You might think, just by looking at the newest Mercedes-AMG C43, that the compact C-Class’s entry-level performance variant is seeing a simple changeover to a new generation. True, the C43 AMG model is making the jump to the new-for-2022 C-Class’s all-new body, just as you’d expect following the C’s debut this year (a new, more powerful C63 surely won’t be far behind). But beneath its muscular hood sits a big change: Gone is the old C43’s turbocharged V-6—in its place sits a new mild-hybrid inline-four with electric turbocharging tech adapted from F1 racing.

Power goes up. So, too, does efficiency, or at least Mercedes-Benz says so. Final EPA fuel economy figures are forthcoming. But who cares about boring fuel efficiency? Let’s get into the new four-cylinder engine’s spicier numbers. The gas engine hails from Mercedes’ M139 engine family, the same turbocharged I-4 that’s made its way into smaller AMGs of late such as the A35/45, CLA45, GLA35/45, and GLB35/45 models.

AMG designates this version the M139L, as it’s been adapted from those other AMG’s transverse fitment to a longitudinal layout. It also adopts Benz’s new electric turbocharging tech, where the 2.0-liter engine’s turbo can be driven by exhaust gases—as in a typical turbo engine—or spun up by an electric motor to fill torque gaps and combat low-speed turbo lag by spooling up the turbo instantaneously.

The technology overload doesn’t stop there. That e-turbo is powered by a 48-volt electrical system, which is fed by a motor/generator unit on the engine’s accessory drive belt. When not capturing energy from the crankshaft while the car slows or on overrun, the MGU can deliver a 13-hp boost to the engine via the drive belt. AMG also installs a “two-stage gasoline injection” setup that combines direct injection with “intake manifold duct injection” using solenoid valves, which we understand to be capable of dumping extra fuel into the chamber necessary to produce big power high in the rev range.

Speaking of that big power, here are the pertinent figures: 402 hp at 6,750 rpm and 369 lb-ft of torque at 5,000 rpm. As mentioned already, the motor/generator can add up to 13 hp during brief spurts. Compare that to the previous-generation C43’s 3.0-liter V-6, which put out 385 hp and 384 lb-ft of torque, as well as to the similar mild-hybrid M139L setup in the new SL43 roadster offered overseas (389 hp and 354 lb-ft). Yes, that means the new C43 makes less torque than before, but an additional 27 hp.

This output is delivered to all four wheels via a nine-speed automatic transmission with a clutch instead of a torque converter and AMG’s Performance 4Matic all-wheel drive system with a 31-percent front, 69-percent rear torque split.

Mercedes-AMG says the new powertrain setup is good for a 4.6-second zero-to-60-mph time, more or less the same as the outgoing C43’s estimated time. We’ll know for sure whether this is an overly conservative estimate when we eventually strap our test equipment to a 2023 Mercedes-AMG C43, so stay tuned for that.

Standard issue equipment on the new C43 includes a fresh rear-wheel steering setup, which can angle the rear wheels at up to 2.5 degrees to either tighten up the turning circle at low speeds (under 37 mph) by turning against the front tires, or enhance stability at higher speeds by moving in phase with the front tires up to 0.7 degrees. The C43’s brakes are larger than normal C-Class models’ units, with big 14.6-inch rotors up front squeezed by four-piston fixed calipers and 12.6-inch pieces in back grabbed by single-piston floating calipers.

Somewhat surprisingly for a modern performance car, the base wheel/tire setup is fairly mild, measuring 18 inches in diameter. Those looking to potentially sacrifice some ride comfort for extra style and possibly bigger tires can opt for 19- and 20-inch options, which also raise the top speed from an electronically limited 155 mph to 165. An adaptive suspension with AMG-specific tuning is standard.

We’re intrigued by what sort of noise the new C43 will make, but owners keen to make more of it can look forward to a variable exhaust that will adjust the sound and and volume via flaps to match the selected drive mode. An optional AMG Real Performance Sound feature will pipe actual exhaust sound into the interior by way of the audio speakers, for those in need of even more snort.

All of the C43’s mechanical newness is well camouflaged by its predictable styling upgrades. To the new C-Class AMG has added the expected snarling intakes, bulging hood, quad exhaust outlets, and vertical-slat grille now endemic to AMG models. The usual AMG playbook applies inside, too, where there is a sportier steering wheel with an AMG drive mode selector and shift paddles; heavily bolstered seats; red seat belts; and AMG-themed designs for the 12.3-inch digital gauge cluster and 11.9-inch central touchscreen.

Pricing for the newest C43 is forthcoming, but we know the sedan will go on sale here in the U.S. by the end of the year. There is no word yet on the expected C63 variant, which we know will get an even more powerful version of this four-cylinder powertrain, one with full hybridization (including a 201-hp electric motor) that’s said to deliver power rivaling that of the old C63’s twin-turbo 4.0-liter V-8 engine.