BMW Once Put The Engine From The M2 In The Frumpy X4 Crossover

There’s something cool about a performance car engine in something that isn’t anything close to the purest cohesive distillation of a performance car. The concerningly testosterone-rich Viper V10-engined Dodge Ram SRT-10, the Mercedes-Benz R 63 AMG intercontinental ballistic minivan, the straight-line sleeper that is the tenth-generation Honda Accord 2.0T with the 10-speed automatic transmission, you know the drill. Among these gems sits a relatively recent creation that many people forget is a little bit special. The first-generation BMW X4 M40i shared a heart with the original BMW M2, technically the only other Bimmer to do so.

Coupe crossovers are a weird proposition, in that they largely marry the bulk and thirst of an SUV with the practicality of a sedan. The BMW X6 has been a contentious machine for the past 17 years, but when the time came to create its mini-me, the resulting X3-based F26 X4 looked decidedly strange. Here was a bulldog-faced, saggy-rumped crossover that was effectively just a taller 3 Series Gran Turismo. Two cars sharing more or less the same size, form factor, and space. However, the X4 separated itself from its sibling when the M40i trim became available for 2017.

Under the hood of the X4 M40i, you’ll find an N55 turbocharged straight-six, but not the one you’re thinking of. Instead of just pilfering a regular one from the X3, BMW built the N55B30T0, and the engineers changed a lot. Enough that this engine also saw duty in the M2, the only other application of this particular engine variant.

It starts with the forged crankshaft from the S55 engine used in the M3, then builds on that with forged connecting rods, new bearings, unique pistons, a revised ignition system, new spark plugs, and revised intake and exhaust systems. The result isn’t just a stronger engine than a regular N55, but an output of 355 horsepower and 343 lb.-ft. of torque. That’s ten fewer horsepower and the same peak torque as the M2, but 53 more horsepower and 48 more lb.-ft. of torque than the X3 35i with the regular garden-variety N55.

As a result, the X4 M40i was quick. Properly, amusingly quick. Back in 2016, Car And Driver clocked one of these hunchbacked crossovers at 4.4 seconds from zero-to-60 mph, and through the quarter-mile in 13.1 seconds at 105 mph. That’s nearly a second quicker than an X3 35i, and it wasn’t the only party trick of the X4 M40i. BMW increased the negative camber up front, strengthened the wishbones, and stiffened the ride frequency so that when optioned with the available summer tires, this weird machine really stuck. As Car And Driver wrote:

As you’d expect, the M-inistrations to the X4 include the suspension, with firmer springs, stiffer anti-roll bars, and retuned adaptive dampers. And the M40i’s cornering blithely defies the vehicle’s height and weight—body roll is all but nonexistent, and we recorded a phenomenal 0.95 g on the skidpad, a major leap over the X3’s 0.83 g (and also besting the 0.87 g posted by the Macan). At least partial credit should go to this X4’s sticky footwear: Michelin Pilot Super Sport tires wrapping the optional 20-inch wheels.

Granted, the steering was still Novocaine numb, albeit quick, but what do you expect when starting out with a crossover utility vehicle fitted with electric power steering? Put it all together, add in quick shifts from the ZF 8HP eight-speed automatic transmission, and you get a strange-looking crossover that can cut a rug. Sure, the tradeoff is a somewhat brittle ride, but it’s nowhere near as harsh as the ride on an X3 M. Oh, and because this thing isn’t a full M-car, second-hand examples can be had for sensible coin.

Looking to go cheap? Here’s a Carbon Black 2017 X4 M40i with 108,023 miles on the clock up for sale in Pennsylvania. It’s got some mileage on it for an eight-year-old car, but it also has a clean history report, unusual Mocha leather, and a Harman/Kardon sound system. Better still, the asking price is $17,399, not much coin for something this quick.

If you care a bit more about color and mileage, how about this Long Beach Blue 2018 model up for sale in Texas? It’s had one owner since new and was spec’d to the nines with the big wheels, the Harman/Kardon system, adaptive cruise control, the works. The history report’s clean, the odometer reads a reasonable 58,510 miles, and the asking price is $24,991. That’s what … mid-range new-Corolla money?

Granted, even though the X4 M40i doesn’t suffer from M-specific problems, it does still have its weaknesses. It’s important to change the oil filter housing gasket at the first sign of leakage, as oil can drip on the belt, the belt can slip off its pulleys, and the engine can ingest the belt. Charge pipes for the air induction system can leak, and water pumps aren’t exactly lifetime parts. However, the X3 35i shares all these issues, and it’s a lot slower, so as long as you’re willing to trade some ride comfort and practicality for speed, you won’t find any reliability downsides over its closest alternative.

Of course, the caveat to all this is that B58-powered BMWs are also getting cheap. The three-liter turbocharged straight-six that succeeded the N55 was a huge improvement from a performance perspective, from its closed-deck block to its massive potential for horsepower. Still, sharing an engine with the M2 is a cool bit of history, and that alone makes the F26 X4 M40i more interesting than it otherwise would have been.

Top graphic image: BMW

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