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Cummins B Series engine

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Cummins B-Series Engine
6.7 Euro 4 / 4+
Also called4B/4BT/4BTA
ConfigurationI4, I6
  • 3.9 L (3,922 cc; 239.3 cu in)
  • 4.5 L (4,460 cc; 272.2 cu in)
  • 5.9 L (5,883 cc; 359.0 cu in)
  • 6.7 L (6,690 cc; 408.2 cu in)
Cylinder bore
  • 102 mm (4.02 in)
  • 107 mm (4.21 in)
Piston stroke
  • 120 mm (4.72 in)
  • 124 mm (4.88 in)
Cylinder block materialCast iron
Cylinder head materialCast iron
2 (B-Series) or 4 (ISB, QSB) valves/cylinder
Compression ratio17.2:1, 17.3:1, 17.5:1, 19:1
TurbochargerHolset Engineering (variable)
Fuel systemCommon rail high pressure direct injection, symmetrical combustion chamber with 7-hole injectors
ManagementBosch mechanical with electronic advance
Fuel typeDiesel
Oil systemWet sump
Cooling systemWater cooled
Power output53–420 hp (40–313 kW)
Torque output265–1,075 lb⋅ft (359–1,458 N⋅m)
Dry weight1,100 lb (499 kg)
Emissions control systemsElectronic fuel control, DPF and EGR

The Cummins B Series is a family of diesel engines produced by American manufacturer Cummins. In production since 1984, the B series engine family is intended for multiple applications on and off-highway, light-duty, and medium-duty. In the automotive industry, it is best known for its use in school buses, public service buses (most commonly the Dennis Dart and the Alexander Dennis Enviro400) in the United Kingdom, and Dodge/Ram pickup trucks.

Since its introduction, three generations of the B series engine have been produced, offered in both inline-four and inline-six configurations in multiple displacements.

General engine features


The B-series features engine bores machined directly into the block (rather than the wet liners used on earlier Cummins engines). It is also set apart by the use of a shallow one-piece head, requiring closer tolerances than in other Cummins products.[1] Unlike earlier diesel engines the B-series Cummins used direct injection and did not need glow plugs for cold starting.[2] The engine was first manufactured in Rocky Mount, North Carolina, and other plants were later added in Mexico, Brazil, Turkey, and Darlington, UK.[3]

Every Cummins powered Dodge Pickup (since initial production in 1989) has come equipped with a turbocharger. It uses a gear-drive camshaft for extra reliability. Also specified is a deep-skirt engine block and extra-strong connecting rods. A Holset turbocharger is used. The original B Series was updated with 24 valves and an electronic engine management system to become the ISB in 1998.

Engine specifications

Engine Specifications
Model Cylinders Fuel Power Torque Production
3.9 L
4B 4 Diesel
4BT 105 HP 265 lb-ft 1984? - 1998?
4BTA 170 HP 440 lb-ft 1998 - ?
4.5 L
ISB 4 Diesel 185 HP Euro 5 (2008–2014)

Euro 6 (2015–present)

5.9 L
6B 6 Diesel
6BT 160 HP 400 lb-ft 1989 - 1998
ISB 1998 - 2007
6.7 L
ISB 6 Diesel 2007–present

Euro 4 (2005–2008) Euro 5 (2008–2013) Euro 6 (2014–present)

B6.7N? Natural Gas

B engine


3.9 L


The 3.9-liter 4B/4BT/4BTA Cummins is categorized under the B Engine family alongside the 5.9-liter 6B/6BT/6BTA Cummins diesel engines. The 3.9 is an inline four-cylinder, either naturally aspirated (4B) or turbodiesel (4BT/4BTA), which was popular for many step van applications including bread vans and other commercial vehicles. Additionally it has seen broad usage in agricultural equipment. It has also gained popularity as an engine swap into smaller trucks and SUVs.



The lowest powered, naturally aspirated 3.9-liter Cummins, the 4B, produces 53 hp (40 kW).[1] This variant is most commonly found in equipment such as generators and wood chippers.



The 4BT is one of two turbocharged variants of the 3.9L B-Series engine. It has two valves per cylinder for a total of eight. The most common output of this variant is 105 horsepower.



The 4BTA is the updated version of the 4BT, also turbocharged, with four valves per cylinder for a total of sixteen. The most common output of this variant is 170 horsepower.

5.9 L

5.9L 6BT Cummins in 1991 Dodge RAM with the valve covers removed exposing the valvetrain
5.9 L B-Series Cummins
Production: 1984–1998
Camshaft drive: Gear driven
Crankshaft: Forged steel, 7 main bearings
System capacity with filter: 3.5 US gal (13 L; 2.9 imp gal)
Cooling system: 6 US gal (23 L; 5.0 imp gal) coolant
System capacity incl heater: 6.5 US gal (25 L; 5.4 imp gal) coolant
Power output: 160–230 hp (119–172 kW) at 2500 rpm
Torque: 400 - 400–440 lb⋅ft (542–597 N⋅m) at 1600 rpm
Compression ratio: 17.5:1

The 5.9 L Cummins, also known as the "12-Valve" Cummins was the first member of the Cummins B-Series to be used in a light truck vehicle. The 6BT used Bosch fuel systems, injector, and VE rotary pump and P7100 inline injection pumps. Some early 6BTs were supplied with CAV rotary pumps instead, before the Bosch system became the sole standard. This engine started life in 1984 designed as an agricultural engine, for use in Case agricultural equipment.[4][full citation needed] After 1989, the 6BT engine was used in light duty, medium duty and select heavy duty trucks and buses.[citation needed] The 6BT engine has recently become very popular for use in repowering various vehicles.



The 6B is the naturally aspirated version of the 6BT with the power output of between 150 and 173 hp and with the compression ratio of 19:1. There were no OEM automotive applications for 6B engines.



Appearing in the 1989–1998 Dodge Ram pickup truck, it became a popular alternative to the large gasoline V8 engines normally used in full-size pickup trucks, since it produced torque at low engine RPM, and achieved significantly better fuel mileage. Due to the direct fuel injection, the 6BT has no glowplugs.[4]



ISB engine


4.5 L ISB


The 4.5 L ISB is essentially a four-cylinder, two-thirds version of the 6.7 L ISB rated at 185 hp (138 kW), used in the New Routemaster, a series hybrid diesel-electric doubledecker bus in London.[5][6][7]

5.9 L ISB

5.9 L ISB Cummins
Production: 1998.5–2007
Camshaft drive: Gear driven
Crankshaft: Forged steel, 7 main bearings
System capacity with filter: 3 US gal (11 L; 2.5 imp gal)
Fuel system: Common rail High pressure direct injection, symmetrical combustion chamber
Management: Bosch Mechanical with electronic advance
Power output: 325 hp (242 kW) at 2900 rpm
Torque: 610 lb⋅ft (827 N⋅m) at 1600 rpm
Compression ratio: 17.2:1
Emissions control: Electric fuel control

The 5.9 L; 359.0 cu in (5,883 cc) ISB (Interact System B) is one of the largest straight-six engines used for light truck vehicles and school buses, and the improved high output 600 version was on the Ward's 10 Best Engines list for 2004.

One unusual feature of the ISB is that it is a multi-valve pushrod engine design, with four valves per cylinder (popularly referred to as the "24-Valve" Cummins). The engine displaces 5.9 L; 359.0 cu in (5,883 cc), with a 102 mm × 120 mm (4.02 in × 4.72 in) cylinder bore and piston stroke. A turbocharger is used to increase the output in the high-compression (17.2:1 in recent versions) diesel. It is an all-iron engine with forged steel connecting rods, an assembled camshaft, and a cast aluminum intake manifold. The engine is produced in Columbus, Indiana.

The ISB uses electronically controlled Bosch fuel systems, unlike the 6BT systems which were mechanical. Early ISB engines utilize Bosch injectors and a Bosch VP44 high pressure pump. Later ISB designs have common rail fuel injection, Bosch injectors, and a Bosch CP3 high pressure pump.[4]

Dodge Ram ISB


Midway through model year 1998, the Dodge Ram switched from the 6BT to the ISB to meet updated emissions requirements. Like other ISB's, these engines started out using the Bosch VP44 rotary injection pump. The VP44 setup meant that timing and fuel could be precisely controlled, which led to cleaner emissions. However, VP44 failure rates were higher than the older P7100 injection pump. The compression ratio in these engines was 17.2:1. The 1998–2000 ISB was rated at 215 hp (160 kW; 218 PS) and 420 lb⋅ft (569 N⋅m) when equipped with the 47RE automatic transmission. The 1998–2000 ISB was rated at 235 hp (175 kW; 238 PS) and 460 lb⋅ft (624 N⋅m) when equipped with a manual transmission. For the 2001–2002 years, a standard output and a high output ISB Cummins engine were offered. The standard output, which was the same as the previous engines was rated to 235 hp (175 kW; 238 PS) and 460 lb⋅ft (624 N⋅m) when equipped with either a manual transmission or automatic. The high output ISB was rated at 245 hp (183 kW; 248 PS) and 505 lb⋅ft (685 N⋅m), with only a NV5600 six-speed manual transmission available. The high output engine was different in a few ways from the standard output engine; it had higher compression (17.3:1), powdered metal valve seat inserts, a larger flywheel, the Bosch fuel system was reworked to allow higher fuel flows, and fuel-injection timing was altered.

Dodge Ram ISB CR

5.9 Cummins Common rail fuel injection system

For the 2003 model year, the Cummins was introduced with Bosch high pressure common rail fuel injection, again increasing power output. On automatic equipped vehicles, the 47RE was upgraded internally to increase durability and torque capacity, now known as the 48RE. The 2003 rating for the Dodge truck was released at 305 hp (227 kW; 309 PS) and 555 lb⋅ft (752 N⋅m). Midway through the 2004 model year, the Cummins 600 was introduced, producing 325 hp (242 kW; 330 PS) at 2,900 rpm and 600 lb⋅ft (813 N⋅m) at 1,600 rpm. This engine was noticeably quieter than the previous engines.[8][non-primary source needed]

6.7 ISB

6.7 Demo
6.7 L ISB Cummins
Production: 2007 – Present
Displacement: 6.7 L; 408.2 cu in (6,690 cc)
Bore x stroke: 107 mm × 124 mm (4.21 in × 4.88 in)
Max power: 150–420 hp (112–313 kW; 152–426 PS) at 2800 rpm
Torque: 610–1,075 lb⋅ft (827–1,458 N⋅m) at ~1600 rpm
Compression ratio: 17.3:1
Emissions control: EGR and DPF
Turbocharger: Holset Engineering (variable)
Fuel system: Common rail High pressure direct injection with 7-hole injectors
Camshaft drive: Gear driven
Crankshaft: Forged steel, 7 main bearings
Oil System capacity with filter: 3 US gal (11 L; 2.5 imp gal)

The 6.7 L ISB is the latest version of the B Series. It is currently the largest straight-six engine produced for a light duty truck or school bus. It produces 350 hp (261 kW; 355 PS) and 650 lb⋅ft (881 N⋅m) in the 2007.5 and newer Dodge 2500/3500 pickup trucks with the Chrysler-built six-speed 68RFE automatic transmission built at the Kokomo Transmission plant in Kokomo, Indiana. Engine torque is slightly reduced with the Mercedes G56 6-speed manual transmission at 350 hp (261 kW; 355 PS) and 610 lb⋅ft (827 N⋅m). The 2007 and newer 3500 Cab & Chassis trucks only get the 305 hp (227 kW; 309 PS) and 610 lb⋅ft (827 N⋅m) version of the B6.7, whether it has the Aisin AS68RC or the Mercedes G56 6-speed manual transmission. As for the 2008 4500/5500 medium duty Chassis Cabs or the Sterling Bullet Trucks, they receive the 350 hp (261 kW; 355 PS) and 610 lb⋅ft (827 N⋅m) version of the B6.7, whether it has the Aisin AS68RC or the Mercedes G56 6-speed manual transmission. Late model 2011 Ram trucks produce 350 hp (261 kW; 355 PS) and 800 lb⋅ft (1,085 N⋅m), with the exhaust brake rating boosted from 150 hp (112 kW; 152 PS) to 222 hp (166 kW; 225 PS).[9]

For 2019 this engine has been updated to produce 400 hp and 1000 ft-lb torque.

It is also used in the Blue Bird Vision, Thomas Saf-T-Liner C2, and IC CE school buses and BMC Procity city buses

Changes over the 5.9 L ISB


There are many changes over the previous 5.9 L ISB for the Dodge truck, the most obvious being the larger displacement. The 6.7 ISB had an increase of cylinder bore and piston stroke to 107 mm × 124 mm (4.21 in × 4.88 in), respectively, thereby giving a displacement of 6.7 L; 408.2 cu in (6,690 cc).[10][full citation needed]

With the 6.7 L ISB came the introduction of the Variable Geometry Turbocharger (VGT). The VG Turbocharger was introduced to reduce turbo lag by adjusting the vanes by sliding a steel ring in the exhaust housing dependent on engine RPM creating more or less pressure inside the exhaust housing and controlling the speed of the turbocharger. It also works as an integrated exhaust brake system and is all controlled by an electronic actuator on the turbocharger. This VGT system has been an extremely common issue with the 6.7 L ISB and is typically diagnosed by the loss of the trucks exhaust brake.[11]

QSB engine


5.9 QSB


The 5.9 L QSB (Quantum System B) is an off-road, heavy duty version of the ISB. Typically used in marine, agricultural, and construction applications, these engines share many of the same parts as the ISB and utilize the same Bosch fuel system.[citation needed]

Fuel system


Mechanical injection with mechanical timing


In the earlier models of the Cummins B-Series Engine, it was almost entirely mechanical including its fuel system. The fuel pump used in these engines was the Bosch P7100 injection pump, this pump is driven off the camshaft gear and drives its own internal camshaft to inject fuel to the individual injectors.[12] This pump itself was one of the most popular options for fueling for the B-Series Engines because of this simplistic design and how reliable it was. The P7100 injection pump also allows for large amounts of fuel to be delivered into the system with simple tweaking to the system to allow for larger injection events.

Mechanical injection with electronic timing


In the later models of B-Series Engine, the fuel system was switched from mechanical injection and timing to mechanical injection with electronic timing. This was all thanks to Bosch's new VP44 radial distributor injection pump.[13] The VP44 injection pump is driven at half the camshaft speed and produces an injection pressure of up to 140 MPa (20,300 lbf/in2).[14]

Mechanical injection with electronic timing and common rail pressurization


The most recent method of fuel injection used in Cummins B Series engines is electronically controlled common-rail injection. It has been used in Cummins B Series engines and the B-Series based NEF engine since 2003.[15]


  1. ^ a b Kennett, Pat (June 1986). "The Cummins Beat". TRUCK. London, UK: FF Publishing Ltd: 54–55.
  2. ^ Maupin, Artie (2022-06-22). "5.9-Liter Cummins Engine History and Specs". MotorTrend. Retrieved 2022-06-23.
  3. ^ Kennett, p. 57
  4. ^ a b c Cummins 5.9-liter and 6.7-liter inline six-cylinder diesel engines. Allpar.com. Retrieved on 2011-08-04.
  5. ^ "New Bus for London: Your New Routemaster questions answered". CBS Interactive. January 5, 2012. Retrieved 2017-11-27.
  6. ^ "LESA44T" (PDF). Wrights Group Limited. 2014. Archived from the original (PDF) on 2016-01-26. Retrieved 2017-11-27.
  7. ^ Wrights Hybrid Archived 2016-01-26 at the Wayback Machine Wrightbus
  8. ^ "ISB web". Retrieved 30 April 2012.
  9. ^ 2011 Ram 2500 and 3500 – Capability – Powertrain Archived 2011-02-24 at the Wayback Machine. Ramtrucks.com. Retrieved on 2011-08-04.
  10. ^ Cummins Engines Archived 2009-04-25 at the Wayback Machine. Everytime.cummins.com. Retrieved on 2011-08-04.
  11. ^ "Turbo Failure on your 6.7L Cummins? Here's what you need to know". Dirty Diesel Customs. Retrieved 2019-11-05.
  12. ^ "Bosch P7100 Fuel Pump Information". Big Bear Engine Company. 2017-04-10. Retrieved 2020-04-29.
  13. ^ Frailey, Mike; Norton, Paul; Clark, Nigel; Lyons, Donald W. (2000-10-16). An Evaluation of Natural Gas versus Diesel in Medium-Duty Buses. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International. p. 4. doi:10.4271/2000-01-2822. ISSN 0148-7191.{{cite conference}}: CS1 maint: location (link)
  14. ^ Krieger, Klaus; Hummel, Hans-Georg; Naik, L. M. (2000-01-15). Diesel Fuel Injection Technology - An essential contribution towards an environment friendly powerful diesel engine. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International. p. 165. doi:10.4271/2000-01-1429. ISSN 0148-7191.{{cite conference}}: CS1 maint: location (link)
  15. ^ Signer, Meinrad; Melton, Charles; Hawkins, Mike; Hawkins, Mike (2003-10-27). New Family of 1.1 Liter/Cylinder Structural/Agricultural Engines with High Pressure Common Rail Injection. 400 Commonwealth Drive, Warrendale, PA, United States: SAE International. p. 4. doi:10.4271/2003-01-3116. ISSN 0148-7191.{{cite conference}}: CS1 maint: location (link)