Protecting Perfection – Direct-Fit Oil Cooler R&D – Concept, Design, and Production Sample

Oil is the lifeblood of any vehicle. Its lubrication properties keep all the metal bits inside of the engine from shredding each other to dust. While the M3 and M4 rise above just about every other run-of-the-mill commuter car, nothing knocks them down a few pegs quite like overheated oil or oil that finds its way out of the system.

External air-to-air oil coolers are typically seen on the sportier variants of any car, but we tend to find a lightweight, tube-and-fin construction. These are cheap and easy to produce but are often better suited for daily driving or maybe the occasional spirited rip down some back roads. They also tend to be more susceptible to damage.

The M3 is all about balance, as we went over in our intro post. For that reason, the engineers at BMW incorporated their own thermostatic oil cooler system on the front of the M3. The idea is to keep the oil at the optimal temperature during a commute to work, or if you decide to drive past the office and directly to the track instead. However, given the mounting location of the F80/F82’s factory air-to-air oil cooler, keeping oil in the system poses a slight challenge for some. These M’s are delivered from the factory with a much sleeker and more aggressive look, and being that these are German vehicles we’re talking about here, that mean mug has a function. One purpose is to grant more airflow to the plethora of coolers stacked in the front of the vehicle. The other is for additional aerodynamics to boost efficiency and keep the car planted.

In true BMW fashion, there is an exceedingly efficient use of space with regards to the M3’s oil cooler. It mounts horizontally along the bottom of the car, perpendicular to the rest of the cooling stack. The graphic above demonstrates the means in which this cooler receives airflow. Essentially, the undertray creates a low-pressure zone behind the underside of the cooler. Basic laws of physics determine that high pressure wants to move to zones of low pressure, which draws some of the airflow from the front of the car. The downside to this method…parking barriers.

The low-slung sports sedan (or coupe) is at an increased risk of gashing the factory cooler on any sort of raised road hazard, especially once the car is lowered even more, like ours. So, you really have two options. Either go full baja M3, or add some heft to your oil cooler. We here at Mishimoto have already started on the strength option.

The core isn’t the only thing getting a new suit of armor. To make sure that every part of the oil cooler is protected, Dan also made some updates to the cooler’s end tanks. Instead of thinly walled tubing, the end tanks on our design are billet aluminum and TIG-welded to the core for a secure connection to the oil system.

Our updates in durability come with the added benefit of cooling capacity as well. Since we based our new design on BMW’s, we still incorporated a large fin surface area, but now combined with a 39mm core thickness, the core size is increased by 46%. Combined with the robust bar-and-plate core and increased oil capacity, we expect to see more manageable engine oil temperatures, especially on the track.

Whether it’s keeping it cool or keeping it in the car, protecting your oil is key for the sports sedan benchmark. While the S55 is a dynamo of both power and efficiency, that all starts to crumble once the stock cooler soaks with heat or gets lacerated. Our new design has a cool head under a suit of armor that keeps your M-powered sedan doing what it was designed to do.

Beef up your F8X’s oil cooler today:

2015-2020 BMW F8X M3/M4 Oil Cooler

Thanks for Reading!

-Nick

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