The BMW N74 engine is BMW’s first turbocharged V-12 engine, which has been in production since 2008.
The main difference from the predecessor N73, in addition to the presence of turbines, is the absence of the Valvetronic system.
Design features
The motor replaced the 12-cylinder N73, and although it was developed from scratch, the designers borrowed a lot in the design of the engine from the N63.
The lubrication system, cooling system, air intake and exhaust, crankcase ventilation and HPI fuel system (injectors, high pressure pumps) are all borrowed from the N63 and adapted to this V12, taking into account its design.
With the predecessor of the N73, the engine is related to the exhaust gas recirculation system. It is distinguished by the presence of only two (against five in the N73) engine control units.
One acts as a leader, and the other acts as an executive mechanism. Moreover, the MSD87-12 ECUs are located to the right and left of the engine.
Unlike the N73, when designing the N74, engineers abandoned the Valvetronic valve lift system.
The main difference between the N74 and its predecessor is the presence of two Garrett GT2260S turbochargers , one for each cylinder block, with the turbines located outside the engine.
The turbochargers of the N47 are double, in the form of a snail. BMW ‘s TwinPower Turbo two-speed turbo technology delivers power without lag.
Cooling of the turbocharger is achieved by a separate unit from the engine cooling unit on top of the engine.
The cooling of the engine itself runs diagonally, that is, the antifreeze flows through the cylinder head from the outside to chamber V.
The cylinder head is made of cast aluminum, it is two-shaft ( DOHC ), equipped with a Double – VANOS variable valve timing system.
The N74 uses HPI high precision fuel injection with outward opening piezo injectors. The injection nozzles are built into the cylinder head with the spark plug in the center of the combustion chamber.
The cylinders in the block are collapsed at an angle of 60 degrees, its design resembles the N63, the pistons and connecting rods are also borrowed from the N63, but the crankshaft is new.
The toothed roller chain is taken from the N63 and has been optimized in terms of length and tooth spacing.
The block material is aluminum alloy, so this V12 weighs only 150 kg.
The power of the 6.0-liter N74, which is installed on the top models of the BMW 7-series, is 544 hp. at 5300 rpm. The torque reaches 750 Nm at 1500-5000 rpm.
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N74 Engine Modifications
1. N74B60
The six-liter version with the index N74B60 U0 / U1 develops 536 hp. (750 Nm) and was installed on the BMW 760i, 760Li in the back of F01, F02, F03 from 2009 to 2015.
2. N74B66
This 6.6 liter V12 has been installed since 2009 on the Rolls-Royce Ghost and since 2013 on the Rolls-Royce Wraith.
Its power ranges from 563 to 593 hp. (780 – 840 Nm) of torque depending on the model.
3. N74B66TU
The “charged” version of the 6.6-liter unit has been installed since 2016 on the BMW M760Li xDrive. Engine power – 602 hp at 800 Nm of torque.
4. N74B68
This version of the BMW N74 engine was created specifically for the new 2018 Rolls-Royce Phantom. Next year, the N74B68 will also be installed on the off-road Rolls-Royce Cullinan. Its power is 563 hp. (900 Nm).
Operation N74
This powerful V12 excels in any kind of workload. But the attention of the owner requires priority, and service – impeccable.
The design of the N74 compares favorably with its predecessor N73 and N63 , including due to the placement of turbochargers outside the block, which solves a number of issues regarding the heat load of the unit.
The main thing is to give the V12 only to professionals who understand its specifics, including the maintenance of the Double VANOS system and the HPI injection system.
You need to fill this engine with the best available gasoline, not lower than AI-95.
Engine oil – strictly according to the manufacturer’s recommendations, experts recommend changing it every 6-7 thousand km.
The main recommendation to N74 owners is to turn off the engine without the need for parking. The turbine quickly fails when operating in conditions of high temperature with low pressure in the oil supply system – in particular, at idle.
N74 Engine Most Common Problems
1. Turbine failure
The main enemy of the TwinPower Turbo snail is overheating at low pressure in the lubrication system. As a result, the oil lines of the turbines coke, and there it is not far to replace the expensive turbocharger.
2. Malfunctions of the VANOS system
Even with decent service, every 180-200 thousand km, owners are faced with noise in the engine compartment and unstable engine operation. Most likely, the time has come to replace the components of the Double-VANOS variable valve timing system.
3. Overheat
The engine block is made of aluminum alloy, and the family disease of all N-series engines – overheating – did not bypass the V12. As a preventive measure, the owner needs to monitor the quality and volume of engine oil in the crankcase, regularly clean the radiator and inspect the tightness of the cooling system. Of course, you can’t save on the quality of antifreeze either.
4. Maslozhor
On a run above 50 thousand km, the owner may be unpleasantly surprised by the oil burner of the engine. The complexity of the problem is exacerbated by the fact that the design of the N74 does not provide for an oil dipstick. The owner relies on the readings of an electronic sensor that monitors the oil level in the crankcase, and over time it falters and starts to lie.
Conclusion
N74 engines are quite reliable, subject to quality and regular maintenance.
The main enemy of this motor is high operating temperature, and qualified service every 7-8 thousand km will be the best prevention and regular diagnostics.
In February of this year, it became known that BMW intends to stop producing V12 engines – they are increasingly difficult to adapt to tightening eco-standards.
In addition, the demand for models with top-end 12-cylinder engines is low. V12 engines, including the N74, will remain only on Rolls-Royce cars.
