Brief description:

M 271 EVO
From September 2009 the M 271 EVO will be used in
the BlueEFFICIENCY models of the CClass and
EClass. There are three power variants: 115, 135 and
150 kW.
The development of the M 271 EVO combines the
following objectives:
• Improved responsiveness due to increased power
and higher torque
• Improved comfort thanks to smoother running
• Significantly lower fuel consumption and reduced
CO2 emissions
• Compliance with the Euro 5 standard
The M 271 EVO therefore combines the
BlueEFFICIENCY requirements for economy and
environmental compatibility with comfort and driving
pleasure.
These objectives are realized by a variety of technical
innovations and improvements:
• Lownoise and lowmaintenance chain drive
• Camshaft adjustment
• Lanchester balancer
• Homogeneous direct injection with 140 bar
injection pressure
• Fuel injectors
• Quantitycontrolled fuel pump
• Turbocharger
• Lambda control
• Secondary air injection for rapid heating of the
catalytic converter
• Twodisk thermostat with threedisk functionality
• Radiator shutters
• Regulated oil pump with high efficiency
• Ignition system
• ECO start/ stop system
Overview of new features and improvements
1 Exhaust system with turbocharger, optimized lambda control and secondary air injection
2 Ignition system
3 Homogeneous direct injection with quantitycontrolled fuel pump
4 Fuel injectors
5 ECO start / stop system
6 Regulated oil pump
7 Lanchester balancer
8 Radiator shutters
9 Twodisk thermostat with threedisk functionality
10 Lownoise and lowmaintenance chain drive with optimized camshaft adjustment

Cylinder head:

The cylinder head and the intake valves have been
adapted to cope with the demands of homogeneous
direct injection.
The M 271 EVO operates according to the fourvalve
concept with two camshafts, two camshaft adjusters
and central spark plugs.

Camshaft adjuster
The camshaft adjusters of the forged intake and
exhaust camshafts are vanecell adjusters and have
been further improved. They allow the timing to be
varied steplessly and more quickly than before.
The camshaft adjuster is a hydraulic swivel drive. The
adjustment angle is 40° (crank angle) – corresponding
to an angle of 20° performed at the adjuster
(exhaust). The adjustment of the camshafts optimizes
the engine torque curve and improves exhaust charac
teristics.
A springloaded pin locks the camshaft adjuster in the
basic position when the engine is switched off in order
to prevent uncontrolled movement of the adjuster
during startup.
The new camshaft adjuster is 34% lighter while the
rate of adjustment is twice as fast.

Crankcase
Crankcase ventilation
The M 271 EVO features two crankcase ventilation
systems:
• Partial load ventilation with single cyclone oil
separator
• Full load ventilation with double cyclone oil
separator
Partial load ventilation
The single cyclone oil separator is responsible for
separating the oil at the partial load ventilation line.
The partial load ventilation line runs from the left
engine support flange into the charge air distribution
line downstream of the throttle valve actuator.
Via an opening in the crankcase the blowby gas (blow
by quantity) flows into the single cyclone separator
which is located behind the left engine support. The oil
separator is in the form of a cyclone: Incoming air is
made to spiral and the resulting centrifugal forces
separate the oil, which flows back into the housing.
The air cleaned in this way leaves the oil separator
through a combination valve installed above the
cyclone, which acts as a check valve in the event of
overpressure in the charge air distribution line and as
an air shutoff valve to protect the catalytic converter.