We don’t need to tell you that BMW makes an incredible inline six-cylinder engine. The automaker has been doing so almost continuously for the greater part of a century, and they’ve only gotten better with the march of time and evolution of technology. While the N55 appeared on the annual Ward’s Auto 10 Best Engines list no fewer than three times though, the B58 has now surpassed it in terms of accolades, with Ward’s recognizing BMW’s current inline-six as one of the best in production—of any architecture—four times, with the version used in the M340i selected for the 2020 edition of the list.
We suspected the B58 would be an exceptional engine when it arrived for the 2016 model year in the F30 340i, and after a few years and an untold number of miles racked up, it has done an excellent job of confirming our intuition. Capitalizing on the success of the N55, which used solenoid-based direct fuel injection and a single twin-scroll type turbocharger integrated with the pulse-tuned exhaust manifold, the B58 takes things a step further, with modular design that’s more efficient to manufacture, and a closed-deck architecture that increases durability. As we’ve noted before, the B58 shares its perfect 500cc individual cylinder displacement with the B48 and B46 four-cylinder engines, and will likely have commonality with the new V8 that BMW is rumored to be working on as well.
Since it hit the market, the B58 has been landed itself on Ward’s list in 2016, 2017, 2019, and 2020. The versions highlighted haven’t just been in cars that are also perfectly capable with a four-cylinder, like the 3 Series (2016, 2020) or the 2 Series (2017), as the variant used in the G05 X5 was also showered in praise for 2019. It’s a string of success that BMW has been enjoying for over two decades now, with the manufacturer having earned the award for various engine designs more than 30 times in approximately 25 years. The vast majority of those engines have been of an inline design, and the bulk of those have, of course, been straight-sixes.
Although an M version has already been spawned from the same underlying design, taking the form of the S58, BMW’s current modular engine designs seem like they still have a significant production runway in front of them. With the V12 likely (and ever so sadly) to be phased out some time during the next decade, and the V8 assumedly just now being transitioned to a modular architecture, the B48 four and B58 six may be sticking around for while in the current forms—and there’s nothing wrong with that.
Unlike the old days, when BMW’s M engines were derived from designs used in motorsport competition, it’s now the other way around, with the M4 GT4 relying on a version of the S55, the upcoming M4 GT3 being designed with an S58, and the M235i Racing and M240i Racing relying on the N55 and—you guessed it—the B58. Speaking of the S58, we wouldn’t be surprised to see it make an appearance on Ward’s list before too long as well.—Alex Tock
[Photos courtesy BMW AG.]