BMW S85 V10 and S65 V8 Engines

BMW S85 engine

S85 V10 5.0 Formula 1 inspired engine.


When the E39 with it's five litre V8 M5 retired BMW looked to formula one for inspiration. They'd had a good deal of success with a three litre V10 in partnership with Sauber. So in 2005 the idea of a V10 powered E60 M5 was born.

Whilst the race engine had been a three litre the new road going engine would displace five litres, just like the outgoing M5. Previously M engines had been based to varying extents on normal BMW production engines, the S85 was the first exception to that rule and there was never to be a normal V10 engine. It could be had with a six speed manual or 7 speed SMG (sequential manual gearbox) gearbox.

In addition to the M5 the S85 also saw service in the E63 M6 from 2005 until 2010.

The E90 three series came to market in 2007, it's predecessors used the S50 / S54 series of inline sixes and had done so since the early 90s. Sadly there were to be no more inline sixes, the V10 was cut down to a four litre V8 with most of the same engineering features. In fairness to BMW they were in a horsepower war with other German manufacturers and had little choice but to abandon the sixes.

The E90 M3 was a very special car and the new V8 did it justice until the end of production in 2013. A rare 4.4 litre S65 was used in the M3 GTS coupe and M3 CRT (Carbon Racing Technology) saloon.

BMW S85 engine

S85 in an E60 M5.


Because the S85 was designed from the outset only to be a Motorsport engine there were few compromises in it's design. Along with the expected ten individual throttle bodies and forged steel intervals the engine boasted a strong block with cast alloy bed plate and a racing style quasi-dry sump. The bed plate needed cast iron inserts to support the forces generated under the lower crank bearings. The beast could rev to 8250rpm and made over the magical 100bhp / litre figure, amazing for a road car engine of this size. Compression was very high at 12:1.

The cooling system was effectively split, each cylinder had it's own coolant feed from the radiator. The radiator itself was split in two with upper and lower banks assigned to their own side of the engine.

Whilst many M engines used two part cylinder heads the S85 used a single piece design. The camshafts were hollow and cam lobes were shrink fitted to it by chilling the shaft and heating the valves. Naturally there was VANOS on all four camshafts, but the usual 100 bar oil operating pressure was raised to 115. VANOS adjustment on the intake was 60 degrees, 37 on the exhaust side. The exhaust valve stems were joined to the valve heads by friction welding.

The timing chains were single row but for the first time the two camshafts in each head were connected by a gear train instead of a chain. Cam operation was by a similar zero-lash hydraulic tappet system to the S62 although the actual tappets were box type.

The oil system included two electrically operated scavenger pumps which were activated under hard cornering.

The S65 V8 was technically very similar to it's larger brother. One major difference was the use of a conventional wet sump. Another was the use of a single air box in place of the pair needed for the V10.

BMW S85 engine

S65 V8 in an E90 M5.


Code Size Power
Made Bore x
Timing Weight
VANOS Used in
S65 4.0
420 @ 8300
444 @ 8300
295 @ 3900
320 @ 3750
2007 - 2013
2010 - 2011
Chain 202 Dual E90 M3
S85 4 507 @ 7750 384 @ 6100 101.4 76.8 2005 on 92x75.2 Chain ? Dual E60 M5, new M6


BMW S85 engine

S85 showing it's 10 intake trumpets.


As with all M engines these like a drink and you MUST regularly check the level and use the correct grade of oil. Tolerances are tight and the wrong oil or oil starvation will prove very expensive very quickly.

S85 and S65s produced from 2007 until late 2008 had a problem with the conrod bearings. The clearances were too tight and this resulted in reduced oil flow and premature failure. BMW allowed lighter oil grades as a short term fix to mitigate the issue. By now many will have been fixed under warranty.

The two throttle actuators can wear on these engines. The problem lies in two plastic gears in each mechanism, basically the grade of material is insufficient. BMW charge 700 quid for each new actuator assembly but all you need are the gears and much less expensive after market options are now available.

These are regarded as strong and durable engines.