BMW E30 M3 four-cylinder S14: Tuner builds a better S14 engine

The S14 is one of those engines whose name alone makes enthusiasts' eyes light up. Yet it was originally conceived out of pure necessity: For the homologation of the E30 M3 in motorsport – specifically for the German Touring Car Championship – BMW needed a high-revving four-cylinder engine suitable for racing trim. A six-cylinder was out of the question due to space and weight constraints.

In just two weeks, Paul Roche created a new engine from existing parts. The block of the proven M10, paired with a cylinder head based on the M88 (known from the BMW M1). The result was the S14. Starting in 1986, he worked on the E30 M3, and BMW developed several evolutionary stages.

The key figures still sound impressive today: In the road version, the four-cylinder initially produced 192 hp, later 200 hp (S14B23), and in the limited-edition EVO3, even 235 hp at 7,000 rpm. In the DTM, the engine even produced up to 374 hp – from a displacement of just 2.5 liters. Revs beyond 8,500 rpm were not uncommon. Its sound remains unique to this day: a mixture of intake roar, mechanical clarity, and snotty anger.

But for all its fascination, the S14 also had its flaws: oil leaks, thermal issues, often rough throttle response, and components prone to wear under heavy use. Redux believes it can eliminate some of these problems. The British tuning company's goal is "to preserve the soul of the S14 while eliminating its weaknesses," writes Carbuzz. Nevertheless, there's no way around a radical overhaul of the S14. This ultimately led to the engine's new name – the S14B27.

The mechanics replaced the original cast iron block with a machined aluminum housing. All other cast iron parts, such as the cylinder head, dry sump, valves, and engine cover, are now also made of aerospace-grade billet aluminum. This measure reduces the overall weight of the engine by over 15 kilograms.

The crankshaft, connecting rods, and pistons are all new developments and are made from a combination of titanium, steel, and aluminum. The goal is to achieve maximum strength with minimal weight. A key issue with the original engine was always the oil supply during high lateral and longitudinal acceleration. Redux completely replaces this system with a modern dry sump system with an enlarged reservoir that delivers constant oil pressure even at speeds up to 9,000 rpm. The camshafts come from German specialist Schrick, with whom Redux works closely. The goal was to retain the intake characteristics and sound of the original – despite completely new internals. After all the modifications, the engine has a power output of 334 hp on the dyno.

The sound should remain original

So much technology – and yet, Redux still values the emotional aspect. The original sound, especially the legendary intake noise, was to be preserved. But that's more difficult than you might think: New pistons, new compression ratios, different materials – all of this changes the acoustics. However, according to Redux, they managed to preserve the S14's signature "induction bite."

In terms of driving dynamics, the new engine is not intended to outperform the standard S14, but rather to enhance its virtues: direct throttle response, smooth power delivery, and high-revving performance.

There will be 30 vehicles worldwide, each one unique. The engine will only be available as part of a complete E30 M3 restomod project by Redux. Redux hasn't disclosed a price. However, given the materials used, the effort involved, and the limited production run, the conversion is unlikely to be a bargain.

In the picture gallery you can see the BMW E30 M3 Cecotto Edition.