The powerful Cummins Westport 8.3 liter C Gas Plus has the highest power-to-weight ratio in its class and is offered in many of the world’s finest buses and trucks. Building on the rugged, reliable design of Cummins Bus C Gas+ EngineCummins diesel engines, the Cummins Westport C Gas Plus engine is an 8.3 liter, six-cylinder Lean-Burn Spark- Ignited (LBSI) natural gas vehicle engine that delivers from 187 to 209 kW (250-280 hp) with ultra-low emissions. It provides excellent torque, high fuel efficiency and reliable, robust performance, with excellent ratings for both medium-duty and garbage collection truck and urban bus applications. The C Gas Plus is known for easier maintenance and longer service with extreme reliability and durability. Service intervals are similar to the base diesel engine. Since it was introduced in 2001, more than 5,500 of these clean natural gas engines have powered transit fleets, medium-duty trucks and refuse collection vehicles in cities throughout the world. The C Gas Plus Electronic Control Module (ECM) allows engine performance to be tailored to fit the vehicle mission with road speed governing and cruise control, as well as an engine protection system and complete self diagnostics.

Fuel Capability

The C Gas Plus is capable of operating on compressed or liquid natural gas (CNG, LNG). With its simple chemical make-up of one molecule of carbon and four molecules of hydrogen , natural gas is a low carbon, clean-burning fuel choice. The C Gas Plus can also operate on up to 100% biomethane – renewable natural gas made from biogas or landfill gas that has been upgraded to pipeline and vehicle fuel quality. Biomethane fuel is carbon dioxide neutral and using it as fuel reduces vehicle greenhouse gas emissions by up to 90%.


  • Factory Built, Dedicated Natural Gas Engine   -   Built on the same assembly line as Cummins diesels, the C Gas Plus shares many components and parts with the Cummins C Series diesels.
  • Air/Fuel Regulation   -   Cummins closed-loop electronic control system is based on Cummins CM556 ECM which maintains efficient operation using sensors to monitor and control various engine parameters, exhaust backpressure, intake manifold temperature, fuel inlet pressure, knock detection, air-fuel ratio and fuel mass flow. Electronically controlled wastegated turbocharger.
  • Air Intake System   -   Charge air cooling is utilized to reduce emissions by lowering intake manifold air pressures.
  • Accessory Belt Drive System   -   Self-tensioning serpentine polyvee belt accessory drive system for water pump, engine-mounted fan hub and most alternators. Gear driven air compressor with provision for gear-driven hydraulic pump.
  • Catalyst   -   Required for all models. Engine is certified to Euro III standards.
  • Maintenance-Free After treatment   -   The C Gas Plus oxidation catalyst is packaged as a muffler and is maintenance free. No SCR is required.
  • Crankshaft   -   Eight counterweight, fully balanced, high-tensile-strength steel forging with induction hardened fillets and journals for outstanding durability.
  • Cylinder Block   -   Full-skirted block increases rigidity and strength. The design provides superior durability, as well as superior piston ring and bearing life.
  • Fuel Tolerance   –  Designed for compressed (CNG) or liquefied (LNG) natural gas vehicles. Its wide fuel tolerance – down to methane number 65 – increases uptime worldwide.
  • High-Energy Ignition System   –   ECM-controlled for better performance and longer service intervals, improved spark plug and coil durability, plus selfdiagnostics. Multiple Spark Discharge (MSD) for smooth idle and spark plug life. Coil-on-plug technology for reliable performance.
  • Oil Filter   -   The combination full-flow and bypass ® Fleetguard oil filter improves filtration while minimizing oil filter replacement and disposal costs.
  • Pistons   –   For extended piston and ring life, a Ni-Resist insert is cast into the aluminum piston and carries the top piston ring.

Proven “Plus” Technology
Maximizes the Equation

The “Plus” technology of the C Gas Plus features a highly efficient ECM to control its fuel system, engine sensors and high-energy ignition system. Additional “Plus” technology benefits include full drive-by-wire, programmable engine parameters, cruise control, road speed governing, idle speed control and shutdown, accelerator interlock, engine protection system and more. It also features state-of-the-art data links TM and the ability to interface with Cummins INSITE and QuickCheck diagnostic service tools for fast troubleshooting. Life-to-rebuild is the same as a diesel engine.

A Cost Efficient Way To Meet Every Emissions Challenge

The low carbon content of natural gas leads to lower emissions, and lower fuel costs can lead to lower total fleet costs. The C Gas Plus met the lowest emissions standards of the day when it was first introduced in 2002. Its reliability, performance and durability set new operating and cost of ownership standards for alternative fuel engines. To meet the future Euro emission regulations targeting nitrogen oxides (Nox), hydrocarbons (HC), and particulate matter (PM), engine manufacturers will apply advanced technologies including exhaust gas re-circulation (EGR), particulate filters and selective catalytic reduction (SCR). The technology for natural gas engines will not require complex exhaust after treatment.


Displacement (Litre) Rated Power (HP @ RPM)) Peak Torque
(Nm @ RPM)
Application Emission Norms
ISC8.3 Gas 8.3 250 @ 2500 895 @ 1400 Bus Euro - IV/V
ISC8.3 Gas 8.3 280 @ 2500 1152 @ 1400 Bus Euro - IV/V

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