BMW S70 and S70/2 V12 Engines

S70 5.6 in an E31 850CSi.
Chronology
This is really a tale of two separate engines, but both are simply epic. The lesser of the two is the S70, it was derived from the 5.0 V12 M70 and was used to power the E31 850CSi 5.6. There was no four valve per cylinder M8 other than three prototypes, but the idea wouldn't simply go away.
It fell to McLaren to ask BMW for a 6.0 V12 for it's 1993 F1 supercar, Paul Rosche obliged with his career masterpiece - the S70/2. Although called by the same name as the 5.6 it really was a very different engine. In many ways it was a pair of S50B32's bolted together. It every way it was incredible.
The S70/2 and 3 were used by BMW's LMR racing cars and won LeMans in 1999. In 1995 the engine won LeMans in a McLaren F1.

M8 prototype with individual throttle bodies
Design
The S70 5.6 was based heavily on the M70 5.0 V12. In addition to the extra displacement it ran a higher 9.8:1 compression ratio and lower back pressure catalytic conterers to produce 380bhp. It was still a two valve per cylinder engine.
The S70/2 was a whole new engine, few components were shard with the M70. The basic layout of the lower engine is similar to the M70 but there are many detail differences. The two cylinder heads had four valve per cylinder and were based on those from the S50B32 found in the E36 M3 Evo.
Unlike the S70 there was one coil per cylinder, double VANOS and 12 individual throttle bodies which are fed from a carbon fibre airbox.
The engine had a light aluminium flywheel, four oil scavenger pumps to ensure lubrication under high cornering forces and a dry sump. There were two sets of fuel injectors per cylinder, not uncommon in racing engines.
If full race trim it was said that power levels approaching 1000bhp were possible.
Other than Ferrari nobody really made V12s to this level.

Paul Rosche with the back end of a McLaren F1.
Variants
Code | Size | Power bhp@rpm |
Torque lb/ft@rpm |
BHP/ litre |
Torque/ litre |
Made | Bore x Stroke |
Timing | Weight (kg) |
VANOS | Used in |
S70 | 5.6 | 380 @ 5300 | 406 @ 4000 | 68 | 72.5 | 92 - 96 | 86x80 | Chain | ? | No | 850CSi |
S70/2 | 6.1 | 618 @ 7400 | 480 @ 6700 | 103 | 80 | 93 - 2000 | 86x87 | Chain | 274 | Dual | McLaren F1 |

BMW believe strongly in product testing......
Problems
At least if you do have a problem the McLaren F1 has a built in modem to let you download the fault codes remotely.
The S70/2 uses similar VANOS gear to the S50B32 it's reasonable to suppose the seals fail in the same way.