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E46 M3-Swapped BMW X3 With a Six-Speed Is the M SUV You Want

That S54 inline-six sounds killer and for $19,840, it's a whole lot cheaper than a new X3 M.

If you have around $80,000 to spend, BMW will sell you a new X3 M. The automaker drops the M3 and M4’s 473-hp turbocharged inline-six into its popular crossover, along with a host of suspension and brake upgrades that make the Ultimate Family Machine defy physics. But what if that recipe existed two decades earlier?

That’s the question one enterprising builder set out to answer by swapping the S54 inline-six from an E46 M3 into a first-generation BMW X3. Oh, and it’s a six-speed manual. The car is posted for sale on M3List and at an asking price of $19,840—or a quarter of what you’d spend on a new X3 M—it’s hard to argue with the result.

The naturally aspirated, 8,000-rpm S54 is one of the most legendary engines BMW has ever made. Original equipment in the E46 M3 as well as the late Z3 M and Z4 M Coupe and Roadster, it revs to the moon and produces a slightly unhinged metallic rasp unlike any other six-cylinder’s note. People have been swapping them into E30 and E36-chassis 3-Series for as long as I can remember, but I’ve never seen one in an X3 before. Here’s a reminder of what the S54 sounds like.

The seller claims the engine swap was performed around 15,000 miles ago, and that they’ve been daily-driving the car for about a year since then. The donor engine has approximately 140,000 miles on it, but the rod bearings and VANOS variable valve timing system were serviced at the time of the swap. 

In addition to the M motor, the X3 has been converted to rear-wheel drive but can be switched back to X-drive if the buyer prefers all-weather traction to tail-out shenanigans. Other performance-oriented mods include BC Racing coilovers, a custom oil pump and pan, aftermarket headers (the better to hear you with, my dear), and a catless exhaust system that the seller claims still passes emissions in Georgia. Uh-huh.

The X3 base, on the other hand, has 213,000 miles, but it looks to be in remarkably good shape for the mileage. Cosmetically, it’s been updated with an M-Sport body kit, a black interior out of another car, an M3 steering wheel, ASA aftermarket wheels, and a CarPlay-capable infotainment system. CarPlay is nice to have for directions, but if I owned this car I doubt I’d spend much time listening to the radio.

This thing is quite the sleeper. A keen eye will notice a few degrees of negative camber on the rear wheels, but apart from that, it looks like a normal grocery-getter. According to the seller, it’s just a passenger’s weight heavier than an E46 M3 convertible, yet its form factor is infinitely more practical—and invisible. They’ve even wired the toggle for the S54’s “Sport Mode” throttle mapping into the X3’s SOS switch.

There must be better ways to spend 20 grand, but I seem to have forgotten what they are. Now if you’ll excuse me, I’ll be looking at S54 exhaust clips on YouTube.

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