Cat C6.6 Specifications
| Engine Model: Caterpillar C6.6 |
| Engine Type: 4-cycle 6-cylinder common-rail direct injection ADEM liquid-cooled diesel |
| Total Displacement: 403 cu.in (6.6 L) |
| Rated Engine Power: 125-250 Hp (93-186 kW) at 2200 rpm |
| Aspiration Type: Turbocharged |
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The Caterpillar C6.6 is a mid-displacement,
electronically controlled, turbocharged inline six-cylinder diesel
engine engineered for construction, agricultural, forestry, and
industrial applications. It was developed as a successor to earlier CAT
3126/C7 family designs, offering improved power density, better fuel
efficiency, refined combustion through ACERT technology, and compliance
with Tier 3, Tier 4 Interim, and Tier 4 Final emissions regulations.
Used widely in wheel loaders, excavators, telehandlers, agricultural
sprayers, forestry harvesters, and generator sets, the C6.6 is valued
for its reliability, long service intervals, smooth operation, and
robust cast-iron construction. Its compact dimensions allow easy
integration into a wide range of OEM equipment platforms.
The Caterpillar C6.6 is a four-stroke, water-cooled, turbocharged
direct-injection inline six-cylinder diesel engine with displacement of
approximately 6.6 liters (403 cubic inches). Bore is typically 105 mm
(4.13 in), and stroke is 127 mm (5.00 in), giving it a long-stroke
configuration that favors strong low- and mid-range torque.
Power ratings:
— Construction/industrial: 125–250 hp (93–186 kW) @ 1,800–2,400 rpm
— Agricultural: 140–225 hp (104–168 kW)
— Generator sets: 90–200 kW at 1,500–1,800 rpm
Compression ratio varies by emissions tier, generally ranging from
16.0:1 to 17.0:1. Peak torque: 500–900 Nm (369–664 lb-ft) @ 1,400–1,600
rpm. Idle speed: 700–800 rpm. Maximum governed speed: 2,200–2,400 rpm.
Firing order: 1-5-3-6-2-4.
The crankshaft is forged steel with full counterweights and supported by
seven main bearings. Pistons are cast-aluminum alloy with steel crowns
or reinforced bowls for high cylinder pressures. Connecting rods are
forged steel with replaceable bearing inserts.
The block is cast iron with parent-bore cylinders and deep structural
ribbing for rigidity. The crankcase design includes reinforced
main-bearing saddles and a robust skirt structure. Coolant passages
fully surround the cylinders to reduce thermal gradients and prolong
engine life.
The head is cast iron with four valves per cylinder—two intake and two
exhaust. Combustion chambers are optimized for efficient direct
injection and low-emissions performance. The valvetrain uses pushrods
and rocker arms actuated by a gear-driven camshaft.
Typical valve lash (cold):
— Intake: 0.25–0.30 mm (0.010–0.012 in)
— Exhaust: 0.30–0.35 mm (0.012–0.014 in).
The C6.6 employs a high-pressure common-rail fuel system controlled by
an ADEM ECM. Injection pressures are typically in the range of
1,200–1,800 bar.
Fuel-system features:
— Electronic injection timing and quantity control
— Multi-event injection for improved combustion
— Water separator with drain
— High-efficiency filtration
— Optional fuel-transfer pump depending on installation
Fuel-system maintenance:
— Replace filters every 250–300 hr
— Drain water separator as required
— Inspect injectors every 1,000–1,500 hr.
A full-pressure wet-sump lubrication system is used with a gear-driven
oil pump.
Oil capacity: 14–18 liters (14.8–19.0 qt)
Operating oil pressure: 300–450 kPa (44–65 psi)
Idle oil pressure: 100–150 kPa (15–22 psi)
Recommended oil grades: SAE 10W-30 or 15W-40 (API CI-4, CJ-4, CK-4)
Oil change intervals: 250 hours (industrial/agricultural duty).
Cooling is provided by a belt-driven or gear-driven centrifugal water
pump depending on configuration.
Thermostat characteristics:
— Begins opening: 82°C (180°F)
— Fully open: 95°C (203°F)
Cooling-system capacity: 20–25 liters (21–26 qt)
Cooling-system pressure: 70–100 kPa (10–15 psi).
| Intake and Exhaust Systems |
Turbocharging is standard across all C6.6 models. Many versions include
air-to-air aftercooling.
Air filtration options:
— Dry dual-stage filters
— Cyclone pre-cleaners (agriculture/forestry)
— High-capacity industrial filters
Exhaust systems may incorporate DOC, DPF, and SCR depending on emissions
tier. Exhaust manifolds are cast iron.
| Electrical and Starting Systems |
Electrical systems are available in 12-volt and 24-volt configurations.
Components include:
— Alternator: 80–150 amps
— Starter motor: 4–6 kW
— ECM sensors: boost, oil pressure, coolant temperature, fuel
temperature, intake temperature, crankshaft position, camshaft position,
emissions sensors
The ADEM ECM manages:
— Fuel injection
— Turbocharger performance
— Aftertreatment
— Engine-protection logic
— Diagnostic monitoring.
C6.6 engines may be configured with:
— PTO drive pads
— Hydraulic pump drives
— Air compressors
— Remote cooling systems
— Generator heads
— Belt-driven auxiliaries.
Approximate dimensions:
— Length: 1,050–1,200 mm (41–47 in)
— Width: 750–900 mm (30–35 in)
— Height: 950–1,150 mm (37–45 in)
Dry weight: 570–680 kg (1,257–1,499 lb).
— Oil and filter: 250 hr
— Fuel filters: 250–300 hr
— Air filter: inspect every 50 hr
— Coolant: replace every 2 years
— Valve-lash adjustment: 1,000 hr
— Injector inspection: 1,000–1,500 hr
— Compression test: 2,000 hr
— Belt inspection: every service cycle.
— Cylinder head bolts: 200–230 Nm (148–170 lb-ft)
— Main-bearing caps: 260–300 Nm (192–221 lb-ft)
— Connecting-rod bolts: 110–130 Nm (81–96 lb-ft)
— Flywheel bolts: 240–280 Nm (177–207 lb-ft)
— Crankshaft pulley bolt: 300–350 Nm (221–258 lb-ft)
— Oil drain plug: 40–55 Nm (30–41 lb-ft)
— Injector hold-down bolts: 25–30 Nm (18–22 lb-ft).
The Caterpillar C6.6 engine is used in:
— Wheel loaders
— Excavators
— Compact track loaders
— Forestry harvesters
— Agricultural sprayers
— Industrial pumps and compressors
— Generator sets (90–200 kW)
— Material handlers
— Telehandlers.
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