Cat 3608 Specifications
| Engine Model: Caterpillar 3608 |
| Engine Type: 4-stroke inline 8-cylinder turbocharged liquid-cooled diesel |
| Total Displacement: 8,909 cu.in (146 L) |
| Rated Engine Power: 2,300-3,300 Hp (1,715-2,460 kW) at 1000 rpm |
| Fuel System Type: Unit Injector |
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The Caterpillar 3608 is a heavy-duty,
industrial diesel engine designed for continuous duty in the most
demanding applications. As part of the renowned 3600 Series, this engine
is a testament to durable engineering, prioritizing longevity,
reliability, and serviceability over transient power peaks. It is a
large-bore, medium-speed power unit intended for prime power generation,
marine propulsion, and heavy industrial drive applications. The engine’s
architecture focuses on a robust in-line configuration, allowing for
“in-frame” overhaul capabilities that minimize downtime.
Its construction utilizes high-strength gray iron for the block and
features individual cylinder heads, a design choice that simplifies
maintenance and improves sealing integrity. Available with either
mechanical or electronic fuel systems depending on the generation, the
3608 is also notable for its fuel flexibility, capable of being
configured to operate on distillate fuels, heavy fuel oil (HFO), or
crude oil, making it a versatile solution for global operations where
fuel quality varies.
Engine Type: 4-cycle, In-line, 8-cylinder diesel.
Displacement: 146 L (8,909 cu.in).
Bore and Stroke: 280 mm x 300 mm (11.0 in x 11.8 in).
Aspiration: Turbocharged and Aftercooled.
Compression Ratio: 13.0:1.
Rotation: Counterclockwise or Clockwise (facing flywheel).
Firing Order: 1-4-7-6-8-5-2-3.
Power Range: 2,300 HP to 3,300 HP (1,715-2,460 kW).
Generator Output (60 Hz): 1,830 ekW to 2,660 ekW (Prime/Standby).
Generator Output (50 Hz): 2,050 kVA to 3,250 kVA.
Rated Speed: 720 RPM to 1000 RPM.
Brake Mean Effective Pressure (BMEP): Approx. 22.4 bar (325 psi) at
rated power.
The cylinder block is a massive, single-piece casting produced from
high-strength gray iron, a material selected for its excellent vibration
damping properties and structural rigidity. The block design is of a
deep-skirt configuration, extending the cylinder walls below the
crankshaft centerline to provide superior support for the main bearing
caps, which are secured with side bolts in addition to vertical
fasteners. This construction minimizes bore distortion and crankshaft
flex under heavy loads.
The block features large, removable side covers that provide direct
access to the connecting rod bearings, main bearings, and crankshaft,
facilitating “in-frame” overhaul procedures without requiring the
engine’s removal from its foundation. The cylinder bores are machined
directly into the block and are fitted with replaceable, water-cooled
cylinder liners. These are wet-type liners that allow for easy
replacement during major overhauls, restoring the engine to original
specifications.
0The engine utilizes individual cylinder heads for each cylinder, a
design choice that significantly improves serviceability and reduces
repair costs compared to a single multi-cylinder head. Each head is an
iron casting that can be removed independently, allowing for targeted
maintenance without disturbing adjacent cylinders.
Each head incorporates a four-valve arrangement - two intake valves and
two exhaust valves - to optimize airflow efficiency, improving both
combustion and scavenging. The valves are actuated by a single overhead
camshaft per cylinder head, driven by a gear train at the flywheel end
of the engine. This gear drive ensures precise timing and eliminates the
maintenance associated with belts or chains.
The valve train includes adjustable bridge pieces and pushrods, allowing
for precise valve lash settings. The individual head design also
improves the sealing of the high-pressure combustion gases, utilizing a
robust metallic gasket to withstand the thermal and mechanical stresses
of continuous high-power operation.
The Caterpillar 3608 is equipped with a fuel system that varies by
production year and engine control module (ECM). Earlier models utilize
a Mechanical Unit Injection (MUI) system. This system relies on a
camshaft-actuated unit injector for each cylinder, delivering fuel at
high pressure for injection directly into the combustion chamber. Fuel
injection timing and duration are mechanically controlled via the engine
governor, known for its simplicity and reliability in remote
applications.
Later models employ an Electronic Unit Injection (EUI) system, managed
by either an ADEM A3 or ADEM A4 ECM. In this configuration, each unit
injector is electronically controlled, allowing the ECM to precisely
regulate injection timing, duration, and pressure based on real-time
sensor inputs such as engine speed, load, and temperature. This results
in improved fuel efficiency, reduced emissions, and enhanced transient
response. The fuel system is designed for high fuel viscosity, a
critical feature for engines configured to operate on Heavy Fuel Oil
(HFO), which requires a heated fuel supply system upstream of the
engine.
The lubrication system is a full-flow, forced-feed design, engineered to
provide a continuous supply of clean oil to all critical moving parts
under extreme operating conditions. A heavy-duty gear-driven pump draws
oil from the sump and routes it through a series of full-flow spin-on or
canister-type oil filters. An integral oil cooler, typically
water-cooled, maintains the oil at a stable temperature to prevent
thermal degradation.
Oil Capacity: 710 to 880 L (188-232 U.S. gal) depending on the sump
type.
Oil Change Interval: 1,000 to 2,000 hours, depending on oil analysis
results and fuel quality.
The system is equipped with a high-capacity sump designed to accommodate
the engine’s tilt angles in marine applications. A centrifugal oil
cleaner is often included as a secondary filtration stage, removing fine
particulate matter that bypasses the primary filters, extending the
service life of both the oil and the engine components.
The cooling system is a high-volume, thermostatically controlled circuit
designed to dissipate the immense heat generated by a 146 L engine. It
features a gear-driven centrifugal water pump that circulates coolant
through the cylinder block, cylinder heads, and the turbocharger
aftercooler. Coolant Capacity: Approx. 440 L (116 U.S. gal) for the
engine only.
The engine utilizes a Separate Circuit Aftercooled (SCAC) system. In
this configuration, the aftercooler (charge air cooler) operates on a
separate, low-temperature cooling circuit independent of the main engine
jacket water system. This allows the intake air to be cooled more
effectively than if it were using the main engine coolant, resulting in
denser air charge, higher power output, and lower peak cylinder
pressures. The main engine jacket water system is designed to maintain
consistent operating temperatures, with thermostats ensuring rapid
warm-up and stable thermal regulation regardless of ambient conditions.
Starting System: Compressed air is the exclusive starting method for the
3608. The engine can be configured with an air starter motor that
engages with a ring gear on the flywheel, or a direct-in-cylinder air
start system where high-pressure air is admitted directly into the
cylinders to initiate rotation. The direct-in-cylinder system is
particularly robust for large-bore engines, providing high starting
torque even in cold conditions.
Air System: The engine is turbocharged to maximize power density.
Depending on the specific power rating, it may utilize single or dual
turbochargers configured for series or parallel operation. The
aftercooler is integral to the SCAC system, reducing intake manifold
temperatures to optimize combustion and component life.
Governor: For MUI engines, a mechanical-hydraulic governor controls the
fuel rack. For EUI engines, the ADEM A3/A4 ECM provides electronic
governing with features such as droop adjustment, speed trimming, and
remote control capabilities.
Weight (Dry): 19,000 kg to 20,410 kg (41,890-45,000 lb) for the engine
only.
Length: 5,034 mm (198 in)
Width: 1,733 mm (68 in)
Height: 3,195 mm (126 in)
Valve Lash (Cold): Intake: 0.60 mm (0.024 in); Exhaust: 1.15 mm (0.045
in)
Oil Filter Change: Every 500 to 1,000 hours, dependent on oil analysis.
Fuel Filter Change: Every 1,000 hours or as indicated by differential
pressure.
Air Filter: Service based on air filter restriction indicator, varying
significantly with ambient dust conditions.
Injector Timing: For MUI engines, timing is set via a specific tool and
measured in degrees of crankshaft rotation. For EUI engines, timing is
controlled electronically and requires no manual adjustment.
Routine maintenance intervals are guided by the engine’s electronic data
logger (on EUI models) or a combination of hour-meter readings and fuel
consumption. The use of Scheduled Oil Sampling (S.O.S.) is mandatory for
maximizing component life, providing predictive data on wear metals and
coolant contamination.
Connecting Rod Nuts: 2,900 Nm (2,140 lb-ft)
Main Bearing Bolts (Vertical): 2,500 Nm (1,840 lb-ft)
Main Bearing Side Bolts: 1,200 Nm (885 lb-ft)
Cylinder Head Nuts (Individual Head): 1,800 Nm (1,330 lb-ft)
Flywheel to Crankshaft Bolts: 1,200 Nm (885 lb-ft)
Injector Clamp Bolt (MUI/EUI): 150 Nm (110 lb-ft)
Rocker Arm Pedestal Nuts: 500 Nm (370 lb-ft)
Marine Propulsion: The engine serves as a primary propulsion unit for a
wide array of vessels including tugboats, push boats, offshore supply
vessels, ferries, and fishing trawlers. Its high torque at low RPM and
ability to run on HFO make it economical for long-haul and
high-towing-force operations.
Marine Auxiliary: As a generator set (genset), the 3608 provides
shipboard electrical power. Its compact in-line footprint is
advantageous for engine room layouts where space is constrained.
Electric Power Generation: In prime power applications, 3608 generator
sets are installed in mines, remote industrial sites, and as continuous
base-load power for isolated grids. They are also utilized in standby
power for critical facilities such as data centers and hospitals where
load acceptance and reliability are critical.
Industrial Drives: The engine is used to directly drive heavy machinery
such as large pumps for irrigation and water management, gas compressors
for pipeline transmission, and crushers in mining and aggregate
operations. Its low rated speed makes it well-suited for applications
requiring sustained power output with minimal wear rates.
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