{{Infobox automobile engine | name = Mercedes-Benz M291<ref>{{cite web|url=https://sportlichleicht.com/info/engines/m291|title=Mercedes-Benz M291 engine|access-date=22 May 2022 |website=sportlichleicht.com}}</ref><ref>{{cite web|url=https://mercedes-benz-publicarchive.com/marsClassic/en/instance/picture/Motor-M-291.xhtml?oid=90362|title=Motor M 291 |website=Mercedes-Benz Public Archive|access-date=22 May 2022}}</ref> | manufacturer = {{flagicon|Germany}} [[Mercedes-Benz]] | production = 1991–1992 | configuration = 180° [[Flat 12 engine]] | displacement = {{cvt|3.5|L|cuin|0|lk=on}} | bore = {{cvt|86|mm|in}} | stroke = {{cvt|50.1|mm|in}} | valvetrain = 48-valve, [[DOHC]], four-valves per cylinder | power = {{cvt|550–718|hp|kW|0|lk=on}}<ref>{{cite web | url=https://www.gtplanet.net/forum/threads/mercedes-benz-sauber-c292-group-c-prototype-1992.333047/ | title=Mercedes-Benz Sauber C292 Group C Prototype 1992 |website=gtplanet.net| date=12 August 2015 }}</ref> | torque = {{cvt|400|N.m|lb.ft}} | fuelsystem = [[Fuel injection]] | oilsystem = [[Dry sump]] }} The '''Mercedes-Benz M291 engine''' is a 3.5-liter [[Flat-twelve engine|flat-12]] [[motor racing|racing]] [[internal combustion engine|engine]], designed, developed and produced by [[Mercedes-Benz]], for their [[Group C]] racing program. It was introduced in 1991, along with their new [[Mercedes-Benz C291]] [[Sports prototype|prototype]] race car chassis.<ref>{{cite web | url=http://www.speedhunters.com/2009/10/retrospective_gt_gt_schumacher_and_mercedes/ | title=Retrospective>> Schumacher and the Mercedes C291 | date=13 October 2009 |website=speedhunters.com}}</ref><ref>{{cite web | last=Goodwin | first=Graham | title=DSC Retro: Mercedes C291, A Star Is Born | website=dailysportscar.com | date=2020-11-04 | url=http://www.dailysportscar.com/2020/11/04/dsc-retro-mercedes-c291-a-star-is-born.html |quote=Mercedes used the interval wisely, as did Jean Todt with the Peugeots. Under the direction of Dr Hiereth, the C291’s injection system was improved with 12 butterfly flaps instead of four, raising the power to 640 horsepower at 13,200 rpm.}}</ref><ref>{{cite web | title=1991→1991 Sauber Mercedes C291 | website=Supercars.net | date=2016-04-22 | url=https://www.supercars.net/blog/1991→1991-sauber-mercedes-c291/}}</ref><ref>{{cite book | url=https://books.google.com/books?id=029YEAAAQBAJ&dq=mercedes-benz+c291+engine+rpm&pg=PT139 | title=SAUBER-MERCEDES – The Group C Racecars 1985–1991: World Champions | isbn=9781787118256 | last1=Starkey | first1=John | date=10 January 2022 | publisher=David & Charles Publishers }}</ref><ref>{{cite web | url=https://historicmotorsportcentral.com/2017/08/25/motorsportfail-the-1991-mercedes-benz-c291/ | title=#MotorsportFail – the 1991 Mercedes-Benz C291 | date=25 August 2017 | website=Historic Motor Sport Central}}</ref>
==Background== The [[1991 World Sportscar Championship|1991 season]] marked the introduction of the [[FIA]]’s new, and controversial, 3.5-liter formula which replaced the highly successful Group C category that had been used in the [[World Sportscar Championship]] since 1982, though due to a small number of entries for the 3.5-liter formula heavily penalized Group C cars (which were subject to weight penalties and started behind the new-style C1 entries on the grid) were allowed to participate in the season's C2 category.
==Engine== The primary feature of the new regulations was the use of a 3.5-liter naturally aspirated engine. This made it impossible for Mercedes-Benz to use the engines from its previous Group C cars. Also, to produce similar power to the Group C cars a 3.5-liter naturally aspirated engine had to be very high-revving and be constructed from different materials in order to rev highly.
As Jaguar was part of Ford since 1990, the [[XJR-14]] could use the proven [[Ford-Cosworth HB engine]] from the [[Benetton B190B]] Formula One car (the engine regulations for the new 3.5-liter formula were identical to Formula One). Mercedes-Benz had to design an all-new purpose-built racing engine and its M-291 3.5 L [[Flat-12]]<ref>{{Cite news|title=That time Mercedes almost built an 18-cylinder engine|url=https://driving.ca/auto-news/news/that-time-mercedes-almost-built-an-18-cylinder-engine|access-date=2021-08-08|website=driving|language=en-CA}}</ref> unit was the result. The engine only produced about {{Convert|550–600|bhp}}, compared to over {{Convert|730|bhp}} produced by [[Mercedes-Benz_M119_engine#5.0|M119 5.0-liter V8 twin-turbo]] found in the C291's predecessor, the [[Mercedes-Benz C11|Sauber-Mercedes C11]].
==Applications== *[[Mercedes-Benz C291]] *[[Mercedes-Benz C292]] (stillborn [[Concept car|concept]])
==References== {{reflist}}
[[Category:Mercedes-Benz engines]] [[Category:V12 engines]] [[Category:Engines by model]] [[Category:Gasoline engines by model]]