The BMW M50 is a straight-6 DOHC petrol engine which was produced from 1990 to 1996. It was released in the E34 520i and 525i, to replace the M20 engine. In September 1992, the M50 was upgraded to the M50TU ("technical update"), which was BMW's first engine to use variable valve timing. Called single VANOS by BMW, the system adjusted the phasing of the intake camshaft. The M50 began to be phased out following the introduction of the M52 engine in 1994. The E36 M3 is powered by the S50 engine series, which is a high output version of the M50. Design A significant advance over its M20 predecessor, the M50 features dual overhead camshaft (DOHC) with four valves per cylinder (the M20 has a single overhead camshaft with 2 valves per cylinder), coil-on-plug ignition, a knock sensor and a lightweight plastic intake manifold. Both engines use an iron block with an aluminum alloy head. The redline is 6,500 rpm for the M50B25 and 6,750 rpm for the M50B20 (7,000 rpm for S50 models), the same as the final version of the M20. The location of the oil pan (sump) varies according to the model the M50 is installed in. It is in the front on the E34 5 Series (like the M20), whereas it is in the rear on the E36 3 Series. Models M50B20 The M50B20 was introduced with the 1990 520i. It has a bore of , a stroke of and produces . The compression ratio is 10.5:1. Applications: 1990-1992 E34 520i 1991-1992 E36 320i M50B20TU The M50B20 was updated with single VANOS in 1992. Peak torque became available at 4,200 rpm. It produces at 5,900 rpm and at 4,200 rpm. The compression ratio was raised to 11.0:1. Applications: 1992-1994 E36 320i 1992-1996 E34 520i M50B24TU This is a engine used in the Thailand and Oceania markets. It is based on the M50B25TU with the stroke reduced to and produces at 5,900 rpm and at 4,200 rpm. The compression ratio is 10.5:1. Applications: 1993-1995 E36 325iA/2.4 1992-1996 E34 525iA/2.4 M50B25 The M50B25 was introduced with the 1990 525i and 525ix. It has a bore of , a stroke of and produces at 6,000 rpm and at 4,700 rpm. The compression ratio is 10.0:1. Applications: 1990-1992 E34 525i, 525ix 1991-1992 E36 325i, 325is M50B25TU The M50B25 was updated with single VANOS in 1992, resulting in peak torque becoming