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bcredliner 07-14-2015 12:06 AM

Replaced clutch fan with electric fan
6 Attachment(s)
About a year ago I decided to remove the clutch fan and replace it with an electric fan. The following summarizes why I made the change, what I did and the results:

Whether or not the removal of the clutch fan in favor of any aftermarket fan is beneficial has been debated for years and I wouldn't expect the debate to stop anytime soon. It is similar to a debate on whether or not transmission fluid should ever be changed on an E53. Obviously, I believe there are worthwhile benefits of an electric fan.

IMO, for daily driving, there can be benefits such as improved mileage, less stress on the water pump bearings, better cooling at low RPMs, engine reaching operating temp faster, and controlling radiator heat after the engine is off. Performance gains are transferable to a lessor degree since daily driving is not often at the high end of engine RPM range where electric fan performance gains are at their peak.

There are so many variables in daily driving such as temp, humidity, terrain, varying speeds, etc. that drawing any conclusion is not logical. There is no way to know if the life of a water pump is extended due to an electric fan. Water pumps don't fail at a specific number of miles regardless of the fan in place.

It is important to note that the clutch fan cooling potential has shown to be sufficient and the clutch fan is designed to facilitate warming up the engine, and control the coolant temp when idling for an extended period of time or in extreme conditions.

There are also those that change to an electric fan for no other reason than there is history that their particular fan has been known to throw blades off causing damage to other engine or body components. IMO the E53 clutch fan is not prone to fail in that manner.

Racers have been installing electric fans for decades. The primary reason being to increase the available HP by eliminating that consumed by a clutch fan. In addition, the electric fan can be controlled. As an example the fan can be turned off during a drag race, the equivalent of no fan at all, and turned on without the engine running to cool the engine between races.

My only reason to remove the clutch fan in favor of an electric fan is to have available the HP used to turn the clutch fan. I have been racing on and off for 50+ years. I have always changed the stock fans to aftermarket fans. The change has always been worthwhile.

My particular application is on a 2002 4.6 with Dinan air box, MAF, throttle body, engine and trans software and exhaust. In addition, I have meth injection, 150 shot of nitrous and electric exhaust dumps. The transmission shifts at 6,500 RPMs when at wide open throttle.

I know of claims of additional HP made available from 0-17. I spoke with techs from Spal, Flex-A-Lite, and Bimmerworld about my particular application. I spoke with my favorite BMW speed shop that gives me the benefit of their experience and did my nitrous install. I also spoke with members of the BMW club I am in and did considerable research on my own. The conservative estimate for my particular application is 4-5 HP with a reasonable potential of up to 10 HP. Generally speaking, a 10 HP increase is equal to .1 improvement in elapsed time or a car length in a quarter of a mile drag race.

I choose to purchase a Flex-A-Lite Slimline fan model number 118 costing $179, their adjustable temperature control module model number 31148 at $50 and associated wiring harness at a cost of $48. I was unable to find the CFM rating of my clutch fan. The model 118 is rated at 2,500 CFM that will handle up to a 600HP big block. The fan draws 18.5 amps.

The performance of the fan has exceeded my expectations. There is a noticeable difference in how fast the engine revs which should transfer to improved performance. Apart from performance I really like that the engine reaches operating temperature faster and the normal radiator temp is maintained after the key is removed. (The fan will run for about 20 seconds every few minutes for around 20 minutes. The battery handles the usage just fine).

I can't imagine a controlled set of test parameters that could quantify additional available HP using an electric fan. There are just too many variables and even if the test happened to be accurate the results could only be applied to that particular application, in those particular conditions and on that specific dyno. Sometimes you just gotta have faith in the history of hundreds of thousands of racers that swear by the benefits of an electric fan. Regardless the debate will go on with neither camp able to present conclusive proof one way or the other.

Recently the controller fried. I don't know the cause although the previous day I was re-checking the original setting by dialing the temp that the fan engages higher and lower. I replaced the controller with the same model. My guess is that particular controller was faulty.

The fan I chose is a straight blade 16" fan that covers more than 70% of the radiator required for the fan to cool to maximum potential. I used the stock shroud with no modifications.

I placed the controller on the driver's side near the primary 12v source. The install is straightforward and can be done with basic tools with the exception being the removal of the clutch fan nut. The nut is 32mm. An inch and a quarter wrench is equivalent. Some suggest using a wrench on the nut and holding the water pump pulley with a screwdriver lodged between the bolt heads to lock the pulley in place and then whacking the wrench with a hammer. I don't use that method. There is an inexpensive special wrench set that does the job easily and without risking damage to the water pump bearing. FYI-The nut is removed going clockwise--righty loosey in this case.

It was necessary to lower the fan and the shroud together making it difficult to center the fan on the radiator. I glued a dowel on the water pump shaft and a dowel centered on the on the fan. Once the two dowels were lined up I used small punches that fit into the radiator fins to keep the fan in place until I secured it to the radiator. The fan is secured through the radiator fins with the provided straps.

The controller has a radiator probe that is pressed between radiator fins. The probe spreads the fin to a slight press fit but not enough to cause damage. There is no concern for the accuracy of the probe because the controller is adjustable. I have the controller set to power the fan just prior to when the aux fan starts up when the A/C is off.

If you decide to make the change feel free to PM me with any questions.

UCrewX5 07-14-2015 01:30 PM

Excellent write-up. Thanks for sharing this with the Xoutpost community!

crystalworks 07-14-2015 04:46 PM

Again, nice writeup redliner. A wiring diagram might help complete the picture of the installation. After reviewing the pictures should be fine, but without captioning or something kind of look jumbled... if that makes any sense.

PS: Nice hydrodipped engine cover.

mam4.6 07-14-2015 09:44 PM


bcredliner 07-14-2015 10:08 PM


Originally Posted by crystalworks (Post 1044729)
Again, nice writeup redliner. A wiring diagram might help complete the picture of the installation. After reviewing the pictures should be fine, but without captioning or something kind of look jumbled... if that makes any sense.

PS: Nice hydrodipped engine cover.

Wiring diagram comes with the controller, I didn't do anything special. There are options as to how to wire it in the directions. I chose to have fan activated only by the thermostat so that it will keep the radiator at reasonable temperature after the engine is shut off and the key removed.

tonycajjo 07-26-2015 04:32 PM

Going to be putting an electric fan in my 3.0, cause the clutch fan is all worn out.

i plan to use something like the following as opposed to the controller you used.

i'm just not sure where i wanna install the Autometer hose adapter / temp probe. I'm thinkin after the Radiator.

I've seen where some use a piece of aluminum to mount the fan to the shroud which looks great but i think is more work than necessary. but i was thinking of getting this fan, or maybe larger that just fits in place and getting some of the mounting bracket kits they have you can see them to the right on this page:
A1 Electric Online Store: Spal 30102049 16" High Performance Fan

EH6TunerDaniel 07-26-2015 09:54 PM

Hey Tony, I used the exact same hose adapter and fan controller you linked. If you have any questions Ill be glad to answer.

tonycajjo 07-27-2015 10:26 AM


Originally Posted by EH6TunerDaniel (Post 1045900)
Hey Tony, I used the exact same hose adapter and fan controller you linked. If you have any questions Ill be glad to answer.

thanks! so what fan did you use? and how did you mount it to the radiator or to the shroud?

bcredliner 07-27-2015 01:36 PM

The fan is a good choice. Be sure it covers at least 70% of the radiator so that you get the cooling you need.

The controller is fine but it is not necessary to go to that extent to control the fan properly. A temp probe will work just fine and and doesn't require any modifications or electrical work. The controller you list will give you an exact reading of the coolant and it does not disturb the radiator fins. An exact reading of the coolant temp is not necessary. All you need to do is set any controller so that the fan comes on just prior to the aux fan. You can't lower the engine operating temp with a controller as that is regulated by the thermostat. I was concerned about the probe in the fins. The probe happens to be just the right diameter to be a press fit in the fins but not great enough to damage the fins. Not saying you are making a mistake. I considered both but just so you know why I didn't go that route. I did fry a controller.

Any electric fan is mounted on the radiator and IMO should mount properly using the existing shroud.

EH6TunerDaniel 07-27-2015 11:28 PM

Here is the fan I used. Summit Racing Street & Strip® Electric Fans SUM-G4904 - Free Shipping on Orders Over $99 at Summit Racing

I mounted the fan with those zips that go through the rad, and a 5/8" spacer to keep the fan off of the rad. It's meant to be temporary until I can mount it to a shroud, but in the meantime it works well.

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