– Budapest, Hungary

Make no mistake, the Mercedes-AMG GLA45 is a hot hatchback. It might be based on the GLA “crossover” rather than Europe’s sexier A45 hatchback, and its upright body and relatively tall ride height might appear more suburbs than slalom. Yet the car’s stiff ride, grumbling exhaust, sharp brakes, and millimeter-precise steering all announce the GLA45’s intentions without question. This is a car for going fast and having fun while doing so.

This year, the feisty 2.0-liter turbo-four gets cranked up to 375 horsepower and 350 pound-feet of torque (previously 355 hp and 332 lb-ft). It’s “still the most powerful four-cylinder engine in series production in the world,” notes Mercedes-AMG’s Steffen Jastrow. The engine, hand-built by specially trained AMG engineers in Kölleda, Germany, lets this all-wheel-drive rocket get to 60 miles per hour in just 4.3 seconds (down from 4.8 previously).

As was the case even before the power upgrade, the big-turbo AMG has a somewhat bipolar personality. It’s easy to catch the powertrain flat-footed as the turbo dozes and the dual-clutch transmission hunts for a lower gear among its seven possibilities. If predictable, always-on power is what you’re after, the GLA45 will disappoint.

But once the turbo gets spinning and the gearbox has found an appropriate ratio (use the manual shift paddles for best re...