The BMW M88/3 is an in line 6 cylinder (I6) piston engine. It was based on the M88/1 that was used in the BMW M1's street version, with double overhead cam and four valves per cylinder. The M88/1 was in turn based on the M49 engine which was used in the BMW 3.0CSi. The M88/3 was used in the early BMW M635CSi/"M6" and BMW M5 (E28) and produced 286 PS (210 kW/282 hp).
BMW engineers used a 4-valve head and a single-row chain. The cylinder head was made in two parts. The lower part formed the combustion chambers and water jackets, and the upper half contained the camshaft bearings and the bores for the tappets.
Kugelfischer fuel injection was used with individual throttle valves and the distinctive six inlet pipes. The M88 produced 277 bhp in the version built from 1978 to 1981 for the BMW M1.
For the Procar M1's, the M88 was tuned to 470 to 490 bhp. The resulting M88/1 engine had new camshafts, bigger valves, reshaped ports, forged pistons, use of throttle slides (instead of butterfly valves), and improved exhaust.
For Group 5 racing, the engine was pushed to between 850 and 900 bhp by the addition of two turbochargers. This was the M88/2 powerplant.
From 1985 to 1987 the M88 was used in the European-market 5 Series M5 (E28) and from 1983 to 1989 in the 6 Series M635CSi Coupe (E24). The engine was designated M88/3 and produced 286 bhp.
The S38 was an updated M88/3 and produced in three versions :
S38 B36 - all US-spec and '89-'92 European-spec BMW M5 (E34)
S38 B38 - '92-'96 European-spec BMW M5 (E34)
The S38 B35 was a revision of M88/3 with dual-row timing chain, reduced compression, catalyst-equipped and fitted with cast iron manifolds rather than equal length "bundle of snakes" headers.
For the S38 B36 displacement was enlarged from 3453 to 3535 cc. Thanks to the use of a Bosch Motronic 1.2 engine management, power grew to 315 PS (232 kW/310 SAE hp) at 6900 rpm. a dual-stage intake plenum helped to improve flexibility over the rev range. All versions were catalyst-equipped.
In 1992, with the introduction of Euro I emission legislation, BMW opted to enlarge the engine once more, to 3795 cc, with power climbing to 340 PS (250 kW/335 SAE hp) and torque going up to 400 Nm (295 ft·lbf). Coil-on-plug ignition replaced the traditional distributor from the B35 & B36. The B38 engine also received a Motronic 3.3 engine management. This engine was used in the M5 until the E34 finished production in 1996.