BMW S42 and the German Super Tourenwagen Cup

BMW S42 and the German Super Tourenwagen Cup

When you think of BMW's motorsport legacy, the spotlight often shines on legendary engines like the M88 inline-six. But among the rare gems in BMW's racing history lies a true underdog: the BMW S42 engine. Built for the trials of competition, the S42 is a high-revving, precision-crafted powerhouse that took the M42 platform to extraordinary heights. Let’s take a closer look at what made the S42 so special:

Born for the Track

First of all, why a four-cylinder and not a six? It all came down to the rules. The German Super Tourenwagen Cup (STW) imposed strict regulations on engine displacement and vehicle weight, making a high-revving four-cylinder the ideal choice for balancing power and agility. BMW Motorsport saw an opportunity to maximize performance within these constraints by refining the M42 platform, creating an engine that could hold its own against larger competitors.

In the early 1990s, BMW Motorsport set out to develop a competitive engine for their BMW 320 4-door touring car to race in the German Super Tourenwagen Cup (STW) and other high-profile touring car championships. The foundation? The M42B18, a 1.8-liter inline-four found in the E30 and early E36 318is models. What emerged was a purpose-built racing beast: the S42.

Key Specs and Performance

The S42 took the M42 and turned every dial up to eleven:

  • Displacement: Increased from 1,796 cc to 1,999 cc (122.0 cu in).

  • Power Output: The first version in 1994 produced 206 kW (276 hp), climbing to 235 kW (315 hp) by 1997.

  • RPM Limit: Screamed all the way to 9,000 RPM.

What Set It Apart?

Compared to its road-going sibling, the S42 was an entirely different animal:

  • Intake System: Equipped with individual throttle bodies for sharper response and improved airflow.

  • Fuel System: Featured two fuel injectors per cylinder to optimize fueling at high RPM.

  • Compression Ratio: Increased for greater power output.

  • Cylinder Head: Redesigned for higher flow and efficiency.

  • Valvetrain: Upgraded with solid lifters, high-lift camshafts, and stiffer valve springs.

  • Lubrication System: Introduced a dry sump system to prevent oil starvation under extreme cornering.

  • Materials: The valve cover and airbox were made from carbon fiber to reduce weight.

  • Bottom End: Reinforced with lightweight forged pistons, custom rods, and a balanced crankshaft.

  • Exhaust System: Custom headers and a lightweight exhaust maximized flow and reduced backpressure.

The Super Tourenwagen Cup

The Super Tourenwagen Cup (STW), or German Supertouring Championship, was a premier touring car racing series held between 1994 and 1999 in Germany. It emerged after BMW and Audi left the Deutsche Tourenwagen Meisterschaft (DTM) in 1992 due to rising costs associated with the adoption of Class 1 Touring Cars rules.

STW ran under Super Touring regulations throughout its six-year existence, providing a more accessible platform for manufacturers to showcase their engineering prowess. The championship's conclusion in 1999 led to the revival of Deutsche Tourenwagen Masters (DTM) in 2000, as factory teams pivoted to the new series. The STW's legacy lived on through its successor series, the Deutsche Tourenwagen Challenge and later the ADAC Procar Series.

Dominating the Track

The S42-powered BMW E36 320i became a force to be reckoned with on the touring car circuit. Its reliability and high-revving nature made it a favorite for endurance racing, holding its own against fierce competition in series across Europe.

A Rare Gem

With only a handful of S42 engines ever produced, it remains a unicorn in BMW history. While it may not enjoy the same fame as the inline-six monsters that have dominated BMW Motorsport past, the S42 stands as a testament to BMW engineering.

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