Photo: Andrew P. Collins

The 2018 BMW M550i is sort of a quieter alternative to the hot rod M5. It’s still plenty fast, just a little more low key. But what if you threw a bunch of parts and power at this thing? We might have an unstoppable sleeper on our hands.

This particular M550i has been blessed with thousands of dollars in aftermarket parts from BMW expert Dinan. A computer tune, stainless exhaust, spring set, suspension tune, enormous wheels and subtle pieces of carbon fiber bring this “S1” demo car’s total as-tested value to just shy of $100,000. A base M550i rings up at about $73,000, so this car’s kit goes a little beyond a casual upgrade.

While the standard car is supposed to make 456 horsepower and 480 lb-ft of torque, Dinan claims this car is putting out 606 HP and 635 lb-ft. Apparently that translates to a dyno-tested 488 HP and 523 lb-ft of torque at the wheels. Being an xDrive car it is, of course, all-wheel drive.


I’ve only put a few miles on it but I can already promise you these photos don’t do the dark blue paint job justice. And even though the four exhaust tips, at a whopping four inches a piece, look intimidating the car is actually not very loud. At least, not in LA traffic.

We’re hoping to cut it loose in the canyons and backroads this weekend. So shoot me some questions and I’ll have a few things to think about while I’m shaking it down.