a bit more (the slicone fluid is available from Toyota.....

)

Have also heard of the same thing happening on a Land Rover Defender, after me telling the bloke that ram air took over above 50km/h and he was wasting his money replacing the viscous clutch

Of course thermo fans would technically be better here for the reasons you described, but they are shockingly unreliable in off roaders that are used off road, unlike a viscous clutch.

 

[Shannow]

Completely off topic, but one Torana I had had the starfire 4 (low thermal load). I fitted a big radiator, blocked off the top part of the grill (making the air come in beneath the bumper), lifted the back of the bonnet a couple inches to let the air out at the highest point possible. It was an attempt to make a "thermosyphon" cooling system.

It could idle for a suprisingly long time with little movement of the temperature guage.

The slightest breeze in the wrong direction would upset that badly.

Also had one of John Bennet's lower hose thermostats which helped a bit.

 

[tdi-rick]

Quote:

---

Completely off topic, but one Torana I had had the starfire 4 (low thermal load). I fitted a big radiator, blocked off the top part of the grill (making the air come in beneath the bumper), lifted the back of the bonnet a couple inches to let the air out at the highest point possible. It was an attempt to make a "thermosyphon" cooling system.

It could idle for a suprisingly long time with little movement of the temperature guage.

The slightest breeze in the wrong direction would upset that badly.

Also had one of John Bennet's lower hose thermostats which helped a bit.

---

only problem with lifting the trailing edge of the bonnet is that it only lets the underbonnet air out when the vehicle is stationary.
Any reasonable speed and the base of the windscreen becomes a high pressure area.
This is how the A9X Torana's bonnet scoop worked all those years ago.

I've wool tufted a few bonnets experimenting with this and the tufts blow back under the trailing edge of the bonnet every time.

PS, a 'bonnet' is a 'hood' to you North American's

 

[obbop]

Dear Brits and sundry jovial blokes in other parts of the empire.

Here in the colonies a hood can be a outter covering of an enigine compartment or a thug-like human, usually a male, who typically possesses anti-social tendencies and can be prone to violence or law-breaking activities.

You're welcome.

 

[moribundman]

But obbop, the word "hoodlum" comes from German word "Hudel," while the word "hood" comes from another German, or more specifically, Frisian word, "Hod." Those two words are not related. These days we don't use "Hudel" as a noun, but we use it as a verb, "hudeln." It means to do something sloppily, quickly, in a careless manner.

PS: Little Red Riding Bonnet?

 

[brianl703]

Quote:

---

It always wants to turn the fan on ..even if you're going 60 mph. I haven't managed to overcome that challenge in any reliable manner (visions of micro-switches that react to flaps that open @ a certain mph)

---

Frequency-to-voltage converter connected to the vehicle speed sensor feeding into a comparator which has an adjustable setpoint feeding into a relay wired into the fan control should do it...

You could probably get all the parts at Radio Shack..or you used to be able to, anyway..

According to Ford's manuals, they shut the engine cooling fan off above 45MPH.

 

[Gary Allan]

It's called "cowl induction" across the way here. The outlets need to be behind the leading edge a bit. Louvers are the usual facia of choice.

 

[XS650]

Quote:

---

The only draw back is the air conditioning. It always wants to turn the fan on ..even if you're going 60 mph. I haven't managed to overcome that challenge in any reliable manner (visions of micro-switches that react to flaps that open @ a certain mph)

---

It might not be worth much effort to "fix". If you have good fast airflow through the radiator, the fan motor isn't working as hard to spin the fan.

Are you sure the fan doesn't cut off at high speed, even when the AC is on? I recall that mu 96 GM product's fan did, but I no longer have the manual to verify.