S5x

The BMW S5x range of engines are a line of 6-cylinder engines, fitted to BMW Motorsport models between 1992 and 2001. The range is comprised of two main units; the S50 and the S52. All S5x engines are fundamentally based on the M5x series of engines that powered the E34 M5 and E36 M3, and are therefore very popular engine swaps.

Versions

S50

The S50 engine first saw action under the bonnet of the E36 M3 as a 3.0 engine. These phenomenal units were complete rebuilds of M50 engines; the blocks had a wider bore, the crank had a longer stroke and the whole compression was raised to 10.8:1. Compared to the simple 24V head of the M50, these engines featured VANOS technology and independent throttle bodies (six in all) for improved top-end performance.

In 1995 they went through an upgrade, with an increased bore and stroke taking displacement to 3.2 litres. To cope this this, the heads were fitted with Double VANOS to regulate both the intake and exhaust valves. Continuing to serve duty in the E36, these bigger lumps were also stuffed into the Z3 M-Coupe.

S50 engines weigh 151kg

Engine	Displacement	Power	Torque	Redline	Bore	Stroke	Year
S50B30	3.0 L (2990 cc/182 in³)	210 kW (282 hp) @ 7000	320 N·m (236 ft·lbf) @ 3600	7200	86mm	86mm	1992
S50B32	3.2 L (3201 cc/195 in³)	236 kW (321 hp) @ 7400	350 N·m (258 ft·lbf) @ 3250	7600	86.4mm	91mm	1995

S50US

Unfortunately for the US market, the phenomenal performance of the S50 engine came at too high a cost, both in dollars and pollution. To import such an engine and tune it to meet stringent emissions regulations would put a standard M3 far above the price bracket at which it was marketed.

Rather than rebuilding the S50, BMW adapted the existing M50 design to offer a tuned engine that performance half way between. Power and torque output are significantly decreased in contrast to the "original" S50, but are a massive improvement on the M5x design. At 240hp, the S50B30US slots neatly between the M50B25 at 191hp, and the S50B30 at 282hp.

This S50B30US is a strange beast. It features a VANOS head, but not the same VANOS system as the "genuine" S50 - it's stepped rather than variable - and also hasn't undergone the significant porting and polishing required to get the best gas flows. Most importantly, it lacks the independent throttle bodies found on every Motorsport engine since the M1 back in 1978.

Engine	Displacement	Power	Torque	Redline	Bore	Stroke	Year
S50B30US	3.0 L (2990 cc/182 in³)	177 kW (241 hp) @ 6000	305 N·m (225 ft·lbf) @ 4250	6500	86mm	85.8mm	1994

S52

Despite being heavily based on the M50, the M52 was a whole new engine, and it feels it. 20kg slimmer and a lot more responsive at the pedal, these engines are the most desirable of the M5x swaps.

S52 engines weigh 118kg

Engine	Displacement	Power	Torque	Redline	Bore	Stroke	Year
S52B20	2.0 L (1990 cc/121 in³)	110 kW (148 hp) @ 5900	190 N·m (140 ft·lbf) @ 4700	6500	80mm	66mm	1994
S52B25	2.5 L (2494 cc/152 in³)	123 kW (170 hp) @ 5500	245 N·m (181 ft·lbf) @ 3950	6500	84mm	75mm	1995
S52B28	2.8 L (2793 cc/170 in³)	142 kW (193 hp) @ 5300	280 N·m (207 ft·lbf) @ 3950	6500	84mm	84mm	1995

S52TU

Another Technical Update came in 1998, affecting all the M52 engines with a system called Double-VANOS, which applied the existing VANOS technology to the exhaust camshaft as well. Alongside that, the Block of the engine was changed from cast iron to aluminium, and the engine management system was upgraded. Unfortunately, all this complexity somehow robbed the M52 of its charm, and these Double-VANOS units are best avoided.

Engine	Displacement	Power	Torque	Redline	Bore	Stroke	Year
S52TUB20	2.0 L (1990 cc/121 in³)	110 kW (148 hp) @ 5900	190 N·m (140 ft·lbf) @ 3500	6500	80mm	66mm	1998
S52TUB25	2.5 L (2494 cc/152 in³)	123 kW (170 hp) @ 5500	245 N·m (181 ft·lbf) @ 3500	6500	84mm	75mm	1998
S52TUB28	2.8 L (2793 cc/170 in³)	142 kW (193 hp) @ 5500	280 N·m (207 ft·lbf) @ 3500	6500	84mm	84mm	1998