Mercedes-Benz M273 Specifications
| Engine Model: Mercedes-Benz M273 |
| Engine Type: 4-cycle 8-cylinder V-block DOHC 32-valve liquid-cooled gasoline |
| Total Displacement: 284.6-333.3 cu.in (4.66-5.46 L) |
| Rated Engine Power: 335-388 Hp (250-289 kW) at 6000 rpm |
| Fuel System Type: Sequential multi-point fuel injection |
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The Mercedes-Benz M273 is a family of V8 engines
produced between 2005 and 2013. Developed alongside the M272 V6, it shares much
of its architecture, including the 90-degree V-angle and four-valve-per-cylinder
heads.
This engine family replaced the three-valve M113 V8 and represented a
significant advancement in naturally aspirated V8 technology for Mercedes-Benz,
incorporating dual overhead camshafts, continuous variable valve timing on both
intake and exhaust sides, and a magnesium variable intake manifold.
The M273 was designed to deliver improved power output, enhanced fuel
efficiency, and reduced emissions compared to its predecessor. It was eventually
succeeded by the twin-turbocharged M278, which offered further gains in
efficiency and torque.
The M273 engine is recognized for its robust power delivery, smooth operation,
and the refined characteristics expected of a Mercedes-Benz V8. Its all-aluminum
construction, featuring Alusil cylinder liners, contributes to reduced weight
while maintaining durability. The dual-stage variable intake manifold optimizes
volumetric efficiency across the engine speed range, providing ample low-end
torque for large sedans and SUVs while allowing for strong top-end power.
The continuous variable valve timing on both camshafts enhances throttle
response and fuel economy. However, early production engines are susceptible to
timing chain idler gear wear, a known issue requiring significant repair. Intake
manifold tumble flap actuator failures and camshaft expansion plug oil leaks
represent additional service considerations for higher-mileage examples. Despite
these concerns, the M273 remains a popular choice for its combination of power,
refinement, and the naturally aspirated V8 driving experience.
Engine Type: 90-deg V8, 4-cycle, water-cooled naturally aspirated gasoline
engine.
Valvetrain: DOHC, 32 valves (4 valves per cylinder).
Fuel System: Sequential multi-point fuel injection.
Induction: Magnesium dual-stage variable intake manifold with tumble flaps.
Firing Order: 1-5-4-8-6-3-7-2.
4.7L Variant (M273.92x / E47)
Displacement: 4,663 cc (284.6 cu.in), equivalent to 4.7 L.
Bore: 92.9 mm (3.66 in).
Stroke: 86.0 mm (3.39 in).
Compression Ratio: 10.7:1.
Maximum Power: 335 hp (250 kW) @ 6,000 rpm.
Maximum Torque: 460 Nm (339 lb-ft) @ 2,700-5,000 rpm.
5.5L Variant (M273.96x / E55)
Displacement: 5,461 cc (333.3 cu.in), equivalent to 5.5 L.
Bore: 98.0 mm (3.86 in).
Stroke: 90.5 mm (3.56 in).
Compression Ratio: 10.7:1.
Maximum Power: 382-388 hp (285-289 kW) @ 6,000 rpm.
Maximum Torque: 530 Nm (391 lb-ft) @ 2,800-4,800 rpm.
The cylinder block is constructed from aluminum alloy
utilizing the Alusil (silicon-aluminum) casting process. In this design, the
cylinder bores are formed directly in the aluminum block without cast-iron
liners. The high silicon content creates a hard, wear-resistant surface after
etching, which exposes the silicon crystals to serve as the running surface for
the piston rings.
The block features a 90-degree V-angle with a deep-skirt design extending below
the crankshaft centerline, providing structural rigidity and minimizing
vibration. The cross-bolted main bearing caps, with four bolts per cap, ensure
crankshaft stability under high loads. Integrated oil passages supply the piston
cooling jets and the variable valve timing actuators.
Each cylinder head is manufactured from cast aluminum
alloy and houses the DOHC arrangement with four valves per cylinder. The
pent-roof combustion chambers are optimized for high compression ratios and
efficient flame propagation. Intake valves measure 35.0 mm (1.38 in) in diameter
for the 4.7L variant and 36.0 mm (1.42 in) for the 5.5L variant; exhaust valves
measure 30.0 mm (1.18 in) across both displacements.
The valvetrain utilizes bucket-type tappets with hydraulic lash adjusters,
eliminating the need for manual valve clearance adjustments. The camshafts are
hollow for reduced mass and feature continuous variable valve timing on both
intake and exhaust sides. Adjusters mounted to each camshaft sprocket are
actuated by engine oil pressure, providing a total adjustment range of 40
degrees on the intake side and 38 degrees on the exhaust side.
The fuel system employs a sequential multi-point
injection architecture with returnless fuel delivery. Fuel pressure is regulated
within the fuel tank at 3.8 bar (55 psi) and delivered to the intake manifold
where eight injectors are positioned in the intake ports, each aimed directly at
the back of its respective intake valve. The plastic composite intake manifold,
constructed from magnesium in the upper section and reinforced plastic in the
lower section, houses the dual-stage variable induction system.
Tumble flaps within the intake runners pivot under ECU control to generate swirl
and turbulence at low engine speeds, improving mixture formation and combustion
stability. At higher engine speeds, the flaps open fully to maximize airflow and
volumetric efficiency.
The lubrication system is a forced-feed, wet-sump type
utilizing a rotor-type oil pump mounted to the front of the crankshaft. The pump
is driven directly by the crankshaft nose and features a variable displacement
design to reduce parasitic losses at higher engine speeds. Oil is drawn from a
steel oil pan through a baffled strainer before pressurization.
A full-flow cartridge-type oil filter is mounted externally on the cylinder
block. The system supplies lubricant to the crankshaft main bearings, connecting
rod bearings, camshaft journals, bucket tappets, variable valve timing
actuators, and timing chain tensioners. Piston cooling jets, integrated into the
cylinder block, direct oil to the underside of each piston crown to manage
thermal loads under sustained high-speed operation.
The cooling system is a pressurized, water-cooled setup
utilizing a centrifugal water pump driven by the engine’s serpentine accessory
belt. A wax-type thermostat with a rated opening temperature of 85°C (185°F)
regulates the engine operating temperature. Coolant circulates through the
aluminum cylinder block and cylinder heads before passing through a cross-flow
radiator equipped with an electric cooling fan controlled by the Engine Control
Unit (ECU).
The system incorporates separate coolant circuits for the heater core and, in
certain applications, an auxiliary water pump maintains circulation for cabin
heating during engine idle conditions. The expansion tank is pressurized and
incorporates a coolant level sensor to alert the driver of low coolant
conditions.
| Intake and Exhaust Systems |
Intake System: The magnesium dual-stage variable intake
manifold incorporates a switching mechanism that alters the effective intake
runner length. Long runners are engaged at low engine speeds to enhance low-end
torque, while short runners are selected at higher engine speeds to favor peak
power. The tumble flaps operate independently of the runner length switching.
Exhaust System: A stainless-steel exhaust system with dual outlets is employed.
Each cylinder bank has its own exhaust manifold and downpipe, converging at a
central muffler. The system includes four oxygen sensors (two upstream, two
downstream) for closed-loop fuel control and catalytic converter monitoring.
Ignition System: The engine utilizes a direct ignition
system with individual pencil-type ignition coils mounted directly over each
spark plug. The coil-on-plug design eliminates high-tension spark plug wires.
Iridium-tipped spark plugs are specified for extended service intervals.
Timing System: The camshafts are driven by a dual-chain system from the
crankshaft. A primary chain connects the crankshaft to an intermediate sprocket
mounted on a fixed idler shaft. Secondary chains then drive the left and right
cylinder bank camshafts. Hydraulic chain tensioners maintain proper chain
tension. Early production engines manufactured before September 2006 utilized a
timing chain idler gear with a soft coating; wear on this gear can cause timing
drift and diagnostic trouble codes P0016 or P0017.
Crankshaft Assembly: The forged steel crankshaft is a one-piece casting with
cross-plane design. Forged steel connecting rods feature fracture-split caps for
precise bearing alignment. Aluminum pistons with low-friction ring packs are
utilized to reduce mechanical losses.
Overall Engine Length: 630 mm (24.80 in).
Overall Engine Width: 820 mm (32.28 in).
Overall Engine Height: 710 mm (27.95 in).
Dry Weight: The complete engine assembly weighs 195 kg (430 lb), inclusive of
the intake manifold, fuel system components, and all ancillary systems.
Engine Oil Capacity (with Filter): 8.0 liters (8.5 qt)
for the 4.7L variant; 8.5 liters (9.0 qt) for the 5.5L variant. Engine Oil
Specification: Mercedes-Benz approved oil meeting MB 229.3 or MB 229.5
specification; SAE 5W-30, 5W-40, or 0W-40 viscosity recommended.
Coolant Capacity: 12.0 liters (12.7 qt) inclusive of the radiator and heater
circuits. Spark Plug Type: NGK ILZFR5A or equivalent iridium-tipped plug for
4.7L; NGK ILZFR6D or equivalent for 5.5L. Spark Plug Gap: 1.0-1.1 mm
(0.039-0.043 in). Spark Plug Replacement Interval: 80,000 km (50,000 mi).
Timing Chain Inspection: Inspection of the timing chain idler gear and
tensioners is recommended for engines produced before September 2006. Wear may
be indicated by rattle at startup or check engine light illumination with timing
correlation codes.
Intake Manifold Tumble Flaps: The plastic actuator levers on the intake manifold
are prone to wear in higher-mileage applications. Replacement with metal
aftermarket components is available as an alternative to full manifold
replacement.
Cylinder Head Bolts, Step 1: 40.0 Nm (4.1 kgf-m, 30
lb-ft).
Cylinder Head Bolts, Step 2: 60.0 Nm (6.1 kgf-m, 44 lb-ft).
Main Bearing Cap Bolts: 20.0 Nm (2.0 kgf-m, 15 lb-ft).
Connecting Rod Cap Bolts, Step 1: 20.0 Nm (2.0 kgf-m, 15 lb-ft).
Connecting Rod Cap Bolts, Step 2: 50.0 Nm (5.1 kgf-m, 37 lb-ft).
Camshaft Bearing Cap Bolts: 10.0-12.0 Nm (1.0-1.2 kgf-m, 7-9 lb-ft).
Intake Manifold Bolts: 10.0-12.0 Nm (1.0-1.2 kgf-m, 7-9 lb-ft).
Exhaust Manifold Nuts: 35.0-40.0 Nm (3.6-4.1 kgf-m, 26-30 lb-ft).
Crankshaft Pulley Bolt: 200.0 Nm (20.4 kgf-m, 148 lb-ft).
Spark Plugs: 23.0-25.0 Nm (2.3-2.5 kgf-m, 17-18 lb-ft).
Oil Filter Cartridge Housing: 25.0 Nm (2.5 kgf-m, 18 lb-ft).
Timing Chain Tensioner Bolts: 40.0 Nm (4.1 kgf-m, 30 lb-ft).
Flywheel / Drive Plate Bolts: 100.0 Nm (10.2 kgf-m, 74 lb-ft).
The Mercedes-Benz M273 engine was utilized across the
Mercedes-Benz passenger car and SUV lineup from 2005 through 2013.
Applications include:
4.7L Variant (M273.92x / E47)
GL-Class (X164): GL 450 (2007-2012).
S-Class (W221): S 450 (2006-2009) in select markets.
5.5L Variant (M273.96x / E55)
E-Class (W211): E 500 (2006-2009); (W212): E 500 / E 550 (2009-2011).
S-Class (W221): S 500 / S 550 (2006-2011).
CL-Class (C216): CL 500 / CL 550 (2007-2011).
CLS-Class (C219): CLS 500 / CLS 550 (2006-2010).
M-Class (W164): ML 500 / ML 550 (2006-2011).
GL-Class (X164): GL 500 / GL 550 (2007-2012).
SL-Class (R230): SL 500 / SL 550 (2006-2011).
G-Class (W463): G 500 / G 550 (2008-2012).
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