Mercedes-Benz M266 Specifications
| Engine Model: Mercedes-Benz M266 |
| Engine Type: 4-cycle inline 4-cylinder SOHC 8-valve liquid-cooled gasoline |
| Total Displacement: 91.4 cu.in (1.5 L), 103.7 cu.in (1.7 L), 124.1 cu.in (2 L) |
| Rated Engine Power: 95-193 Hp (70-142 kW) at 5500 rpm |
| Fuel System Type: Sequential multi-point electronic fuel injection |
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The Mercedes-Benz M266 engine is a family of
compact, inline-four cylinder gasoline engines engineered exclusively
for transverse installation in the brand's pioneering front-wheel-drive
compact car platforms. Introduced in 2004, this engine family was
critical to the Mercedes-Benz A-Class (W169) and B-Class (W245).
Its defining characteristic is a steep installation angle of 59 to 60
degrees, which facilitates the innovative "sandwich floor" chassis
design, allowing major driveline components to be positioned beneath the
passenger compartment for enhanced crash safety.
The M266 employs a simple single overhead camshaft (SOHC) layout with
two valves per cylinder, prioritizing packaging, cost-efficiency, and
low-end torque over high-revving power. The family includes naturally
aspirated 1.5L, 1.7L, and 2.0L displacements, alongside a turbocharged
2.0L variant, offering a wide power range for its vehicle applications.
Engine family: Mercedes-Benz M266.
Engine type: Inline-four cylinder, four-stroke Otto cycle, inclined
59-60 degrees.
Displacement: 1498 cc (91.4 cubic inches) for M266.920; 1699 cc (103.7
cubic inches) for M266.940; 2034 cc (124.1 cubic inches) for M266.960
and M266.980 (turbo).
Bore: 83.0 mm (3.268 inches) for all versions. Stroke: 69.2 mm (2.724
inches) for 1.5L; 78.5 mm (3.091 inches) for 1.7L; 94.0 mm (3.701
inches) for 2.0L.
Compression ratio: 11.0:1 for naturally aspirated versions; lower for
turbocharged version.
Maximum power output: 95 Hp (70 kW) at 5200 rpm for M266.920; 116 Hp (85
kW) at 5500 rpm for M266.940; 136 Hp (100 kW) at 5750 rpm for M266.960;
193 Hp (142 kW) at 5000 rpm for M266.980 (turbo).
Maximum torque output: 103 lb-ft (140 Nm) at 3500-4000 rpm for 1.5L; 114
lb-ft (155 Nm) at 3500-4000 rpm for 1.7L; 142 lb-ft (193 Nm) at
3500-4000 rpm for 2.0L naturally aspirated; 207 lb-ft (280 Nm) at
1800-4850 rpm for 2.0L turbo.
Firing order: 1-3-4-2.
Engine orientation: Transverse, inclined.
Aspiration: Naturally aspirated (M266.920/.940/.960); Turbocharged
(M266.980).
Fuel type: Premium unleaded gasoline.
Recommended oil grade: SAE 5W-30 or 5W-40, meeting Mercedes-Benz
specification 229.5.
Oil capacity: 4.5 liters (4.8 U.S. quarts), including filter.
Coolant capacity: 7.0 liters (7.4 U.S. quarts).
The cylinder block is an aluminum alloy casting with integrated grey
cast iron cylinder liners. This construction reduces overall weight
while providing a durable bore surface. The block is a closed-deck
design for increased rigidity. The crankshaft is supported by five main
bearings. The crankshaft is a forged steel component.
Connecting rods are forged from steel. Pistons are aluminum alloy, with
a specific crown design for the required compression ratio. Each piston
is fitted with two compression rings and one oil control ring. The block
is cast and machined to accommodate the extreme installation angle, with
all ancillary mounting points and fluid passages designed accordingly.
The cylinder head is a cast aluminum alloy unit. It uses a single
overhead camshaft (SOHC) valvetrain with two valves per cylinder (one
intake, one exhaust). This simplified design reduces complexity, cost,
and engine height, aiding packaging. Valve actuation is via roller
rocker arms, with hydraulic lash adjusters providing automatic valve
clearance compensation.
The camshaft is driven by a timing chain from the crankshaft. Intake
valves are larger than exhaust valves to promote volumetric efficiency.
Valve seats are hardened, and valve guides are pressed into the head.
The combustion chamber is a pent-roof design.
The fuel system is a sequential multi-port electronic fuel injection
system. It is managed by a Bosch ME 9.7 or Siemens engine control unit.
The system uses a hot-film air mass meter for load calculation. Fuel is
delivered by an in-tank electric fuel pump to a common fuel rail. The
fuel pressure regulator is integrated into the pump module.
The injectors are positioned in the intake manifold. The turbocharged
M266.980 version includes corresponding software mapping and likely a
higher-pressure fuel pump to accommodate increased demand. The system
incorporates knock sensors for ignition timing adjustment.
The lubrication system is a pressure-fed wet-sump design. An oil pump is
driven by the crankshaft. Due to the steep engine angle, the oil pan
design is critical; it is a cast aluminum sump with a specific internal
baffling and oil pickup location to ensure reliable oil supply during
all vehicle maneuvers.
Oil is drawn through a pickup screen, pressurized, and routed through a
full-flow spin-on oil filter. From the filter, oil feeds the main
gallery, supplying the crankshaft bearings, camshaft bearings, and
hydraulic lash adjusters. An oil cooler is integrated into the filter
housing on some versions, particularly the turbocharged model.
The cooling system is a pressurized circuit with an electric coolant
pump on most versions, a design that allows for continued coolant
circulation after engine shutdown (a feature known as "after-run") to
manage turbocharger heat soak on the M266.980. The thermostat is
electronically controlled. The radiator is mounted low in the front of
the vehicle.
The ignition system is a coil-on-plug design. A key feature is the
intake manifold with tumble flaps (on certain versions) to optimize
airflow at low engine speeds; these flaps are vacuum-operated and a
known failure point. The turbocharged version uses a single turbocharger
with an integral wastegate and an air-to-air intercooler.
The external dimensions are compact by design. Approximate length is 500
mm (19.69 inches). Approximate width is 650 mm (25.59 inches).
Approximate height is 600 mm (23.62 inches), crucial for the sandwich
floor concept. The weight of a complete M266 engine varies by
displacement but is approximately 110-120 kg (243-265 lbs) dry, owing to
its aluminum block construction.
Engine oil and filter change interval is 15,000 km (9,321 miles) or
annually under the Flexible Service System. Spark plug replacement
interval is 60,000 km (37,282 miles) or 4 years. The timing chain and
its tensioner are critical maintenance items; inspection for stretching
and guide wear is recommended from 100,000 km (62,137 miles) onward, as
premature wear is a documented concern. The accessory drive belt should
be inspected every 60,000 km. The intake manifold tumble flaps should be
inspected for sticking or failure during major services.
Cylinder head bolts are tightened in a multi-stage angular torque
procedure: final stage is a 90-degree turn. Main bearing cap bolts: 50
Nm (37 lb-ft) plus an additional 90-degree angle. Connecting rod cap
bolts: 30 Nm (22 lb-ft) plus an additional 90-degree angle. Crankshaft
pulley bolt: 200 Nm (148 lb-ft) plus an additional 90-degree angle.
Camshaft sprocket bolt: 100 Nm (74 lb-ft). Spark plugs: 25 Nm (18
lb-ft). Oil drain plug: 40 Nm (30 lb-ft).
The Mercedes-Benz M266 engine family was used exclusively in the
second-generation A-Class (W169, 2004-2012) and the first-generation
B-Class (W245, 2005-2011). Applications include: A 150 (M266.920), A 170
(M266.940), A 200 (M266.960), and the performance-oriented A 200 Turbo
and B 200 Turbo (M266.980).
The engine was not used in any other Mercedes-Benz model line and was
phased out with the introduction of the W176 A-Class and its new engine
family. Its design is intrinsically linked to the specific architecture
of its host vehicles.
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