Cat C3.8 DIT Specifications
| Engine Model: Caterpillar C3.8 DIT |
| Engine Type: 4-cycle inline 4-cylinder common-rail direct injection liquid-cooled diesel |
| Total Displacement: 232 cu.in (3.8 L) |
| Rated Engine Power: 70-115 Hp (52-86 kW) at 2400 rpm |
| Aspiration Type: Turbocharged |
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The Caterpillar C3.8 DIT (Direct Injection
Turbocharged) engine is a modern, high-efficiency, mid-displacement
diesel engine engineered for construction, agricultural, industrial, and
generator-set applications. As part of Caterpillar’s small-to-mid engine
lineup, the C3.8 DIT provides a balance of compact size, high torque
output, low fuel consumption, and emissions compliance. Designed for
both regulated and unregulated markets, the engine delivers dependable
power for compact wheel loaders, telehandlers, agricultural tractors,
skid-steer equipment, industrial pumps, and other machinery requiring
strong mid-range torque and continuous-duty performance.
Built around a robust cast-iron block, high-pressure fuel system,
advanced turbocharging, and electronic engine control (in
emissions-regulated variants), the C3.8 DIT is known for durability,
long overhaul intervals, and stable performance in harsh operating
environments. Its compact exterior and flexible auxiliary configurations
make it suitable for OEMs requiring versatile installation options.
The Caterpillar C3.8 DIT is a four-stroke, water-cooled, inline
four-cylinder diesel engine featuring direct injection and
turbocharging. The engine displacement is approximately 3.8 liters (232
cubic inches). Bore diameter is about 100 mm (3.94 inches), and stroke
length is approximately 120 mm (4.72 inches). The long-stroke
design-enhances pulling power, fuel efficiency, and smoothness at
low-to-mid RPM ranges.
Compression ratio ranges from 16.5:1 to 17.5:1 depending on
configuration and emissions compliance.
Power output varies widely depending on
application and emissions tier:
– Industrial: 75–115 horsepower (56–86 kW) at 2,200–2,500 rpm
– Agricultural: 70–110 horsepower (52–82 kW)
– Generator-drive: 50–90 kW at 1,500–1,800 rpm
Peak torque typically falls between 350 and 450 Nm (258–332 lb-ft) at
1,300–1,700 rpm. Idle speed is commonly 800–900 rpm, and maximum
governed speed usually ranges from 2,400 to 2,600 rpm. Firing order is
1-3-4-2.
The crankshaft is forged steel, fully counterweighted, and supported by
five main bearings for strength and vibration control. Pistons are
cast-aluminum alloy with strengthened crowns and machined
direct-injection combustion bowls. Piston rings include two compression
rings and an oil-control ring. Connecting rods are forged steel with
replaceable bearing inserts. The camshaft is mounted in the block and
driven by gears for long-term timing stability.
The cylinder block is cast iron with thick walls and a rigid crankcase
structure. Deep reinforcing ribs minimize distortion and increase
durability under high cylinder pressures. Parent-bore cylinders allow
for honing and oversizing during overhaul. Coolant passages fully
surround each cylinder for uniform thermal distribution.
The block includes mounting bosses for hydraulic pumps, alternators,
compressors, and powertrain components, making the engine adaptable
across many machine platforms.
The cylinder head is cast iron with direct-injection combustion chambers
and four valves per cylinder—two intake and two exhaust. Valves are
actuated by rocker arms and pushrods derived from a gear-driven
camshaft.
Typical valve lash (cold):
– Intake: 0.20–0.30 mm (0.008–0.012 in)
– Exhaust: 0.30–0.40 mm (0.012–0.016 in)
Hardened valve seats and precision-machined ports promote efficient
airflow and extended wear life.
Fuel delivery depends on emissions certification:
Mechanical DIT versions:
– Mechanical or electronically modulated rotary pump
– Lift pump
– Water separator
– Paper-element fuel filter
– Multi-hole direct-injection nozzles
Injection pressures generally range between 250 and 350 bar.
Tier 4 Final / Stage V (electronic)
versions:
– High-pressure common-rail system
– ECM-controlled piezoelectric or solenoid injectors
– Injection pressures above 1,200–1,800 bar
– Multiple injection events for clean combustion
Fuel system maintenance:
– Replace fuel filters every 250–300 hours
– Drain water separator regularly
– Inspect injectors every 1,000–1,500 hours
– Verify injection timing on mechanical versions.
The lubrication system is a full-pressure wet-sump system with a
gear-driven oil pump. Oil flows through a full-flow filter before
entering the main oil gallery.
Oil capacity: 9–11 liters (9.5–11.6 US quarts)
Operating oil pressure: 300–450 kPa (44–65 psi)
Idle pressure: 100–150 kPa (15–22 psi)
Recommended oil viscosities include SAE 10W-30 and 15W-40 meeting API
CI-4 or higher. Typical oil change interval is 250 hours under
industrial operation.
Cooling is provided by a belt-driven centrifugal water pump circulating
coolant through the block, head, radiator, and optional oil coolers or
aftercoolers. A thermostat regulates coolant flow.
Thermostat opening temperature: 82°C (180°F)
Fully open: 95°C (203°F)
Cooling-system capacity typically ranges from 10 to 14 liters (10.6–14.8
US quarts). System pressure is maintained at 70–100 kPa (10–15 psi).
| Intake and Exhaust Systems |
Turbocharging is standard on DIT versions, significantly improving
torque and fuel efficiency. Some versions include air-to-air
aftercooling for lower intake temperatures.
Air-filtration systems vary:
– Construction: dual-stage dry filters
– Agricultural: cyclone pre-cleaners
– Stationary engines: enclosed industrial filters
The exhaust system uses a cast-iron manifold designed for repeated
thermal cycling. Emissions-certified versions may include DOC, DPF, or
SCR systems.
| Electrical and Starting Systems |
The C3.8 DIT supports 12-volt and 24-volt electrical systems.
Alternators typically produce 40–100 amps. Starter motors range from 2.5
to 4.0 kW.
Electronic versions include an ECM that
manages:
– Fuel injection timing
– Turbocharger response (if VGT-equipped)
– Emissions aftertreatment
– Engine protection (overheat, low oil pressure, overspeed)
Sensors include coolant temperature, oil pressure, crank position, boost
pressure, intake-air temperature, exhaust sensors (aftertreatment), and
fuel temperature.
Depending on installation, the engine may
support:
– Hydraulic pump drives
– PTO drives
– Industrial belt-driven accessories
– Generator heads
– Remote cooling packages
– Air compressors.
Approximate physical dimensions:
– Length: 700–800 mm (27.6–31.5 in)
– Width: 550–650 mm (21.7–25.6 in)
– Height: 750–900 mm (29.5–35.4 in)
Dry weight generally ranges: 300–380 kg (661–838 lb).
– Oil/filter: every 250 hours
– Fuel filters: every 250–300 hours
– Air filter: inspect every 50 hours
– Coolant: replace every 2 years
– Valve adjustment: every 1,000 hours
– Injector inspection: every 1,000–1,500 hours
– Belt inspection: every service interval
– Compression testing: every 2,000 hours.
– Cylinder head bolts: 140–160 Nm (103–118 lb-ft)
– Main bearing caps: 180–210 Nm (133–155 lb-ft)
– Connecting-rod bolts: 70–85 Nm (52–63 lb-ft)
– Flywheel bolts: 160–200 Nm (118–148 lb-ft)
– Crankshaft pulley bolt: 220–260 Nm (162–192 lb-ft)
– Oil drain plug: 35–45 Nm (26–33 lb-ft)
– Injector hold-downs: 25–30 Nm (18–22 lb-ft).
The C3.8 DIT is used in:
– Compact wheel loaders
– Telehandlers
– Agricultural tractors
– Skid-steer and track loaders
– Industrial pumps
– Compressors
– Generator sets
– Forestry equipment
– Hydraulic power units.
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