An Alternative Fuel System With A Diesel-Like Twist

Vancouver, B.C.-based Westport Innovations says an independent test using a Cummins ISX engine confirmed that its natural-gas fuel system can match the torque output offered by diesel fuel and still meet 2002 emissions standards for heavy-duty truck engines.

Westport says its fuel system achieves higher torque levels than other natural gas systems because it eliminates the “detonation limit” that occurs because air and fuel is mixed and compressed together through the intake valve. The resulting hot air ignites the fuel too early in the engine cycle, sending the piston downward at the same time the crank is trying to send it up. “That is a problem every automotive engineer knows about and is trying to avoid,” says Westport spokesman Alan Bayless.

On Westport’s system, air is compressed by itself and natural gas is then quickly added. A small amount of diesel and a large amount of natural gas are applied through the same injector, but through separate plumbing systems. “Natural gas won’t always ignite just from the heat of compressed air.but it will ignite from (the small amount) of combusting diesel,” Bayless said.

“With this system, we can get as much air and fuel into the engine at the exact same time, like you would with diesel fuel.” Westport’s first commercial fuel system is likely to be sold as an option for the Cummins ISX 400, but is not expected until at least 2002.