4 Of BMW's Iconic Inline Six Engines, Ranked By Horsepower

BMW's iconic inline six engines have had a long and storied history for the Bavarian brand. The company's inline six origins go back as far as the company's first engine, known as the IIIa, developed for aircraft in 1917. Since those early beginnings, inline sixes have been an integral part of BMW's DNA. 

BMW continued building on its inline six development history with the engine used in the 1936 BMW 328. This inline six engine with an aluminum head had a displacement of 2.0 liters, could rev to 5,000 rpm, and produced 80 horsepower. Back in the day, this provided sporty performance in the 1,800-pound BMW 328. Over the years, BMW has continued to refine and develop its inline six engines. The company has remained faithful to the inline six configuration up to the present day, unlike fellow German automaker Mercedes-Benz' switch to V6 engines around the turn of the 21st Century.

BMW's inline six engine development program has produced engines with increasingly high power outputs. Our list here will rank them by horsepower, starting with the less powerful and proceeding through time to the most powerful of BMW's iconic six-cylinder engines.

The 2003-04 BMW M3 CSL (which stands for Coupe/Sports/Lightweight) was the high-water mark for the BMW S54 inline six engine that sat under its hood. BMW engineers managed to coax 360 horsepower from this 3.2-liter inline six, achieving a world's-best 111 horsepower per liter for a naturally-aspirated, six-cylinder production engine at the time it was released. The CSL also went through a weight-reduction program, resulting in a curb weight that's 243 pounds less than a standard E46 M3. The M3 CSL was produced as a limited-edition version of the M3, with only 1,383 made. A CSL-only identifying feature is the air intake "porthole" in the front bumper. 

The 2003 BMW M3 CSL combined its powerful inline six engine with BMW's sequential SMG gearbox, sending all those horses to the rear wheels. The M3 CSL could do 0-60 mph in 4.8 seconds with a top speed of 155 mph. It also put down a time of 7:50 at the famed Nürburgring Nordschleife, knocking 30 seconds off the time of the standard M3.

Other unique light-weighting features of the 2003-04 BMW M3 CSL included the first visible carbon-fiber roof on a production BMW M car, a carbon-fiber airbox on the engine, a composite rear diffuser and front apron, an aluminum hood, a thinner glass rear window, and a thin-walled exhaust system. Hardcore track enthusiasts could even delete the automatic climate control and the radio.

The 2019 BMW ALPINA B4 S Bi-Turbo uses the BMW N55 inline six engine as the basis for its highly tuned version. ALPINA was BMW's approved outside tuning house until 2022 when BMW acquired the company. ALPINA was founded in Bavaria in 1965 and has been involved in tuning and racing BMWs since its early days. ALPINA is actually recognized as an official automotive manufacturer whose upgraded versions of BMWs have been sold under the ALPINA brand. Today, ALPINA vehicles like the B8 Gran Coupe can be configured on the BMW website and purchased from BMW dealers.

The upgraded ALPINA version of the N55 in the B4 S Bi-Turbo put out 440 horsepower, much more than the earliest versions of this engine that produced around 300 horses. Its turbo system has been upgraded with two ALPINA-specified turbochargers and an improved cooling system for both water and oil. An Akropovic-designed stainless steel exhaust system improves exhaust gas flow and can be tuned from the cockpit for either a quiet or loud exhaust "soundtrack." 

The ALPINA B4 S Bi-Turbo's power is channeled through an eight-speed sport automatic transmission on its way to either the rears or all four wheels (AWD version pictured above). Performance stats include 0-62 mph (0-100 kph) in 4.2 seconds and a top speed of 190 mph (306 kph).

The 2017 BMW M4 DTM Champion Edition carried the highest-powered version of the BMW S55 inline six engine produced for a street car. It was created to commemorate Marco Wittmann winning the driver's title for BMW during the 2016 season of the DTM (German Touring Car Championship). 

Producing a nice, round 500 horsepower in the limited-edition M4 DTM Champion Edition (only 200 were made), the S55 was the high-performance variant of the BMW N55 engine, which itself was used in a wide variety of BMW models. The BMW S55 inline six was introduced in the M3 and M4 models in the 2014 model year, with its final appearance being in the 2017 M4 DTM Champion Edition. This version of the S55 engine was also used in the 2016 BMW M4 GTS, of which only 803 came off the line. The 2017 BMW M4 DTM Champion Edition is one of the fastest cars BMW has ever made.

The S55 uses two single-scroll turbochargers, each of which feeds three cylinders. It also features Valvetronic variable valve lift tech, direct injection, a closed-deck design for its crankcase, and aluminum alloy pistons coated with Grafal, a screen-printed friction-reducing treatment. In the M4 DTM Champion Edition, the S55 is fitted with a water-injection system, which boosts the S55's output by 69 horsepower compared to that year's standard M4. A seven-speed DCT connects the engine to the rear wheels, making the 0-62 mph run (0-100 kmh) in 3.8 seconds with a top speed of 189 mph.

The inline six found in the 2025 BMW M4 CS is the S58, the most powerful BMW inline six currently available in a street-legal car that comes from the BMW factory. It produces 543 horsepower from 3.0 liters of displacement. This has been done by increasing the twin-scroll turbo's boost pressure up to 30.5 psi, which generates 20 additional horses, compared to the M4 Competition model. This is the same engine that appeared in the limited-edition 2022 M4 CSL, an extremely track-focused car that was not well-suited to use on the street. Lower-powered versions of this capable engine are used by BMW's other M4 models, its M3, and the M2.

The S55 uses forged pistons, connecting rods, crankshaft, and camshaft, while the engine block and cylinder head are made of cast aluminum alloy. The M4 CS sends its 543 horsepower through an eight-speed automatic and then to all four wheels. Sport seats with a minimal amount of padding hold you securely in place during the push-the-envelope use that this car encourages. Carbon-ceramic brakes are optional if you desire them. Performance stats for this monster engine, according to Car & Driver, include 0-60 mph in 2.7 seconds and 0-100 mph in 6.4 seconds. The top speed is 188 mph.