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Cummins ISG12 Specifications
| Engine Model: Cummins ISG12 |
| Engine Type: 4-cycle inline 6-cylinder HPCR or XPI fuel injection liquid-cooled diesel |
| Total Displacement: 720 cu.in (11.8 L) |
| Rated Engine Power: 310-490 Hp (231-365 kW) at 2100 rpm |
| Aspiration Type: Turbocharged and aftercooled |
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| General Technical Data |
The Cummins ISG12 is a technologically advanced, electronically controlled, turbocharged and aftercooled inline six-cylinder diesel engine designed for heavy-duty on-highway trucks, vocational vehicles, buses, and certain industrial machinery. Introduced within the Cummins global heavy-duty engine lineup, the ISG12 delivers a combination of lightweight design, high-strength structural integrity, excellent fuel efficiency, reduced emissions, and modern diagnostics.
Its modular architecture simplifies
manufacturing and serviceability, while advanced air-handling and fuel
systems ensure strong low-end torque, efficient cruising behavior, and
compliance with global emissions standards such as Euro III, Euro IV,
Euro V, and China IV/V depending on calibration. The ISG12 is
particularly valued for its power-to-weight ratio, noise reduction, and
improved thermal efficiency, making it highly competitive against other
11–13-liter engine platforms.
The Cummins ISG12 is a four-stroke, inline six-cylinder diesel engine
with a displacement of approximately 11.8 liters (720 cubic inches),
depending on the exact variant. Bore typically measures 132 mm (5.19
inches), while stroke is approximately 144 mm (5.66 inches). Compression
ratios generally range from 17.0:1 to 18.0:1 depending on calibration
and emissions requirements. Power output spans a wide range, commonly
between 310 and 490 horsepower (231–365 kW) at around 1900–2100 rpm.
Peak torque values usually range from 1500 to
2300 Nm (1106–1696 lb-ft), typically delivered at 1000–1400 rpm. Idle
speed is normally around 600–650 rpm. Firing order is 1–5–3–6–2–4. The
combination of high-pressure fuel injection, optimized combustion
geometry, cooled EGR (depending on emissions tier), and a sophisticated
turbocharging system helps achieve strong torque and greater fuel
efficiency.
The cylinder block is cast from high-strength compacted graphite iron
(CGI) or heavy-duty gray iron depending on variant. This material
selection reduces weight while increasing structural rigidity.
Reinforcement ribs provide stiffness to minimize deformation under high
cylinder pressures. The forged-steel crankshaft is supported by seven
large main bearings designed for long service life under severe-duty
operation. Integrated piston cooling nozzles deliver oil to the crown
for temperature control.
Machined oil galleries distribute lubrication
evenly to all critical surfaces. Cast-in coolant jackets ensure even
heat dissipation. The block includes a structural ladder frame or
stiffening bedplate in some configurations, improving durability under
high torque loads. Threaded mounting pads support installation of
accessories such as alternators, PTO units, air compressors, and
hydraulic pumps.
The cast-iron cylinder head contains direct-injection combustion
chambers optimized for high-pressure common-rail or Cummins XPI (Extreme
Pressure Injection) technologies. Four valves per cylinder–two intake
and two exhaust–improve airflow efficiency. Valve actuation is
controlled by rocker arms and pushrods driven by a block-mounted
camshaft. Depending on the variant, hydraulic lash adjusters may be used
to reduce maintenance needs.
Hardened valve seats and high-strength guides withstand elevated exhaust temperatures. Coolant passages are integrated into the head casting to maintain uniform temperature. Combustion chamber geometry enhances swirl and mixing, improving power density and reducing emissions. A multi-layer steel head gasket ensures durability and sealing integrity under high peak firing pressures.
| Fuel System |
The ISG12 employs either high-pressure common-rail (HPCR) or Cummins XPI fuel system technology depending on specific emissions tier. Rail pressures commonly exceed 1800–2000 bar (26,000–29,000 psi). A lift pump supplies fuel to the high-pressure pump, which maintains stable rail pressure. Electronically actuated injectors deliver precise, multiple injection events–pilot, main, and post injections–for improved power, reduced emissions, and lower noise.
The ECM adjusts timing, pressure, injection duration, and quantity based on crankshaft position, camshaft position, rail pressure, boost pressure, intake temperature, coolant temperature, exhaust temperature, and EGR/aftertreatment feedback. High-efficiency filtration with water separation protects injectors from contaminants.
| Lubrication System |
The lubrication system is a full-pressure wet-sump configuration with a gear-driven pump. Oil flows through a strainer, then a full-flow filter, before entering the main oil gallery. Pressurized oil lubricates crankshaft bearings, connecting rods, camshaft bearings, rocker arms, and turbocharger bearings. Piston cooling jets regulate crown temperature.
Normal oil pressure ranges between 300 and 500 kPa (44–72 psi). Idle pressure typically falls between 100 and 150 kPa (15–22 psi). Oil capacity generally ranges from 28 to 36 liters (29.6–38 US quarts), depending on sump design. Engines equipped with aftertreatment require low-ash lubricants to protect components such as DPFs and SCR catalysts.
| Cooling System |
The cooling system is a liquid-cooled arrangement with a belt-driven centrifugal water pump. Coolant circulates through cast-in passages to maintain stable cylinder and head temperatures. Thermostat opening begins around 82°C (180°F) and becomes fully open near 95°C (203°F). Cooling system pressure typically ranges from 90 to 110 kPa (13–16 psi).
Coolant capacity ranges from 35 to 50 liters (37–52.8 US quarts). Air-to-air or air-to-water charge-air cooling reduces intake temperatures, improving torque and lowering emissions. The ECM monitors coolant temperature and enforces derate strategies to prevent overheating and component damage. Proper coolant mixture prevents corrosion, scale, and cavitation.
| Other Systems |
Turbocharging systems include wastegated and variable-geometry turbochargers (VGT), depending on emissions calibration. VGT provides rapid boost response, enhanced low-end torque, and efficient EGR flow where required. Intake filtration is provided by a heavy-duty dry-element system. The exhaust system may include DOC, DPF, SCR, EGR valves, and ammonia slip catalysts, depending on emissions tier.
Electrical systems operate on 12 or 24 volts with alternators rated 80–150 amperes. Sensors throughout the engine provide feedback to the ECM for diagnostics, derate functions, emissions compliance, and adaptive control. Optional PTOs, hydraulic pump mounts, and auxiliary drive configurations support vocational and industrial applications.
| Dimensions and Weight |
Engine physical dimensions:
Length: 1350–1550 mm (53.1–61.0 in)
Width: 800–950 mm (31.5–37.4 in)
Height: 1150–1400 mm (45.3–55.1 in)
Dry weight generally ranges between 820 and 980 kg (1808–2160 lb)
depending on turbocharger type, cooling configuration, emissions
hardware, and accessories. Lightweight yet strong construction
contributes to improved vehicle payload capacity and reduced operating
cost.
| Maintenance Data |
Oil and filter changes are usually recommended every 500 hours or according to manufacturer mileage guidelines based on duty cycle. Fuel filters typically require replacement every 400–500 hours. Air filter replacement depends on environmental conditions and ranges between 200 and 400 hours. Coolant should be replaced every two years.
Valve lash inspection may be necessary on versions without hydraulic lash adjusters. Aftertreatment components require periodic inspection, regeneration, or cleaning depending on usage. ECM diagnostic logs assist technicians with troubleshooting and predictive maintenance planning.
| Tightening Torques |
Cylinder head bolts: 220–260 Nm (162–192 lb-ft)
Main bearing caps: 180–220 Nm (133–162 lb-ft)
Connecting rod bolts: 90–120 Nm (66–89 lb-ft)
Flywheel bolts: 300–350 Nm (221–258 lb-ft)
Crankshaft pulley bolt: 280–320 Nm (207–236 lb-ft)
Injector hold-down: 25–30 Nm (18–22 lb-ft)
Glow plug/intake heater (if equipped): 10–15 Nm (7–11 lb-ft)
Oil drain plug: 40–50 Nm (30–37 lb-ft).
| Vehicle Applications |
The Cummins ISG12 is used in heavy-duty trucks, long-haul tractors, dump trucks, buses, construction machinery, agricultural machinery, industrial power units, cranes, and some generator sets. Its strong torque curve, emissions capability, reduced weight, and advanced electronics make it suitable for global markets requiring a modern, efficient heavy-duty diesel engine.
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