Mercedes-Benz M186 engine#M199
{{Infobox automobile engine
|name=Mercedes-Benz M186 engine
|image=Mercedes 300 SL Engine EMS.jpg
|caption=M198 in a 300SL Roadster
|production=1951–1967
|configuration=inline-6
|displacement={{convert|2996|cc|L cuin|1|abbr=on|order=flip}}
|bore={{convert|85|mm|2|abbr=on}}
|stroke={{convert|88|mm|2|abbr=on}}
|valvetrain=SOHC 2 valves x cyl.
|head=Aluminum
|fueltype=Gasoline
|fuelsystem=3 downdraft Solex carburetors
Bosch Fuel injection
|coolingsystem=Water-cooled
|power={{convert|115|–|240|bhp|0|abbr=on}}
|torque={{convert|294|Nm|lbft|0|abbr=on}} (M198 300 SL)
}}
The Mercedes Benz M186 Engine was a 3.0–litre single overhead camshaft inline-6 developed in the early 1950s to power the company's new flagship 300 "Adenauer" (W186) four-door saloon. It made its debut at the Frankfurt Motor Show in April 1951.
Designed to give reliable service under prolonged hard use, the iron block/aluminum head engine featured deep water jackets, an innovative diagonal head-to-block joint that allowed for oversized intake and exhaust valves, reverse-flow cylinder head, thermostatically controlled oil cooling, copper-lead bearings, and a hardened crankshaft.
Variants of the M186 went on to be used in the exclusive 300 S/300 Sc gran tourer, W194 300SL racer, iconic gullwing 300SL sports car and roadster, and Mercedes top-end 112-series 300SE sedans and limousines, and coupes and cabriolets of the early to mid-1960s. Production ended in 1967, four years after the introduction of the 600 Grosser Mercedes and the {{convert|386.4|cuin|L|1|abbr=on|order=flip}} M100 V-8.
The various versions of the engine (M186 – M199) produced from {{convert|115|–|240|bhp|0|abbr=on}} as compression ratios rose and the number of carburetors multiplied or were replaced with fuel-injection.http://wiki.mercedes-benz-classic.com/ Mercedes-Benz classic wiki
While sharing many design features with Mercedes' {{convert|134|cuin|L|1|abbr=on|order=flip}} M180 engine introduced at the same show (such as staggered valve arrangement and rockers running off a single overhead camshaft driven by a duplex cam-chain), the two were of completely different design with little or no inter-changeability of parts.“Six Appeal”, Mercedes Enthusiast, May 2007, pp 52–58
The term "big six" is sometimes used to distinguish the large block 3.0 L M186 from the small block M180 and its derivatives.
{{anchor|M186|M188|M189||M198|M199}}M186 Variants
=M186=
The 3.0–litre ({{convert|2996|cc|L cuin|1|abbr=on}}) M186 was introduced in 1951 for use in the company's flagship 300 "Adenauer" (W186) four-door saloon. It had a slightly under-square bore and stroke of {{convert|85x88|mm|2|abbr=on}}, featured an overhead cam, and an aluminum head with an innovative 30-degree diagonal head-to-block joint that allowed for oversized intake and exhaust valves. Designed to give reliable service under prolonged hard use, the engine featured deep water jackets, thermostatically controlled oil cooling, copper-lead bearings, and a hardened crankshaft.
Fitted with twin downdraft Solex carburetors it produced {{convert|115|bhp|PS kW|0|abbr=on}}http://wiki.mercedes-benz-classic.com/ Mercedes-Benz classic wiki at a 6.4:1 compression ratio.
=M188=
=M189=
The M189 was released in August 1957, replacing the 1955 M199's high-strung Bosch mechanical direct fuel-injection
with a Bosch indirect fuel injection system[https://motoren.vaeth.com/mercedes-benz-300-sel-motor-w109-m189/ Mercedes-Benz 300SEL Motor W109 M189], Vaeth Motors in the (W189) 300d pillarless limousine. The change substantially upped performance from the underpowered {{convert|115|bhp|PS kW|0|abbr=on}} M186 used in the final version of the W186-based 300, the 300c, to {{convert|180|PS|kW hp|0|abbr=on}} at 5500 rpm.{{cite web|author=Jeff Miller |url=http://www.mbzponton.org/valueadded/other/adenauer.htm |title=Mercedes-Benz Type 300 "Adenauer" limousine © www.mbzponton.org |publisher=Mbzponton.org |date=2002-03-02 |accessdate=2010-10-01}}
The engine then appeared in 1961 in the W112 300SE series of sedan, coupe, and cabriolet, as well as its long wheelbase derivative (also called 300SE; the SEL nomenclature would first be used on the subsequent W109 LWB sedans) two years later. From 1964, power output was {{convert|170|hp|0|abbr=on}}. The final incarnation of the M189 was in the W108 300SEb and W109 300SEL of 1965–1967.
=M194=
{{main|Mercedes-Benz M194 engine}}
The M194 engine was developed in 1952 for the W194 300SL racer. Only 10 were made, the first three producing around {{convert|170|kW|hp|0|abbr=on}}, while the remaining seven put out around {{convert|180|kW|hp|0|abbr=on}}.{{Cite news|url=https://www.motortrend.com/news/12q3-1952-mercedes-benz-300sl-w194-00002/|title=1952 Mercedes-Benz 300SL W194 00002 - Motor Trend Classic|date=2013-01-09|work=Motor Trend|access-date=2018-08-16|language=en-US}}
Like the W188 used in the ultra-exclusive 300 S coupé/cabriolet, the M194 was outfitted with three two-barrel Solex carburetors.{{Cite web|url=https://mercedes-benz-publicarchive.com/marsClassic/instance/ko.xhtml?grp=INFOTYPE_RENNWAGEN.R_TECH_DATA.&oid=6855#toRelation|title=Mercedes-Benz 300 SL (W 194) racing sports car, 1952 {{!}} marsClassic|website=marsClassic|language=en-EN|access-date=2018-08-16}} Similar to the M198 used in the production 300SL, the engine is titled 50 degrees to the left in order to reduce the height of the hood, and uses a dry sump lubrication system instead of an oil pan and reservoir.{{Cite magazine|url=https://www.wired.com/2014/08/one-of-historys-most-beautiful-cars-may-also-be-the-most-innovative/|title=One of History's Most Beautiful Cars May Also Be the Most Innovative|magazine=WIRED|access-date=2018-08-16|language=en-US}} It is also mounted behind the front axle for better weight distribution.{{Cite web|url=https://www.hemmings.com/magazine/hsx/2016/11/Legend---1956-Mercedes-Benz-300-SL/3750230.html|title=Legend - 1956 Mercedes-Benz 300 SL|website=www.hemmings.com|access-date=2018-08-16}}
=M198=
File:Mercedes 300 SL Engine EMS.jpg
The high-performance, fuel-injected M198 was created in 1954 for the first generation of the 300SL, known colloquially as the "Gullwing". To fit under its low profile hood the engine was tilted 50-degrees to the left.{{cite book |title=Mercedes 300 SL Technical data booklet |date=1957 |publisher=Daimler-Benz Aktiengesellschaf|edition=MB order no. 6510 1257 00}}{{cite book |title=Mercedes-Benz Workshop Manual Type 300SL |date=1956 |publisher=Daimler-Benz Aktiengesellschaf}} The result for the car was aerodynamic efficiency, and an enormous sand-cast aluminum intake manifold that stretched across the engine's entire breadth.[https://www.hemmings.com/blog/article/1957-63-mercedes-benz-300-sl-roadster-2/ 1957-’63 Mercedes-Benz 300 SL Roadster, hemmings.com] In order to deliver track-ready performance, race-derived features were built in, including a dry sump lubrication system and Bosch mechanical direct fuel-injection, one of the first production cars with fuel injection. This engine originally produced {{convert|215|PS|kW hp|0|abbr=on}} DIN net at 5,800 rpm and {{convert|275|Nm|lbft|0|abbr=on}} DIN net of torque at 4,600 rpm{{cite web
|url=https://www.automobile-catalog.com/car/1954/1460975/mercedes-benz_300_sl_opt__3_42_axle.html
|website=Automobile-catalog.com
|title=1954 Mercedes-Benz 300 SL opt. 3.42 axle
|accessdate=2018-12-08
|first1=Pawel
|last1=Zal}} and {{convert|243|PS|kW hp|0|abbr=on}} net (brake hp) at 6,100 RPM and {{convert|294|Nm|lbft|0|abbr=on}} net torque at 4,800 RPM. An optional high-performance "Sport" camshaft was also available: this was the only available configuration for the Roadster version of the 300 SL when it made its debut in 1957. Production ended in 1964.
=M199=
A significantly detuned version of the 300SL's M198 mechanical direct fuel-injected, dry sump oil system engine was used in the late W188-series 300 Sc of 1955 to 1958, producing {{convert|175|hp|0|abbr=on}} at 5400 rpm and 8.55:1 compression ratio, and {{convert|255|Nm|lbft|0|abbr=on|disp=flip}} at 4300 rpm.[https://mercedes-benz-publicarchive.com/marsClassic/en/instance/ko/300-Sc-Roadster.xhtml?oid=4526 300 Sc Roadster] Mercedes-Benz Archive
It utilized a Bosch 6-plunger injection pump.[https://mercedes-benz-publicarchive.com/marsClassic/en/instance/ko/300-SL--W-198-I-1954---1957.xhtml?oid=4699&ls=L3NlYXJjaHJlc3VsdC9zZWFyY2hyZXN1bHQueGh0bWw_c2VhcmNoU3RyaW5nPTMwMCtzbCZzZWFyY2hJZD0wJnNlYXJjaFR5cGU9ZGV0YWlsZWQmcmVzdWx0SW5mb1R5cGVJZD0yMTU1JnRodW1iU2NhbGVJbmRleD0xJnJvd0NvdW50c0luZGV4PTUmdmlld1R5cGU9bGlzdCZzb3J0RGVmaW5pdGlvbj1TT1JULTE!&rs=3 300 SL], Mercedes-Benz Archive