{{Infobox automobile engine |name=BMW M40 engine |manufacturer=BMW |production=1987–1994 |configuration=Naturally aspirated straight-4 |displacement= {{unbulleted list | {{convert|1596|cc|L|1|abbr=on|disp=flip}} | {{convert|1796|cc|L|1|abbr=on|disp=flip}} }} |bore={{convert|84|mm|in|2|abbr=on}} |stroke={{convert|72|mm|in|2|abbr=on}}<br/>{{convert|81|mm|in|2|abbr=on}} |predecessor=BMW M10 |successor=BMW M43 |valvetrain = SOHC |fueltype=Petrol |fuelsystem=Fuel injection |coolingsystem=Water cooled |image = M40B16.JPG |management=Bosch Motronic 1.3 or 1.7 |block=Cast iron |head=Aluminium }}

The '''BMW M40''' is an SOHC straight-four petrol engine which was produced from 1987 to 1994.<ref name="M40B18 Archive">{{cite web |title=BMW M40B18 automotive engine |url=https://bmw-grouparchiv.de/research/detail/index.xhtml?id=3942278 |website=bmw-grouparchiv.de |accessdate=15 August 2019 |archive-date=5 November 2018 |archive-url=https://web.archive.org/web/20181105045345/https://bmw-grouparchiv.de/research/detail/index.xhtml?id=3942278 |url-status=dead }}</ref><ref name="M40B16 Archive">{{cite web |title=BMW M40B16 automotive engine |url=https://bmw-grouparchiv.de/research/detail/index.xhtml?id=3942253 |website=bmw-grouparchiv.de |accessdate=15 August 2019 |archive-date=5 November 2018 |archive-url=https://web.archive.org/web/20181105045108/https://bmw-grouparchiv.de/research/detail/index.xhtml?id=3942253 |url-status=dead }}</ref> It served as BMW's base model four-cylinder engine and was produced alongside the higher performance BMW M42 DOHC four-cylinder engine from 1989 onwards.

Compared with its M10 predecessor, the M40 uses a belt-driven camshaft,<ref name="e30zone">{{cite web|title=M40 - E30 Zone Wiki|url=http://www.e30zone.net/e30zonewiki/index.php/M40|website=www.e30zone.net|accessdate=27 January 2017|language=en|archive-date=4 October 2008|archive-url=https://web.archive.org/web/20081004061209/http://www.e30zone.net/e30zonewiki/index.php/M40|url-status=dead}}</ref> and hydraulic tappets. Like the M10, the M40 uses an iron block and an aluminium head. Fuel injection for the E30 versions is Bosch Motronic 1.3,<ref>{{cite web|title=3' E30 318i Uncoded DME control unit|url=http://www.realoem.com/bmw/enUS/showparts?id=AF51-EUR-04-1990-E30-BMW-318i&diagId=12_0856#12141734100|website=www.realoem.com|accessdate=1 February 2017}}</ref> and the E36 versions use Bosch Motronic 1.7.<ref>{{cite web|title=3' E36 318i Uncoded DME control unit|url=http://www.realoem.com/bmw/enUS/showparts?id=CA31-EUR-03-1990-E36-BMW-318i&diagId=12_1979#12140028569|website=www.realoem.com|accessdate=1 February 2017|date=27 October 1975}}</ref><ref name="usautoparts">{{cite web |author=Roy McNeill, Copyright BMW World 1999–2005 |url=http://www.usautoparts.net/bmw/engines/4cyl.htm |title=BMW World – 4-Cylinder Engines |publisher=Usautoparts.net |accessdate=2012-05-29 |url-status=dead |archiveurl=https://web.archive.org/web/20140302135705/http://www.usautoparts.net/bmw/engines/4cyl.htm |archivedate=2014-03-02 }}</ref>

Following the introduction of the BMW M43 engine in 1991, the M40 began to be phased out.

== Versions == {|class="wikitable sortable" |- ! Version !!Displacement!!Power!!Torque!!Year |- |'''M40B16-''' <br/> E30 version || rowspan=2| {{cvt|1596|cc|cuin|1}} || {{cvt|73|kW|PS hp|0}} <br/> at 5,500 rpm || {{cvt|141|Nm|lbft|0}} <br/> at 4,250 rpm ||1987 |- |'''M40B16-''' <br/> E36 version ||{{cvt|75|kW|PS hp|0}} <br/> at 5,500 rpm || {{cvt|143|Nm|lbft|0}} <br/> at 4,250 rpm ||1991 |- |'''M40B18-''' <br/> E30 version || rowspan=2| {{cvt|1796|cc|cuin|1}} || {{cvt|83|kW|PS hp|0}} <br/> at 5,500 rpm || {{cvt|162|Nm|lbft|0}} <br/> at 4,250 rpm||1987 |- |'''M40B18-''' <br/> E36 version || {{cvt|85|kW|PS hp|0}} <br/> at 5,500 rpm || {{cvt|165|Nm|lbft|0}} <br/> at 4,250 rpm ||1991 |}

== M40B16 == The M40B16 is a {{convert|1596|cc|cuin|1|abbr=on}} version of the M40, which has a bore of {{convert|84|mm|in|1|abbr=on}} and a stroke of {{convert|72|mm|in|1|abbr=on}}.<ref name="unixnerd">{{cite web|title=BMW M40 and M43 Four Cylinder Engines|url=http://www.unixnerd.demon.co.uk/m40.html|website=www.unixnerd.demon.co.uk|accessdate=10 February 2017|archive-date=28 September 2015|archive-url=https://web.archive.org/web/20150928214048/http://www.unixnerd.demon.co.uk/m40.html|url-status=dead}}</ref> It produces {{Convert|73|kW|0|abbr=on}} and {{convert|105|lbft|Nm|0|abbr=on|order=flip}}.<ref>{{cite web|url=http://www.bmwheaven.com/database/engine.php?type=M40 |title=BMW Heaven Specification Database &#124; Engine specifications for M40 engines |website=www.bmwheaven.com |date= |accessdate=2012-05-29}}</ref>

Applications: *1988–1994 316i (E30) *1990–1994 316i (E36) *1992–1993 Bertone Freeclimber 2

== M40B18 == The M40B18 is a {{cvt|1796|cc|cuin|1}} version of the M40, which has a bore of {{cvt|84|mm|in|1}} and a stroke of {{cvt|81|mm|in|1}}.<ref name="unixnerd" /> It produces {{cvt|83|kW|PS|0}} and {{cvt|120|lbft|Nm|0|order=flip}}.<ref name="usautoparts" />

Applications: *1987–1994 318i (E30) *1992–1993 318i (E36) *1989-1994 518i (E34)

== See also == * List of BMW engines

== References == {{Reflist}}

{{BMW automotive petrol engines: 1960s to 1980s}}

M40 Category:Straight-four engines Category:Gasoline engines by model Category:1980s automobile engines