Why did they not include the S85? 
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The greatest naturally aspirated engines of BMW
An ode to one of the best in the business.
By Thierry Godard January 10, 2014 / Photos by Wiki Commons
In early December 2013, BMW revealed the twin-turbocharged M3 and M4. Their launch marked the official end of the naturally aspirated engines for BMW M GmbH, a company that has built a legacy on precise, high-revving performance. We take a look at the engines at the core of some legendary performance cars.
M49
Wiki Commons
BMW Motorsport was founded in 1972 to transform BMW's E9-chassis 3.0 CS into the 3.5 CSL, giving it a competitive edge against the Ford Escort in the European Touring Car Championship (ETCC). With limited time and money, BMW Motorsport engineers took to increasing the displacement of BMW's popular road-going M30 3.0-liter straight-six, added mechanical fuel injection, and formed a new aluminum head based on their Formula 2 race car. The result was the 24-valve 3.5-liter M49. In race trim, it helped the BMW 3.5 CSL deliver 450 hp—about enough to launch the careers of Hans Stuck and Sam Posey.
M88
BMW
After meeting with stiff competition in the ETCC, BMW began the development of an all-new engine, code-named 'the M88,' for a mid-engined race car: The BMW M1. The 3.5-liter M88 produced 272 hp in road trim but as much as 900 hp in the M88/2 powering the M1 turbo race cars. Things didn't get interesting until production of the M1 ended, and BMW placed the M88/3 under the shark-nosed hood of the M635csi and later the Euro-spec M5.
S38
BMW
Facing more stringent emissions regulations, BMW began to develop a more efficient version of the M88 for road use. The end result, with little changes to bore, stroke, and cylinder heads, appeared in the mid-1980s, powering the US-spec BMW M5 and M6. Called the S38B35, the 3.5-liter inline-six made 252 hp and 243 lb-ft of torque. The power reduction came thanks to a lower compression ratio and restrictive catalytic converters. But the personality remained.
Evolution of the S38 engine continued into the next-generation (E34-chassis) M5. Launched in 1989, the S38B36 featured an increased stroke, which bumped displacement to 3.6 liters, and innovations to the intake manifold and engine management software allowed it to produce a potent 310 hp and 266 lb-ft of torque. But BMW M didn't stop there. In 1992, it released the S38B38—a 3.8-liter 10.5:1 version that made 335 hp and 295 lb-ft.
S14
BMW
The four-cylinder fury at the heart of the beloved E30 M3 is nearly identical to the M88 and S38 six-cylinder engines that came before it. The S14’s four-cylinder block was based on BMW’s pedestrian M10 engine, but the cylinder head came from the M88—with two cylinders lopped off. The resulting engine produced 192 hp from only 2.3 liters—one of the highest specific outputs of its time. By the time production of the E30 M3 ended, the 1990 M3 Sport Evolution featured a 2.5-liter S14 that produced 235 hp and 177 lb-ft of torque.
S50b32
BMW Blog
While the E36 M3 may be one of the greatest BMW chassis of all time, its US engines (first the S50 and then the S52) were major source of a disappointment for American enthusiasts. While we got slightly massaged, enlarged versions of the regular 325i engine, it was high-revving business as usual for the rest of the world. First came the 3.0-liter S50B30, then the screaming S50B32. Released in 1995, the 7600-rpm S50B32 made an impressive 316 hp and 258 lb-ft from just 3.2 liters of displacement and had a stratospheric 11.3:1 compression ratio. Like all real M engines (and unlike the US E36 M3 engines), it had a throttle butterfly for each cylinder—and variable valve timing for both intake and exhaust cams.
s70/2
BMW
McLaren F1. Buried mid-ship in a palace of gold and carbon fiber lies BMW's S70/2, based on the S70B56 from the ultra rare 850CSi. Where the S70B56 used a cast iron block, the S70/2 is all-aluminum, with its displacement increased to 6.1 liters. It utilized BMW's VANOS system on both engine banks and twelve individual throttle bodies to produce 618 hp and 479 lb-ft of torque. BMW continued to evolve the S70/2 until it became the S70/3, the 700-hp lifeblood of its Le Mans-winning BMW V12 LMR.
S54
BMW
The S54 is the last of the Mohicans, the end of the high-revving naturally aspirated inline-six engines that had become synonymous with the 'M' logo. The S54 featured throttle by wire, continuously variable valve timing by way of double VANOS, and one of the most complex ECUs available at the time. The result was an engine that produced 333 hp from 3.2 liters (343 hp in Euro-spec, and 360 hp in CSL trim) and 269 lb-ft of torque—and revved to 8000 impossible rpm. It found its way into the engine bay of two generations of M Coupe and Roadster as well as the E46 M3M3 CSL.
S65
BMW
Based on the V10 S85 from the E60-chassis M5, the S65 was BMW M's farewell to high-revving engines. And what a grand exit it was for the last naturally aspirated M3. The all-aluminum 32-valve 4.0-liter V8 was a screamer of an engine; it produced 414 hp at 8300 rpm and 295 lb-ft of torque, all while being lighter than the S54 it replaced. It will be missed.
Honorable mention: S62
BMW M has produced no shortage of great engines, but we didn't really have room for the S62 because it would mean choosing between the S65 and the last naturally aspirated inline-sixes, the S54. This doesn't mean that the eight thumping fists producing 400 hp under the svelte hood of the E39 M5 should be forgotten. But as amazing as that engine was (and was it ever), it’s the E39 chassis that’s never been beaten. The S62, on the other hand, was outdone by the S65.
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