Cat 3612 Specifications
| Engine Model: Caterpillar 3612 |
| Engine Type: 4-cycle 12-cylinder direct injection liquid-cooled diesel |
| Total Displacement: 13527 cu.in (221.7 L) |
| Rated Engine Power: 2400-4200 Hp (1790-3130 kW) at 2000 rpm |
| Aspiration Type: Turbocharged |
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The Caterpillar 3612 is a high-output,
heavy-duty V12 diesel engine engineered for continuous-duty industrial,
power-generation, and marine propulsion applications. Part of the
renowned CAT 3600 engine family, the 3612 is recognized for its
exceptional durability, long overhaul life, low specific fuel
consumption, and ability to operate reliably under sustained high-load
conditions. Designed for large mechanical drive systems, offshore
equipment, drilling applications, compressor drives, and marine
propulsion, the 3612 offers massive torque, stable operation, and robust
structural integrity essential for severe-duty environments.
With a displacement exceeding 46 liters, advanced turbocharging, modular
construction, and CAT’s established heavy-frame design, the 3612 has
demonstrated proven performance in harsh environments worldwide.
Operators rely on the engine for long service intervals, excellent fuel
efficiency, clean combustion for its class, and straightforward
maintenance procedures enabled by its modular, service-friendly layout.
The Caterpillar 3612 is a four-stroke, water-cooled, V12 diesel engine
with direct injection and turbocharging. Total displacement is
approximately 221.7 liters (13,527 cubic inches). Bore is about 280 mm
(11.02 in), and stroke is approximately 300 mm (11.81 in). The engine
uses a 60° V configuration for optimal balance.
Compression ratio typically ranges from 13.0:1 to 14.5:1 depending on
emissions tier, turbocharger configuration, and application.
Output ratings vary widely based on
application:
– Industrial/mechanical drive: 2,400–4,200 hp (1,790–3,130 kW)
– Marine propulsion: 2,800–4,100 hp (2,090–3,060 kW)
– Generator-drive: 1,800–3,900 kW at 720–1,000 rpm
Peak torque often exceeds: 15,000–20,000 Nm (11,063–14,750 lb-ft),
depending on calibration.
Rated speeds typically fall between:
– 720 rpm
– 900 rpm
– 1,000 rpm
Firing order varies by configuration but generally follows CAT’s
standard V12 sequence optimized for vibration reduction.
The crankshaft is a massive forged-steel component supported by multiple
large main bearings with high-strength bearing caps. Pistons are forged
aluminum or steel-crown composite types with internal cooling galleries.
Connecting rods are forged steel with heavy-duty bearings designed for
long-term continuous load.
The 3612 block is a cast-iron, reinforced heavy-frame structure designed
for very long service life. Each bank supports six cylinders with
replaceable wet sleeves, allowing full rebuild without machining the
parent bore. Deep cross-bolted main-bearing saddles, longitudinal
reinforcing ribs, and exceptionally thick structural members ensure
rigidity under extreme cylinder pressures.
Each cylinder has its own cylinder head (individual-head design),
significantly improving serviceability. Heads are cast iron with
direct-injection combustion chambers and four valves per cylinder: two
intake and two exhaust.
Valve lash (cold):
– Intake: 0.30–0.40 mm (0.012–0.016 in)
– Exhaust: 0.60–0.70 mm (0.024–0.028 in)
Large valve diameters and high-flow ports support efficient combustion
at low engine speeds. The camshaft system varies: some versions use a
single cam per bank; others use modular cam segments. Camshafts are
gear-driven.
The 3612 uses heavy-duty direct injection. Fuel systems vary between
mechanically governed and electronically controlled high-pressure fuel
systems depending on production era.
Fuel system features:
– Inline mechanical or electronically controlled pumps
– High-capacity lift pumps
– Multi-stage filtration with water separation
– Individual mechanical injectors or electronically governed unit
injectors
Injection pressures:
– Mechanical systems: 600–900 bar
– Electronic/modern systems: 1,200–1,500 bar
Fuel-system maintenance:
– Primary/secondary filters every 250–500 hr
– Injector testing every 2,000–3,000 hr
– Pump timing/inspection during major overhaul.
The lubrication system is a full-pressure wet- or dry-sump design
depending on application. A large gear-driven oil pump circulates oil
through full-flow filters and optional centrifugal bypass filters.
Oil capacity: 400–700 liters (105–185 gallons), depending on
configuration
Oil pressure:
– Operating: 350–500 kPa (50–72 psi)
– Idle: 120–200 kPa (17–29 psi)
Lubrication targets include main bearings, rod bearings, piston cooling
jets, camshaft bearings, turbocharger bearings, and accessory drives.
Cooling is handled by high-capacity centrifugal pumps moving large
coolant volumes through block, heads, oil coolers, and aftercoolers.
Cooling-system features:
– Dual-circuit cooling (jacket water + aftercooler water)
– Thermostats regulating flow to maintain 82–95°C (180–203°F) operating
temperatures
– Marine engines use seawater-cooled heat exchangers
Cooling capacity: 600–1,000 liters (158–264 gallons), depending on
installation
System pressure: 70–120 kPa (10–17 psi).
| Intake and Exhaust Systems |
Turbocharging is standard. Some engines use
twin-turbo setups with aftercooling via:
– Jacket-water aftercoolers (JWAC)
– Seawater aftercoolers (SWAC)
– Air-to-water aftercoolers
Air filtration system:
– Large dual-stage industrial filters
– Optional cyclone pre-cleaners
– Marine air silencers
Exhaust:
– High-temperature cast-iron manifolds
– Optional water-cooled marine exhaust elbows.
| Electrical and Starting Systems |
The 3612 uses 24-volt electrical systems.
Components:
– Alternators: 50–130 amps
– Starters: 10–20 kW
– Sensor suite for monitoring coolant temperature, oil pressure, boost
pressure, speed, and various protection circuits
Electronic versions use an ECM to manage:
– Fuel delivery
– Load sharing
– Engine protection
– Diagnostics.
Depending on configuration, the engine
supports:
– PTOs
– Hydraulic pump drives
– Compressor drives
– Generator heads
– Marine gearboxes
– Remote cooling systems
– Air-start systems (optional).
Approximate dimensions (vary by
configuration):
– Length: 3,100–3,500 mm (122–138 in)
– Width: 1,400–1,700 mm (55–67 in)
– Height: 1,800–2,200 mm (71–87 in)
Dry weight: 9,000–11,000 kg (19,800–24,250 lb).
– Oil/filter: 500 hr
– Fuel filters: 250–500 hr
– Air filters: inspect 100 hr
– Coolant: replace every 2–3 years
– Valve adjustment: every 1,500–2,000 hr
– Injector service: 2,000–3,000 hr
– Compression: 5,000 hr
– Turbocharger inspection: 3,000–5,000 hr.
– Cylinder head bolts: 400–500 Nm (295–369 lb-ft)
– Main bearing caps: 1,200–1,600 Nm (885–1,180 lb-ft)
– Connecting-rod bolts: 450–550 Nm (332–406 lb-ft)
– Flywheel bolts: 900–1,100 Nm (664–811 lb-ft)
– Crank pulley bolt: 1,300–1,600 Nm (958–1,180 lb-ft)
– Oil drain plug: 120–180 Nm (89–133 lb-ft)
– Injector hold-downs: 50–60 Nm (37–44 lb-ft).
The Caterpillar 3612 is used in:
– Marine propulsion (freighters, ferries, offshore vessels)
– Offshore drilling equipment
– Gas compressor drives
– Mechanical-drive pumps
– Large industrial power modules
– Generator sets (1–4 MW classes).
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