Engine Components/Systems Overview

The following provides an overview of the features of the N74 engine:

• Engine block 

  The main components of the engine block have been re-designed, although most features are already used on other BMW engines.

• Crankshaft 

  Although the Pistons and connecting rods have been borrowed from the N63 engine, the crankshaft is a new design.

• Valve train 

  The VANOS units from the N63 engine are used and the camshafts are manufactured in the same way. The N74 does not use a VALVETRONIC system.

• Camshaft 

  The tooth-roller type chain of the N63 engine is used. Only the chain length and the layout of the timing gears have been adapted to suit the twelve-cylinder engine.

• Belt drive 

  The structure of the belt drive includes a "revolver" tensioning system and is identical to that on the N63 engine.

• Oil supply 

  Though the oil supply system has been designed for the N74 engine, in principle, it's the same as that on the N63 engine. Consequently a volumetric-flow-controlled oil pump is also used here.

• Crankcase ventilation 

  The engine uses the same crankcase ventilation principle as N63 engine with a new feature called register ventilation. With this feature, the oil separators now have four cyclones per cylinder bank and in naturally-aspirated operation, ventilation only occurs via cylinder bank 2.

• Cooling system 

  Two separate cooling circuits are used as on N63, one to cool the engine and turbocharger bearings and one for charge air cooling, this latter circuit also provides cooling for the two engine control units.

• Air intake and exhaust system 

  The air intake and exhaust systems are the same as that on the N63 engine.

  This means there are two conventional exhaust turbochargers with wastegate and blow-off valves. In contrast to the N63 engine, however, the exhaust turbochargers are located on the outside.

• Secondary air system 

  As with N73 engine, the N74 is equipped with a secondary air system.

  One new feature, however, are the two pressure sensors that monitor system operation.

• Vacuum system 

  The N74 engine has a two-stage vacuum pump as on the N63. The vacuum system only differs in that it has two vacuum reservoirs.

• Fuel system 

  The N74 engine uses "injection guided" (HPI) high precision injection in homogeneous operation at all times, as on the N54 and N63 engines. The structure of the system is the same as that on the N63 engine. Consequently, the same injectors are used and the high pressure pumps are also very similar.

• Engine electrical system 

  A total of five control units were used on the N73 for engine control purposes.

  The N74 now has two engine control units, one of which has the role of the master (primary), the other the secondary. The two MSD87-12 control units are located to the left and right of the engine compartment and are cooled by the low temperature cooling circuit of the engine intercoolers.

The N74 engine uses the most current BMW systems. Although the N74 engine has been designed from scratch, from a technology point of view it is, the same as the N63 engine and has also borrowed many individual components from this engine.