Cooling systems on older BMW models have been recognized as a frequent failure point requiring regular replacement to avoid catastrophic failure. This includes anything made of plastic within the system. So far we have a few remedies – an aluminum radiator and a silicone coolant hose kit. The mechanical fan is next on our list to be addressed.

The stock fan setup is certainly efficient in keeping your straight six cool. That said, a fan failure can get quite ugly with shrapnel tossed around the engine bay, often damaging other components. To reduce vehicle downtime and expense, it would be wise to replace this component before failure occurs.

Swapping your antiquated mechanical setup for an efficient electric system is a great way to improve reliability, and even free up some power on your vehicle. Check out the process we took to bring you guys a slick fan setup!

First Prototype Design

Before even starting our design, we wanted to explore a few new features that could be included with our fan shroud. For years we have been developing and releasing functional and effective aluminum shrouds, but once in a while we like to try something new to see if a positive impact is made on the end product.

For our first test we installed some air flaps on our shroud to allow airflow at driving speeds and then close when the fan is operating at a stop. When closed, the fan can then take full advantage of the shroud and its ability to pull air through the radiator. Check out a few shots during some basic bench testing.

We also set up one of our intercooler dyno fans, which achieves 30–40 mph wind speeds, to see the effect on the flap movement and airflow through the core.

Modeling the Shroud

Testing seemed positive on the bench (off the vehicle), but we also wanted to test this system on the road. So next, we created a 3D model depicting our plans for this shroud. Check out a few images from the Solidworks design software.

A few things to note on this design. First, the fan has been offset to the driver side of the radiator. This provides greater clearance between the engine pulley systems. Bushings for the E36 engine and transmission mount can wear and cause significant movement of the engine. If our tolerances are too tight, this could mean big problems for your new electric fan setup. Next, we have incorporated a stock overflow bottle mount on the passenger side of the shroud. Our shroud is being designed to function with the stock unit. Additionally, we are designing an aluminum counterpart that will also function with our shroud (and the stock shroud). Last, we have mounted our fan controller to the driver’s upper corner, which allows the fan activation temperature to be adjusted to the owner’s liking.

First Prototype Testing

When we left off last time we were exploring our first prototype design. This unit is a traditional aluminum fan shroud with air flaps to improve core airflow at speed. Once we had a working prototype, we decided to perform some idle testing to see how well our single electric fan would perform on a mostly stock E36 M3.

To get started, we began removing the stock setup.

Next, we installed the Mishimoto prototype along with our temperature sensors for data collection.

Our goal with this particular testing was to ensure that our fan could control and properly regulate idle temperatures for an extended time. We positioned the vehicle on the dyno, adjusted the fan controller, and kept an eye on the gauges.

We recorded inlet and outlet temperatures to see how quickly and effectively our fan setup reduced temperatures. After a lengthy test, we were pleased with the results. At this point, we still wanted to test the impact of our airflaps during speed driving. However, we ended up taking a different route for this project.

Second Prototype

This project was progressing toward the end of testing our electric fan setup for the E46 M3, which is shown below.

We found that this system provided a great amount of airflow during driving speeds. Additionally, our electric fan easily cooled the S54 at idle conditions, even in extreme environments. . We decided to give this design a try for our E36 electric fan setup.

With this new direction, we put a design into a 3D model and quickly fabricated a mount.

We mounted our electric fan and attached the entire assembly to our new E36 radiator.

The oddly shaped portion of the passenger side of the mount is a reservoir mounting system that will function with the stock reservoir. As mentioned earlier, we are also working on an aluminum replacement reservoir. 

Once again we conducted our idle testing and ended up with similar results. Yes, it is extremely likely that this fan will provide greater efficiency with the use of an enclosed shroud. That said, our idle tests showed that this new shroud performed similarly, having no issues with controlling temperatures, even for an extended period of time. This shroud offers much greater airflow through the core at speeds in which improved cooling is needed, such as repeated high-rpm driving.

Dyno Testing

With this in mind, it was time for some more exciting tests. We wanted to see what kind of power gains, if any, we could achieve by removing the stock mechanical unit.

Our results are shown below!

Output is similar for most of the pull, however from around 55 mph to 71 mph we see some slight gains. These gains are shown a bit more clearly in the scaled plot below.

These plots show the power output both with and without the mechanical fan installed.  A slight increase occurs from around 55–70 mph to the tune of 1–3 whp. This isn’t the 5 whp we saw from the E46, but every little bit certainly helps.

What’s Next?

Now that we have positive results from our testing, we could move forward with designing this component in 3D. Check back with us next time for a look at our 3D model and actual prototype!

Our final prototype is complete and looks fantastic. The fan mount is constructed from 1/8” steel that has been cut to a specific shape allowing for additional airflow through the radiator core at speed. Additionally, the mount is powder coated black to provide a durable finish. As noted in our last post, we tested this unit extensively with our 16” fan to ensure that coolant temperatures were properly regulated during both idle and all driving conditions.

Check out a few shots of the mount!

This shroud has been designed to function with the stock expansion tank as well as the aluminum expansion tank we have been working to develop. Check out the mounting system our engineering team designed to secure the tank properly in the stock location.

Test Fitting

After inspecting our final prototype, it was time to pop this piece into the car and ensure that all our mounting points were correct. We also modified the fan location slightly and checked clearance with the fan pulley.

First, a fan-less engine bay with our E36 X-line radiator installed. This radiator is quite massive and should provide a worst-case situation in terms of evaluating fitment.

Next we installed our prototype fan mount and fan.

Here’s a shot of our drawing next to the installed component!

Fan pulley clearance was more than acceptable with the adjustments we made to fan placement. Check out a few shots depicting the space with our X-line radiator.

Shroud and Prototype Expansion Tank

As noted earlier, we are also developing an expansion tank for the E36. Check out a shot of our prototype component mated to our final shroud design!

More images will be available within the expansion tank thread we have here on the forums.

Wiring Details

Wiring an electric fan may seem like a daunting task, but our kit includes all necessary wiring and components to make this a cake-walk. Our team is also working to finalize an installation guide that provides in-depth details for install. Below is a shot of the wiring kit for our E46 setup, which is very similar.

Included within our wiring kit for the E36 are the following items:

(1) Inline fuse holder

(2) Butt splices

(2) 0.25” Wide quick-disconnect terminals

(2) 3/8” Stud size ring terminals

(1) 3/8” Black wire cover, 5’ length

(1) 3/16” Black shrink wrap, 6” length

(1) 1/4” Black shrink wrap, 2” length

(3) 7.5” Black zip ties

All these components will provide a clean, factory-appearing installation. Power will come from a fuse adapter that will plug directly into the factory fuse panel. From there, some simple wiring work is needed for the controller, the temperature-sending unit, and the fan itself.

Final Kit

With positive testing complete and perfect fitment demonstrated by our prototype unit, we are now prepared to begin manufacturing these kits. So what will the full kit include?

• Mishimoto powder-coated fan mount
• Mishimoto 16” electric fan
• Mishimoto fan controller with 1/8” NPT or temperature sensor probe
• Mishimoto BMW E36 wiring kit for electric fan (individual items referenced above)

This kit will be offered with either a 1/8” NPT temperature sensor or a probe-style sensor. The 1/8” NPT is for vehicles with an existing 1/8” port. The Mishimoto E36 X-line radiator includes a tank-mounted port of this size. This sensor would then thread into the port to acquire temperature data. For those utilizing a stock radiator, the probe sensor can be used, and it fits within the fins of the radiator. Both sensor styles have proven to be very accurate during testing.

Our team is putting together a detailed installation guide that highlights the fan mount install as well as the wiring details. The Mishimoto electric fan conversion kit is a bolt-on upgrade for the stock clutch fan, providing a reduction in engine rotational mass along with efficient, reliable cooling during all driving conditions.