Cummins QSF3.8 Specifications
| Engine Model: Cummins QSF3.8 |
| Engine Type: 4-cycle inline 4-cylinder HPCR direct injection liquid-cooled diesel |
| Total Displacement: 229 cu.in (3.76 L) |
| Rated Engine Power: 74-130 Hp (55-97 kW) at 2600 rpm |
| Aspiration Type: Turbocharged |
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The Cummins QSF3.8 is a modern, compact,
high-efficiency diesel engine engineered for small to mid-sized
construction machinery, agricultural equipment, industrial applications,
and customized OEM platforms. As part of Cummins’ F-Series, the QSF3.8
represents the electronically controlled, emissions-compliant evolution
of the earlier ISF3.8 and mechanical 4BT/4B engines.
Designed for Tier-3, Tier-4 Final, and Stage-V emissions levels, the
QSF3.8 delivers low fuel consumption, strong torque at low RPM, quiet
operation, and long service intervals. It has become a popular choice
for compact loaders, telehandlers, industrial forklifts, pumps,
compressors, agricultural sprayers, mobile light towers, and specialized
construction equipment.
The Cummins QSF3.8 is a four-stroke, turbocharged, water-cooled
inline-four diesel engine. Displacement is 3.76 liters (229 cubic
inches). Bore is 102 mm (4.02 in), stroke is 115 mm (4.53 in)–a
long-stroke geometry optimized for torque production and fuel
efficiency. Compression ratio varies depending on emissions calibration
but generally falls between 16.5:1 and 17.2:1.
Power ratings (std):
– Industrial machines: 74–130 hp (55–97 kW) @ 2,200–2,800 rpm
– Agricultural machinery: 85–130 hp (63–97 kW)
– Generator-drive (QSF3.8-G): 45–90 kW @ 1,500–1,800 rpm
Peak torque: 330–500 Nm (243–369 lb-ft) @ 1,200–1,600 rpm
Idle speed: 750–850 rpm
Governed speed: 2,500–2,800 rpm
Firing order: 1-3-4-2.
The crankshaft is forged steel supported by five main bearings. Pistons
are aluminum alloy, featuring cooling galleries and reinforced
combustion bowls. Connecting rods are forged steel with replaceable
bearings. The camshaft is gear-driven for permanent timing accuracy and
minimal maintenance.
The QSF3.8 uses a high-strength cast-iron
block with:
– Parent-bore cylinders
– Deep-skirt architecture
– Full cylinder-wall water-jacket cooling
– Reinforced ribbing for vibration reduction
– Wide main-bearing saddles
The block is engineered for durability under repeated full-load
operation and supports multiple rebores for overhaul.
The cast-iron cylinder head includes:
– Four valves per cylinder (16-valve design)
– Hardened valve seats and guides
– High-flow intake and exhaust ports
– Central injector positioning
– Roller tappets and pushrods (depending on configuration)
Cold valve-lash specifications:
– Intake: 0.20–0.30 mm (0.008–0.012 in)
– Exhaust: 0.45–0.55 mm (0.018–0.022 in).
The QSF3.8 uses high-pressure common-rail (HPCR) injection controlled by
an ECM.
Fuel-system components:
– High-pressure pump (1,600–1,800 bar / 23,000–26,000 psi)
– Electronically actuated injectors
– Rail-pressure sensor
– Electric lift pump
– Dual fuel filters (primary + secondary)
– Water separator
– Fuel-temperature and supply-pressure sensors
Injection strategy:
– Pilot injection for reduced noise
– Main injection for power
– Post-injection for emissions control (DPF variants)
Maintenance intervals:
– Fuel filters: 250–500 hr
– Water separator: daily
– Injector testing: 1,200–1,800 hr
– HPCR pump inspection: overhaul interval.
A full-pressure wet-sump lubrication system ensures smooth and reliable
operation.
Oil capacity: 7–10 liters (7.4–10.6 qt)
Oil pressure:
– Operating: 275–380 kPa (40–55 psi)
– Idle: 70–100 kPa (10–15 psi)
Recommended oil: SAE 10W-30 or 15W-40 (API CI-4, CJ-4, CK-4, ACEA E9)
Oil-change intervals:
– Industrial: 250–500 hr
– Automotive applications: up to 20,000 km.
Cooling is provided by:
– Belt-driven centrifugal water pump
– Thermostat-regulated water flow
– Engine-oil cooler
– Full water-jacket coverage
Thermostat:
– Opening: 82°C (180°F)
– Fully open: 95°C (203°F)
Cooling capacity: 10–15 liters (10.6–15.8 qt)
System operating pressure: 70–100 kPa (10–15 psi).
| Intake and Exhaust Systems |
Turbocharging:
– Fixed-geometry turbocharger
– Oil-lubricated center housing
– Optional wastegate for boost control
Aftercooling:
– Air-to-air charge-air cooling (most versions)
Intake:
– Dry-type single or dual-stage filters
– Optional heavy-duty cyclone pre-cleaner
Exhaust:
– Cast-iron manifold
– Optional emissions components: Cooled EGR, DOC, DPF, SCR.
| Electrical and Electronic Systems |
The QSF3.8 uses full electronic management
via an ECM controlling:
– Injection timing and metering
– Rail-pressure regulation
– Turbocharger logic
– EGR and after-treatment control (if equipped)
– Idle control
– Cold-start assistance
– Fault-code logging.
Sensors include:
– Crankshaft/camshaft position
– MAP/boost pressure
– Coolant temperature
– Oil pressure and temperature
– Fuel temperature and rail pressure
– EGT sensors (multiple points, depending on emissions level)
– DEF/NOx sensors (SCR variants)
Alternator output: 45–120 amps depending on application.
Available configurations may include:
– PTO pads
– Hydraulic pump mounts
– Remote radiator connections
– Industrial accessory-drive packages
– A/C compressor brackets
– Custom OEM interface harness.
Approximate physical dimensions:
– Length: 780–900 mm (30–35 in)
– Width: 650–750 mm (26–30 in)
– Height: 830–950 mm (33–37 in)
Dry weight: 250–335 kg (551–738 lb).
Recommended service intervals:
– Oil and filter: 250–500 hr
– Fuel filters: 250–500 hr
– Air filter: inspect every 50–100 hr
– Valve-lash: every 1,000 hr
– Injector calibration: 1,200–1,800 hr
– Coolant replacement: every 2 years
– Compression test: every 2,000 hr.
– Cylinder-head bolts: 150–170 Nm (111–125 lb-ft) + angle
– Main-bearing caps: 175–200 Nm (129–148 lb-ft)
– Connecting-rod bolts: 65–75 Nm (48–55 lb-ft)
– Flywheel bolts: 100–120 Nm (74–89 lb-ft)
– Crankshaft damper bolt: 200–225 Nm (148–166 lb-ft)
– Oil-drain plug: 40–55 Nm (30–41 lb-ft)
– Injector hold-down: 20–30 Nm (15–22 lb-ft).
The Cummins QSF3.8 is used in:
– Compact wheel loaders
– Skid-steer loaders
– Telehandlers
– Mini and mid-size excavators
– Agricultural tractors and sprayers
– Forklifts and material-handling equipment
– Compressors and pumps
– Small generator sets (45–90 kW)
– Municipal and utility vehicles
– Industrial OEM power units.
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