The much celebrated new N54 Bi-turbo engine found in the 135i and the 335i is not BMW’s first inline-6 turbocharged petrol engine. If you look back in history to the old E23 BMW 7-Series back in the 70s and 80s, you will notice that there was a special high performance model called the BMW 745i Turbo.
Under the E23 745i Turbo’s hood was a 3.2 litre inline-6 engine that was turbocharged to produce the then-equivalent of a 4.5 litre normally aspirated engine. This engine was the M102B32, and it was based on the M30 engine.
Later, a 3.4 litre M106 engine replaced the M102, also turbocharged, and was pretty much similiar to the M102 except it used the newer Bosch Motronic fuel injection instead of the M102’s L-Jetronic fuel injection. The M106B35 produced the same output power as the M102 at lower RPM at only 0.4 bar compared to its predecessor’s 0.7 bar.
The 3,430cc M106B35 produced 252 horsepower at 4,200rpm (M102 made the same power but at 5,200rpm), and 380Nm of torque at 2,200rpm. It revved up to a redline of 6,200rpm. Compression ratio was 8.0:1, and turbo boost was 0.4 bar (M102 had 7.0:1 compression and 0.7 bar). The engine had 6 cylinders arranged in an inline formation, and had a bore and stroke of 92mm x 86mm.
Because of turbocharger packaging reasons, it could only be installed in left hand drive versions of the 7-Series, so the South African 745i got the M88 normally aspirated engine used in the M635i and the E28 M5.