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Cummins QSB4.5 Specifications
| Engine Model: Cummins QSB4.5 |
| Engine Type: 4-cycle inline 4-cylinder common-rail direct injection liquid-cooled diesel |
| Total Displacement: 275 cu.in (4.5 L) |
| Rated Engine Power: 99-174 Hp (74-130 kW) at 2400 rpm |
| Aspiration Type: Turbocharged |
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| General Technical Data |
The Cummins QSB4.5 is a high-performance, electronically controlled, four-cylinder, turbocharged and aftercooled diesel engine engineered for modern industrial, agricultural, construction, and off-highway equipment. As part of the Cummins Quantum System (QS) engine family, the QSB4.5 emphasizes advanced electronic control, improved fuel efficiency, low emissions, compact packaging, reduced noise, and long-term durability.
Meeting global emissions standards including
Tier 3, Tier 4 Interim, Tier 4 Final, Stage IIIA, Stage IIIB, and Stage
V (depending on version), this engine is widely used in tractors, wheel
loaders, excavators, compact equipment, generator sets, forestry
machinery, and specialized industrial platforms. The combination of a
high-pressure common-rail fuel system, robust cast-iron construction,
and sophisticated electronics delivers smooth power, enhanced torque,
low fuel consumption, and excellent reliability across diverse duty
cycles.
The QSB4.5 is a four-stroke, inline four-cylinder diesel engine with a
displacement of approximately 4.5 liters (275 cubic inches). Bore
typically measures 107 mm (4.21 inches), and stroke measures 124 mm
(4.88 inches), forming a long-stroke configuration optimized for torque
production. Depending on emissions tier, the compression ratio ranges
approximately between 16.5:1 and 18.0:1. Power output generally ranges
from 74 to 130 kW (99–174 horsepower) at around 2200–2500 rpm depending
on configuration.
Peak torque typically falls between 450 and 600
Nm (332–443 lb-ft), commonly achieved at 1500–1600 rpm. The firing order
is 1–3–4–2. Idle speed is often set around 750–800 rpm. The
electronically controlled turbocharger and high-pressure common-rail
system ensure fast throttle response, efficient combustion, smooth
operation, and altitude compensation.
The cylinder block is cast from high-strength iron with deep structural
ribbing for stiffness and vibration reduction. Precision machining
ensures correct bore alignment and long-term structural integrity. The
forged-steel crankshaft is supported by five main bearings designed for
high load capacity. The long-stroke combination supports strong torque,
low-speed power density, and smooth operation.
Cast-in coolant jackets maintain uniform heat
distribution, enhancing longevity. Machined oil galleries supply
pressurized lubrication to the crankshaft, rod journals, camshaft
bearings, and other critical components. Accessory mounting bosses allow
integration of alternators, hydraulic pumps, air-conditioning
compressors, and application-specific equipment.
The QSB4.5 uses a cast-iron cylinder head engineered for advanced
combustion performance. Four valves per cylinder (two intake and two
exhaust) improve breathing efficiency, gas flow, and high-speed
performance. Valve actuation is managed by pushrods and rocker arms
connected to the camshaft located in the block. Hydraulic valve lash
adjusters may be equipped depending on tier, reducing maintenance needs.
Combustion chamber geometry optimizes air–fuel mixing for clean emissions, low smoke, better fuel economy, and improved cold-starting behavior. Hardened valve seats and high-strength guides withstand high thermal cycling typical of turbocharged operation. Integrated coolant passages manage head temperature consistently, reducing hotspots and preventing warping.
| Fuel System |
0The QSB4.5 is equipped with a high-pressure common-rail fuel system. Pressures typically exceed 1600–1800 bar (23,200–26,000 psi). A low-pressure fuel lift pump supplies fuel to the high-pressure pump, which pressurizes the common rail. Electronically actuated injectors deliver fuel with precise timing, duration, and multiple injection events to reduce emissions and noise while increasing efficiency.
An electronic control module (ECM) continuously monitors engine speed, load, temperature, boost pressure, and emissions data to adjust injection strategy in real time. Filtration includes primary and secondary fuel filters with water separation capability. This fuel system allows the QSB4.5 to meet stringent emissions standards while providing smooth operation, reduced vibration, and improved power delivery.
| Lubrication System |
The lubrication system is a full-pressure, wet-sump configuration. A gear-driven oil pump supplies oil through a high-capacity, full-flow filter to the main gallery. Pressurized oil lubricates main bearings, connecting rod journals, camshaft bearings, rocker arms, turbocharger bearings, and other moving parts. Many versions incorporate piston cooling jets to maintain optimal piston temperatures and prevent thermal overloading.
Normal operating oil pressure typically ranges from 300 to 500 kPa (44–72 psi), with idle pressure around 100–150 kPa (15–22 psi). Oil capacity is commonly between 11 and 13 liters (11.6–13.7 US quarts), depending on sump configuration. Low-ash oil may be required for engines equipped with diesel particulate filters (DPF).
| Cooling System |
The QSB4.5 utilizes a liquid cooling system with a belt-driven centrifugal water pump. Coolant flows through cast-in jackets to remove heat from the engine block and head. A thermostat begins opening at around 82°C (180°F) and fully opens near 95°C (203°F). Coolant capacity varies, but commonly ranges from 12 to 14 liters (12.7–14.8 US quarts).
Applications requiring high thermal rejection may include larger radiators or remote cooling modules. The electronic control system monitors coolant temperature and engages derate modes to protect the engine from overheating. Optional cold-weather starting aids include block heaters and thermostatically controlled intake heaters.
| Other Systems |
The turbocharging system includes a wastegate or variable-geometry turbocharger (depending on tier). Charge-air cooling is achieved via air-to-air or air-to-water aftercooling. Heavy-duty filtration systems protect the turbo and engine internals from particulate damage. The intake system uses a dry-element air filter, with dual-stage filtration available for high-dust environments. The exhaust manifold is cast from heat-resistant iron.
Emission control systems may include DOC (Diesel Oxidation Catalyst), DPF, SCR (Selective Catalytic Reduction), and EGR (Exhaust Gas Recirculation) depending on emissions tier. Electrical systems may operate at 12 or 24 volts, with alternators rated between 60 and 120 amperes. ECM-controlled sensors continuously monitor engine conditions, enabling advanced diagnostics and fault detection.
| Dimensions and Weight |
Physical dimensions include:
Length 800–1000 mm (31.5–39.4 inches)
Width 700–800 mm (27.6–31.5 inches)
Height 900–1100 mm (35.4–43.3 inches)
Dry weight commonly ranges from 430 to 500 kg (948–1102 lbs), depending
on emissions equipment, aftercooler type, and accessory configuration.
The compact design supports installation in tight machine compartments.
| Maintenance Data |
Regular maintenance is essential for long-term reliability. Oil and filter replacement intervals typically occur every 500 hours, though severe-duty schedules may require shorter intervals. Fuel filters should be replaced every 500 hours, with water separators drained routinely. Air filter service intervals vary between 250 and 500 hours depending on dust levels.
Coolant replacement commonly occurs during major service intervals or every two years, depending on coolant chemistry. Valve lash inspection may be necessary if hydraulic lifters are not installed. Aftertreatment components require periodic regeneration, cleaning, or replacement depending on emissions tier. The ECM logs operational data useful for planning maintenance tasks and diagnosing performance issues.
| Tightening Torques |
Tightening values include:
Cylinder head bolts: 180–210 Nm (133–155 lb-ft)
Main bearing caps: 140–160 Nm (103–118 lb-ft)
Connecting rod bolts: 60–75 Nm (44–55 lb-ft)
Flywheel bolts: 180–220 Nm (133–162 lb-ft)
Crankshaft pulley bolt: 220–260 Nm (162–192 lb-ft)
Injector hold-down: 20–25 Nm (15–18 lb-ft)
Glow plugs or intake heaters: 10–15 Nm (7–11 lb-ft)
Oil drain plug: 30–40 Nm (22–30 lb-ft).
| Vehicle Applications |
The QSB4.5 is widely used in agricultural tractors, wheel loaders, excavators, telehandlers, compact construction equipment, forestry machinery, industrial pumps, compressors, generator sets, and specialized off-highway equipment. Its balance of power, emissions compliance, fuel efficiency, compact size, and reliable operation makes it suitable for diverse working environments.
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