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Engine & Fuel System Integration

How First Generation Westport HPDI is Integrated with a Heavy-Duty Truck

Engine & Fuel System

Liquid, or liquefied, natural gas is stored in the LNG tank and drawn out with a unique LNG pump. The LNG is vaporized, using excess heat from the engine coolant, and exits the tank module at approximately 100 ºF and 4,500 psi (40 ºC and 30 MPa). The warm, high-pressure gas is filtered and delivered to the fuel conditioning module, where it is regulated and fed to the Westport HPDI injectors.  The engine is electronically managed, allowing continuous adjustments that provide optimal and unparalleled engine efficiency.

1st Gen. Westport HPDI Technology

Westport HPDI technology uses natural gas as the primary fuel along with a small amount of diesel as a pilot ignition source, or "liquid spark plug". At the heart of the engine is a revolutionary patented injector with a dual-concentric needle design. It allows for small quantities of diesel fuel and large quantities of natural gas to be delivered at high pressure to the combustion chamber. The natural gas is injected at the end of the compression stroke.

Under the pressures found in the combustion chamber of a normal diesel engine, natural gas requires a higher ignition temperature than diesel. To assist with ignition, a small amount of diesel fuel is injected into the engine cylinder followed by the main natural gas fuel injection. The diesel acts as a pilot, rapidly igniting the hot combustion products, and thus the natural gas. Westport HPDI replaces approximately 92% of the diesel fuel (by energy) with natural gas.

Westport HD System
LNG tank & pump module
high-pressure accumulator
warm, high-pressure
Westport HPDI
HPDI fuel injectors
(under valve cover)
fuel conditioning module
compressed natural gas