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Westport announces SI natural gas technology for medium-duty trucks

23 September 2014

Westport Innovations announced its new engine technology—the “enhanced spark-ignited” (ESI) natural gas system that uses a downsized, spark-ignited (SI) natural gas approach. The Westport™ ESI combustion system is targeted at sub-9 L engines for Class 6 and 7 truck applications and is also adaptable for sub-2 L automotive and non-automotive applications. The ESI engines are compatible with both compressed natural gas (CNG) and liquefied natural gas (LNG) fuels.

The ESI technology is a downsized engine, presumably utilizing high boost pressures. The system is designed to provide up to 10% improvement in power and torque over the base diesel engine, according to Westport. The higher power density allows a 4 L natural gas engine to replace a 6 L diesel engine, which results in substantial mass reduction.

The new engines use cooled EGR technology to provide high brake thermal efficiency (BTE) of up to 40%—which is better than most SI natural gas engines on the road. Compared to state-of-the-art diesel engines at around 45%, this still represents a 10-15% BTE disadvantage.

The ESI system utilizes port fuel injection, Westport WP580 engine management system and Westport fuel system components. A stoichiometric operation enables simple and compact three-way catalyst (TWC) aftertreatment, which can be packaged as part of the muffler. The engines are designed to meet the Euro VI and US EPA 2014 emission standards.

In North America, SI natural gas engines are supplied by the Cummins-Westport joint venture, CWI. CWI currently offers four natural gas engines, including models with 5.9 L, 8.3 L, 8.9 L and 12 L displacement. A new model, ISB6.7 G announced for 2015 appears to be using the new downsized combustion technology. The ISB6.7 G will meet US EPA 2014 and Euro VI emission requirements.

Westport said it is currently in various stages of development and negotiation with several vehicle and engine OEMs for ESI applications in medium-duty truck and automotive applications.

This development suggests that natural gas engine manufacturers are turning their attention away from long-haul trucking to focus on the medium-duty CNG trucks market. The adoption of natural gas engines in long-haul trucks has been slower than expected, due to the necessity of using cryogenic LNG fuels to provide the necessary range and/or other complex and expensive engine technologies.

Source: Westport