Cooled to Perfection – 2021+ BMW G8X M3/M4 S58 Performance Heat Exchanger R&D, Part 1 – Stock Review and Design Plans

BMW’s M Division is locked in the perpetual pursuit of driving perfection. So with the launch of each new M3, the bar for the luxury performance sedan is raised. From the scrappy S13 powered E30 to our big nostriled G80, BMW evolved the M3 to harness mind-bending performance while keeping you, the driver, quilted in utmost luxury. 

In a perfect world, we wouldn’t need to tear down our brand new M3 shortly after it rolls into the Mishimoto R&D facility, but BMW isn’t the only one chasing perfection. Plenty who choose the M3 or M4 for their means of transportation are attracted by the platform’s additional potential. One of the keys to unlocking that potential is through the intercooler’s heat exchanger.

If you’re scratching your head at the notion of a heat exchanger, that’s ok. We’ll get you up to speed. Like the last generation, the S58 under the hood of the G8X M’s utilize an air-to-water intercooler system to manage air temperatures, including a secondary radiator to dissipate heat, more commonly known as the heat exchanger. The diagram below shows the basic roadmap of an air-to-water intercooler setup, but if you want to dig deeper, make sure that you head over to our post on the F8X intercooler system to learn more.

If the G8X M3 and M4 are already approaching the level of true driving perfection, then why would the heat exchanger need to be updated? We’re glad you asked. While, as mentioned above, a perfect world would mean that our M3 wouldn’t be in pieces, manufacturing costs and processes bring us back to reality. For BMW’s continued existence, even the M cars need to be affordable, which in turn means some components are decidedly less than perfect, precisely when it comes to the heat exchanger. 

Based on outward appearances, the G8X’s heat exchanger has also been the product of evolution. Close observers might notice that the unit extracted from our 2021 M3 Competition bears a stark resemblance to the cooler found in B58 powered vehicles, like the M340I, Z4, or Supra.

Most of the similarities are more than just skin deep, too, as this heat exchanger uses the same dual-pass flow pattern with those characteristic BMW quick disconnect ports. This heat exchanger also uses plastic injection molded end tanks, which are suitable for most daily driving but will begin to degrade and potentially spring leaks as the Bimmer ages.

Things are a little different once we take a look at the core. Like the B58’s heat exchanger, the S58’s core sports densely packed louvered fins to add theoretical core thickness. The serrations in these fins force the air through diagonally, providing additional contact with the core to promote heat dissipation. Where this core differs, though, is thickness. BMW opted to adapt their design to better suit the power-packed S58 by adding 7mm to the core’s thickness, bumping it out to 34mm. 

Even as BMW evolves its components to suit the M cars better, we still see room to improve, quite literally. A 34mm core might provide adequate cooling for most daily commuters and spirited drivers, but pushing the size of this core is the key to unlocking even more performance from your S58. That’s exactly what we plan to do. Our performance heat exchanger design is based around our new core, which will add even more core volume and cooling power to the G80’s intercooling system. We’re also planning to incorporate a similar louvered fin design for even more cooling potential.

An updated core would be useless without the proper channels for the coolant to flow through, and we didn’t want to retain any plastic on our new design. So, we’re plotting a pair of full-aluminum end tanks, which will be TIG-welded to the uprated core. 

Perfection is in the eye of the beholder. The G8X platform cars might roll off of the factory floor as the ultimate driving machine, but for those chasing pure driving perfection, we need to unlock more of the S58’s potential. With our design plans in place, we still need to double-check our work with prototypes, so stay tuned for a look at the physical manifestation of our designs.

Thanks for Reading!

-Nick

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