Cummins ISB 6.7L Engine: Specs, Problems, and Reliability

Cummins ISB 6.7L Engine: Specs, Problems, and Reliability. Cummins ISB 6.7-liter straight-six turbodiesel engine is the most up to date and biggest version of the B series. The ISB 6.7 is also one of the most powerful diesel engine produced by Cummins (350 hp and 650 lb-ft of torque) for light/medium-duty trucks.

Cummins ISB 6.7L Engine Specs, Problems

Its predecessor, the ISB 5.9, has been produced almost ten years. At that moment, it was outdated and depleted the limits of possibilities for improvements in regards to fuel consumption and emissions. The marketplace wanted a new engine for medium-duty trucks and buses, and the ISB 6.7 engine became the explanation for that. The 6.7 ISB had an increased cylinder bore (4.21 inches or 106.9 mm) and piston stroke (4.88 inches or 124.0 mm). That increased its displacement to 6.7 liters (408 cubic inches).

The engine block is still made from cast iron. In addition to the block, there is a 24-valve cast iron cylinder head similar to the ISB 5.9. The difference between ISB 5.9 and 6.7 cylinder head is the ISB6.7 head has holes (Sensor Hole Style head) from the air intake plenum side. There are many changes compared to the last generation B5.9 version, but the overall design remains the same. The 6.7 L Cummins engine had a high-pressure Common Rail fuel injection system, electronically controlled fuel injection pump, and new equipment for emissions reduction.

Cummins ISB 6.7L Engine: Specs, Problems, and Reliability

Cummins ISB 6.7L Engine: Specs, Problems, and Reliability

The new version was designed guided by stricter demands on Federal emissions regulations. In 2007, the first year in production, the engine was the first Cummins diesel equipped with a diesel particulate filter (DPF). The DPF filter cleans the exhaust gases from soot by more than 90 percent. A diesel particle filter has a ceramic matrix, which filters soot particles and regenerates them under heat, heated by exhaust gases.

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Also, the engine had the exhaust gas recirculation system (EGR) with cooling. In the 2010 model year, the engine received an additional DEF (diesel exhaust fluid), SCR (selective catalytic reduction), and EGR cooler. The DEF fluid is injected inside the DPF to help the regeneration process of soot at the lower temperature. So 2 liters of DEF is consumed for each 100 liters of diesel fuel.

Holset HE351VE variable geometry turbocharger (VGT) is another interesting new feature of the engine. This turbocharger can block exhaust flow to increase temperatures inside the DPF, which reduces emission levels. The VGT also has an integrated exhaust brake function. It does the engine braking by restricting exhaust flow. All ISB6.7 engines are equipped with an air-to-air intercooler.

The improvement process has never been stopped during the last ten years of production, so the 2017 model year engines already produce up to 900 lb-ft of torque. The ISB6.7 also was laid into the basis of the smaller version – ISB4.5 (a 4.5-liter straight four-cylinder turbodiesel engine).

Cummins ISB 6.7L Engine: Specs

Manufacturer Cummins
Production years 2007- current
Cylinder block material Cast iron
Cylinder head material Cast Iron
Fuel type Diesel
Fuel system Direct injection, electronically controlled Bosch high pressure common rail injection.
Configuration Inline
Number of cylinders 6
Valves per cylinder 4
Valvetrain layout OHV
Bore, mm 4.21 inch, 106.9 mm
Stroke, mm 4.88 inch, 124 mm
Displacement, cc 408 cubic inches, 6.7 liters
Type of internal combustion engine Four-stroke, turbocharged
Compression Ratio 17.3 : 1
Power, hp 305-385 hp /2,800-3,000
Torque, lb ft 610-900 lb-ft (827-1220 Nm)/1,500-1,700
Engine weight 1050-1150 lbs, 476-522 kg, dry
Firing order 1-5-3-6-2-4
Engine oil weight SAE 15W40 diesel oil
Engine oil capacity, liter 12 qts (11.4 liters) with filter.
Oil change interval, mile 15,000 (24,000 km) or 6 month (7,500 miles or 6 months for 2007.5 – 2012 model years).
Applications Dodge Ram pickup trucks, buses, medium duty trucks
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Cummins ISB 6.7 L Engine Specs, Problems & Reliability

Cummins ISB 6.7-liter straight-six turbodiesel engine is the current and biggest version of the B series. The ISB 6.7 is also the best powerful diesel engine produced by Cummins (350 hp and 650 lb-ft of torque) for light/medium-duty trucks.

Its predecessor, the ISB 5.9, has been produced almost ten years. At that moment, it was outdated and depleted the limits of possibilities for improvements in terms of fuel consumption and emissions. The market place wanted a new engine for medium-duty trucks and buses, and the ISB 6.7 engine became the answer for that. The 6.7 ISB had an increased cylinder bore (4.21 inches or 106.9 mm) and piston stroke (4.88 inches or 124.0 mm). That increased its displacement to 6.7 liters (408 cubic inches). The engine block is still made from cast iron.

In addition to the block, there is a 24-valve cast iron cylinder head similar to the ISB 5.9. The difference between ISB 5.9 and 6.7 cylinder head is the ISB6.7 head has holes (Sensor Hole Style head) from the air intake plenum side. There are many changes compared to the last generation B5.9 version, but the overall design remains the same. The 6.7 L Cummins engine had a high-pressure Common Rail fuel injection system, electronically controlled fuel injection pump, and new equipment for emissions reduction.

Cummins ISB 6.7 L Engine problems

The new version was designed guided by stricter criteria on Federal emissions regulations. In 2007, the first year in production, the engine was the first Cummins diesel equipped with a diesel particulate filter (DPF). The DPF filter cleans the exhaust gases from soot by more than 90 percent. A diesel particle filter has a ceramic matrix, which filters soot particles and regenerates them under high temperature, heated by exhaust gases.

Also, the engine had the exhaust gas recirculation system (EGR) with cooling. In the 2010 model year, the engine received an additional DEF (diesel exhaust fluid), SCR (selective catalytic reduction), and EGR cooler. The DEF fluid is injected inside the DPF to help the regeneration process of soot at the lower temperature. So 2 liters of DEF is consumed for every single 100 liters of diesel fuel.

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Holset HE351VE variable geometry turbocharger (VGT) is another interesting new feature of the engine. This turbocharger can block exhaust flow to increase temperatures inside the DPF, which reduces emission levels. The VGT also has an integrated exhaust brake function. It does the engine braking by restricting exhaust flow. All ISB6.7 engines are equipped with an air-to-air intercooler.

The improvement process has never been stopped during the last ten years of production, so the 2017 model year engines already produce up to 900 lb-ft of torque. The ISB6.7 also was laid into the basis of the smaller version – ISB4.5 (a 4.5-liter straight four-cylinder turbodiesel engine).

Modifications

Dodge ISB 6.7 Truck’s Transmissions and Power:

In 2007 the 6.7 liters engine was launched in 350 hp and 650 lb-ft version with Chrysler-built six-speed 68RFE automatic transmission, and 350 hp and 610 lb-ft modification connected to the Mercedes G56 6-speed manual transmission. The 2007 and newer 3500 trucks had only 305 hp and have being equipped with the Aisin AS68RC or the Mercedes G56 6-speed manual transmission.

The 2008 4500/5500 medium duty trucks received the 350 hp and 610 lb-ft version of the engine, which include the Aisin AS68RC or the Mercedes G56 manual. Since 2011, the 68RFE automatic transmission offered with 350-370hp and 800 lb-ft version of 6.7 liter engine. Since 2013, the Aisin AS69RC transmission became available for 3500 only with B6.7 engine produced 385 hp and 850-900 lb-ft of torque.