Mercedes-AMG C63 (W204) exhaust: M156 cross-plane V8 sound

Mercedes-AMG C63: mechanical breakdown

Twenty-six seconds of M156 exhaust

A W204 C63 exhaust clip, 26 s long. The caption names no parts and no events, so there is nothing to attribute to modifications. What the sheet supports is the source: a 6208 cc naturally aspirated V8, which is why the note is deep and loud.

Cross-plane crank and the M156 bellow

Cross-plane is the layout of the M156 crankshaft, and that is the root of its sound. It sets the engine apart from flat-plane V8s, which rev freely but sound thinner. Here the result is a deep, loud bellow, carried up to a 7200 rpm redline from 6208 cc of displacement. Nothing in the intake or exhaust path softens it, because the engine is naturally aspirated and has no turbine to take energy from the pulses. Output is 451 hp and 600 Nm in the base car. The price of the big bore is in the hardware: earlier M156 engines suffer head bolt failure, and camshaft and lifter wear is also documented.

Headers, tune and exhaust trade-offs

Headers come first on the M156. They add power and a sharper, louder note, but they cause emissions-legality issues and a check-engine light unless the car is retuned. An ECU tune gives modest gains and a raised rev limiter above the stock 7200 rpm. The gains are smaller than on a turbocharged engine, since there is no boost pressure to increase. A full aftermarket exhaust amplifies the V8 sound, and the cost is drone at cruise. Given the known head bolt failures on earlier engines, extra power from headers and a tune is added to a block with a documented weak point.