"In this new Special Series named “S85-002”, I earn a badge of honour: I blew up my V10.

I document the service history of my original S85 engine and diagnose its failure. I go through the process to source, refresh, cam and refit the replacement V10 into the E60.

In this entry, I go in-depth on the history of the V10 F1 era, the BMW Motorsport F1 program and what remained of its influence on the S85 V10 development."
- Matt

A caricature of an era. 

In most conversations around the S85, the F1 lineage starts and ends at an unnamed foundry where both the F1 & S85 engine blocks where made. As you're about to discover, this was merely the tip of the iceberg. 

For most, the F1 heritage a laughable proposition in light of fitting this V10 into a mid size, 4100 lbs saloon. At best, it's a a rationalization used by V10 owners when they ultimately face yet another 3,000$ repair bill. 

The perception was compounded with BMW M using and abusing the comparison in its superficial marketing campaigns around the launch of the M5 V10. The technical lineage was left to technical training documentations.

The journalists salivated: Fifth Gear famously reminded us our V10 was fitted in a saloon chassis.

The S85 was from a different breed. 

The S85 was engineered with a vastly different core design philosophy than the S50B32.  Along with 4 extra cylinders and 12.0:1 compression ratio, the S85 was made to rev beyond 8,000 RPM. It was designed as an over-square with a 92mm bore x 75.2mm stroke, equating to a Bore : Stroke ratio of 1.22. 

The major shift in design philosophy, engineering and manufacturing capabilities had to come from somewhere. 

The S85 had purely bespoke parts, differing from every other Sxx engines ever designed. 

Standing on the shoulders of giants. 

The S85 was designed and engineered following some of the greatest of BMW M street engine masterpieces: the S50B32 in the Euro E36 M3 and the S72 found in Gordon Murray's legendary creation.

These engines all have one thing in common: they were developed by Paul Rosche's team. 

M. Rosche held the post of Technical Director for BMW Motorsport. He was a fixture of BMW Motorsport, having headed development of production and racing engines for the BMW M1 amongst others, from 1979 to 1996.

He was responsible for the development of various technological features of S series engines such as dual VANOS first found in these legendary engines.

With a bigger stroke than bore, the S50B32 and S72 were under square powerhouses. They made significant torque for their displacement, but were rev limited below 8,000 RPM. 

The E36 M3's Euro engine was essentially half of the Mclaren F1 engine - or a quarter of those pictured here.

Yet, Paul's signature achievement was the Mclaren F1's V12 engine. 

M. Rosche retired in 1999 on top of his craft. 

I've compiled the comparison below between the S85 and S72. There were fundamental differences. If you find further information about the S72, reach out!

The F1 bloodlines. 

To better understand the context in which the S85 was developed, we need take in the scope of what was a bonanza-era of F1 engine development.

The sound.

We need to get the fanboy argument out of the way first: the unique sounds produced from this era. The V10 sang at higher pitch than the V12s, and rev'ed way, way higher - by over 2,000 RPM. 

This video has been on repeat for the hours spent researching, compiling, uploading, writing, aligning narratives correcting, re-editing and staying true to its goal:

The S85 is the greatest BMW M engine ever made. 

Peak money.

The FIA imposed little regulations beyond restricting engines to 10 cylinders, its 3.0 displacement limitations and a yearly focus on increasing engine life.

The hype around the V10 era is in large part due to the implication of many large scale automotive manufacturers in what was the best manufacturer-represented era of Formula One. 

The timeframe was short, the team wasn't accustomed to one another, operational processes were lacking and what were QA standards anyways? Derived from various V12 concept engines from the 1990s, the E40/41 was the first engine produced. 

The even firing order was a straight take away from V12 engine development. 

It wasn't perceived as ideal in terms of vibrations and it made for a tall engine with a high centre of gravity. As the 2000 Australia GP rolled around, the E41/4 was not yet race-ready and the failure rate was high.

The intake ports and pneumatic valvetrain of the E41/4 wasn't well optimized for the V10 - still, pay attention to the head's casting. 

The 94mm bore and 42.3mm stroke had a 2.2 B:S ratio. They were behind Ferrari. 

The 90 degree V, and its uneven firing order. 

The S85 was designed in similar fashion: the V10 arranged the two cylinder banks at an angle of 90° with a 17 mm offset to create a compact design. The 90° angle in a V10 is a direct descendant of the P8x engine series. 

They used learnings from the F1 Program to achieving the right balancing in an inherent unbalanced V10 design. The 90 degrees and offset were deemed as the equilibrium between limiting vibrations and maximizing stiffness of the block.

The uneven firing order is a fundamental component to the legendary exhaust sound. 

The equal length headers. 

The F1 V10 era pushed the designed of exhaust components to their limits: using thin walled inconel, engineers had to design systems that optimize for aero, heat, and exhaust pulses of ever more powerful, high revving engines. 

The S85's header design is a direct successor to the F1 program, it featured the first equal length header design to maximize performance.

On the V10, BMW M used stainless steel materials using hydroforming - eliminating needs for welding.The alloy's wall thickness was +/- 0.8 mm, optimizing for weight in the process. 

Unfortunately, BMW M fitted a primary catalytic converter right at the merge collector, limiting performance and incorporating design compromises in the primary tubes.

The V8 got the perfect set of F1 derived headers later on with the cats moved further downstream. 

The block's bedplate design. 

Th S85 was the first Sxx V engine to feature a bedplate design with integrated iron inserts as found on the E40/1E. While the F1 program ditched this design to favour aero, the E60 does not have such immediate concerns. 

The bedplate designs from Paul Rosche had a significant durability benefit: they were extremely stiff. It enabled precise fitment of the crankshaft to maintain main bearings clearance minimal over the entire operating temperature range.  

Clearances were tight - some say, too tight. 

The diamond like coatings.

During the F1 program, the mechanical production facility designed to deliver maximum precision was expanded to cover various surface treatment processes. 

It is this team that was responsible for the development of in-house DLC carbon coating technologies, allowing BMW to break up a supply monopoly. This expertise is now also used in the BMW production network.

The S85 made use of hydraulic tappers, reducing valvetrain weight, maintenance and improving performance. 

Unfortunately, durability was a minimum threshold. 

In 2000, a new engine was used every day, on Friday, Saturday and Sunday of a race weekend. Back then, Formula 1 racing engines only had to travel 800 kilometres in one racing weekend. 

The V10s eventually evolved into a planned engine life up to 1,600km. When they V8s were introduced, 1,600km was the regulatory benchmark and eventually evolved to 2,000km by 2009. 

With the goal of achieving longer service life, the road going V10 had a reduced piston speed of approximately 20 metres per second while the BMW Williams F1 reached as much as 40 metres per second.

In 87 starts, BMW Motorsport suffered 38 retirements. 

The S85 had to last the lifetime of the vehicle, regardless of the climate, traffic situation and style of motoring - and we know how that went. 

Up next: I document every little changes and production updates made to the S85 by BMW M to the S85 in an attempt to improve reliability.