The BMW M30 is a straight-6 SOHC piston engine which was produced from 1968 to 1994. The first model to use the 2494 cc version of the M30 was the E3 2500. Over its 28-year lifespan, the M30 was used in many BMW models. Although there was no direct replacement for the M30 engine, effectively the v8 M60 and straight-6 M50 (smaller capacity than the M30, but with DOHC) took over from the M30.

Initially, the engine code was "M06", before it was renamed the M30 in the mid 1980s. The engine has been given the nicknames of 'Big Six' and 'Senior Six', following the introduction of the smaller BMW M20 straight-6 in the late 1970s.

Development

The M30 was originally developed in the late 1960s, loosely based on the straight-four BMW M10 engine first used in the 'Neue Klasse' BMW 1500. Several features, including a profile lowering 30-degree slant to the right, a crossflow head (a gas flow head in later desgins) and a chain-driven single overhead cam with rocker arm valve actuation are common between the M10 and the M30.Further similarities include a cast-iron block with an aluminium head and a forged crankshaft. The first two engines introduced were the 2.8 and the 2.5 litre option, both short-stroke engines sharing a common bore.

The engine block with a cylinder clearance of 100 mm is made of gray cast iron , the crankshaft is mounted seven times. 

The cross-flow cylinder head is made of light metal. The by a timing chain , in many variants, a duplex chain, driven overhead camshaft operated two valves per cylinder . By varying the bore and the stroke , engines with 2.5; 2.8; 3.0; 3.2; 3.3 and 3.5 liters capacity.

For mixture formation were carburetor or intake manifold injection ,1979 for the 3.2 and 3.5 l versions of the digital engine electronics, since 1986 in conjunction with the catalyst , to the application. End of the 70s, in the 5 series from the E28 1981, vertically arranged suction systems were used for weight reasons,  . Images injection versions. When the engine was introduced in 1968 new for a soft and also favorable in terms of exhaust combustion as a three-ball swirl tank with volume concentration around the spark plug designed combustion chamber. This also protects the bearings.  Also versions with turbocharger were developed; in series came in the 1980s, the 745i .

As a tuning base, the M30 engine was used among others the companies Alpina , Hartge and Schnitzer .

The M30 was finally replaced by the equipped with four-valve technology BMW M50 (six-cylinder in-line engine, 24V). For the BMW E32 was parallel to the eight-cylinder - V-engine BMW M60 (32V) continue to be offered the M30B30.

Turbocharging

The M30 was the basis for the turbocharged M102 and M106 engines.

The Alpina B10 Biturbo used a modified version of the M30, with two turbochargers and forged pistons. Producing 265 kW/360 hp at 6000 rpm and 520Nm/384 lb-ft at 4000 rpm, the engine made this car the fastest sedan in the world. The final 50 M30 blocks were shipped to Alpina for use in the final 50 B10 Biturbos.

Motorsport

The M30 powered a series of BMW 6-cylinder E9 and BMW E24 coupes to European Touring Car Championship (ETCC) throughout the 1970s and into the middle 1980s, even though a more powerful DOHC 24-valve head had been developed for high-performance motorsports and street use.

The BMW M88 high-performance engine is based on the M30 block.

M90

The M90 engine, used in several models from 1979-1982, combines the block from the motorsports BMW M88 engine with the M30's SOHC cylinder head.

Data 

The weight of the engines is between 192 kg in the 2.5 l variant for the BMW 525 from 1976, 199.5 kg for the engines in 3.0s / si, up to 212 kg of the M30B35. The turbo versions weigh 225 kg. 

2.5 litre

The first model to use the 2494 cc version of the M30 was the E3 2500 in 1968. Unless otherwise noted, these engines use a carburetor.

Applications:

• 1968-1977 E3 2500
• 1974-1975 E9 2.5 CS
• 1973–1976 E12 525 (107 kW)
• 1975-1979 E23 725 (110 kW)
• 1976–1981 E12 525 (110 kW)
• 1981–1987 E28 525i (110 kW, fuel injected)

2.8 litre

A 2.8 litre version of the M30, this appeared in 1968 in the then new E3 2800 and E9 2800CS. It has a bore of 86 mm, a stroke of 80 mm and a displacement of 2,788 cc (170.1 cu in). In the E24 628 CSi, it uses Bosch L-Jetronic fuel injection. Originally, two Solex Zenith "35/40 INAT" carburetors are used, the compression ratio is 9.0:1 and the engine produces 170 PS (125 kW) and 24.0 kg·m (235 N·m; 174 lb·ft).

Applications:

• 1968-1974 E3 2800
• 1971 E3 Bavaria
• 1968-1971 E9 2800CS
• 1975-1976 E12 528 (125 kW, carburetor)
• 1977-1979 E23 728 (125 kW, carburetor)
• 1976-1978 E12 528 (130 kW, carburetor)
• 1977-1978 E12 528i (129 kW, fuel injected, lower compression ratio, North America only)
• 1978-1981 E12 528i (135 kW, fuel injected)
• 1979-1986 E23 728i (135 kW, fuel injected)
• 1979–1987 E24 628CSi (135 kW, fuel injected)
• 1981-1987 E28 528i (135 kW, fuel injected)

3.0 litre

This version was produced from 1971 until 1992. It has a bore of 89 mm, a stroke of 80 mm and a displacement of 2986 cc. The first model to use the carburetted version of the 3 litre M30 was the E9 3.0CS. There was also the first fuel-injected M30 version for the CSi and later Si models, which uses the Bosch D-Jetronic fuel injection system.

Applications (carburettor)

• 1971-1975 E9 3.0CS
• 1972-1974 E3 3.0S
• 1972-1974 E3 Bavaria
• 1976–1979 E24 630CS (Pierburg 4A1 downdraft carburetor)
• 1977-1979 E23 730 (135 kW)

Applications (fuel injected)

• 1971-1975 E9 3.0CSi
• 1972-1973 E9 3.0CSL
• 1974-1975 E3 3.0Si
• 1975–1978 E12 530 (130 kW, South Africa only)
• 1975–1978 E12 530i (131 kW, North America only)
• 1976 E12 530 MLE (147 kW, South Africa only)
• 1977–1978 E24 630CSi (North America only)
• 1986–1992 E32 730i (138 kW)
• 1988–1990 E34 530i (not sold in North America)

M30B32

Despite having a capacity of 3210 cc, this engine appeared in many cars badged so as to suggest 3.3 litres of displacement, such as the 633i, 3.3 Li, and 733i. It has a bore of 89 mm, a stroke of 86 mm and a capacity of 3210 cc. In the E24 633CSi, it uses Bosch L-Jetronic fuel injection. The US version used L-Jetronic from 1978 until mid-1981, changing over to Motronic fuel injection in June of that year. The 1979 732i is BMW's first use of Bosch's Motronic fuel injection.

Applications:

• 1976–1984 E24 633CSi
• 1976-1977 E3 3.3 Li
• 1977-1979 E23 733i (145 kW)
• 1979 E12 533i
• 1979–1986 E23 732i (144 kW)
• 1983–1984 E28 533i (North America only)
• 1984-1986 E30 333i (145 kW, South Africa only)
• 1982 Cumberford Mantique prototype

M30B34

This engine has a bore of 92.0 mm, a stroke of 86.0 mm and a displacement of 3428cc. In the E24 635CSi, it uses Bosch Motronic 1.0 fuel injection.

Without catalytic converter
The version sold in Europe and most other markets used a 10.0:1 compression ratio and produced 160 kW (210 hp).

Applications:

• 1982-1986 E23 735i
• 1982-1986 E24 635CSi
• 1985-1988 E28 535i/M535i

With catalytic converter
The version sold in markets such as North America and Japan used an 8.0:1 compression ratio and produced 136 kW (182 hp).

Applications:

• 1982–1987 E24 635CSi
• 1982-1987 E23 735i
• 1985-1988 E28 535i
• 1985-1987 E23 735i
• 1986-1987 E23 L7
• 1987 E24 L6
• 1987-1988 E28 535is

M30B35

It has a bore of 92 mm, a stroke of 86 mm and a capacity of 3428 cc. In the E24 635CSi, it uses Bosch Motronic 1.3 fuel injection.

• 9.0:1 compression ratio
• 155 kW (208 hp) at 5,700 rpm
• 305 N·m (225 lb·ft) torque at 4,000 rpm
• 87 AKI / 91 RON octane fuel or better recommended

Applications:

• 1988–1989 E24 635CSi
• 1988–1992 E32 735i (155 kW)
• 1988–1993 E34 535i
• 1988-19?? Rayton Fissore Magnum 3.5