Mercedes-Benz M180 engine#M129

The original {{convert|2196|cc|L cuin|1|abbr=on|order=flip}} carburetted M180 engine was rated at {{convert|80|PS|abbr=on}}. It powered the W187 220 sedan, coupé, and cabriolet (Type A and B) from 1951 to 1955, the W180 220a sedan, coupé, and cabriolet from 1954 to 1956, the W105 219 4-door sedan from 1956 to 1959, and the W111 220b and 220Sb from 1959 to 1965.

It also powered the Unimog 404, a military version of the Unimog, which was built from 1955 until 1980.

The W180 220S sedan, coupe and cabriolet of 1956-1959 received the up-rated twin-carburetor 2.2-litre six M180.924, which initially delivered {{convert|99|hp|kW PS|0|abbr=on}}, raised to {{convert|105|hp|kW PS|0|abbr=on}}.

===M127===

The M180.924 was given Bosch multi-point injection in 1958, redesignated the M127, and used in the luxury W128 220SE sedan, coupe, and cabriolet. Output was raised to {{convert|113-134|bhp|kW PS|0|abbr=on}}.

The M127 continued on in the fuel-injected W111 220SEb introduced in 1959 (which received a lower case ‘b’ {{from whom|reason=Mercedes? By whomever, an authoritative citation is needed in support of the claim.|date=September 2024}} to differentiate the W128 220SE.

The M127’s Bosch-made multi-point injection system operates on an intermittent group injection scheme, with two pistons controlling a group of three cylinders each. The injection pump is mechanically driven, and mechanically controlled. The injection pressure is 15 atü (ca. 1570 kPa). The engine is rated, according to DIN 70020, {{cvt|120|PS|kW|0}} at 4800/min, and produces a maximum torque of {{cvt|19.3|kpm|Nm|0}} at 3900/min, equivalent to a BMEP of {{cvt|11.1|kp/cm2|MPa|2}}. Daimler-Benz achieved this BMEP by using, in addition to the manifold injection, resonance effect induction, giving the engine a volumetric efficiency greater than 100 per cent.{{cite book | last=Bussien | first=Richard | title=Automobiltechnisches Handbuch | publisher=Technischer Verlag Herbert Cram | location = Berlin | date=1965 | isbn=978-3-11-002712-9 | language=de | page=670}}

The M127 was bored out {{convert|2|mm|abbr=on}}, creating a bore × stroke of {{convert|82x72.8|mm|2|abbr=on}} and displacement of {{convert|2307|cc|L cuin|1|abbr=on|order=flip}}, referred to as the M127 II.[https://mbmanuals.com/engines/m127eng.htm M127 II 2.3 Liter Displacement], Mercedes Manuals.com[https://motor-car.net/mercedes/mercedes-engines/item/20047-mercedes-m-127 Mercedes-Benz M127 Petrol Engine], Motor Car History.net With a compression ratio of 9.31 in the W113 it produced {{convert|150|bhp|kW PS|0|abbr=on}} at 5,500 rpm and {{cvt|146|Nm|kpm lbft|0}} at 4,400 rpm.

The M180's stroke was increased to {{convert|2496|cc|L cuin|1|abbr=on|disp=flip}} in 1965 to produce the 2.5 L M108 engine, produced in carbureted form for the new Mercedes-Benz W108 250S. A {{convert|6|mm|abbr=on}} increase resulted in a bore × stroke of {{convert|82x78.8|mm|2|abbr=on}}. A change from four to seven main bearings was necessary in order to smoothly handle the resulting increase in power. A larger capacity oil pump was also specified. Connecting rods were slightly shortened, reflecting the {{convert|6|mm|abbr=on}} longer stroke in a block of unchanged overall height. The redesigned cylinder heads incorporated larger ports, and the valve diameters were increased by {{convert|2|mm|abbr=on}}.

A variant of the 2.5 L M108 was produced for the fuel-injected 250SE, the M129, which received a mechanically controlled six-piston Bosch injector pump in place of the W111 220SE's M127's two plunger pump. The injectors were repositioned to give a more direct angle towards the inlet valve heads. The engine cooling fan received six blades instead of four and incorporated a viscous coupling which activated the fan only when engine speed exceeded 3,000 rpm or the radiator water temperature reached a preset limit.

{{Main articles|Mercedes-Benz M114 engine}}

In 1968 the W114/W115 models were introduced, along with a change to the venerable mid-size six. The M180 engine of the 230/230S was continued in the W114 230 and 230.6, while the M180 of the 250S underwent a few changes and was renamed the M114.{{citation needed|date=August 2019}} This was also available with Bosch D-Jetronic fuel injection, as fitted to the 250CE.

In 1968 the 2.5L M129 of the 250SE was superseded by the 2.8L M130, the ultimate variant of the mid-sized six, obtained by increasing the bore by {{convert|4.5|mm|abbr=on}}. The result was a bore × stroke of {{convert|86.5x78.8|mm|2|abbr=on}}; {{convert|2778|cc|L cuin|1|abbr=on}}), the maximum practical enlargement of the engine given the limitations of the block, which required deletion of water passages between the cylinders. It was used in the W108 280S and 280SE, in the W109 300SEL from December 1967 to January 1970, and in the W113 280SL. It was also used in the W114 250C from July 1969 and 250 (from July 1970) until July 1976 - originally as an export model for the North American market, it substituted the M114 powered 250 and 250C in April 1972 on the home market and retained the 250 badging, as not to confuse with the M110 powered 280 and 280C models, that became available in parallel. https://mercedes-benz-publicarchive.com/marsClassic/en/instance/ko/250-C-28-liter-engine--W-114-V-28-1969---1973.xhtml?oid=4585

{{main|Mercedes-Benz M123 engine}}

The final incarnation of the M180 line of engines was the 2.5L M123, fitted with a Solex four-barrel carburetor in the W123 250 produced between 1975 and 1985.

• Mercedes-Benz M186 engine
• List of Mercedes-Benz engines

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M180

Category:Straight-six engines

Category:Gasoline engines by model