BMW S70 and S70/2 V12 Engines

BMW S70 engine

S70 5.6 in an E31 850CSi.


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.

BMW S70 engine

M8 prototype with individual throttle bodies


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.

BMW S70 engine

Paul Rosche with the back end of a McLaren F1.


Code Size Power
Made Bore x
Timing Weight
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 S70 engine

BMW believe strongly in product testing......


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.