Mercedes-AMG A45 S (W177) owner clip: hand-built M139

Mercedes-AMG A45: mechanical breakdown

Owner showcase of an A45 S

A 12-second owner clip of a Mercedes-AMG A45 S. The Portuguese caption calls it a dream come true and names no parts, work or events. The S badge means the M139 in its 421 PS, 500 Nm tune, which the fact sheet rates at 3.9 s to 100 km/h through AMG Performance 4MATIC+.

One technician builds each M139

Every M139 is hand-assembled by a single technician in Affalterbach under the 'One Man, One Engine' principle, and the engine carries that technician's name. It is a 1,991 cc inline-4 with one twin-scroll turbo and a 7,200 rpm redline. A four-cylinder turbo note is what you get, and on European cars the gasoline particulate filter mutes it heavily. The louder moments come from Sport+, where the AMG Performance exhaust flap opens and the car pops and crackles on overrun.

Why W177 owners remap and open the exhaust

The caption names no work, so the usual route starts with an ECU remap. Software alone adds large power and torque; the trade-off is warranty risk and extra stress on the gearbox and drivetrain. The muted GPF-equipped exhaust is the next target: a downpipe or GPF delete is louder and leaves more headroom for tuning, but it is usually not road-legal and can fail an emissions inspection. An uprated intercooler lowers intake temperatures so power stays consistent on repeated runs. It costs more and takes effort to install. Early cars already show low-speed jerkiness from the dual-clutch gearbox, so added torque lands on a known sore spot.