The BMW N73 is a direct-injection 12-cylinder V-twin gasoline engine that was produced from 2003 to 2016. The BMW N73 replaced the M73 engine, and from 2008 it was gradually replaced by its turbocharged successor, the N74.
The N73 was the world’s first production V12 engine with direct fuel injection.
The motor has an open crankcase, like its predecessor, and the body is made of alusil (aluminum-silicon alloy). The pistons are made of cast aluminum coated with steel, and the crankshaft is forged steel. Cast aluminum was used for the cylinder heads. The N73 has four-valve technology. The B60 variant operates with two MED 9.2.1 engine control units. Compared to its predecessor, the N73 has dual overhead camshafts, dual VANOS (variable valve timing) and Valvetronic (variable valve lift), which varied the intake valve opening lift from 0.30-9.85 mm depending on engine speed and load.
The variable valve timing system is infinitely variable and is present on both the intake and exhaust camshafts. The VANOS units were designed as integral components of the chain drive, and the adjustment ranges are 63 degrees for the intake camshaft and 60 degrees for the exhaust camshaft. The red line for the N73 is 6500 rpm.
N73 Features and Applications
The 6.0-liter N73 atmospheric motor was used in the top-of-the-line 7 Series cars, and its older 6.7-liter model in the Rolls-Royce Phantom.
N73B60 (445 hp and 600 Nm)
2003-2008 – E65 760i
2003-2008 – E66 760Li
N73B67 (460 hp and 720 Nm)
2003-2016 – Rolls-Royce Phantom (RR01)
2007-2017 – Rolls-Royce Phantom Drophead Coupé (RR2)
2008-2017 – Rolls-Royce Phantom Coupé (RR3)
N73 disadvantages and recommendations
The N73 family of motors have not received major revisions from the manufacturer, and their problems are similar to those of the N-series direct-injection atmospheric motors. The major N73 deficiencies are Vanos and Valvetronic system failures, oil consumption and leaks, coking, timing chain and spark plugs.
1. Increased oil consumption and leaks.
Problems with increased oil consumption in N73 are observed after 150 thousand kilometers. Seals also wear out with time. It is necessary to diagnose and eliminate the problem in time to prevent oil starvation of the engine.
2. Vibrations at low speeds.
Uneven operation and vibrations from the engine at low speeds are caused by improperly working Valvetronic system, as well as its failure. The solution is to diagnose and replace the Valvetronic system.
3- Vanos system malfunctions.
Approaching the mark of 150-200 thousand kilometers of mileage should pay attention to the Vanos system and replace the solenoid valves.
4. Coke.
Fouling and deposits are a “disease” of all motors with direct injection – it is necessary to inspect and preventive cleaning of the intake system.
5. What oil should be used in N73?
Synthetic motor oil with viscosity 5W-40 is recommended for the N73 gasoline engine.
In conclusion – is the BMW N73 reliable?
Atmospheric motor BMW N73 is a powerful and reliable engine with a high resource. This motor has no serious drawbacks and if the above mentioned problems are eliminated in time, this motor will serve long and trouble-free. Regular oil change and quality fuel are vital for N73.
With timely maintenance every 10 thousand kilometers, the N73 engine resource is more than 400 thousand kilometers of mileage without major overhaul.