A new natural gas fuel system optimal for medium and light-duty vehicles

Westport™ HESI 1.0 offers a revolutionary approach to diesel-engine-derived natural gas combustion technology. It builds on the simplicity of stoichiometric natural gas combustion with cooled EGR and 3-way catalyst to deliver the same power, torque, and fuel economy of a larger diesel engine with reduced complexity and cost. Westport™ HESI 1.0 technology does this by removing the constraint of carrying over the diesel engine cylinder head, which was not designed for Otto-cycle spark-ignited combustion. By re-architecting the combustion chamber geometry, developing a unique cylinder head based on proven techniques use in state-of-the-art gasoline engines, and combining it with the robust bottom end of the diesel engine, the combustion and thermal management of the engine can be fully optimize to take full advantage of the ultra-high octane properties of natural gas.

Westport™ HESI 1.0 is targeted at sub 10L engines for medium-duty truck applications and is also adaptable for use in light-duty automotive and non-automotive applications.


30% More Torque per Liter


30% more torque per liter than existing diesel-engine-derived natural gas approaches allows a smaller, more efficient engine to be used.
Approaching Diesel Fuel Economy

Low-End Torque

Optimized combustion and thermal management with high boosting in a smaller engine packages means faster response times and more low-end torque.
Ultra Low Emissions

Reduced Cost
Reduced Emissions

Through the use of natural gas and advanced 3-Way-Catalyst , end-users can both reduce fuel costs and product cost while reaching ultra-low levels of NOx and particulate emissions. The use of renewable natural gas can reduce well-to-wheels GHG emissions by more than 85%.


Primarily designed for CNG, LNG and RNG, Westport™ HESI 1.0 is also adaptable to LPG / propane.


HESi Engine Head

  • Tumble air motion promoting fast combustion and a simplified piston
  • Cascading design improvements to piston, fuel, intake and exhaust systems
  • Optimized thermal management: no hot spots and increased knock resistance
  • VVT residuals control, combustion optimization and dethrottling for greater efficiency
  • Compact combustion chamber with maximum heat dissipation
  • Even airflow distribution cylinder to cylinder.
  • Integrated EGR with high flow rate for knock control and dethrottling

Market Opportunity

Westport’s next generation HESI technology is a solution that reduces transportation costs while meeting both climate change and urban air quality challenges by offering ultra-low emissions and operating on cost effective, low carbon and renewable fuels.

According to the Global Transportation Energy and Climate Roadmap (International Council For Clean Transportation, 2012), in the absence of policies to reduce emissions, well to wheels CO2 equivalent emissions from heavy duty vehicles are expected to more than double from year 2000 levels by 2030.  Even with the policy actions in the pipeline, emissions are expected to grow significantly from 2010 to 2030.

Couple this with the challenge of increased urbanization and ultra-low vehicle emissions solutions for cities will become increasingly important to maintain or improve air quality and public health. 

Contact us for more information at sales@wfsinc.com.

News Releases

Industry News

Published: April 19

US-based Clean Energy Fuels Teams With Amazon on Rng

A significant confirmation for renewable natural gas playing an important role in the overall energy mix for transportation moving forward. The focus on reducing carbon will continue to bring renewable natural gas solutions to the spotlight.

Published: February 8

Amazon orders hundreds of trucks that run on natural gas

Amazon.com Inc has ordered hundreds of trucks that run on compressed natural gas as it tests ways to shift its U.S. fleet away from heavier polluting trucks.

Published: October 6

Volvo Trucks sees increased interest in LNG

Swedish truck maker Volvo said it’s seeing hauliers and transport buyers moving towards refrigerated liquefied gas as a cheaper and more environmentally friendly alternative to diesel.

Published: September 30

India: Maruti Suzuki sells 300,000 units of the WagonR S-CNG

The Maruti Suzuki WagonR S-CNG has emerged as the highest selling natural gas vehicle in the country, as this greener and safer factory-fitted CNG model has surpassed 300,000 units in sales.

Published: September 24

Why Fleet Managers Anheuser Busch Kehe Distributors are Fueling Renewable Natural Gas

While much attention has shifted to the potential for battery-electric or hydrogen vehicles, another technology with a vast infrastructure — renewable natural gas — is gaining traction among fleet managers.

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