BMW M73

From Wikipedia, the free encyclopedia
BMW M73 engine
BMW 750iL Individual - Flickr - The Car Spy (21).jpg
Overview
ManufacturerBMW
Production1993–2002
Layout
Configuration60° V12
Displacement5.4 L (5,379 cc)
Cylinder bore85 mm (3.35 in)
Piston stroke79 mm (3.11 in)
ValvetrainSOHC
Timing drive systemChain
Combustion
Fuel type
Chronology
PredecessorBMW M70
SuccessorBMW N73

The BMW M73 is a naturally-aspirated, SOHC, V12 petrol engine which replaced the BMW M70 and was produced from 1993 to 2002. It was used in the BMW E38 7 Series, E31 8 Series and Rolls-Royce Silver Seraph.

Design[edit]

Compared with its M70 predecessor, the M73 features an updated roller-rocker valve-train and an increased displacement, due to a bore increase of 1 mm (0.04 in) ending with a cylinder bore of 85mm and a stroke increase of 4 mm (0.16 in) to have a final piston stroke of 79mm.[1] While most other engines in the BMW range had switched to dual overhead camshafts with four valves per cylinder, the M73 used a single overhead camshaft and with two valves per cylinder. However, BMW engineers did create a prototype four-valve per cylinder V12, called the M72, which developed 265 kW (360 PS; 355 hp) and 530 N⋅m (391 lb⋅ft) of torque. However, this 48-valve engine did not fulfill the comfort demands of the large sedan class in all respects and, as a result, did not go into production.[2]

Some versions of the engine have two separate Bosch Motronic engine control units,[3] while others use a single Siemens ECU.[4]

The hydrogen versions of the engine feature a lean burn concept,[5] which allows quality torque control similar to a Diesel engine (i. e. no engine throttling).[6] Due to the lower LHV of a hydrogen-air mixture, and the fact that the engine was designed as a Bi-Fuel (petrol and hydrogen) engine, the power output is reduced by 38 per cent compared to the petrol only version of the engine.[5]

Models[edit]

Version Displacement Power Torque Year
M73B54 5,379 cc (328.2 cu in) 240 kW (322 hp)
at 5,000 rpm
490 N⋅m (361 lb⋅ft)
at 3,900 rpm
1994
M73TUB54 1998
M73 (Hydrogen)[7] 150 kW (201 hp) at 5800/min 300 N⋅m (221 lb⋅ft) at 3000/min 2001

M73B54[edit]

Applications:

  • 1994-1998 E38 750i/750iL/L7
  • 1994-1999 E31 850Ci

M73TUB54[edit]

Due to more stringent emissions standards, the 1999 model year marked the addition of an electronically heated catalyst,[8] variable MAP thermostat, and water cooled alternator.

Applications:

M72B54 prototype[edit]

In 1989, as part of a feasibility study, BMW's engine development department produced a four-valve version of its V12 engine. Only one engine was produced, having an up-sized variant of the M70B50 engine called the M72B54. Bore and stroke was increased to 85mm and 79mm and the total displacement of 5.4L was achieved, matching the values of the standard M73 engine. The power and torque both increased to 265 kW (355 hp) and 530 N⋅m (391 lb⋅ft) respectively.[9]

Awards[edit]

References[edit]

  1. ^ "Information on M73 engines". www.bmwheaven.com. Retrieved 5 August 2017.
  2. ^ a b "BMW Super Bild Of The Day: 5.4 liter BMW V12". www.bmwblog.com. Retrieved 5 August 2017.[dead link]
  3. ^ M73 Training Reference Manual (PDF). p. 2. Retrieved 10 April 2017.
  4. ^ "E38 750iL Engine electrical system engine". www.realoem.com. Retrieved 10 April 2017.
  5. ^ a b Schüers, Andreas; Abel, Alois; Fickel, Hans-Christian; Preis, Michael; Artmann, Richard (February 2002). "Der Zwölfzylinder-Wasserstoffmotor im BMW 750hL". MTZ Motortechnische Zeitschrift. 63 (2): 100. doi:10.1007/BF03226613.
  6. ^ Schüers, Andreas; Abel, Alois; Fickel, Hans-Christian; Preis, Michael; Artmann, Richard (February 2002). "Der Zwölfzylinder-Wasserstoffmotor im BMW 750hL". MTZ Motortechnische Zeitschrift. 63 (2): 103. doi:10.1007/BF03226613.
  7. ^ Schüers, Andreas; Abel, Alois; Fickel, Hans-Christian; Preis, Michael; Artmann, Richard (February 2002). "Der Zwölfzylinder-Wasserstoffmotor im BMW 750hL". MTZ Motortechnische Zeitschrift. 63 (2): 99. doi:10.1007/BF03226613.
  8. ^ "BMW M70, M72 and M73 V12 Engines". www.unixnerd.demon.co.uk. Archived from the original on 7 January 2016. Retrieved 5 August 2017.
  9. ^ "BMW M72 twelve-cylinder four-valve engine". www.mwrench.com.

See also[edit]