BMW M73#M73B54

{{Infobox automobile engine

| name = BMW M73 engine

| image = BMW 750iL Individual - Flickr - The Car Spy (21).jpg

| production = 1993–2002

| manufacturer = BMW

| configuration = 60° V12

| valvetrain = SOHC

| timing = Chain

| fueltype = {{ubl|Petrol 95 RON|Hydrogen}}

| displacement = {{convert|5379|cc|L|1|order=flip|abbr=on}}

| bore = {{convert|85|mm|2|abbr=on}}

| stroke = {{convert|79|mm|2|abbr=on}}

| predecessor = BMW M70

| successor = BMW N73

}}

The BMW M73 is a naturally-aspirated, single overhead camshaft (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

Compared with its M70 predecessor, the M73 features an updated roller-rocker valve-train and an increased displacement, due to a bore increase of {{convert|1|mm|in|2|abbr=on}} ending with a cylinder bore of 85mm and a stroke increase of {{convert|4|mm|in|abbr=on}} to have a final piston stroke of 79mm.{{cite web|title=Information on M73 engines|url=http://www.bmwheaven.com/database/engine.php?type=M73#/153|website=www.bmwheaven.com|access-date=5 August 2017}} 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 {{convert|265|kW|PS hp|0|abbr=on}} and {{convert|530|Nm|lbft|0|abbr=on}} 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.{{cite web|title=BMW Super Bild Of The Day: 5.4 liter BMW V12|url=http://www.bmwblog.com/2012/05/24/bmw-super-bild-of-the-day-5-4-liter-bmw-v12/|archive-url=https://archive.today/20130118080006/http://www.bmwblog.com/2012/05/24/bmw-super-bild-of-the-day-5-4-liter-bmw-v12/|url-status=dead|archive-date=January 18, 2013|website=www.bmwblog.com|access-date=5 August 2017}}

These engines have two separate Bosch Motronic engine control units,{{cite book|title=M73 Training Reference Manual|page=2|url=http://www.meeknet.co.uk/E38/Pdf/M73TechBrief.pdf|access-date=10 April 2017}} which are connected to a third single Siemens control unit, called EML.{{cite web|title=E38 750iL Engine electrical system engine |url=http://www.realoem.com/bmw/enUS/showparts?id=GJ01-EUR-07-2001-E38-BMW-750iL&diagId=12_0885|website=www.realoem.com|access-date=10 April 2017}}

The engine utilizes four knock sensors mounted on the heads, a cam position sensor mounted on the right head and two crank sensors, one for each ECU. Throttle by wire is used. Similar to its predecessor, the M70, spark distributors are still present for each cylinder bank.

The hydrogen versions of the engine feature a $\lambda \ge 3.0$ lean burn concept,{{cite journal |last1=Schüers |first1=Andreas |last2=Abel |first2=Alois |last3=Fickel |first3=Hans-Christian |last4=Preis |first4=Michael |last5=Artmann |first5=Richard |date=February 2002 |title=Der Zwölfzylinder-Wasserstoffmotor im BMW 750hL |url=https://link.springer.com/article/10.1007/BF03226613 |journal=MTZ Motortechnische Zeitschrift |volume=63 |issue=2 |pages=100 |doi=10.1007/BF03226613 |access-date=}} which allows quality torque control similar to a Diesel engine (i. e. no engine throttling).{{cite journal |last1=Schüers |first1=Andreas |last2=Abel |first2=Alois |last3=Fickel |first3=Hans-Christian |last4=Preis |first4=Michael |last5=Artmann |first5=Richard |date=February 2002 |title=Der Zwölfzylinder-Wasserstoffmotor im BMW 750hL |url=https://link.springer.com/article/10.1007/BF03226613 |journal=MTZ Motortechnische Zeitschrift |volume=63 |issue=2 |pages=103 |doi=10.1007/BF03226613 |access-date=}} 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.

Models

Version	Displacement	Power	Torque	Year
class= "wikitable sortable"
M73B54 \|rowspan=3\|{{convert\|5379\|cc\|cuin\|1\|abbr=on}} \|\|rowspan=2\|{{convert\|240\|kW\|0\|abbr=on}} at 5,000 rpm \|\|rowspan=2\|{{convert\|490\|Nm\|lbft\|0\|abbr=on}} at 3,900 rpm \|\|1994
M73TUB54 \|1998
M73 (Hydrogen){{cite journal \|last1=Schüers \|first1=Andreas \|last2=Abel \|first2=Alois \|last3=Fickel \|first3=Hans-Christian \|last4=Preis \|first4=Michael \|last5=Artmann \|first5=Richard \|date=February 2002 \|title=Der Zwölfzylinder-Wasserstoffmotor im BMW 750hL \|url=https://link.springer.com/article/10.1007/BF03226613 \|journal=MTZ Motortechnische Zeitschrift \|volume=63 \|issue=2 \|pages=99 \|doi=10.1007/BF03226613 \|access-date=}} \| {{cvt\|150\|kW\|hp\|0}} at 5,800 rpm \|\| {{cvt\|300\|Nm\|lbft\|0}} at 3000/min \|2001

=M73B54=

Applications:

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

=M73TUB54=

Due to more stringent emissions standards, the 1999 model year marked the addition of an electronically heated catalyst,{{cite web|title=BMW M70, M72 and M73 V12 Engines|url=http://www.unixnerd.demon.co.uk/m70.html|website=www.unixnerd.demon.co.uk|access-date=5 August 2017|archive-date=7 January 2016|archive-url=https://web.archive.org/web/20160107232007/http://www.unixnerd.demon.co.uk/m70.html|url-status=dead}} variable MAP thermostat, and water cooled alternator.

Applications:

1998-2001 E38 750i/750iL/L7/hL
1998 Cardi Curara
1999-2002 Rolls-Royce Silver Seraph
2009–2010 Simbol Design Lavazza GTX
2013 Monte Carlo Automobile Rascasse

= M72B54 prototype=

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 {{convert|265|kW|hp|0|abbr=on}} and {{convert|530|Nm|lb·ft|0|abbr=on}} respectively.{{cite web|title=BMW M72 twelve-cylinder four-valve engine|url=http://www.mwrench.com/pictures/general/V12%2048%20valve.jpg/|website=www.mwrench.com}}

Awards

1999 International Engine of the Year - Best Above 4.0 Litre category winner