Cat C3.4B Specifications
| Engine Model: Caterpillar C3.4B |
| Engine Type: 4-cycle inline 4-cylinder common-rail direct injection liquid-cooled diesel |
| Total Displacement: 207.5 cu.in (3.4 L) |
| Rated Engine Power: 70-115 Hp (52-86 kW) at 2400 rpm |
| Aspiration Type: Turbocharged |
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The Caterpillar C3.4B is a compact,
high-performance, electronically controlled, turbocharged diesel engine
designed for a wide range of off-highway machines, including compact
construction equipment, agricultural machinery, industrial pumps,
compressors, and generator sets. It represents a modern evolution in
CAT’s small-displacement engine family, integrating high-pressure
common-rail fuel injection, advanced electronic management, air-to-air
aftercooling, and emissions technologies that meet Tier 4 Final / Stage
IIIB / Stage V standards in regulated markets.
The C3.4B balances strong low-speed torque, high fuel efficiency,
reduced noise, and simplified maintenance. With a durable cast-iron
block, robust rotating components, and an electronically optimized
combustion system, the engine is engineered for long overhaul life and
reliable operation even in harsh working environments. Its compact
footprint and multiple auxiliary-drive options make it very attractive
for OEM equipment manufacturers.
The Caterpillar C3.4B is a four-stroke, water-cooled, turbocharged,
direct-injection inline four-cylinder diesel engine. Total displacement
is approximately 3.4 liters (207.5 cubic inches). Bore measures around
99 mm (3.90 in), stroke around 110 mm (4.33 in), creating a long-stroke
layout designed for high torque at low RPM. Compression ratio: typically
16.5:1 to 17.5:1.
Power ratings:
— Industrial and construction: 75–115 hp (56–86 kW) at 2,200–2,500 rpm
— Agricultural: 70–110 hp (52–82 kW)
— Generator-drive: 40–85 kW standby at 1,500–1,800 rpm
Peak torque: 320–420 Nm (236–310 lb-ft) at 1,400–1,700 rpm. Idle speed:
850–950 rpm. Maximum governed speed: 2,400–2,600 rpm. Firing order:
1-3-4-2
The crankshaft is forged steel and supported by five main bearings.
Pistons are cast-aluminum alloy with strengthened crowns and
direct-injection combustion bowls. Connecting rods are forged steel with
precision-machined bearing inserts. A gear-driven camshaft provides
reliable long-term timing stability.
The cylinder block is cast iron with deep structural ribbing for
stiffness and vibration control. It features parent-bore cylinders
capable of multiple overbore rebuilds. Coolant passages completely
surround the cylinder bores for uniform heat distribution and reduced
thermal distortion. The block includes reinforced main-bearing saddles,
a stiff crankcase skirt, and mounting bosses for auxiliary components.
The cylinder head is cast iron with direct-injection combustion chambers
and four valves per cylinder—two intake and two exhaust. This
configuration enhances airflow, combustion efficiency, and emission
performance. The valvetrain consists of rocker arms and pushrods
actuated by the camshaft.
Cold valve-lash settings:
— Intake: 0.20–0.30 mm (0.008–0.012 in)
— Exhaust: 0.30–0.40 mm (0.012–0.016 in).
The C3.4B uses an electronically controlled high-pressure common-rail
fuel system. A supply pump draws fuel through the primary water
separator and delivers it to the high-pressure pump feeding the rail.
Electric or mechanical lift pumps may be used depending on
configuration.
Key fuel-system features:
— Injection pressures: 1,200–1,800 bar
— Multi-event injection for clean combustion
— ECM-controlled injection timing and duration
— High-efficiency dual-stage filtration
— Water-separation protection
Fuel-system maintenance:
— Replace primary and secondary filters every 250–300 hours
— Drain water separator daily
— Inspect injectors every 1,000–1,500 hours
— Maintain ultra-clean fuel to protect high-pressure components.
A full-pressure wet-sump lubrication system is used. A gear-driven oil
pump moves oil through a full-flow filter and delivers it to the main
gallery feeding crankshaft bearings, connecting rods, camshaft bearings,
turbocharger, and valvetrain.
Oil capacity: typically 8–10 liters (8.5–10.6 qt)
Operating oil pressure: 300–450 kPa (44–65 psi)
Idle oil pressure: 100–150 kPa (15–22 psi)
Recommended oils: SAE 10W-30 or 15W-40 diesel oils meeting API CI-4,
CJ-4, CK-4, or better.
Oil-change interval: 250 hours under industrial operation.
Cooling is provided by a belt-driven centrifugal water pump circulating
coolant through block, head, turbocharger center housing, aftercooler
(if equipped), radiator, and optional oil cooler. A thermostat regulates
coolant flow.
Thermostat settings:
— Opening temperature: 82°C (180°F)
— Fully open: 95°C (203°F)
Cooling capacity: typically 10–14 liters (10.6–14.8 qt)
Cooling-system pressure: 70–100 kPa (10–15 psi).
| Intake and Exhaust Systems |
Turbocharging is standard. Many versions include air-to-air aftercooling
to reduce intake temperature and improve torque and emissions
performance.
Air filtration varies by application:
— Construction: dual-stage dry filters
— Agriculture: cyclone pre-cleaners
— Stationary units: high-capacity canister filters
Exhaust systems may include DOC, DPF, and SCR catalysts for emissions
compliance. Exhaust manifolds are cast iron and designed to withstand
repeated thermal cycling.
| Electrical and Starting Systems |
Available in 12-volt and 24-volt configurations. The ECM manages
injection timing, cold-start aid, turbo performance (with optional
wastegate or VGT), engine protection modes, and emissions aftertreatment
monitoring.
Common components:
— Alternator: 40–120 amps
— Starter motor: 2.5–4.0 kW
— Sensors: boost pressure, fuel temperature, coolant temperature, oil
pressure, air-intake temperature, crankshaft position, aftertreatment
pressure/temperature.
Depending on installation, the C3.4B may
support:
— PTO drives
— Hydraulic pump drives
— Air compressors
— Generator heads
— Remote cooling packages
— Belt-driven auxiliary systems.
Approximate physical dimensions:
— Length: 700–820 mm (27.6–32.3 in)
— Width: 550–650 mm (21.7–25.6 in)
— Height: 750–900 mm (29.5–35.4 in)
Dry weight: 280–360 kg (617–794 lb).
— Oil and filter: every 250 hours
— Fuel filters: every 250–300 hours
— Air filter: inspect every 50 hours
— Coolant: replace every 2 years
— Valve lash adjustment: every 1,000 hours
— Injector inspection: every 1,000–1,500 hours
— Compression test: every 2,000 hours
— Belt inspection: every service interval.
— Cylinder head bolts: 140–160 Nm (103–118 lb-ft)
— Main-bearing caps: 180–210 Nm (133–155 lb-ft)
— Connecting rods: 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 Caterpillar C3.4B is widely used in:
— Compact wheel loaders
— Compact excavators
— Skid-steer loaders
— Track loaders
— Agricultural tractors and sprayers
— Telehandlers
— Industrial pumps and compressors
— Generator sets
— Forestry machinery
— Mobile hydraulic power units.
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